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ELEMENTS
TECHNOLOGY,
A COURSE OF LECTURES
TAKEN CHIEFLY FROM                           ,
                    DELIVERED

              AT CAMBRIDGE,

                     ON THE

APPLICATION OF  THE  SCIENCES

                     TO THE

             USEFUL ARTS.

                 NOW PUBLISHED

  FOR THE USE OF SEMINARIE^ AND STUDENTS.
BY JACOB  BIGELOW, M.  D.
Professor of Materia Medica, and late Rumford Professor in Harvard University ; Correspond-
 ing Secretary of the American Academy of Arts and Sciences;  Member of the American
 Philosophical Society ; of the Linnxan Societies of London and Paris, &c.

                BOSTON;
HILLIARD, GRAY, LITTLE, AND WILKINS.
1  ■}
1829. 
35<73e
                  DISTRICT OF MASSACHUSETTS, TO WIT:

                                                         District Clerk's Office.

  Be it remembered, that on the ninth day of July, A. D. 1829, in the fiftyfourth year of the
Independence of the United States of America, Jacob Bigelow, of the said district, has deposit-
ed in  this office  the title of a book, the  right whereof he claims as Author, in the words
following, to wit:
  ' Elements of Technology, taken chiefly from a Course of Lectures delivered at Cambridge,
on the Application of the Sciences to the Useful Arts.  Now published for the Use of Semi-
naries and  Students.  By Jacob Bigelow, M. D., Professor of Materia  Medica,  and late
Rumford Piofessor in Harvard  University; Correspomling  Secretary of the  American
Academy of Aits and  Sciences; Member of  the American Philosophical Society; of the
Linnseun Societies of London and  Paris, &c.'
  In conformity to the  act of the Congress of the United States, entitled '  An act for the en-
couragement of learning, by securing the copies of maps, charts, and books, to the authors
ami proprietors of such copies, during the tiui'is  therein  mentioned;'  and also to an act,
entitled  ' An act supplementary to an act, entitled,  " An act  for  the  encouragement of
learning, by securing tiie copies of maps, charts, and  books, to the authors and proprietors
of such  copies, during the times therein mentioned ; "  and extending the  benefits thereof to
the arts of designing, engraving, and etching historical and other prints.'
                                                          JNO. W DAVIS,
                                            Clerk of the District of Massachusetts.
KXAMIHER  PRESS—SCHOOL  STREET. 
ADVERTISEMENT.
  A course of Lectures on most of the subjects which occupy
this volume, has been delivered at Cambridge, during ten years
past, in pursuance of the  will of the late Count Rumford, by
whose bequest a professorship is founded in Harvard University,
on the  Application of the  Sciences to the Useful Arts.  Parts
of the  same course have been repeated in Boston, to large
audiences.
  The degree  of interest  which  has been  taken in these
Lectures, has led me to believe that the subject is, in itself,
peculiarly  capable  of exciting the attention and  curiosity  of
students.   There can be no doubt that the  knowledge, which
this study is intended to furnish, is of great use in the common
affairs  of life ;  and probably its advancement  has  contributed
more than  that of any other science, to the improved condition
of the  present age.
  A certain degree  of  acquaintance with the  theory  and
scientific principles of the common arts, is found so generally
important, that most educated men, in the course of an ordinary
practical life, are obliged to obtain it  from  some source, or to
suffer  inconvenience  for  the want of it.   He  who  builds  a
house,  or buys an estate, if he would avoid disappointment and
loss, must  know  something of the  arts,  which render them 
IV
ADVERTISEMENT.
appropriate, and tenantable.   He who travels abroad to instruct
himself, or enlighten his countrymen, finds in the works of art,
the  most commanding  objects of his attention  and  interest.
He  who remains at home, and limits his ambition to the  more
humble object of keeping his  apartment  warm,  and himself
comfortable, can only succeed through the instrumentality of
the arts.
   There has probably never been an age in which the practical
applications of science have employed so large a portion of the
talent and enterprise of the  community, as in the present; nor
one  in  which their  cultivation has yielded such abundant
rewards.   And it is not the least of the distinctions of our own
country,  to have contributed to the advancement  of  this branch
of improvement, by  many splendid  instances  of inventive
genius, and successful perseverance.
   The importance of the subject, and the prevailing interest,
which exists in regard to the arts and their practical influences,
appear to me to have created  a  want, not yet provided for, in
our  courses of  elementary  education.  Information on  these
subjects is scattered through the larger works on  mechanics,
on chemistry,  mineralogy, engineering,  architecture, domestic
economy, the  fine arts, &c,  so that it rarely happens, that a
student in  any of our colleges, gathers  information enough to
understand the common technical terms which he  meets  with
in a  modern book of travels, or periodical  work.  It is only by
making the elements of the arts themselves,  subjects of direct
attention, that this deficiency is likely to be supplied.
   To embody,  as far as possible,  the various  topics which
belong to such  an  undertaking, I have adopted  the  general
name of Technology, a word  sufficiently  expressive,  which is
found in some of the older dictionaries, and is beginning to be
revived in  the literature  of practical men  at the present day. 
ADVERTISEMENT.
V
Under this title it is attempted to include such an account as
the limits of the volume permit, of the principles,  processes,
and  nomenclatures of the more conspicuous  arts, particularly
those which involve  applications of science, and which may be
considered useful, by promoting the benefit of society together
with the emolument of those who pursue them.
   In preparing for the press the lectures on which this work is
founded, some variations from the original form have been  made,
together with such additions  as my leisure  from professional
engagements has permitted.   In  doing  this, occasional  use
has  been made  of the works of Robison, Young,  Tredgold,
and  several of the late chemical writers.   But as the present
elementary  volume  is  composed  for  the  instruction of the
uninitiated, rather than for the perfection of adepts, it has been
found  necessary to  condense  and  to endeavor  to render
intelligible the subjects of consideration, rather than  to dilate
them by minute expositions and details.   For the use  of those
students, who may wish to extend their  inquiries in reference
to any  of the particular subjects, a list of some of the more
prominent  authors, and works of  value,  that treat upon the
several  subjects, is  subjoined at the  end of each  chapter.
Among some of these works, the authorities for the facts stated
in the preceding  chapters, will in most instances  be found.
   For the  convenience of seminaries which may make use of
this work, the wood  cuts  and  diagrams which are interspersed
with  the text, are reprinted at the end of the volume.
   BOSTON, JULY 1829.                               J. B, 
                              CORRECTIONS.

Page  16, line  3, for corbonate, read carbonate.
  "  125,  "  10 from bottom, for 120, read 148.  The height of the dome of
                 the Capitol.   This I am informed by Mr Bulfinch the architect,
                 is the  actual height, though it is differently stated in books.
  "  127,  "  1, for will, read may.
  "  206,  "  3, for pieces, read piers.
  "  292, bottom line, for excentric, read eccentric. 
CONTENTS.
                            CHAPTER I.


               Of  the Materials used in the Arts.

  Materials from the  Mineral  Kingdom, Stones  and  Earths, Marble,
page 7.  Granite, 8.   Sienite, 9.  Freestone,  Slate,  Soapstone,  10.  Ser-
pentine, Gypsum, Alabaster, 11.   Chalk, Fluor Spar, Flint, Porphyry^ 12.
Buhrstone, Novaculite, Precious Stones, Emery, 13.  Sand, Pumice, Tripoli,
Clay, 14.  Asbestus, Cements, Limestone, 15.  Puzzolana, 16.  Tarras, Other
Cements, 17.  Maltha, 18.  Metals, Iron, Copper, 19. Lead, tin, 20.  Mercury,
Gold, Silver, 21.   Platinum, Zinc, Antimony, Bismuth, Arsenic, Manganese,
22.   Combustibles, &c, Bitumen, Amber, Coal, Anthracite, 23.  Graphite,
Peat, Sulphur, 24.  Materials from the  Vegetable Kingdom, Wood, Bark,
Oak, 25.  Hickory, Ash,  Elm, Locust, 26.  Wild  Cherry, Chesnut, Beech,
Basswood, Tulip Tree, 27.  Maple,  Birch, Button Wood, 28.   Persimmon,
Black Walnut, Tupelo, Pine, 29.  Spruce, Hemlock,  White Cedar, Cypress,
30.   Larch, Arbor Vitse, Red  Cedar, Willow, Mahogany,  31.   Boxwood,
Lignum Vitae, Cork, Hemp, 32.  Flax, Cotton, 33.  Turpentine, Caoutchouc,
34.   Oils, 35.  Resins, Starch, Gum, 36.—Materials from the Animal King-
dom.—Skins, Hair and Fur, Quills, and Feathers, 37.   Wool, Silk, 38.  Bone
and Ivory,  Horn, Tortoise Shell, Whale Bone, 39.   Glue, Oil, 40.  Wax,
Phosphorus, 41.

                            CHAPTER II.


     Of the Form, Condition, and Strength of Materials.

  Modes of Estimation, Stress and  Strain, 42.   Resistance, Extension,  43.
Compression, 44.  Lateral Strain, Stiffness, 45.  Tubes,  Strength, Place  of
Strain, 46.   Incipient Fracture, Resilience, 47.   Shape of Timber, Torsion,
Limit of  Bulk, 48. Practical Remarks, 49. 
Vlll
t ONTF.NTS.
                           CHAPTER  III.

               The Arts of Writing and Printing.

  Letters, Invention of Letters, 53.  Arrangement of Letters, Writing Ma-
terials, 54.  Papyrus,  55.  Herculaneum  Manuscripts,  56.   Parchment,
57.   Paper, Instruments, Inks, 58.  Copying Machines, Printing, 59.  Types,
60.   Case,  Sizes, Composing,  61.   Imposing, 62.  Signatures,  Correcting
the  Press, 63.  Press Work, Printing Press, 65.  Stereotyping, 66.  Machine
Printing, 67.  History, 68.

                           CHAFTER  IV.

                 Arts of Designing and Painting.
  Divisions, Perspective, 71.   Field of Vision, Distance and Foreshortening,
72.   Definitions, 73.   Plate II., 75.  Problems, 76.   Instrumental Perspec-
tive, 77.  Mechanical Perspective,  Perspectographs, 79.   Projections,  80.
Isometrical  Perspective, 81.   Chiaro Oscuro, Light and Shade, 82.  Associa-
tion, Direction  of Light, 83.  Reflected  Light,  Expression of Shape,  84.
Eyes of a Portrait, Shadows, Aerial Perspective, 85.   Coloring, Colors,  86.
Shades, Tone, Harmony, 87.   Contrast, Remarks, 88.

                            CHAPTER V.

               Arts of Engraving  and  Lithography.
  Engraving, Origin, Materials, 90.   Instruments, Styles, Line Engraving,
91.   Stippling,  Etching, 93.   Mezzo Tinto, 95.   Aqua  Tinta, 96.   Copper-
plate Printing, Colored Engravings, 98.  Steel Engraving, Wood Engraving,
99.   Lithography,  Principles, Origin,  100.  Lithographic  Stones,  101.
Preparation,  Lithographic Ink and Chalk, Mode of Drawing, 102.   Etching
the Stone, 103.   Printing, Printing Ink, Remarks, 104.

                            CHAPTER VI.

              Of Sculpture, Modelling, and Casting.

  Subjects, Modelling, 106.  Casting in Plaster, 107.   Bronze  Casting,
Practice of Sculpture, 109.  Materials, 110.   Objects  of Sculpture, Gem  En-
graving, Cameos, Intaglios, 111.  Mosaic, Scagliola, 112.

                            CHAPTER  VII.

                  Of Architecture and Building.
   Architecture, Elements, Foundations,  114.   Column,  115.   Wall,  116.
Lintel, Arch, 118.  Abutments, 120.  Arcade, Vault, Dome, 121.   Plate I., 
CONTENTS.
IX
122.   Roof,  126.  Styles  of Building, 127.  Definitions,  128.   Measures,
Drawings, Restorations, 130.  Egyptian  Style, 131.   The Chinese  Style,
The  Grecian Style, 132.  Orders of Architecture, Doric Order, 133.  Ionic
Order, Corinthian Order,  134.   Caryatides, Grecian Temple, 135.  Grecian
Theatre, 137.  Remarks, Plate IV., 138.   Roman Style, Tuscan Order, Ro-
man Doric, Roman Ionic, Composite Order, 142.   Roman Structures, Remarks,
143.   Plate  V., 144.  Greco-Gothic  Style, 146.  Saracenic Style,  Gothic
Style, 147.   Definitions,  148.   Plate VI., 149.  Plate VII, 150.  Applica-
tion,  152.

                           CHAPTER  vm.

                 Arts of  Heating and Ventilation.

   Production of Heat, Fuel, Weight of Fuel,  153.   Combustible Matter of
Fuel, Water in Fuel, 154.   Charcoal, 155.  Communication of Heat, Radi-
ated  and  Conducted Heat, Fire in the Open Air,  156.  Fire Places, 157.
Admission of Cold Air, Open  Fires, Franklin  Stove,  158.  Rumford Fire
Place, 159.  Double Fire Place, 160.   Coal Grate,  161.  Anthracite Grate,
Burns' Grate, Building a Fire, 162.   Furnaces, Stoves, 163.  Russian Stove,
164.   Cockle, Cellar Stoves, and  Air Flues, 165.   Heating by Steam, 166.
Retention of Heat, Causes  of Loss, 168.   Crevices, Chimnies, Entries, and
Sky Lights,  169.  Windows, Ventilation, Objects, Modes, 170.   Ventilators,
Culverts,  Smoky  Rooms, 171.  Damp Chimnies, Large Fire Places,  172.
Close Rooms, Contiguous Doors, Short Chimnies, Opposite Fire Places, 173.
Neighbouring Eminences, Turncap, &c,  Contiguous Flues, 174.  Burning
of Smoke, 175.

                            CHAPTER   IX.

                       Arts of  Illumination.

   Flame, Support of Flame, 176.  Torches and Candles, Lamps, 177.  Re-
servoirs, Astral Lamp, 178.  Hydrostatic  Lamps, 179.  Automaton  Lamp,
Mechanical Lamps, Fountain Lamp, 180.  Argand  Lamp, 181.   Reflectors,
Hanging  of Pictures, 182.   Transparency  of Flame,  Glass Shades, Sinumbral
Lamp,  Measurement of Light,  183.  Gas Lights, 184.  Coal Gas, 185.  Oil
Gas, 187.  Gasmeter, Portable Gas  Lights, Safety Lamp, 188.  Lamp  with-
out Flame, 189.   Modes of  procuring Light, 190.

                            CHAPTER  X.

                       Arts  of  Locomotion.

   Motion of Animals,  192.   Inertia, Aids to Locomotion, 194.   Wheel Car-
riages, Wheels, 195.  Rollers, Size of Wheels, 196.  Line of Traction, 197.
Broad Wheels, 198.  Form of Wheels, 199.   Axletrees, Springs, Attaching
of Horses, 200.   Highways, Roads, Pavements, 202.  McAdam Roads, 203
Bridges,  1.  Wooden Bridges.  2. Stone Bridges. 204.  3. Cast Iron Bridges,
                  h 
X
CONTENTS.
4.  Suspension Bridges, 205.   5. Floating Bridges, Rail Roads, 206.  Edge
Railway, 207.  Tram Road,  Single Rail,  208.  Passings, 209.  Propelling
Power, 210.  Canals, Embankments, 211.  Aqueducts, Tunnels, 212.  Gates
and Weirs, Locks, 213.  Boats, Size of Canals, 215.  Sailing, Form of a Ship,
216.   Keel and Rudder, 217.  Effect of the Wind, 218.  Stability of a Ship,
Steam  Boats, 220.   Diving Bell, 222.  Submarine  Navigation, 224.  Aero-
station, Balloon, 225.  Parachute, 226

                           CHAPTER  XI.

                     Elements of Machinery.

  Machines, Motion, 228.   Rotary or Circular Motion, Band Wheels, 229.
Rag Wheels, Toothed  Wheels, 230.   Spiral Gear, 231.  Bevel Gear, 232.
Crown  Wheel,  Universal  Joint, Perpetual Screw,  233.   Brush  Wheels,
Ratchet  Wheel,  Distant Rotary  Motion,  234.   Change of  Velocity, 235.
Fusee, 236.  Alternate or Reciprocating Motion, Cams, 237.  Crank, 239.
Parallel Motion, 240.  Sun  and Planet Wheel, 241.  Inclined Wheel, Epicy-
doidal Wheel, 242.   Rack and Segment, Rack and Pinion,  243.   Belt and
Segment, Scapements,  244.   Continued  Rectilinear Motion,  Band, 245.
Rack, Universal Lever, Screw,  Change of  Direction, 246.   Toggle  Joint,
Of Engaging and Disengaging Machinery, 247.   Of Equalizing Motion,
Governor, 248   Fly Wheel, 250.   Friction, 251.   Remarks, 252

                           CHAPTER XII.

            Of the Moving Forces Used in the Arts.
   Sources of  Power, Vehicles of Power,  253.  Animal Power, Men, 254.
Horses,  256.   Water Power, Overshot Wheel, 257.  Chain Wheel, 260.
Undershot Wheel,  261.  Back  Water, 263.  Besant's Wheel, Lambert's
Wheel,  264.  Breast Wheel, Horizontal  Wheel, 265. Barker's Mill, 266.
Wind Power, 267.   Vertical Windmill, Adjustment of Sails, 268.  Horizon-
tal Windmill, Steam Power, Steam, 270.   Applications of Steam,  273.  By
Condensation, by Generation,  274.  By Expansion, 275.  The Steam Engine,
Boiler, 277.  Appendages, 278   Engine, 281.  Noncondensing Engine, 282.
Condensing Engines, 283.  Description, 284. Expansion Engines, 287. Valves,
 288. Pistons, 289.   Parallel Motion, Historical Remarks, 290.   Projected Im-
 provements,  Rotative Engines, 292.  Use of Steam at High Temperatures,
 293.   Use of Vapors of Low Temperature,  Gas  Engines, 294.  Steam Car-
 riages,  295.  Steam Gun,  Gunpowder,  Manufacture,  296.  Detonation,
 Force, 297.  Properties of a Gun, 299.  Blasting, 300.

                           CHAPTER  XIII.

                    Arts of Conveying Water.

   Of Conducting  Water, Aqueducts, 302.   Water  Pipes, 303.   Friction of
 Pipes, 305.  Obstruction of  Pipes, 306.   Syphon,  Of Raising  Water, 308. 
CONTENTS.
X4
Scoop Wheel, Persian Wheel, 309.  Noria, Rope Pump, Hydreole, Archimi-
des'  Screw, 310.  Spiral  Pump, 311.   Centrifugal Pump, Common Pumps,
313.   Forcing  Pump, 314.  Plunger Pump, 315.  Delahire's Pump, Hydro-
static Press, 316.   Lifting Pump, Bag Pump, 317.  Double  Acting  Pump,
Rolling Pump, 318.  Eccentric Pump, 319.  Arrangement of Pipes, Chain
Pump, 320.   Schemnitz  Vessels,  or Hungarian Machine, 321.  Hero's
Fountain, Atmospheric Machines, 322.  Hydraulic Ram, 323.  Of Project-
ing  Water, Fountains, 324.  Fire Engines, 325.   Throwing Wheel,  326.

                           CHAPTER  XIV.

           Arts of Dividing and  Uniting Solid Bodies.

  Cohesion, Modes of Division, Fracture, 328.  Cutting, Cutting Machines,
329.  Penetration, Boring and Drilling, 330.   Turning, 331.   Attrition, Saw-
ing, Saw Mill, Circular  Saw, 332.  Crushing, Stamping Mill, 333.  Bark
Mill, Oil Mill, Sugar Mill, 334.  Cider Mill, Grinding, Grist Mill, 335.  Color
Mill, 336.  Modes of Union, Insertion,  Interposition, 337.   Binding, Lock-
ing, Cementing, 338.   Glueing,  Welding, 339.  Soldering, 340.  Casting,
Fluxes, Moulds, 341.

                            CHAPTER  XV,

               Arts of  Combining  Flexible Fibres.

   Theory  of  Twisting,  343.  Rope  Making. 344.  Cotton Manufacture,
 Elementary Inventions, 346.  Batting, 347.  Carding, Drawing, 348.  Rov-
 ing, 349.   Spinning,  Mule  Spinning,  351.  Warping, 352.   Dressing,
 Weaving,  353.   Twilling, 354.  Double  Weaving,  Cross  Weaving,  355.
 Lace, 356.  Carpeting, Tapestry,  357.  Velvets, Linens, 358.   Woollens,
 359.  Felting, 361.  Paper Making, 362.

                            CHAPTER  XVI.

                         Arts of Horology.

   Sun Dial, 364.   Clepsydra, 365.  Water Clock, Clock Work, 366.  Main-
 taining Power, 367.  Regulating Movement, Pendulum, 368.  Balance, 369.
 Scapement, 370.  Description of  a  Clock, 371.   Striking Part,  373.  De-
 scription of a Watch, 376.

                           CHAPTER  XVII.

                         Arts of Metallurgy.

   Extraction  of  Metals, 385.  Assaying, Alloys, 387.  Gold,  Extraction,
 Cupellation, 389.   Parting, Cementation, 390.  Alloy,  391.  Working, Gold
 Beating, 392.  Gilding on Metals, 393.   Gold Wire, Silver,  Extraction, 394.
 Working,  Coining, 395.  Plating, 397.   Copper, Extraction, Working, 399. 
\n
CONTENTS.
Brass,  Manufactures, 400.  Buttons,  Pins, 401.  Bronze, 402.  Lead,  Ex-
traction, 403.  Manufacture, Sheet Lead,  Lead Pipes, 404.   Leaden Shot,
405.  Tin, Block Tin, Tin Plates, 406.   Silvering of  Mirrors, 407.  Iron,
408.  Smelting, 409.  Crude  Iron, Casting,  410.   Malleable Iron, Forging,
412.  Rolling and Slitting, 413.  Wire Drawing,  415.  Nail  Making, Gun
Making, 416.  Steel, 417.  Alloys of Steel, Case Hardening, 418.   Temper-
ing, 419.   Cutlery, 421.

                          CHAPTER XVIII.

         Arts of Communicating and Modifying Color.

  Of Applying Superficial  Color, Painting, Colors, 425.  Blues, 426.  Reds,
427.  Yellows,  Greens,  428.   Browns, Blacks, 429.  Whites, Preparation,
Application,  Crayons, 430.   Water Colors, Distemper, 431.  Fresco,  En-
caustic  Painting, Oil Painting,  432.  Varnishing, 433.   Japanning, 435.
Polishing,  Lacquering, 436.   Gilding, 427.   Of Changing  Intrinsic  Color,
Bleaching, 438.   Dyeing, 439.   Mordants,  Dyes, 440.  Calico  Printing, 444.

                           CHAPTER XIX.

                       Arts of Vitrification.

  Glass, Materials, 448.  Crown Glass, 449.  Fritting, Melting,  Blowing, 450.
Annealing, 451.  Broad Glass, Flint Glass, Bottle Glass, Cylinder Glass, 452.
Plate Glass, 453.  Moulding, 454.  Pressing, 455. Cutting, Stained Glass, 456.
Enamelling, 458.  Artificial Gems, Devitrification, Reaumur's Porcelain, 459.
Crystallo-Ceramie, Glass Thread, 460.  Remarks, 461,

                           CHAPTER  XX.

                   Arts of Induration by Heat.

  Bricks, 463.  Tiles, Terra Cotta, 465.   Crucibles, Pottery, 466.   Opera-
tions, 467.  Stone Ware, White  Ware, 468.   Throwing, Pressing,  Casting,
470.  Burning, Printing, Glazing, 471.  China Ware, 472.   European Porce-
lain, 473.  Etruscan Vases, 474.

                           CHAPTER  XXI.

          On the  Preservation of Organic  Substances.

  Decomposition, Temperature, 476.   Dryness, 477.  Wetness, Antiseptics,
478.  Timber, Felling, 479.   Seasoning, 480.   Preservation of Timber, 481.
Preservation of Animal Textures, Embalming, 485.  Tanning, 486.  Parch-
ment, Catgut, 488.  Gold Beater's Skin, Specimens in Natural History,  489
Appert's Process, 491. 
INTRODUCTION.
   Whenever we attempt to draw a dividing line between the
sciences, usually so called, and the arts, it results in distinctions,
which are comparative, rather than absolute.   In many branch-
es of human  knowledge, the two are so blended together, that
it is impossible to make their separation complete.  In common
language we apply the name of sciences, to those departments
of knowledge which are more speculative, or abstract, in their
nature, and which are conversant with truths or with phenom-
ena, that are  in  existence at the time we contemplate them.
The arts, on the contrary, are considered as  departments of
knowledge, which have their origin in human ingenuity, which
depend on the active, or formative processes of the  human
mind,  and which without these, would not have existed.  Our
knowledge  may be said to have been found out originally by
discovery and invention.  Discovery is the process of science ;
invention is  the  work  of art.   So  common, however, is the
connexion of the two with each other, that we find both a science
and an art involved in the same branch of study.   For  exam-
ple, chemistry is a science depending on  the immutable rela-
tions of matter, which relations must have existed, had there
never been minds to study them.   Yet these  laws of  matter
would  not have become the  subjects of science, had not man-
kind invented the art of separating their agents, and making them
cognizable to the senses.  To build a ship, to construct a  watch,
                    1 
2
INTRODUCTION.
or to paint a picture, are all operations of art; yet they all have
their foundation in a certain  acquaintance with mathematical
rules, and principles of natural philosophy.   Those artists, who
work with a thorough knowledge of principles, we are accus-
tomed  to denominate scientific ; while those  who experiment at
random, or who blindly copy the results of others, we consider
empirical.   Thus it appears that an intimate connexion and de-
pendence  exists between sciences and arts, and it follows that
the claim which they offer to our attention is in a great measure
of the  same kind.   Of the latter, as well as the former, we al-
ready require some, as branches of a common education; while
of the  rest  there are  few which may not be  advantageously
studied, either  as affording exercise for talents, discipline for
taste, or practical advantage in the common concerns of life.
  The connexion of the arts with the sciences is more common
and obvious in modern times, than it was in the days of antiquity.
During  the  process of civilization, or the whole period which
elapses  between barbarism and complete refinement, the arts
have uniformly taken precedence both of science and literature.
Rude nations commence  the improvement of their state, by an
attention to agriculture, to building, to navigation, and to sculp-
ture.   The  want of an acquaintance with the real or scientific
principles of these arts, obliges them to substitute the effects of
manual  labour and dexterity, for scientific method ;  and hence
the paths in which they excel,  have been usually of a different
character from those of people whose knowledge and resourc-
es are greater.  The ancients, who Were but recently descend-
ed  from barbarians, were obliged to make  the most of small
means, because the stock of previous or common information,
from which they could  draw, was extremely  limited.  The
moderns have  the  accumulated learning of ages before them,
and  have  only to select  and  apply their agents from among a
multitude  of means already  discovered.   The  qualities, by
which the former arrived at excellence, were more or less con-
centrated in individuals;  while with us the means of excellence
are recorded in books, and are at the disposal of communities 
INTRODUCTION.
 They possessed the quick eye, the expert hand, acute taste and
 unwearied  industry.   For these  we  substitute  preparatory
 science,  economical  computation,  and  mechanical  power.
 Their processes differed  from ours, as the process of the savage
 who fashions and polishes his war club, by the truth of his eye,
 and the patience and dexterity of his hand; differs from that of
 the civilized mechanic, who turns  the same kind  of thing,
 in a lathe, which another man has invented for him, in a hundredth
 part of the time.   The ancients were prodigal of means and lav-
 ished men and treasures when any great work was to be accom-
 plished.  The moderns save expense, and labour, and time in eve-
 rything.  The economy of the ancients consisted in diminishing
 their personal wants ; ours, in devising  cheap means  to gratify
 them.  They prepared their soldiers for war by inuring them
 to hunger  and  fatigue ; we, by keeping them well fed and
 clothed.  Their  stateliest edifices were  destitute  of  chimnies
 and glass windows, yet when left to themselves, they have stood
 for thousands of years.  Ours abound in the means of making
 their present tenants comfortable, but are often built too cheaply
 to be durable.  They conveyed water to their cities in  immense
 horizontal channels supported on arcades of prodigious elevation.
 We convey it over mountains and  under vallies  in hydraulic
 pipes of the most trivial  size.  Wherever  art could  precede
 philosophy,  the ancients have exhibited the grandest productions
 of genius and strength ; but, in the application of philosophy to
 the arts, the moderns have  achieved, what  neither genius nor
 strength, unassisted, could have performed.  The imitative arts,
 and  those which required only boldness and beauty of design,
 or perseverance in execution, were carried in antiquity to the
 most signal perfection.  Their sculpture has been the admira-
 tion  of subsequent ages, and their  architecture  has furnished
 models which we now strive to imitate, but do not pretend to
 excel.  We might, if this were the place, add their poetry, and
 their oratory, to the  list of arts  which flourished in perfection
 during the youthfulness of intellectual cultivation.   But  in mod-
ern  times there is a maturity, a cautiousness, a habit of indue- 
4
INTRODUCTION.
tion, which is founded  on the advanced state of philosophic
knowledge.   Our  arts have been the arts of science, built up
from an acquaintance with  principles, and with the relations of
cause and effect.   With less bodily strength, and probably with
not more vigorous intellects, we have acquired a dominion over
the physical and moral world, which  nothing but the aid of phi-
losophy could have enabled us to  establish.   We convert natu-
al agents  into ministers of  our pleasure and power, and supply
our deficiencies of personal force by the application of acquired
knowledge.   Among us, to be  secure, it is not necessary that
a man should be powerful  and  alert; for even where  laws fail,
die weak take rank with the strong, because the weakest man
may arm himself with the  most formidable means of  defence.
The labor of a hundred artificers  is now  performed  by the op-
erations of a single machine.  We traverse the ocean  in secur-
ity, because the arts have furnished us a  more  unfailing  guide
than the stars.  We  accomplish what the ancients only dreamt
of in their fables;  we  ascend  above the  clouds, and penetrate
into the abysses of the ocean.
   The  application  of philosophy to the arts is a more fruitful
theme,  than  can well be  condensed into  a  limited  work,  or
course of instruction.  While it comprises some" of the sources
even  of ancient  refinement, it includes  a great part of the
grounds of modern superiority.  The application of philosophy
to the arts may be said to  have made the world  what it is  at
the present day.  It has not only  affected the physical, but has
changed the moral and political condition of society.   The in-
vention of the printing press, dispersed the darkness of the mid-
dle ages,  and carried truth and knowledge to every portion of
the world.   The  artificial combination  of sulphur, nitre, and
charcoal, has revolutionized the  customs  and the arts of war,
and even in military life, has given the mind the advantage over
the body.  The moderns have imparted  magnetism to a piece
of steel and suspended it on a  pivot, and what has  been the
consequence ?  It has opened to  them a  path across  unknown
seas, and has disclosed a new continent to the inhabitants of the 
INTRODUCTION.
5
old, a successor to their arts and their power.  It has develop-
ed the wealth of unknown  islands, has brought  the* remotest
countries together, and has made the ocean the resort and sup-
port of multitudes.  Let any one, who would know what modern
arts have accomplished, compare the repeating watch, and the
unerring  chronometer  of  the  present day, with the rude sun
dial and clepsydra of the ancients.   Let him consider the mul-
tiplied advantages  which attend the  invention of glass, which
has enabled us to  combine light with warmth in our houses;
which has given sight to the  aged, which has opened the heav-
ens to the astronomer, and  the wonders of microscopic life to
the naturalist.   Let him attend to the complicated engines and
machinery, which are  now introduced into almost every manu-
facturing process, and  which render the physical laws of inert
matter, a substitute for human strength.
   But it is not the contrast with antiquity alone, that enables us
to appreciate the benefits  which modern  arts confer.  In the
present inventive age, even short periods of time bring with
them momentous  changes.    Every  generation takes  up the
march of improvement, where its predecessors had stopped,
and every generation leaves to  its successors an increased cir-
cle of advantages and acquisitions.  Within  the memory  of
many who are now upon  the stage, new  arts have sprung up,
and practical inventions, with dependant sciences ; bringing with
them  consequences  which  have diverted the  industry,  and
changed the  aspect of civilized countries.  The  augmented
means of public comfort and of individual luxury, the expense
abridged  and  the labor superseded, have been  such, that we
could not return to the state of knowledge which existed even
fifty or sixty years ago, without suffering  both intellectual and
physical degradation.   At that time, philosophy was far distant
from its  present mature state,  and the  arts which  minister to
national  wealth  were  in  comparative infancy.   No man then
knew the composition of  the atmosphere, or of the  ocean.
The  beautiful and intricate machinery, which weaves the fabric
of our clothing, was not even in existence.   When George III. 
6
INTRODUCTION.
 visited the works of Messrs Boulton and Watt at Birmingham,
 and was told that  they were manufacturing an  article of which
 kings were fond, and that that article was power; he was struck
 with  the  force  and  disadvantageousness of  the comparison.
 Yet the  steam engine had  not then been  launched upon the
 ocean, and had developed only half its energies.
   So long as the  arts continue to exert the  influence, and to
 yield the rewards, which they have hitherto done, there will be
 no want of competent minds and hands,  to carry forward their
 advancement.  With their increasing consequence,  there must
 also be an increasing attention to their study and dissemination.
 Curiosity keeps  pace with the interest  and  magnitude of its
objects.  And unless the character of the present age is greatly
mistaken, the time may be  anticipated as near, when a know-
ledge of the elements  and  language of the arts will be as essen-
tially requisite to a good education, as the existence of the same
arts is to the present elevated condition of society. 
ELEMENTS  OF TECHNOLOGY.
                      CHAPTER I.

            OF MATERIALS USED IN  THE ARTS.

  The mineral, vegetable, and animal kingdoms, respectively
contribute to supply the substances which are necessary in  the
arts.   Of these  substances, many have been known and used
from the time of the earliest records ;  others are of recent in-
troduction, and additions are still making to the stock previously
known.  The value of a substance to  the arts, may be estima-
ted from  the importance of the object it fulfils, its durability,
the number of purposes  to which it may be applied, and  the
facility with which it is convertible to use.

         MATERIALS FROM  THE MINERAL KINGDOM.

  Stones and Earths.—Marble.—The class of stones denom-
inated calcareous, is exceedingly numerous and abundant in na-
ture.   Of these marble is the most important.   It is a granular
carbonate of lime, varying in color, texture, and hardness.  Mar-
ble is extensively used for building, statuary, decorations, and in-
scriptions.  In warm countries it is one of the most durable of
substances, as is proved by the edifices of Athens, which have re-
tained their polish for more than two thousand years.   Severe
frost, preceded by moisture, causes it to crack and scale.  Great 
8
MATERIALS USED IN the arts.
heat reduces it to quicklime.  Marble is wrought by chiseling,
and by sawing with smooth plates of iron, with sand  and water.
It is polished  by rubbing with sand and  water, and  afterwards
with putty and soft substances.
  Numerous  stones of the  calcareous class, more or less ap-
proaching to marble in their character, have been converted to
use in different  countries.   The  Pyramids of Egypt are  built
of a greyish  white  calcareous stone, inclosing shells. *   The
Parthenon, and other structures of Athens, are of Pentelic mar-
ble,  distinguished by slight greenish  veins.  The mosques of
Constantinople are of a fine grained limestone from Pappenheim,
the same which is now used in lithography.   At Rome, a po-
rous whitish limestone, called tophus by the ancients, and  trav-
ertino by the  moderns, is the material of the Coliseum, of St
Peter's  church, he.  The  ruins of Paestum are  of a stone
nearly similar.   The  building called the Tomb of Theodoric,
at Ravenna, has a dome consisting of a  single stone which  is
thirtyfour feet in diameter.   It is a grey limestone from Istria,
and is computed to have weighed, when taken from the quarry,
more than two million pounds, f   Paris is built with  calcareous
stone, of which  there are five kinds.   The Portland  stone of
which St Paul's and other edifices in London are constructed,
is a calcareous rock called Oolite by mineralogists.   Specimens
of marble  abound in  the United  States, and are  seen in the
City Hall of  New York, the  United  States  and Pennsylvania
Banks, Philadelphia, the Washington Monument, Baltimore, &c.
  In statuary the Venus de Medicis, and Diana  venatrix, are
formed of Parian marble.   The Apollo de Belvidere, accord-
ing to Dolomieu, is  made  of  Luni marble,  and if so  must
be  posterior to the time of Julius CaBsar, before which period
that quarry was not opened.
   Granite.—Granite  is apparently the oldest and the deepest
of rocks.  It is one of the hardest and, most durable  which have
been wrought, and is obtained in larger pieces than any other
* Brard.                        t Borgnis. 
MATERIALS  USED  IN THE ARTS.
9
rock.   Granite  is  a compound stone, varying  in  color  and
coarseness.   It consists of three constituent parts ; viz. quartz,
the material of rock crystal; feldspar, which gives its colors,
and which is the  material of porcelain earth ; and lastly mica,
a transparent, thin,  or foliated substance, which affords a flexible
substitute for glass, when obtained in large pieces.   Granite is
chiefly used for  building.   It is split from the quarries by rows
of iron  wedges driven simultaneously in the  direction of the in-
tended fissure.   This method is thought by Brard to have been
known to the ancient Romans and Egyptians.  The blocks are
afterwards hewn to a plane surface by strokes of a sharp edged
hammer.  Granite is also  chiselled into capitals and decorative
objects, but this operation  is difficult, owing  to its hardness and
brittleness.   It is polished  by long continued friction, with sand
and emery.
   The  largest mass of granite, known to have been transported
in modern times,  is the pedestal of the equestrian statue of Pe-
ter the Great, at St  Petersburgh.   It is computed to weigh three
million  pounds, and was transported nine leagues by  rolling it
on cannon balls. *   Those of cast iron being crushed, others of
bronze  were substituted.   Sixty granite columns at St Peters-
burgh,  consist  each of a single stone twenty  feet high.  The
columns in  the  portico of the Pantheon at  Rome, which  are
thirtysix feet, eight inches  high, are  also of granite, f  The
shaft of Pompey's Pillar, so called, J in Egypt, is sixtythree feet
in height, and of a single  piece.   It is said to be of red gran-
ite, but  is possibly sienite.   In the  Eastern  part of the United
States, a beautiful white granite is found in various places, and
is now  introduced  in building.   The new Market House in
Boston, the United  States  Bank, he. are made of it.
   Sienite.—This rock is related to  granite,  and resembles it in
its general characters.  It consists  chiefly of feldspar and horn-
blende.    Sienite is obtained in large pieces, and possesses all

           * Carburi.                       t Rondelet.
  $ The inscription on this pillar is said by the Earl of Mountnorris in Brande's
Journal, to belong to Dioclesian, and not to Pompey, as was formerly supposed.
               2 
10
MATERIALS USED  IN THE ARTS.
the valuable properties of granite; but being harder, it is some-
what  more  difficult to chisel.   It is  found in Egypt, and con-
stitutes  the  material of many of the  obelisks.   The Romans
imported  it from  that country.   Sienite  is found  abundantly
near  Boston,  and  is introduced into many structures.  The
Washington Bank,  and  the Bunker Hill Monument consist en-
tirely of this stone.   Its extreme hardness renders it one of the
best materials for M'Adam roads.  A railway is built at Quin-
cy for transporting the stone from the quarry to the sea,  and the
name of Quincy Stone is now commonly applied to it.
   Freestone.—Freestone consists of sand, or siliceous particles,
united by a cement.  It is also  called sandstone.   It varies in
color  from greyish white, to red  and dark brown.   It is of mod-
erate  hardness, in  general, and  easily wrought  by the  chisel.
Varieties of freestone are used in building in different  parts of
Europe.  In Africa the temple   of Hermopolis is composed of
enormous masses  of this stone.  In  America, the  Capitol  at
Washington is of the Potomac freestone, likewise the fagade of
St  Paul's Church in" Boston.   This stone is used for  various
other practical purposes,  particularly  the grinding of  steel
instruments, and the filtering of water.
   Slate.—Slates  are valuable  for the  property of splitting in
one direction, so as to afford large fragments which are perfectly
flat, and thin.   The best slates  are those which are even,  com-
pact, and sonorous ;  and  which absorb the least water on being
immersed.   Slates are much used as an incombustible covering
for the roofs  of  houses.  Tablets,  gravestones,  and  writing
slates, are also formed from them. *
   Soapstone.—This stone  is usually of a greyish color, mode-
rately soft, and having an unctuous feel,  which is  compared to
that of soap.    It is remarkable  for bearing heat, and  sudden
changes of temperature, without injury.   It receives a tolerable

   * Various artificial compositions have been employed as substitutes for slate,
in  forming waterproof coverings  for roofs.  One of these, which  appears to
have been successfully used in the north of Europe is formed of bolar earth,
chalk, glue, pulp of paper, and linseed oil.  Franklin Journal, iv. 89. 
MATERIALS USED IN  THE  ARTS.
11
polish.   Soapstone, on account of its softness, is wrought with
the same  tools as wood.   It is sometimes used in building, but
is  not  always durable.  It is, however, of great importance in
the construction of fireplaces and stoves, and is extensively used
for this purpose.   Slabs of good soapstone, when not exposed
to  mechanical  injury, frequently last eight or ten  years, under
the influence of a common fire on one side, and of cold air on
the other.  It grows harder  in the fire, but does not readily
crack, nor change its dimensions sufficiently to affect its useful-
ness.  Owing  to the facility with which it is wrought, its joints
may be made  sufficiently tight without dependance on cement.
Among the best quarries for fireproof stone, is that of Fran-
cestown,  New  Hampshire.   Soapstone  is manufactured into
various vessels and utensils, and is advantageously employed for
aqueducts.   It is lately found to be one of the best materials
for counteracting friction  in machinery, for which purpose it is
used in powder mixed with oil.
    Serpentine.—Serpentine is a smooth, compact stone,  more
or less of a greenish color,  composed  chiefly of magnesia and
silex.   It is sufficiently soft to  be  scratched  with a knife, and
receives a polish like that of marble.  It is used in building, in
 Florence and  other parts of Italy, and,  in  Saxony, is  wrought
 into many small articles of ornament.
   Gypsum.—Gypsum, called in commerce Plaster of Paris, is a
 sulphate of lime, of  which  there  are  many varieties.   When
 dried  by heat, ground to  fine powder,  and mixed with water, it
has the property of becoming  hard in a few  minutes, and  of
receiving accurately the impression of the most delicate moulds.
It is extensively  employed  for  stucco  working, and plastering
of rooms.  It furnishes a delicate, white, and  smooth  material
for casts of statues, architectural  models, impressions of seals,
 8ws.   In the  art of stereotyping it is indispensable.  It is used
 in agriculture to fertilize certain soils.
    Alabaster.—Under this  name two  substances are known in
 commerce.  One is  a carbonate of lime deposited by the drip-
 ping of water in  stalactitic  caves.  The other, and the most 
13
MATERIALS USED IN THE ARTS.
common,  is a compact gypsum.  This is softer  than  marble,
translucent, and susceptible of  a  fine polish.   Many beautiful
ornaments, such as vases, statues, shades for lights, &c, are
made from it.  As alabaster  of the last species is soluble in
five  hundred  parts of water, Mr Moore has  proposed  an easy
method of cleansing it, by immersing it for about ten  minutes
in water, and afterwards rubbing it with a brush dipped in dry,
powdered plaster.
   Chalk.—Chalk is a soft carbonate of lime, the properties of
which are well known.  It is used as the basis of various white
pigments,  and cementing substances.  Common whiting is pu-
rified chalk, prepared by reducing the chalk to fine powder and
agitating it with water.  The sand and coarser  particles first sub-
side, after which the water is drawn off and the whiting suffered
to deposit  itself.  Chalk by  calcination furnishes excellent lime.
   Fluor Spar.—This is a fluate of lime.  The variety chiefly
used is the Derbyshire spar, which is beautifully variegated with
purple and other colors.   Ornamental objects and utensils are
made from it.  Its acid, when disengaged, is sometimes used
to corrode glass.
   Flint.—Flint is found in roundish masses and is composed
almost wholly of silex.   Its  extreme hardness  causes it to strike
fire readily with steel, from which property  its greatest use is
derived.  Gun-flints are formed  by practised  workmen,  who
break them out with a hammer, a roller, and  steel chisel, with
small repeated blows.  Flints are used also in the  manufactures
of glass, porcelain, and Wedgewood's ware.   For this purpose
they are reduced to fine powder by heating red hot  and plung-
ing them  in water ; afterwards by pounding, sifting, and wash-
ing.   Flints are broken  up to form M'Adam roads.
   Porphyry.—Porphyry is a variegated  stone  consisting  of
small crystals of feldspar or  quartz  imbedded in a basis  of a
darker  color.  It receives a beautiful polish, but its extreme
hardness renders it difficult to work.   The ancients made col-
umns and  even statues of this material, but the moderns con-
fine its use chiefly to smaller works, such as vases, boxes, mor-
tars, he. 
MATERIALS USED IN  THE  ARTS.
13
   Buhrstone.—This is a hard, siliceous stone, remarkable for
its cellular structure; containing always a greater or less num-
ber of irregular cavities.   Hence its surface, however worn and
levelled, is  always rough.  This  property  renders buhrstone
an invaluable material for millstones.   When it is not found of
sufficient size for this use, small pieces of it are fitted together,
cemented, and bound with an iron hoop.  It is imported  from
France, and is also found in some localities in the United States.
   JVovaculite.—This stone is commonly known  under the names
of hone, Turkey oilstone, &c.   It is of a slaty  structure  and
owes its power of whetting, or  sharpening steel instruments, to
the  fine siliceous particles wliich it  contains.   Various other
stones are used as whetstones, such as common  slate, mica slate,
freestone, &c.
   Precious Stones.—These are better known as objects of lux-
ury, than of use ; yet  their preparation  gives rise to an exten-
sive branch of  industry.   They are in general distinguished for
their small size, and  great brilliancy, permanency, and hardness.
The latter quality renders them useful in the  arts.  The  dia-
mond is generally employed  for cutting sheets of glass.   The
diamond, ruby, sapphire, and some others, are used by watch-
makers for pivot  holes to diminish the friction of their verges
and axles.  These stones are  wrought by grinding them  with
emery and other hard powders.   The diamond can only be cut
with its own dust.  Various hard, siliceous stones of less value,
as the carnelian, jasper,  agate, &c, are used by  lapidaries, for
engraving seals, cameos, and other objects of ornament.
   Emery.—The best emery is a variety of the  corundum stone,
obtained chiefly from the island of Naxos, in the Archipelago.
Several other substances, however, are  sold  under this  name.
Emery is the hardest of all known substances, except the  dia-
mond, and its powder is extensively used in  grinding and pol
»shing  metals, stones,  and glass.  It is reduced  to powder by
grinding it in a  steel mill, and is afterwards assorted into parcels
of different fineness, by agitating it with water, and separating
the  particles which  deposit themselves at different times; the
finest particles being the last which subside. 
14
MATERIALS USED IN THE ARTS.
    Sand.—Sand of the best quality, is that which consists of
 particles of pure quartz, and such only is used in the manufac-
 ture of fine glass.   It is found in various localities, but is most
 commonly procured, in this country, from the banks of the Del-
 aware.  Impure sand answers only for bottles and inferior glass.
 For mechanical purposes, such as grinding glass  and marble,
 sharp  sand, the particles of which  are angular, is best.  The
 sand used for moulds by brass founders, possesses a somewhat
 argillaceous character, sufficient to render it moderately cohe-
 sive when  wet, in consequence of which  quality it retains its
 shape.   The sand used in  mortar, should be  sharp, and free
 from all  perishable or deliquescent ingredients.
   Pumice.—This is a spongy, porous stone, of a  fibrous tex-
 ture, and so light as often to swim in water.  It is considered
 to be of volcanic origin.   It is employed to grind the surface
 of metals, and other minerals.   On  account of its  lighmess, it
 is sometimes used to construct domes, vaults, and other elevat-
 ed parts of  buildings.   The dome of the mosque of St Sophia,
 at Constantinople, is said to be of this material.
   Tripoli.—This mineral  resembles  certain  clays,  but is rough
 and  friable, and  does not form a paste with water.   It posses-
 ses a fine hard  grit, and is used to polish  metals  and stones.
 Common rotten stone, and polishing slate, are  varieties of
 tripoli.
   Clay.—This abundant and useful earth, is composed princi-
 pally of  alumine and silex.   It possesses the valuable property
 of forming,  when wet, a ductile  and  tenacious paste,  which is
 changed  by heat to a stony hardness.   Common clay, of which
 bricks and coarse potter's ware are made, contains oxide of iron,
 which causes it to turn red in burning.  The purer sorts, such
 as pipe clay, become  whiter when  exposed to a high heat.
 The earthy  smell, which clays emit  when breathed upon, ap-
 pears also to be owing to oxide of iron.  Absolutely pure clays
 emit no smell.   Refractory clays are those  which  endure  the
 greatest heat without  melting.  The best fireproof bricks and
crucibles are made from slate clay, and contain  a good deal of 
MATERIALS USED IN THE ARTS.
15
sand.  Sometimes they are made of old materials, which have
been before exposed to high heat, pounded up and mixed with
fresh clay.   A mixture of two parts of Stourbridge clay and
one part of coke, has been found very refractory.
  Asbestus.—Asbestus is a mineral of a fibrous structure.  One
of its varieties, called Amianthus, is composed of very delicate,
flexible filaments, resembling fibres of silk.   It has been man-
ufactured  into cloth and paper, which possess the property of
being incombustible.  It is  difficult, however, to find fibres of
sufficient length and  firmness, to produce objects of any great
use.  It is sometimes mixed with clay in pottery, to increase its
strength.   It has also been used for the packing of  steam en-
gines which are of high pressure, or in which steam is used at
an elevated temperature.
   Cements.—Limestone.—The substances made use of for
the uniting medium between bricks or stones in building, are
denominated  cements.   The calcareous  cements,  composed
of a mixture of lime,  sand, and water; in consequence of the
facility with which they pass from a soft state to a stony hard-
ness, have in common uses uperseded all others.   Lime in
the  state of quicklime, is obtained by burning in kilns, any of
those natural bodies, in which it exists in combination with car-
bonic acid; such as limestone, marbles, chalk, and shells.   The
effect of the burning, or calcination,  is to drive off the carbonic
acid.  If quicklime, thus obtained, be wet with water, it instantly
swells and cracks, becomes exceedingly hot, and at length falls
into a white,  soft, impalpable powder.  This process is denomi-
nated the slaking of the lime.  The compound formed is called
a hydrate of lime, and  consists of about three parts of lime to
one of water.   When intended for mortar  it should immediately
be incorporated with sand, and used  without delay, before it
 imbibes carbonic acid anew from the atmosphere.  Lime, thus
 mixed with sand, becomes harder and more cohesive and dura-
 ble, than if it were used alone.   It is found that the sand  used
in common mortar, undergoes little or no change; while the lime,
seemingly by crystalization, adheres to its particles, and unites 
16
MATERIALS USED IN THE ARTS.
 them together. *  Cements composed in this manner continue
 to increase in strength and solidity for an indefinite period, the hy-
 drate of lime being gradually converted into a corbonate.  The
 sand  most  proper to form  mortar, is that which is wholly sili-
 ceous, and which is sharp, that is, not having its particles round-
 ed by attrition.   Fresh  sand is to be preferred to that taken
 from the vicinity of the seashore, the salt of which is liable to
 deliquesce and weaken the strength of the mortal'.   The  pro-
 portions of the lime and sand to each other, are varied in differ-
 ent places ; the amount of  sand, however, always exceeds that
 of the lime.   The more sand can  be incorporated with the
 lime, the better, provided the  necessary  degree of plasticity is
 preserved; for the cement becomes stronger, and it also sets, or
 consolidates more  quickly, when the lime  and water are less in
 quantity and more subdivided.   From two to four parts of sand
 are used to one of lime,  according to the  quality of the lime
 and the labour bestowed on it.   The more pure  is the lime
 and the  more thoroughly  it is beaten or worked  over,  the
 more sand  it will take up, and the more firm and durable does
 it become.
   Puzzolana.—Water cements,  or hydraulic  cements, often
 called, also, Roman cements, are those which have the property
 of hardening under water, and of consolidating almost immedi-
 ately on being mixed.  Common mortar, although it  stands the
effect of water very well when perfectly dry, yet occupies a
 considerable  time  in becoming  so, and  dissolves or crumbles
 away, if laid under water before it has had time to harden.   It
is found that certain rocks which possess an argillaceous as well
 as siliceous character, if mixed  with lime or mortar, communi-
cate to them  the property of hardening in a very few minutes
 after the mixture has taken place, as well  under water as out
of it.   Substances of this sort  have therefore  been made the
basis of water cements.   The  ancient Romans, who practised
building in  the  water, and particularly in the sea, to a great ex-
* See Brard and Vicat on this subject. 
              MATERIALS USED IN THE ARTS.            17

tent, first availed themselves of a material of this kind.  The
Bay of Baiae, from the coolness and salubrity of its situation, was
a place of fashionable resort for the wealthy of Rome, during
the summer months.  They erected their villas, not only on the
seashore, but on artificial quays and islands constructed in the wa-
ter.  To enable them to erect these  marine structures, they
fortunately  discovered, at the  town of Puteoli, a peculiar earth,
to which they gave the name of pulvis puteolanys, and which
is the same now known by the name of Puzzolana.   This earth
is a light, porous, friable mineral, various in color, and evidently
of volcanic origin.   When reduced to uniform powder by beat-
ing and sifting, and  thoroughly mixed with lime, either with or
without sand, it forms a  mass of great tenacity, which in a short
time concretes to  a stony hardness, not only in the  air, but
likewise when wholly immersed in water.
   Tarras.—A substance denominated tarras, terras, or trass,
found  near Andernach  in the vicinity  of the Rhine, has been
discovered  to possess the same property with puzzolana, of form-
ing a durable water cement, when combined with lime.  It is
said to be a kind of decomposed  basalt, but resembles puzzo-
lana.   It is the material which  has been principally  employed
by the Dutch, whose aquatic  structures probably exceed those
of any other nation in  Europe.   Tarras mortar, though very
durable in  water, is inferior to the more common kinds, when
exposed to  the open air.
   Other Cements.—It has been found that  various other sub-
stances, such as baked clay reduced to powder, or the common
greenstone  calcined and pulverized, afford  the basis of very
tolerable water cements, with lime.   Some  of the ores of man-
ganese are  also useful for the same purpose.
   There are some limestones  which have the property of form-
ing water cements  when calcined and  mixed with simple sand
and  water.   This is  usually in consequence of these  stones
containing a certain portion of argillaceous; earth, united with
the lime.   A water cement  found in New  York, was used in
constructing the locks of the great canal in that State.   "Another
               3 
IS
MATERIALS USED IN  THE ARTS.
 hydraulic cement, containing lime, silex, and alumine, has been
 found and applied to use in the Union Canal of Pennsylvania. *
   The cause by which these  compounds  become  hard  under
 water, is not satisfactorily known.   It has been supposed, how-
 ever, and not without reason, that  the great attraction for mois-
 ture existing in certain argillaceous earths, causes them to  ab-
 sorb immediately the superabundant moisture from the lime, and
 thus to expedite its solidification.   This  explanation is render-
 ed more  probable, by the  fact, that  burnt clays, which  form
 good hydraulic cements; cease to do  so, if the burning is car-
 ried so far as to vitrify them, f
   Maltha.—The  name  of  maltha,  or  mastich, is  given  to
 those cements into which animal and vegetable substances  enter,
 such as oil, milk,  mucilage, he.   Some of these mixtures have

  * M. Berthier states that with one part of common clay and two parts and a
 half of chalk, a very good hydraulic lime may be made.   He concludes from
 many experiments, that a limestone containing six per cent,  of clay, affords a
 mortar perceptibly hydraulic.  Lime containing from fifteen to twenty per
cent., is very hydraulic, and with from twentyfive to thirty per cent., it sets
 almost instantly.
  According to M. Bruyere, an excellent artificial puzzolana may be formed
by heating together three parts of clay, and one part of slaked lime, for some
hours, to redness.
  t M. Vicat, who has experimented extensively upon the subject, has arriv-
ed at the conclusion, that the solidification of hydraulic cements  formed of or-
dinary mortar, and calcined clays, is the result of a true chemical combination,
 in which the lime is  neutralized by the  silica and alumina.   But in those
formed of hydraulic lime and pure sand, the solidification does  not appear to
result from chemical combination.
  Clays which by slight calcination become good  hydraulic cements, have
 also the same property, though in a less degree, in their natural  state.   It has
been asserted, by M.  Treussart, that the free access of air during the calcina-
 tion of argillaceous cements, is of great consequence to the tenacity of the
 mortar and the quickness  with which it hardens.  To determine whether a
 stone will furnish hydraulic lime, M. Vicat recommends to calcine it by heat,
 then to slake it in the common way, and make a paste of it, which is to  be
 placed at the bottom of a vessel of pure water.  If at the end of eight or ten
days it has become haijd and resists the finger, it will furnish hydraulic lime ;
 but if it remains soft,  it has the character of common lime.
  See Brande's Journal, vol. x, p. 407.—vol. xix, 329.—vol. xx, 50.—vol. xxii,
214.  Also Franklin Journal, ii, 371 and 287.—iii., 305, 355. 
MATERIALS USED IN THE ARTS.
19
afforded, both to  the ancients and moderns, cements of great
hardness and permanency, but they are not much used.
  Metals.—Iron.—Of all the  metals iron is the most  useful,
and one of the most abundantly diffused.   Besides its common
occurrence in earths and rocks, it is held in solution by mineral
waters, it enters largely into the composition of meteoric  stones,
and it circulates in the blood of animals, and the  sap of vege-
tables.   Pure iron is of a bluish white color, of great hardness,
malleable, ductile, and tenacious.   For its fusion, it requires an
intensely high temperature, equal to flne hundred  and  fiftyeight
degrees of Wedgewood's pyrometer.   When combined with
carbon it forms steel, and is increased in  hardness.   At a red
heat, it becomes soft and more malleable ; and at a white heat,
may be joined by welding.   It is strongly attracted by  the mag-
net,  acquires itself the magnetic  power, and when in the form
of steel, retains  it permanently.   Cast iron is brittle, and  fusible
without   difficulty,  owing  to the  carbon which it  contains.
Wrought iron is flexible,  and has the  properties of the pure
metal.  In the  arts, iron is applied to mnumerable uses where
strength and  hardness are  required.  It is, however, deficient
in durability, being  readily corroded  with rust, when  exposed
to the weather, unless protected with a coating of paint.  Me-
tallic iron is wrought, while hot,  by hammering, rolling,  stamp-
ing,  chiselling,  punching, he.; and when  cold, by  the same
means, also by filing, turning, drilling,  cutting,  and  drawing.
Cast iron is commonly melted, when its form is to be changed ;
but it is finished with common tools when cold, and may be cut
with a saw when red hot.  Cast iron is now the most common
material  used in the fabrication of machines, and in Europe it
is applied to the construction of bridges, and of roofs.   Even
ships have  been made of iron.
  To the  chemical compounds of iron, we are indebted for
copperas, writing ink, prussian blue, he.
   Copper.—Copper is a metal of a light red color, ductile, and
malleable, emitting a disagreeable odor when rubbed.  It melts
at twent) seven degrees of Wedgewood.   When exposed to the 
20
MATERIALS I SKI) IN THE ARTS.
atmosphere it loses its lustre and becomes covered with a green
coating, which is carbonate of copper.  This coating preserves
the remainder  from decay, and is  the source of some of its
most important uses.  Copper is employed to cover the bottoms
of ships, and tops of houses ; to form various culinary and manu-
facturers' vessels, also for pumps,  and  water pipes, for engravers
plates, and for coining.   When combined with acids, or oxygen,
it becomes more or less poisonous, on which account  culinary
vessels are coated on the inside  with tin.   It is this poisonous
property, in part, which prevents marine animals from attaching
themselves to the bottoms of coppered  ships.  Copper forms
many valuable alloys, among which are brass, which consists of
copper  and  zinc, and  bronze,  which is made of copper  and
tin.   Its chemical compounds furnish»verdigris, blue vitriol, he.
It  is  wrought by the  same modes as iron, but is more  easily
malleable than that metal when cold.
   Lead.—Lead has a light  bluish  color,  with a bright lustre
which becomes quickly tarnished on  exposure to the air.   It is
soft, heavy, very malleable, and melts at six hundred degrees of
Fahrenheit's  thermometer.   By exposure to the  heat of a fur-
nace, it is converted into a red oxide.  Lead is used for the cover-
ing of roofs, for aqueducts, for lining  cisterns and  tight cavities,
for weights, bullets, and shot.   Some of its alloys are very val-
uable, such  as  pewter, type metal,  &c.   Its oxides and salts
afford paints of different colors,  and  of great use.   Lead is de-
leterious in its influence on health, and  requires  great caution
in those who work it, or  use it, in any other than the metallic
state.   Injury is most frequently received, by inhaling the  dust
which rises in the manufactories of  red, and white lead.  In
leaden  aqueducts a carbonate of lead occasionally forms ; but
this is insoluble in water, and subsides by its weight.
   Tin.—Tin is a white metal, somewhat harder than lead, and
producing a peculiar  crackling  sound when it is  bent.   It is
very malleable, and is beaten for tinfoil into leaves T^1Tnr part of
an inch in  thickness.   Its ductility  and tenacity are not great.
Tin is very fusible, melting at about  four hundred and fortytwo 
              MATERIALS USED IN  THE  ARTS.            21

degrees of Fahrenheit's thermometer.   Exposed to the atmos-
phere its surface  becomes slightly tarnished, but undergoes no
further change.   On this account it is largely employed for coat-
ing other  metals, which are  more liable to oxidation.  Copper
vessels are lined with it, as already stated.  Tin plates are sheets
of iron coated with tin.   Tinfoil with mercury forms the silvering
of looking glasses.   Block tin is used to form vessels not intend-
ed for exposure to heat.  Some of the salts of tin are very val-
uable in dyeing.  The putty used for polishing glass, stones, and
metals, is an oxide of  lead  and tin,
   Mercury.—Mercury, or quicksilver, is  fluid at common tem-
peratures, and on this account is used in many  philosophical
and chemical instruments.  Attempts have been made to intro-
duce it in certain  forms of  the  steam engine ;  but  it is objec-
tionable for this purpose, from its tendency to combine with ox
ygen, and from the unhealthiness of its use to persons occupied
about it.  Mercury is  employed in silvering  mirrors, and large
quantities are consumed in extracting silver and gold from their
ores.   Its alloys with other metals, are called  amalgams.   It
amalgamates readily with gold, silver, tin, lead,  and zinc ; diffi-
cultly with copper and antimony, and  scarcely at all with iron
 and platina.
   Gold.—The value derived  from its scarcity, prevents the
 extensive use of gold  in the arts.    The  power with which  it
resists  tarnishing, and all  changes  from  exposure to  air  and
moisture, renders it desirable for  many purposes, and has  giv-
en rise to the art of gilding.  The  gold  leaf used in gilding  is
often not more than Yvshm Part °f an mcn  thick, owing to the
extreme malleability of the  metal.   Gold is used in coining, in
jewelry, and in coloring porcelain.
   Silver.—Silver  possesses the  same valuable  properties as
 gold, but is more liable to tarnish, especially when  exposed to
 sulphurous  vapors, which  convert  its surface into a sulphuret.
 Silver is very ductile,  but less so than gold,  and the leaves into
 which it is hammered, are usually three times thicker than those
 of gold.   Its uses are well known. 
f)l
MATERIALS USED  IN  THE ARTS.
   Platinum.—Platinum is the heaviest substance  at present
 known, its  weight being twentyone times  and a half, that of
 water.   Like  gold, it resists tarnishing from oxidation by the
 air, and it is furthermore capable of resisting an extremely high
 temperature without melting.  It is very malleable, approaches
 to iron in hardness, and like that  metal, may be welded  when
 hot.   It is used for small crucibles, and  philosophical instru-
 ments.
   Zinc.—Zinc or spelter is a bluish white  metal, imperfectly
 malleable and ductile, but  rendered more so by a heat some-
 what above that of boiling water.   It melts below a red  heat,
 at seven hundred degrees of Fahrenheit.  When ignited it burns
 with a white flame, throwing off an oxide called flowers of zinc.
 Zinc is used as a constituent in brass, and in some other alloys.
 It is an important material in galvanic combinations.   It is easily
 oxidated, and therefore unfit for purposes which  require dura-
 bility.
  Antimony.—Antimony is  a brittle, whitish  metal of a plated
 or scaly  texture.   It is tarnished, but not otherwise  altered by
 exposure to the air.  In type founderies it is much used to give
 hardness to  lead, in the alloy called type metal.
  Bismuth.—Bismuth  is a metal of a reddish white color and
 brittle  consistence, not  readily oxidated by the air.   It is very
 fusible, requiring little more  heat than tin to melt it.   It enters
 into  various  alloys, one of which is the fusible metal, compos-
 ed of eight  parts  of bismuth, five of tin, and three  of lead,
 which melts at a heat less than that of boiling water.
  Arsenic.—Arsenic  in its  metallic  state is of a  bluish white
 color, easily  tarnishing, brittle, and volatile at a low heat.   In
 the state of acid, called  white arsenic, it is well known as a vio-
 lent poison.   Arsenic is used in the manufactures of glass, and
 of shot, and  furnishes the basis of several brilliant pigments.
  Manganese.—Manganese is a metal of a dull whitish color,
brittle, extremely difficult to melt, and speedily  turning to a
dark oxide in the air.   The native black oxide of this metal is
of great use to chemists in  furnishing oxygen.  In the arts, it
is employed in bleaching, pottery, and glass making.
• 
MATERIALS USED IN THE ARTS.
23
  Combustible substances, &tc.—Bitumen.—This is an in-
flammable mineral substance, resembling tar or pitch in its prop-
erties and uses.   Among  different bituminous substances, the
names naphtha, and petroleum, have been given to those which
are  fluid ; maltha, to that which has the consistence of pitch,
and asphaltum, to that which is solid.
  Amber.—Amber is a  yellowish,  translucent,  inflammable
mineral, hard enough to receive a fine  polish, capable of be-
ing  wrought into various ornamental articles, and forming an in-
gredient in some varnishes and lacquers.
   Coal.—This well known  combustible is composed essential-
ly of carbon, with a proportion,  greater or less, of bitumen, a
little sulphur, and a remainder of earthy and incombustible matter.
True coal burns with a white flame, a black smoke and bitu-
minous odor.   Some kinds, as the Cannel coal, burn readily,
with a large flame, and without softening or concreting.   Oth-
ers, as the Newcastle, Liverpool, and Orrel, concrete, or cake,
during combustion, and last longer.   The poorer coals have
usually a large  admixture of  foreign and incombustible sub-
stances.   Coal is of great value  as a fuel, both in the arts, and
for  domestic purposes.  As  it  contains more combustible mat-
ter  in a given volume, than wood, it is capable of evolving and
sustaining more heat than that fuel, within the same furnace, or
other cavity.  When coal is exposed  to heat, but prevented
from  burning, by the exclusion of the  air, it loses its moisture
and bituminous portion, and is  converted into, coke, a  fuel bear-
ing  the same relation to coal,  as charcoal to wood.   Coal has
of late years been usefully applied to the production of inflam-
mable gas, for the purposes of illumination.
   Anthracite.—This  combustible,  of  which  the  Lehigh,
Schuylkill, and Rhode  Island coal are specimens,  is harder,
heavier, and less black, than the true, or butuminous  coals.  It
burns slowly, without smoke,  and with a faint flame.   It is more
difficult to kindle than most fuels,  owing to its greater conducting
power, and the high temperature necessary for its combustion;
but  when once on fire it produces an intense and  lasting heat. 
24
materials used in the  arts.
It is more durable than the bituminous coals, but requires to be
burnt in masses large enough to sustain a high temperature.  An-
thracite has now become a common fuel in many parts of the
United States, and is highly valuable both for domestic and man-
ufacturing purposes.  It is burnt in various furnaces,  forges,
stoves, and grates constructed for the purpose.   In  iron works
it is found to occasion less oxidation and scaling of the metal,
than other fuel.   But in reverberating furnaces,  where a blaze
is required, it does not answer the requisite purpose.   Most of
the anthracites afford inflammable  gas, not, however,  suitable
for purposes of illumination.*
   Graphite.—This mineral, otherwise called plumbago  and
black lead, is composed of carbon,  with a portion of iron.  It
is unctuous to the touch and soils the  fingers.   It is used for
pencils  and crayons, and, mixed with clay, is  formed into cru-
cibles.  Black lead pencils are  made, by inserting the straight
edge of a plate of graphite, into a  groove made in the wood,
and sawing it off, leaving a slender  rod of the  lead inclosed,
which is afterwards covered with wood.
   Peat.—Peat  is a substance of vegetable  origin, dug  from
bogs and marshes, and  capable of reproducing itself in places
from which it has been removed.  Peat, when dry, is combusti-
ble, and is used as such, where better fuel cannot be obtained.
   Sulphur.—Sulphur is a simple inflammable body, melting at
two hundred and twenty degrees, and  taking fire at five  hun-
dred, of Fahrenheit.   When kept  melted for some  time, at
about three hundred degrees, Fahrenheit, it becomes thick and
viscid, and if poured into a basin of water, it becomes ductile like
wax.   In this  state it is used  for taking impressions of seals.
It  is also used to form moulds for plaster casts.  Sulphur is an
ingredient in gunpowder, and enters into many chemical  com-
pounds, which are of great use in the  arts.   Sulphur is burnt
to produce sulphuric acid.

  * See a valuable paper  on the  Anthracites, in Silliman's Journal, vol. x. p
331, by the editor. 
materials used in the arts.           25
       materials from the  vegetable  kingdom.

   Wood.—The woody portion of the trunks of trees, is made
up of minute tubes or vessels,  running longitudinally, having
their parietes strengthened  with rigid fibres, and their intersti-
ces filled with cellular substance.   In the common trees of
temperate climates, these vessels are  arranged  in  concentric
layers or cylinders; one  layer being  added for each  year of
the tree's growth.  The outer layers, being those which trans-
mit the  sap, are more porous,  soft and perishable,  and are
known by the name of alburnum or sap wood.   The inner lay-
ers are commonly darker colored, more solid, compact, and du-
rable ; and are known by the name of heart wood.   The heart
wood is preferred for most purposes in the arts, its vessels hav-
ing become  in  part obliterated by age, and  its density and
strength  increased.   Boards are least liable to warp when they
are cut  through  the centre or  pith of the trunk.  All  wood
shrinks in drying, and decays when  exposed  to the weather;
but the  different trees vary greatly from each  other  in this
respect.
   Bark.—Bark is the external investment of the trunks and
branches of trees, and consists, when young, of three coats or
layers, called the cuticle, the cellular integument, and the liber
or inner bark.   But during every season, a new liber grows on
the inside of the former ones, and pushes  thern outward, so that
old bark is found to consist of numerous cortical layers, each
of which was originally a liber.  The outermost of these lay-
ers gradually become  dead and dry, and merely augment the
thickness of the  bark, without  adding to its usefulness in the
arts.
   Oak.—Numerous  species of the  oak tree  are found in the
United  States.   They are generally  distinguished for  great
strength, but are coarse grained, and  prone to warp and  crack
under changes from moisture to dryness.  The live  oak of the
Southern States (Quercus virens) is prized in ship building, be-
               4 
26            materials  used  in the arts.
 yond any native timber.   The white oak (Quercus alba) is em-
 ployed for  the keels, side timbers, and planks of vessels, also
 for frames of houses, mills and machinery  requiring strength ;
 for wagons, parts of carriages, ploughs, and  other agricultural
 instruments.   Large quantities are consumed  for the staves and
 hoops of casks, for which they furnish one of the best materi-
 als.   The bark of the black oak (Quercus tinctoria) furnishes
 the quercitron used by dyers.   Most of the species of oak are
 employed in  tanning, and they all furnish a valuable fuel.
   Hickory or Walnut.—The wood of the different species of
 native walnut or hickory [Juglans, seu Carya) is eminently dis-
 tinguished for weight, tenacity, and strength.   It has, however,
 important defects.   It warps and shrinks greatly, decays  rap-
 idly when exposed to the weather, and is very liable to the at-
 tacks of worms.  On these accounts it is never used for house or
 ship building, but is chiefly employed for minor purposes, where
 strength  is the chief  requisite;  as in the teeth of mill  wheels,
 screws of presses, handspikes, capstan bars,  bows, hoops, and
 handles of tools.   As fuel, the hickory stands at the  head of
 native  trees, and  commands  a higher price than  any other
 wood.
   Ash.—The white ash (Fraxinus Americana) and some oth-
 er species, are  of great utility in the arts.  Ash wood is strong,
 elastic, tough, and light; and splits with a straight grain.  It  is
 also  durable, and  permanent in its dimensions.   It  furnishes
 the common timber used in light carriages, for the shafts,  frames,
 springs, and part of the  wheels.   Flat hoops, boxes, and the
 handles of many instruments are made of it.  It is almost the
 only material of oars, blocks of pullies, cleats, and similar naval
 implements, in places where it can be obtained.
   Elm.—The  common American elm {Vlmus  Americana)  is
valued for the  toughness of its wood, which  does not  readily
split.   On this account it it chiefly used for the  naves, among
us commonly called hubbs, of carriage wheels.
   Locust.—The common locust (Robinia pseudacacia) is one
of the hardest,  strongest, and  most valuable of native trees. 
materials used in the arts.
27
The larger pieces of its  timber, are used in ship building, and
the smaller pieces are in great request to form the treenails* or
pins which confine the planks to the timbers.   This tree is lia-
ble, in the Northern States, to be perforated by an insect, so that
it is often difficult to procure  sound pieces of any considerable
size.   Locust wood is exceedingly durable, when exposed to
the weather ;  and forms  excellent fuel.
   Wild Cherrytree.—The wood of this tree (Prunus Virgini-
ana) is of a deep color, hard, durable, and, when properly sea-
soned,  very  permanent  in its shape and dimensions.   In the
manufacture  of cabinet  work, it is much used  as  a cheaper
substitute for mahogany.   On the Western rivers it is sometimes
used in ship building.
   Chesnut.—The American chesnut ( Castanea vesca B.) is a
large tree of rapid  growth.  Its  wood is coarse and porous,
very liable to warp, and seldom  introduced into building or fur-
niture.   It is  chiefly used for  fencing stuff, to which use it is
fitted by its durability in the atmosphere.   Chesnut is an unsafe
fuel, in consequence of its tendency to snap and throw its coals
to a distance.                                           *
   Beech.—The  wood of the red  beech (Fagus ferruginea) is
liable to decay when exposed to alternate moisture  and dry-
ness.  It does  not, however, readily warp, and  being smooth
grained it is used for some minor  purposes, such as the mak-
ing of planes,  lasts, and card backs.   It forms a very good
fuel.
  Basswood.—The American linden or basswood tree (Tilia
Americana) produces a fine grained wood, which is very white,
soft, light, and flexible.  It is sometimes employed for furni-
ture, but its chief use is to form the pannels of coach and chaise
bodies, for which its flexibility makes it well suited.
   Tulip tree.—(Idriodendron tulipifera.)  The boards of this
tree  are sold under the name of white wood, and erroneously
under that of poplar.   Its wood  is  smooth, fine grained, easily
wrought, and not apt to split.   It is used for carving and orna-
* Commonly pronounced trunnels. 
28
materials used in the arts.
 mental work, and for some kinds of furniture.   In the Western
 States, where pine is more scarce, the joinery, or inside  work
 of houses, is commonly executed with this material, and some-
 times the outer covering.  In common with basswood, it forms
 an excellent material for coach and chaise pannels.
  Maple.—The rock maple, [Acer saccharinum)  also several
 other species, affords wood which is smooth, compact and hard.
 It is much used for cabinet furniture, and is a common material
 for gunstocks.  The wood in some of the old trunks, is full of
 minute irregularities, like  knots.   These, if cut in one direc-
 tion, exhibit a spotted surface, to which the name of bird's eye
 maple is  given ; while if cut in another direction, they produce
 a wavy or shaded surface, called curled maple.  This last ef-
 fect, however, is more frequently produced by a mere serpen-
 tine direction of the  fibres.   The distinctness of the grain may
 be increased by rubbing the surface with diluted sulphuric acid.
 Maple wood forms a good fuel.   It is not very lasting when
 exposed  to the  weather.  The  sap of the rock maple and of
 one or two other species, yields sugar  on being boiled.
  Birch.—The white or paper birch  (Betula papyracea)  has
 properties similar to those of the maple, and is appropriated to
 the same uses.  Its cuticle or  outer bark, is made by the In-
 dians into canoes.  The lesser white birch (B. populifolia) is
 a perishable tree, of little value.  The black birch,  (B. lenta,)
known for its aromatic bark, affords a  firm, compact, dark col-
 ored wood, much valued for furniture, and sometimes used for
 screws and implements requiring strength.  The yellow birch
 (B. lutea) is applied  to  the same  uses as the last, and makes
 good  fuel.
  Buttonwood.—The buttonwood or  plane tree (Platanus oc-
 cidentalis) is in some of  the Northern  States improperly called
 sycamore.  It  is one of the largest inhabitants of the forest,
 and Michaux states that  trees are found in the  Western States
 which measure forty  feet in circumference.  This majestic tree
is chiefly valuable for its shade, as the wood is perishable, and
 prone to  warp. 
MATERIALS used in the arts.
29
  Persimmon.—[Diospyros  Virginiana.)   The heart wood
is dark colored, compact, hard, and elastic ; and is used in the
Southern States for screws, shafts of  chaises, and  various  im-
plements.
  Black Walnut.—{Juglans nigra.)   This tree is rarely found
north of New York.   Its heart wood  is of a violet color, which
after exposure to the air, assumes a darker shade, and finally
becomes nearly black.   This wood when deprived of its white
part, or sap, remains sound for a long time, even if exposed to
air  and moisture,  and is not attacked  by worms.   It is very
strong and tenacious, and when  seasoned is not liable to warp,
or split.   It is used in the Middle and Western States for fur-
niture, for gunstocks,  for naves of wheels, and to  a certain ex-
tent, in house  and  ship building.
   Tupelo.—Different species of the  genus JYyssa have receiv-
ed in the United  States,  a  great variety  of common  names,
among  which tupelo,  pepperidge, and gum tree are the most
common.  In Massachusetts the name hornbeam is improperly
applied to one of them.   Their wood is  smooth grained, and
remarkable for the decussation  or interweaving of the fibres,
which  renders  it almost impossible to split the logs. . This
 quality causes several of the  species  to be in demand for naves
 of wheels, hatters blocks, and implements  requiring  lateral
 tenacity.
   Pine.—The  American pines exceed all other native trees
 for the value and variety of their uses.   The white pine (Pinus
 strobus)  has a very tall, straight trunk, the wood of which is
 light, soft, homogeneous, and easy to work.   It is remarkably
 exempt from  the common fault of timber, that of decaying in
 the open air, and of changing its dimensions  with  changes of
 weather.  On these  accounts it is  extensively employed for
 most of the  common purposes of  timber.  In the Northern
 States, masts of vessels are commonly made of it.   Frames of
 houses,  and  of bridges  are also formed of it; its defect of
 strength being more than balanced by its  steadiness and dura-
 bility.   Its boards form  almost the only material used in the 
30
materials used in the  arts.
  Northern  States  for the joiner's work,  or  inside finishing of
  houses ; and for this use it is exported  to  other countries.   Or-
  namental carving is commonly executed in this material.   The
  southern pitch pine (Pinuspalustris L.) covers extensive bar-
  rens in the  Southern States, and  yields  vast quantities of tar
  and turpentine.  Its wood is appropriated to the same objects
  as that of the white pine, but is harder and stronger, and there-
  fore preferred for planks, spars, floors, decks, he.  Many oth-
  er species of pine exist on this continent, partaking  qualities
 like those already described, but most of them harder  than the
 white pine.
    Spruce.—The black and white spruce,  belong to the race of
 trees commonly called Firs.   They are both  valuable, but the
 black spruce (Pinus nigra)  unites  in a  peculiar  degree the
 qualities of strength, elasticity, and lightness, together with the
 power of resisting exposure to the weather.  It is much sought
 after for the smaller spars of vessels, such  as the booms, yards,
 and topmasts.
   Hemlock.—The hemlock tree (Pinus Canadensis) is inferi-
 or to the other  firs in quality, though it grows to a large  size.
 It is coarse grained, often twisted,  and  cracks  and  shivers with
 age.   It  furnishes an inferior sort of boards, used in covering
 houses.   Its bark is valuable in tanning.
   White Cedar.—This tree  (Cupressus  thuyoides) occupies
 large  tracts  denominated cedar  swamps.   The wood is soft,
 smooth, of an aromatic smell,  and internally of a red color.  It
 is permanent in shape, and  very durable ;  and esteemed as a
 material for  fences.  Large quantities of shingles are made of
 it.   It is a favorite material for wooden wares, or the nicer kinds
 of cooper's work.
   Cypress.—The cypress tree of the  Southern States (Cu-
pressus disticha) is light, soft, and fine grained ; and at the same
 time elastic, with a considerable share of strength.   It sustains
 heat  and moisture for a long time, without injury.   In  the
 Southern States and  on  the Mississippi, it is much employed
for fences, and  for the frames,  shingles,  and  inside work of
houses. 
MATERIALS USED IN THE ARTS.
31
  Larch.—The American Larch (Pinus microcarpa) is called
hackmatack  and tamarack,  in  different parts of  the Union.
Its wood is strong, elastic, and durable ; and is highly prized, in
places  where a sufficient quantity can  be obtained, for naval
and civil architecture.
  Arbor Vitce.—This tree (Thuya occidentalis) is of  the mid-
dle  size, and  frequently called white cedar.  The  wood is
reddish, fine grained, very soft,  and  light.   It  bears exposure
to the weather with very little change, and is esteemed for the
posts and rails of fences.
  Red Cedar.—(Juniperus  Virginiana.)   The nameofsaum
is in some places improperly applied to this tree.   Unlike  the
white cedar, it grows in the  driest and most barren soils.   The
trunk is straight, and  knotted by small branches.   The heart
wood is of a bright red  color, smooth and moderately soft.  It
exceeds most other native trees in durability,  and is in particular
request for posts of buildings, though it is  difficult  to  obtain it
of large size.
   Willow.—The most common kinds of Salix or willow about
our seaports, are European  species which  have become natur-
alized.  Their wood is  soft, light, and  spongy.   Willow char-
coal is used in the manufactured gunpowder.   The osier and
some other species, with  long  slender shoots, are  extensively
cultivated to form wicker  work, such as baskets, hampers, and
the external coverings of heavy glass vessels.
   Mahogany.—In  the  manufacture of cabinet  furniture, ma-
hogany (Swietenia  mahagoni)  has taken  precedence of all
other kinds of wood.  Its value depends not so much on its
color, as on its hardness, and the invaluable property of remain-
ing constant in its dimensions, without warping or cracking, for
an indefinite length of time.  The same qualities which render
it suitable for  furniture, have given  rise to its employment for
the  frames of philosophical instruments,  and of delicate  ma-
chinery.  Mahogany is  imported from the West Indies, and
different parts of Spanish America. 
32
MATERIALS USED IN THE ARTS.
   Boxwood.—The box tree (Buxus sempervirens) is imported
 from the  south of Europe.   Its wood is of a well known yel-
 lowish color, hard, compact,  smooth, tough, and not liable  to
 crack.  Musical  wind instruments are commonly made of it;
 also mathematical measuring instruments.  The handles of many
 tools, and various articles of turners' work, consist also of this
 material.  Wood engravings are cut upon the end of the grain
 of boxwood.
   Lignum Vita.—The wood of the Guiacum officinale is  em-
 ployed in  the arts  under this name.   It is  dark colored at the
 heart, strong, exceedingly hard, and so heavy as to sink in wa-
 ter.   It is impregnated with resin, and on this account durable
 in liquids.  Handles  of tools, boxes  of  gudgeons,  wheels  of
 pullies, castors, balls,  stopcocks, mallets, he., are made of  it.
 It is imported from the West Indies, and South America.
   Several other tropical woods are imported for use by cabinet
 makers, such as rose wood, ebony, satin wood, he.   They are
 generally  hard, colored woods,  susceptible of a fine  polish.
 Satin wood (Swcitenia chloroxylon) is thought poisonous to the
 hands of the workmen.
   Cork.—Cork is a fungous substance growing on the bark of
 a species of oak (Quercus subef-) in the south of Europe.  Its
lightness and elasticity gives it an aptitude for certain purposes,
in which it would  be difficult to find a substitute.
  Hemp.—Hemp is the fibrous portion of the  bark of an an-
nual plant, (Cannabis sativa) and is of great use in the manu-
facture of cordage and canvass.   The fibres  are separated from
the rest  of the stalks, by the decomposition of the latter.   In
the process of dew rotting, the hemp is exposed  on the grass
for a number of weeks to the weather.   In that of water rotting
it is immersed for a part of the time in water, and subsequently
exposed to the weather.  By these processes, the solid parts of
the hemp  decay; while the flexible fibres remain strong and but
little impaired.  The decayed portion is afterwards broken up,
by the operations of an instrument called a brake ; and some-
times by a mill or stone roller.  The chaff is  separated from 
MATERIALS USED IN THE  ARTS.           33
the fibres by the strokes of a wooden scotching, or swingling
knife ; and the fibres still further cleansed by combing them on
an instrument called a heckle.
  JFlax.—Flax is also  the fibrous bark of an annual plant,
(Linum usitatissimum,) which is smaller and finer than hemp;
and constitutes the material of linen cloth.  Flax is rotted, and
subsequently  dressed,  much in  the  same manner  as  hemp.
When, however, it is intended  for finer  uses, as for cambric,
lace, he., it is scraped with a blunt knife upon leather, and the
fibres separated and straightened with a brush.   A method has
been  introduced in England,  of dressing flax by machinery, in
its recent state, without rotting.   This method is represented
as highly economical, affording more flax, and of a stronger
texture, than that produced in the common way. *   The fibres
of flax and  hemp  are  long,  straight, and unyielding,  so that
they  cannot be  spun by the same machinery which is  used
for cotton and wool.
   Cotton.—Cotton is the product of the Gossypium herbaceum,
an Oriental  plant, now  cultivated in  most parts of the world,
which possess a sufficiently warm climate.   It grows in pods,
forming a light, woolly investment to the  seeds; and seems in-
tended  by  nature to assist in  their  dispersion by  the  winds.
The  fibres  of cotton  are extremely fine, delicate, and flexile.
When examined by the microscope, they are found  somewhat
flat, and two edged or triangular.  Their direction is not straight,
but contorted ; so that the locks can be extended or drawn out
without doing violence to the  fibres.   These  properties render
cotton peculiarly adapted for the operations of machinery, and
have  given employment to a vast amount of manufacturing skill
and industry, both in Great Britain and this country.
   Cotton, after being gathered, is cleansed from the seeds by
a machine  called a gin, of which there  are  two kinds.    The
roller gin consists essentially of two  small cylinders revolving
in contact, or nearly so, with each other.   The cotton is  drawn

            * See Brande's quarterly Journal, vol. iv. p. 329.
               5 
34
MATERIALS USED  IN  THE  ARTS.
between these rollers, while the seeds, being too large to pass,
are left behind, and fall out on one side.   The saw gin, invent-
ed by Mr Whitney, is intended for those  sorts of cotton, the
seeds of which  adhere too strongly to be separated by  the
former method.  It consists of a receiver, having one side cov-
ered with strong parallel wires, placed  like those of a cage, and
about an eighth of  an  inch  apart.   Between these wires enter
an equal number of circular saws, revolving on a common axis.
The teeth of these saws  entangle the  cotton  and draw it out
through the grating of  wires, while  the seeds are prevented by
their size from passing.  The  cotton thus extricated is swept
off from the teethof the saws by a revolving cylindrical brush;
and the seeds fall out at the bottom  of the receiver.
   Turpentine.—Turpentine is  the  juice which  exudes from
pine trees.   The  Southern pitch  pine furnishes  most of that
used in commerce.  It is procured by making incisions, or cav-
ities, in the trunk,  and dipping  out  the turpentine which col-
lects.   Tar is an impure turpentine  obtained by burning.  The
resinous parts of the wood called  lightwood, are collected in
pits, and being set on fire  at the top, a part of  the turpentine is
burnt, while  the rest is melted and flows out at the bottom.
Pitch is tar inspissated by boiling, or burning.   If  turpentine be
distilled, the  volatile portion,  which passes over, is the oil or
spirit of turpentine, while the solid part left behind is rosin.
   Caoutchouc.—This substance, called also elastic gum and In-
dia rubber, is obtained from  different  vegetables, but chiefly
from the Jatropha elastica.   It exists in the form  of juice, and
is dried by applying it, in successive  coatings, to clay moulds of
various shapes.  After it is dry, the  clay is crushed and shaken
out.  This  substance  is  wonderfully  flexible  and elastic, and
restores itself instantly, after being extended to many times its
original dimensions.  It is inflammable and used by the inhabi-
tants of Cayenne for lights.   It is insoluble  in water, and in al-
cohol ;  but dissolves in ether, and in  oils.  These solutions have
been used for varnishes, but have the disadvantage that they do
not readily  dry.   A  mixture of oil of turpentine and  alco- 
MATERIALS USED IN THE ARTS.
35
hol, * is a solvent which has the property of drying more readi-
ly and restoring the elastic properties of the gum.   The crude
juice may also be imported, and manufactured into articles here, f
Slips of India  rubber may be made to cohere by boiling them
in contact for a certain time in water, and in this way some ar-
ticles are made.   Caoutchouc is of great use in the  formation
of many instruments, which require to be elastic, and impene-
trable to water.  Shoes are now made of it in great numbers,
and are found to exclude  perfectly the wet.   The solution of
 this gum spread  upon leather and cloth, renders them water-
 proof, and even air-tight.   Its  adhesiveness and friction are the
 properties by which it erases black lead from paper.
    Oils.—Oil is an inflammable  liquid, which  does not  unite
 with water.    Volatile oils  are those which evaporate, or may
 be  distilled  without  change,  by a moderate  heat.   Of these,
 the oil  of turpentine  is an  example.   They  are  used in the
 arts for solvents,  and in varnishes.   Fixed oils are those which
 do  not evaporate  without decomposition, or chemical change.
 They produce an unctuous stain, which is not discharged by
 heat.    They do not  boil at a temperature much  short of that
 of melting lead.  They  unite  with alkalies,  forming soaps.
 Some of them are called fat oils, which do not lose  their unc-
 tuous character  on exposure to the atmosphere, but assume a
 state like that of tallow; such for  example as Olive oil.   Oth-

   * Chaptal.  Chimie" appl. aux Arts.
    t Mr Faraday states that the liquid caoutchouc, or juice, as it came from the
 south of Mexico, was a pale, yellow, thick, creamy looking substance, of a uni-
 form consistency, with a disagreeable acescent  odor.  When exposed to the
 air in films, it is soon dried, leaving  caoutchouc of the usual appearance and
 color.  One hundred parts of the sap  left  nearly fortyfive of solid matter.
 Heat caused an immediate coagulation of the sap, the caoutchouc separating
 in a solid form.  When the sap is purified by repeated washings with water,
 the caoutchouc rises each time to the surface, it is obtained of a white color,
 and afterwards, when perfectly dry, it becomes transparent, colorless, and elas.
 tic.  A solution of caoutchouc in oil was obtained by mixing the juice with
 olive oil and heating the mixture so as to drive off the aqueous parts.  This
 promises to be a useful element in varnishes.  See Brande's Journal, No. xli,
 page 19. 
36
MATERIALS USED IN  THE  ARTS.
 ers are called drying oils, which become solid in the air, after
 exposure for a certain time, and remain  transparent.  This is
 the case with linseed oil.   Fat oils are used in the arts, to give
 flexibility to  other materials; to diminish their friction, and to
 protect them from water.   Drying oils are largely consumed as
 ingredients in paints, printers' ink, and varnishes.
   Resins.—Various resinous substances  are employed in the
 arts.   They are fusible, inflammable, soluble in oil and alcohol;
 but insoluble in water.  For ordinary purposes the rosin of the
 pine is employed, being  the  cheapest.   For varnishes, copal,
 mastic, anime, and some others are used.   The basis of sealing
 wax is the resin called lac, which is deposited on  trees in In-
 dia by an insect.
   Starch.—Starch or  Fecula,  is a white substance, obtained
 from  farinaceous grains and roots.   It is insoluble in cold wa-
 ter, but dissolves readily in hot water.  In alcohol it does not
 dissolve.  In  Europe  starch  is commonly made  from wheat.
 In this country it is prepared, for manufacturing purposes, from
 potatoes.  For this purpose the potatoes are rasped, or ground
 up, by a machine, to a pulp.   This pulp, when washed  with
 cold water, yields a white  powder, which, on subsiding, proves
to be pure starch.  It is heavier and goes further, for practical
purposes, than the starch  of wheat.  Starch  is largely consum-
ed in cotton factories in the process of dressing, he.
   Gum.—The true gums are those  which dissolve in water,
 either hot or cold, and form with it a thick, mucilaginous  solu-
tion.  They do not dissolve in alcohol, nor melt by heat.  The
species principally used are the gum  arabic, gum  tragacanth,
and gum Senegal.  Gum,  in the state of mucilage,  is employed
to give firmness and lustre to linen.   Calico printers  use  it  in
great quantities, to give their colors such a degree of consisten-
cy, as will prevent them from running  upon the cloth.   It  is
made to form an ingredient in writing  ink, and in water colors,
 for the same reason. 
MATERIALS USED IN  THE ARTS.            37
          MATERIALS FROM  THE  ANIMAL KINGDOM.

   Skins.—The cutis,  or true skin of animals, from which
leather is made, is composed of fibres irregularly situated, and
closely interwoven.  They are  capable of being  dissolved by
long boiling in water, and are found to consist almost wholly of
gelatin, or glue.   The skins of a  great variety of animals are
used in the  manufacture  of  leather.  It has been  found that
those skins which are most flexible, and most easily dissolved,
afford the  poorest  leather and the weakest glue; while  those
which are tough,  and difficult of solution, yield leather and
glue of the best quality.
   Hair and Fur.—The  hairs of animals  consist  of  slender,
flexible tubes, having a consistence like that of horn, and pos-
sessing the chemical properties of coagulated albumen.   The
surface  of hairs are  covered with minute scales or asperities,
which give them a rough feel when they are rubbed upward ;
and which cause them to entangle each other in the processes
of felting and fulling.   Fur consists of very fine hair, thickly
set, and commonly contorted.   It is a  very slow conductor of
heat, and is provided by nature for the clothing of animals in
high  latitudes.  Hair is a durable and  very elastic substance,
and is converted to many useful purposes.  By means of a lin-
en warp, it is woven into cloth for  furniture.   It forms the most
elastic stuffing for  cushions and  mattresses.  It is combined
with  mortar in plastering, to  increase  its cohesiveness.  Furs
are converted to important uses, in clothing and in felting.
   Quills and Feathers.—r-The structure of the quills and  feath-
ers of birds is remarkably fitted to combine strength and  elasti-
city with  lightness; the  mechanism of the tube, shaft, and
feathering,  being all adapted to this purpose. *   The  tube,  or
barrel of  a quill, consists of two  laminae or layers, the outer-
most  of which has transverse fibres, and the inner, longitudinal.
It is the first of these which is scraped off to prepare  the quill
See Chapter II. 
38            MATERIALS USED IN  THE  ARTS.

for  splitting.  Quills are rendered  transparent by  exposing
them  to heat  and moisture.  The  process recommended by
M.  Schloz, is to expose the quills  to hot steam, by suspend-
ing  them in a covered  vessel which contains water in the bot-
tom, and is kept boiling for four hours, the quills being immers-
ed in  the vapor only.  At the end of this  time they are with-
drawn, and the next day cut, wiped, and dried  with a moderate
heat.   Feathers, as they are obtained from common birds, and
down, which is procured from  the  aquatic birds  of northern
climates, are among the most elastic  substances  known, and also
the  slowest conductors of  heat.  These  properties  are the
foundation  of their  usefulness.   The chemical composition of
feathers is  nearly similar to that  of hair. *
   Wool.—Wool is a fine, soft, long, and contorted hair, deriv-
ed chiefly from the  sheep.   It is said to be the result of culti-
vation, and not to be found in the wild sheep, which is covered
with short hair.  Removal to a tropical climate causes the fleeces
of sheep to fall off, and to be succeeded by a covering of short
hair.   Wool is an invaluable material in the clothing of civiliz-
ed nations.  The fineness and position of its fibres  enables it to
be drawn out like cotton, and to be spun by machinery.   Their
roughness and tendency to curl, causes the fibres to be consoli-
dated in the process of felting.
  Silk.—Silk is spun by the larvae or caterpillars belonging to
different species of Phalcena.   It forms the ball or cocoon  in
which the silk worm envelopes himself in passing to the chrysalis
state.   The fibre, which constitutes  this ball, is so small, that a
single thread, when unwound, is often twelve hundred yards in
length.   The  original  threads are too fine for manufacturing
purposes, and therefore in winding or reeling them  off from the
cocoons, the ends or threads of several cocoons are joined to-
gether, and reeled out  of warm  water, which softens their nat-
ural gummy covering,  and causes  them to cohere into a single

  * Feathers are purified by exposing them to heat; also by immersing them
in lime water for several days, and afterwards washing them with pure water,
and  drying.   This process extracts the animal oil. 
               MATERIALS USED IN THE ARTS.            39

 thread.   Silk, as it is spun by the animal, is of a color varying
 from white to reddish yellow.   Its  texture is very strong  and
 elastic.  It communicates to water a mucilaginous character,
 owing to the solution of its gummy part; but the  silk  itself is
 insoluble in water or alcohol.
   Bone and Ivory.—The bones of  animals are composed of a
 white, hard, lamellar substance, consisting chiefly of phosphate
 of lime, with a small portion of  other  earths, and impregnated
 with oily and gelatinous matter.  Exposure to heat causes them
 to soften  and crumble.   Bone  is  used in the arts for the han-
 dles of cutlery, and various articles of turners' work.  It  is
 whitened  by exposure to the sun and  weather, and sometimes
 by the use of chlorine gas.  It is wrought by sawing, turning,
 he., and polished with pumice and tripoli.  Ivory is the mate-
 rial of the elephant's tusks.  It agrees  with bone in its principal
 properties, but is more compact, hard, and white, and receives
 a finer polish.  When burnt in close vessels and afterwards re-
 duced to powder, it  furnishes the  pigment called ivory black.
 The shells of marine animals, differ from bone in being compo-
 sed of carbonate, instead  of phosphate of lime.
   Horn.—Horn differs   from  bone, not only in its  texture,
 which is  softer, but also in its composition, being  composed
 chiefly of  animal matter resembling coagulated  albumen,  and
 containing but little  lime.   Horn  when  heated  becomes soft,
 flexible, and plastic,  capable of being cemented and pressed by
 moulds into a great variety of shapes.
   Tortoise Shell.—This substance exists in the form of plates
 on the outside of the  shell  of a species  of sea turtle  (Testu-
 do imbricata).  It resembles horn  in its general properties, and
 like that article may  be wrought by softening it in boiling water,
 and subjecting it, while hot, to pressure in moulds.   The edges
 of different pieces, by pressing them with heated irons, may be
joined together and made  to cohere firmly.
   Whalebone.—This substance is obtained from the mouth of
 several species of whale, where it exists in the form of plates
arranged on the outer edge of the upper jaw.   These plates 
40
MATERIALS USED IN THE  ARTS.
terminate in a kind of hair.   Whalebone, in its  texture  and
chemical properties, is very similar to horn.   It is strong, light,
and elastic, on which accounts it is applied to various mechani-
cal uses.  Whalebone, when heated by steam, or boiling water,
becomes more flexible,  and if bent into any shape, retains its
form on cooling.   Hence it has been  manufactured into various
woven fabrics.*  It maybe cemented in the same way as horn
or turtle shell.
   Glue.—The skins, tendons, membranes, he. of animals, are
composed principally of a substance known in chemistry by the
name of gelatin.   This  substance is not soluble in cold water,
but dissolves freely in boiling water, and on cooling assumes the
state  of jelly.  It has great affinity  for tannin, which exists in
astringent barks;  and on this  affinity depends the manufacture
of leather.   Common  glue is impure  gelatin, obtained  from
hoofs,  ears,  and  refuse  portions of hides.   These are  first
cleansed, then boiled to  a jelly, which, on cooling, is cut into
squares and  dried  upon nets.  Size is a finer  kind of glue,
made with more care, from select materials.   Isinglass is a still
more delicate sort, prepared  from  the swimming  bladders of
fish.  Glue  is a cementing material of unequalled  strength, for
wood and fibrous substances.  It is employed in different states
of purity, by carpenters, hatters, paper makers, linen manufac-
turers,  gilders, painters in distemper,  and  refiners of liquors-
In the state of a stiffjelly, it forms, with treacle, the elastic cylin-
ders,  used to distribute and apply the ink, in printing.
   Oil.—The oil of animals  belongs to the class of fixed  and
fat oils.  The oil of those animals which live in a cold medium,
as whales, remains  fluid at common temperatures ;  but that of
most land animals, becomes solid, when cooled below the heat
of the living body.   Tallow, the hardest kind, is obtained from
ruminating quadrupeds.   Animal  oils are appropriated to the
same purposes as the vegetable ; but  their great use is to fur-
nish light, by their combustion.
'* Repertory of Arts, 1807, page 411. 
              MATERIALS  USED  IN THE ARTS.            41

   Wax.—Wax,  in  its crude state, is obtained by melting the
honeycomb of the bee.   It is commonly classed with vegetable
substances, but the  experiments of Huber have  shown,  that
it is produced by the  bees  themselves,  and not  gathered by
them directly from  plants,  as was formerly supposed.   Wax
melts with a gentle  heat, at one hundred and fortytwo degrees
of Fahrenheit, is inflammable, dissolves in boiling alcohol, ether,
and  fixed  oils; but is insoluble  in water.   Beeswax is de-
prived  of its  coloring matter by  bleaching.   To effect  this,
the melted wax is suffered to run  through holes in the bottom
of a vessel, upon the surface of a cylinder which is kept revolv-
ing in water, by which means the wax is spread out, and cooled in
the form of thin  laminae or ribbands.  It is then exposed to the
light and air upon frames, and occasionally wet, till the bleach-
ing is completed.   Bayberry  or myrtle  wax is a harder  sub-
stance  than beeswax, obtained from the berries of the myrica
cerifera, by boiling them in water.
   Phosphorus.—Phosphorus  is a simple,  combustible body,
usually obtained from animal bones.  It is of a soft, waxy con-
sistence, and is luminous in the atmosphere at common tempera-
tures.  At one hundred and fortyeight degrees of Fahrenheit,
it takes fire and burns with great  brilliancy.   On this account
it should be kept in water.  Phosphorus is the agent in  some
kinds of apparatus for procuring fire.

   References.  Among the works;, which may be usefully consulted
on the subjects of this chapter, are Cleveland's Mineralogy, 2 vols.
8vo. 1822;—Brard, Mine'rcdogie applique"e aux Arts, 3 torn. 8vo. Paris,
1821;—Evelyn's Silva, 2 vols. 4to. edit, of 1812 ;—Michaux, North
American Sylva, 3  vols. 8vo. 1817;—Tredgold's Elementary Princi-
ples of Carpentry,  4to. 1820 ;—Thomson's Chemistry ;—Ure's  Dic-
tionary ;—Vicat, Recherches sur les Chaux, fyc.
6 
CHAPTER II.
 OF THE FORM, CONDITION, AND STRENGTH OF MATERIALS.

  When  materials are employed for mechanical purposes, the
power or strength with which they resist external force, depends
not  merely upon the nature of the material, but upon its shape,
its  bearings, and upon the  manner in which force is applied to
it.  It is,  therefore, important to consider not only the qualities
of individual substances, but likewise the laws, which are com-
mon to different materials, by which they act in  resisting me-
chanical change, from forces applied to them.
  Modes  of estimation.—Two  methods are employed in esti-
mating the strength of materials, in different forms and situa-
tions ; one by  mathematical computation,  the other  by actual
experiment.   The first supposes the structure of given bodies
to be homogeneous, so that the  cohesion of their particles shall
be  equal throughout.   In the second, a single specimen is tak-
en  as the  representative of a class ; or at most the average of
a number of specimens, is so taken.   Neither method, there-
fore, is to be looked upon  as precisely accurate in its results ;
yet  these  results  furnish approximations  to truth,  which, in
many cases it  is useful to understand.
   Stress and strain.—Professor Robison, and some  other wri-
ters on the strength of materials, have enumerated four modes,
commonly called  strains, by which any force or stress acting
upon a solid body may operate to overcome  the cohesion of its
particles.   These  are, 1. By extension, producing a tendency
to rupture; as in the case of ropes, tie-beams, king-posts, he.
2.  By compression, tending to  shorten or crush the  material;
as in columns, walls, and foundations.   3.  By transverse strain,
tending to produce flexure or fracture ; as in beams, rails, and 
         the form and strength of  materials.      43

oars.   4. By torsion or  twisting; as in  screws, rudders, and
axles fixed to wheels.   To these Dr Young has added another,
viz;—detrusion, or pushing  aside, as in the  case of  a pin op-
erated on by the blades of scissors.   The changes called flex-
ure, or bending ; fracture, or  solution of continuity ; and altera-
tion, or permanent change of form without separation ; are to
be included in the effects of force exerted on materials.
  Resistance.—To these disturbing influences, bodies oppose
certain qualities, which depend, in part, upon the nature of the
material, and  in  part on its form,  condition,  and connexion.
These are  their strength, by which they resist all permanent
changes resulting from mechanical force, but more particularly
fracture.   Their hardness, by which they resist impressions, or
superficial changes.   Their stiffness, by which they resist flex-
ure or bending.   Their  elasticity, by which  they regain  their
original size and form,  after any force producing  mechanical
change  in them, has ceased to  operate.  Their  tenacity,  by
which they  undergo permanent  alteration  without   fracture.
This  quality is called ductility,  when exposed to extension, and
malleability, when exposed to compression.   Some authors add
the term resilience, to express the quality by which a body  re-
sists  impulse, like  that of  a  blow, in contradistinction from
strength, by which it resists pressure.
  Extension.—When a bar of any material  is drawn in the
direction  of its  length, its resistance, or strength, will be pro-
portionate to its size at the weakest point; i.  e. to the area of
its cross  section  at that point.  The tie-beam of a  roof, the
posts of a printing press, and the  shaft or piston rod of a pump,
are exposed to this kind of strain;  and their weakest point is
commonly found at the place where they are perforated, or
mortised, to connect them with the  other parts.   Various ex-
periments have been made to determine the comparative strength
with which different substances resist tension.   Although they
do not fully agree in their results, they nevertheless, when taken
collectively, afford approximations of some use  for practical pur-
poses.  An idea of the relative strength of the  metals, when ex- 
44              THE FORM,  CONDITION,  AND

tended, may be obtained from Mr Rennie's experiments detailed
in the Philosophical Transactions for  1818.   His experiments
were made with bars six inches long, and  a quarter of an inch
square.  The average  number of pounds avoirdupois,  which
they supported respectively, is, in round  numbers, as follows.
Steel,  about  8000  pounds.   Hammered iron,  about  4000.
Gun metal and wrought copper, 2000.  Cast copper and brass,
1000.   Tin, 300.   Lead, 100.  Experiments have been made
on the longitudinal strength of the wood of different European
trees, and similar  experiments, sufficiently varied, on the trees
of this continent, might be a valuable addition to our knowledge.
   Compression.—When a bar or beam  is  compressed  in  the
direction of its length, it resists more powerfully than in any
other way. *   If the beam be long, and its strength be overpow-
ered by pressure, it bends, and then breaks ; but if its thickness
be as much as a seventh part of its length, it commonly swells in
the middle, splits and is crushed.  When a stone block or pillar is
crushed, the parts nearest to the force, break away and slide off
diagonally at the sides, leaving a pyramidal base.  The  lower
stories of buildings,  the  piers and piles of bridges, the  spokes
of carriage wheels, and the  legs of furniture, are subjects of
this force.  According to Mr Tredgold, f a cubic inch of mal-
leable iron  will  support, without alteration, a weight of about
17000 pounds ; cast iron, 15000 ; brass, 7000;  oak and ma-
hogany, nearly 4000 ; tin, 3000; lead, 1500.   Granite is crush-
ed  by  11000 pounds to  the  square inch; white marble, by
6000 ; Portland stone, by 4000.
   When a force acts on a straight column in the direction of
its  axis, it can only extend,  or  compress it  equally through its
whole substance.  But if  the direction of the force is not in the
axis, but  parallel to it, the  extension or compression will then
be partial.   In a rectangular column or block, when the com-
  * Modulus of elasticity.—This term has  been  introduced as a measure to
 express the elastic force of any substance.  The Modulus of elasticity of a
 substance is a column of the same substance, capable of producing a pressure
 on its base, which is to the weight causing a certain degree  of  compression,
 as the length of the substance is to the diminution of its length.
                  t Essay on Cast Iron, p. 269, etc. 
STRENGTH OF  MATERIALS.
45
pressing force is applied to a point more distant from the axis
than one  sixth of the  depth,  the  remoter  surface  will be no
longer compressed, but extended.   In this case the distance
from the axis of the neutral point, or that which is neither com-
pressed nor extended, will be  inversely as that of  the point to
which the force  is  applied.  For example, a  C^A   ||^
weight or compressing  force being applied on   ^^^B?
one side of the block or column C D E F, and   UlUlIf
acting in  a direction parallel  to its  axis, the   g=^^^g
compression will extend only to the line A B,   MM    B
the parts beyond this being extended.          a>    3      E
   Lateral  strain.—When a beam is acted on transversely, or
by a lateral force,  the effect produced is the joint result of  ex-
tension and compression.   For if it be moved or bent by such
a force, from its original direction, the part which becomes con-
vex is extended, while  the part rendered  concave is compres-
sed.   The properties by which a beam resists lateral pressure,
 are its stiffness and its  strength.
    Stiffness.—The stiffness of any substance  is measured by
 the force required to cause it to bend or recede through a given
 small space in the direction of the force.  It appears to be gov-
 erned by different laws from those of the strength which resists
 fracture.   When a force is applied to a beam transversely, its
 stiffness is directly as the breadth, and the cube of the depth of
 the beam, and  inversely as the  cube of its  length.*   Thus if
 we have a beam  which is twice as long as another, we must
 make it, in order to obtain an equal stiffness, either twice as
 deep, or eight times as broad.  When a beam is supported  at
 both ends, its stiffness is twice as great as that of a beam of half
 the length inserted in a wall, or otherwise  firmly fixed, at  one
 end.   If both  ends are  firmly fixed,  the stiffness is  quadru-
 pled, f

   * Gregory's Mathematics for practical men, 389, also Young's Nat. Philoso-
 phy, i. 139, and Tredgold's Elements of Carpentry, 31.
   t The quantity of timber being the same, a beam will be stronger in propor-
 tion as the depth is greater, but there is a certain proportion between the depth 
46
THE FORM, CONDITION, AND
   Tubes.—A tube or hollow beam is much suffer than the same
quantity of matter in a solid form.   The stiffness is indeed in-
creased nearly in proportion to the square of the diameter; since
the cohesion or repulsion are equally exerted, with a smaller cur-
vature ; and act also on a longer lever.  We  see this princi-
ple applied in nature in the stems of reeds, and the bones and
quills of animals.
   Strength.—The  strength of beams  of the same  kind, and
fixed in the same manner, in resisting a transverse force which
tends to break them, is simply as their  breadth, as the square
of their depth, and inversely  as their length.  Thus if a beam
be twice as broad as another, it will also be twice as strong, but
if it be twice as deep, it will be four times as strong ;  for  the
increase of depth not only doubles the number of the resisting
particles, but also gives each of them a double  power, by in-
creasing the length of the levers on which  they  act.   The in-
crease of the  length of a beam  must obviously weaken it, by
giving a mechanical advantage  to the  power which tends  to
break  it;  and  some  experiments  appear to  show, that the
strength is diminished  in a proportion greater  than that in which
the length  is increased.
   The  strength of a beam supported at  both  ends, like its stiff-
ness, is twice as great as that of a single  beam of half the
length, which  is fixed at one end; and the strength of the whole
beam is again doubled, if both the ends  are firmly fixed.
   Place of strain.—If a weight or  other  stress be placed on
any  given point  of a  horizontal bar  which  is supported at both
ends, the strain on that point will be proportional to the rec-
tangle of the two segments into which the point divides the bar.
Hence  the place where the strain  would be  greatest is in  the

and breadth, which, if it be exceeded, the beam will  be liable  to overturn
and break sideways.  To avoid this, the breadth should never be less than that
given by the following rule, unless the beam be held in its position by some
other means.
  Divide the length in feet, by the square  root of the depth in inches, and
the quotient multiplied by the decimal 0.6 will give the least breadth that
should be given to the beam. Tredgold's Carpentry, p. 32. 
STRENGTH  OF MATERIALS.
47
middle of the bar, and a given weight would be most likely to
break it in that place.
  Incipient fracture.—An incipient or partial  fracture, at the
place of  strain, weakens a beam more, than if the whole side
of the beam were cut away to the same depth as the fracture.
This is because the sound, or stronger parts of the beam tend
to straighten themselves, and thus increase the curvature at the
point which  is weakened.   The same cause  occasions the
breaking of glass in the direction of a cut made by a  diamond,
or of a crack which  has commenced.  Mr Emerson  asserts
that a triangular beam, which is so strained that the greatest ex-
tension  takes place  at one of its angles, is rendered  stronger,
rather than weaker, by cutting away this angle to a small depth,
so as to convert the beam  into a four sided figure; thus pro-
ducing the seeming paradox of a part being stronger than the
whole.   A sharp angle is indefinitely weak, and fracture  is
more likely to begin in an angle, than in a broad surface.
  Resilience.—The action which  resists  pressure,  is called
strength, and that which resists impulse, is termed by Dr Young,
resilience.*  The resihence is measured by the  product of
the mass,  and the square of the  velocity  of a body capable of
breaking it, while the strength is merely measured by the great-
est  pressure that it can support in a state of rest.
  The  resilience  of a  prismatic beam, resisting a transverse
impulse,  follows a different law from that which  determines its
strength, for it is simply in  proportion to the bulk or weight of
the  beam, whether it be shorter or longer, narrower  or wider,
shallower or deeper, solid or hollow.   Thus a beam ten  feet
long, will support but  half as great a pressure without breaking,
as a beam  of the  same breadth  and  depth, which is only five
feet in length ; but it will bear the impulse of a double weight,
striking against it with a given velocity, and will require that a
given body should fall from a double  height  in order to break
it.f

           "Nat. Philosophy, p. 143—147.    t Ibid. p. 148. 
48             THE FORM, CONDITION, AND

   Shape of timber.—It may be inferred from the consideration
of the nature of the different kinds of resistance, that if we
have a cylindrical tree a foot in diameter, which is to be form-
ed  into a prismatic beam by flattening its sides, we shall gain
the greatest stiffness by making the breadth or thickness six in-
ches and the depth ten and a half; the greatest strength by mak-
ing the breadth  seven  inches  and the  depth nine and  three
quarters, and the  greatest  resilience  by  making the  beam
square. *
   Torsion.—The kind of strain called torsion or twisting, con-
sists in the lateral  displacement or detrusion of  the  opposite
parts of a solid, in opposite directions;  the central particles only
remaining in  their natural state.   The strength, or rather stiff-
ness, with  which the  shaft of a wheel, or crank resists  torsion,
increases  in a rapid ratio to its diameter.   Professor  Robison
has calculated, that the  power of resisting torsion is as the cube
of the diameter; and the more recent estimates of M.  Duleau
make it as  the fourth power of the diameter.  If the  length
vary, the resistance to the force of torsion  will be  inversely as
the length, for obvious reasons.   It is advantageous in machin-
ery to increase the diameter of shafts which are exposed to this
strain, the amount of  material remaining the  same.  For this
purpose they are sometimes  made hollow, and sometimes wing-
ed with lateral projections.
  Limit of bulk.—It is important to recollect that when the
bulk of a substance employed, becomes very considerable, its
own weight may bear so great a proportion to its strength, as to
add materially to the load to be supported.  In most cases, the
weight of bodies increases more rapidly than their strength, and
thus causes a practical limitation of the magnitude  of our ma-
chines and edifices.   Thus a roof, or a bridge, may be very
strong, when of  small, or moderate size ; but if the size be ex-
tended beyond a certain limit, although the materials and pro-
portion of parts remain the same, yet the structure  will not sup-
' Young's Nat. Philosophy, p. 149. 
/
                 STRENGTH  OF MATERIALS.              49

port its own weight.   We see also a similar limit in nature; for
if trees and animals were made many times larger than we now
find them, and of the same kinds of substance, they would not
sustain their own weight.  Small animals endure greater com-
parative violence, and perform greater feats of strength in pro-
portion to their size, than large ones.  It has been observed
that whales are larger than any land animals, because their weight
is  more  equally supported by the pressure of  the  medium in
which they swim.
   Practical Remarks.—In frames of houses, and  for various
other purposes, beams  are  used of a prismatic  form,  having
straight,  parallel sides.   But such beams, when exposed to  a
lateral strain, are not of equal, or duly proportioned strength
throughout;  and therefore a part of them is superfluous.  This
consideration is not of much  importance in ordinary  practical
cases.  But in cases where  economy of the material is impor-
tant, as in cast iron railroads, also in machinery where it is de-
sirable that the moving parts should be as light as possible, con-
sistently  with the requisite strength; it becomes of consequence
to ascertain the best form for resisting a force with the smallest
amount of material.  Mathematicians have calculated the forms
of different beams, which are suited to give them, at all points,
a strength proportionate to the pressure they  sustain, supposing
the material to be of uniform  texture.  But  the outline which
answers  merely to mathematical truth, is in many cases too
scanty for actual employment; so that in order to obtain suffi-
cient length for a  secure  connexion of the beam with its bear-
ings, it is necessary to include the mathematical figure in a some-
what similar  one, of larger  dimensions.   The  following rules
are, most of them,  given in substance by Mr  Tredgold.*
   If a beam be supported at both ends, and the load applied
at some one point between the supports, and always  acting in
the same direction,  the best plan appears to be, to make the ex-
tended side, or that opposite  the load, perfectly straight; and

               * Essay on Cast Iron, Art. 21. et seq.
               7 
50
THE  FORM, CONDITION, AND
to make the  breadth  equal throughout the whole.  Then  the
mathematical form of the compressed side will be that which is
formed  by drawing two semi-parabolas, A C D and  BCD,
their vertices being at A and B, and C being the point where
the force acts.  Now since the curve terminates at A, it is ne-
cessary, in applying it to use,  to  add some such parts as  are
indicated by the fines extending to E and F at the extremities,
for the sake of better support.
  The same form is proper for a beam supported in the middle,
as the beam of a balance.  If the beam be strained, sometimes
from one side and sometimes from the other, as in the beam of
a steam engine,  then both sides  should be of the same form,
and E A and F B should each be equal to half C D.
A                       D                      B
  It is sometimes desirable to preserve the same depth through-
out; and in  this  case  the  section through the length of the
beam, made perpendicular to the direction of the straining force,
should be a rhombus or trapezium, as in the  annexed figure,
the force acting perpendicularly at C, and the  points of support
being at A and B.   To give this figure stability, the ends may
be formed as  shown in the continued outline.
 
STRENGTH  OF MATERIALS.               51
  If a beam be intended to support a weight uniformly distrib-
uted throughout its length, or a load rolling over it, as in a rail-
way, the line bounding the  compressed side should be a semi-
ellipse, the other side being straight.   In practice the semi-el-
lipse may be included in a portion of a circle, to  give the re-
quisite bearings.
  A,B,  ends of the elliptic curve.   C,D, ends of the circular
curve.
   Where it is necessary that the upper side should be straight,
the above form may be inverted, and the ends adapted to the
bearings.
   Beams which are fixed at one end only and support weights,
should decrease as they recede from the wall, or point of fix-
ture.   If the weight be at the extremity, the outline, in a beam
cut from a vertical plank, should be parabolic ; but if equally
distributed throughout, it may be straight.
  If a beam be firmly fixed at both ends, and supports a weight
in the middle, it should  be largest at the ends and in the mid-
dle, the outlines being  parabolic.   In the annexed  figure the
shaded  part  shows the  mathematical form, and the outline the
form for practical purposes. 
52        THE FORM AND STRENGTH OF MATERIALS.
   For resisting a cross strain, it is advantageous that
the edges of a beam should be made thicker than the
rest  of its  substance, so that a section of the beam
would be  nearly such  as is seen in  the  adjoining
figure. *

   It must be recollected that the foregoing rules prescribe only
a general form, the  proportions of which must  vary  with the
nature of the material, and the degree of resistance, or load to
be supported.
  Works ivhich treat of the strength of materials.—Robison's Mechani-
cal Philosophy, 4 vols. 8vo. 1822; vol. i. p. 369, &c.;—Barlow on Tim-
ber, 8vo. 1823;—Young's Natural Philosophy, 2 vols. 4to. 1807; vol. i.
p. 135, &c.; vol. ii. art. 333, &c.;—Rennie, in the Philosophical Trans-
actions, 1818;—Dtjleau, Annates de Chimie, torn.xii.;—Tredgold's
Elementary Principles of Carpentry, 4to. 1820;—Tredgold's Essay on
Cast Iron, 8vo. 1824;—Emerson's Mechanics;—Gregory's Mechan-
ics, 3 vols. 8vo. edit. 1826;—Gregory's Mathematics for Practical
Men, 8vo. 1825.

  * For the  form best suited to resist longitudinal pressure, see the article
Column in Chap. VII.
 
CHAPTER III.
          THE ARTS OF WRITING AND PRINTING.

   Letters.—The arts of writing  and printing, although com-
paratively simple in their processes, are superior to most other
arts in the importance of their consequences.  Before the in-
vention of letters, the growth of knowledge was  opposed by
insurmountable obstacles.  Tradition,  which was  the  earliest
mode of transmitting knowledge, depended upon the memory
and the  will of individuals,  and was  of  course uncertain of
continuance.   The  principal adventitious  aids brought to the
assistance of traditionary knowledge, were  the erecting of mon-
uments, the celebration  of periodical days or years, the use of
poetry, a language more captivating and  more easily remem-
bered than mere narration of facts ; and  finally an  approach
to written characters in  symbolical  drawings and hieroglyphic
sketches.  All these methods, however, have failed  in the object
for which  they were intended.   The founders of the Pyra-
mids have not been able to convey to us their names,  and the
productions of the earliest sages and poets  can  never be appre-
ciated  from acquaintance.  The  symbolic sculptures  which
cover the antiquities of Egypt, are now  subjects of empty spec-
ulation to the curious.   History must have remained uncertain
and fabulous, and science  been left in perpetual infancy, had it
not been for the invention of written characters.
   Invention of Letters.—The credit of the first introduction of
letters, was  claimed  by  the Egyptians  and Phoenicians, Jews,
Chinese, and other nations.   Their origin is extremely ancient
and of course preceded all authentic  history, which  was not
inspired.  If we believe Pliny, sixteen characters of the  Gre-
cian alphabet were introduced by Cadmus the Phoenician, 1500 
54        THE  ARTS OF WRITING AND PRINTING.

years before Christ.   Four more were added by Palamedes
during the Trojan war,  and four afterward by Simonides.   It
is not probable, however, that the Greek was the oldest alpha-
bet.   Mr Astle  considers the Phoenicians as having the strong-
est claim to be considered the first inventors of letters.
  Arrangement of Letters.—The mode of arranging letters has
been  subject  to  considerable variation, some nations having
written in perpendicular lines, others from right to left, and oth-
ers  in fines alternately  reversed, as in the /3««Tfo<Pfl&»  of the
ancient Greeks. *  The mode of writing from left to right, now
generally pursued, is the most natural; because the hand, as it
advances in this  direction, leaves constantly uncovered that por-
tion of the page, upon which writing has been made.
   Writing  Materials.—The most ancient materials employed
for  writing,, appear te have been the  surfaces of stones and
bricks.   The  ten commandments  were written upon stone, and
the  arrow-headed alphabet, as it is called, belonging to an ex-
tinct language, is only known to us by the pages of inscriptions
which remain  on the Babylonian bricks.   After these, plates of
metal, of various kinds, were employed.   The Romans  wrote
upon tablets of brass thinly coated with wax, using an iron pen-
cil with a sharp point denominated Stylus.    Lead was also used
by them, and  at the siege of Modena a correspondence was car-
ried on by Decimus Brutus, and the consul Hirtius, upon plates
of lead.  Pausanias mentions books of Hesiod, and Pliny speaks
of public records, inscribed on the same material.   A less du-
rable, but more  cheap  receptacle for written characters, was
found in the leaves of trees and their inner bark, denominated

  ' The bustrophedon was disused by the Greeks about 450 years before  the
christian era; but a similar method appears to have been in use among the Irish
at a much later period.  The following example of the Greek bustrophedon is
from an inscription  on a marble in the national museum at Paris.
                    NEKH0E NEM 20AAT
                   API2TOKTAE2 NOH2EN
                        em decalp  sullyH
                    Aristocydes designed me. 
THE ARTS OF WRITING  AND  PRINTING.        55
liber by the Latins.  These were used for the more temporary
or perishable writings.- *
   Papyrus.—As the literature of antiquity advanced, it became
necessary to  find a material adapted for  works of magnitude,
which, besides  permanency and enlarged size, should  have a
fineness of texture sufficient  to permit a large surface to  be
folded into a compact  form.   A species of reed, growing in
Egypt, was  found  capable of being manufactured into a sub-
stance of this sort.  Sheets and rolls were prepared from it of
the  finest texture, and of any dimensions, and it became the
receptacle on which a great part of the ancient manuscripts were
written.   This was  the  celebrated Egyptian papyrus.  The
 discovery of its manufacture, though it afforded a substance far
inferior to modern paper, was nevertheless a great auxiliary to
 ancient learning, and became  the means of a much more exten-
 sive multiplication of manuscripts than could have taken place
had it remained unknown.  The papyrus was an aquatic reed
 growing on the  banks of the Nile, f   The manufacture of paper
 was performed by divesting  this  reed of  its  outer  cover-
 ing  and  then  carefully separating  the internal membranes or
 laminae by the point of a needle or knife. J   These  laminae
 were spread parallel to each other on a table, having their edges
 in contact, in sufficient numbers to form a sheet.   A second

   *  Pliny says that tables of wood were in use for  writing before the time of
 Homer.  In the Slonian library at Oxford, there  are some specimens of an-
 cient Arabic writing on boards about two feet long and six inches wide.
  The  edicts of the Roman Senate were written  on tablets of ivory, thence
denominated libri  elephantini.
  According to Pliny, the most ancient mode of Writing, was upon the leaves
 of Palm trees, afterward upon  the inner bark of trees.  This method is still
common in Tanjore, and some other  parts of the East Indies where the palmy-
ra leaf is used.
  The  old Egyptians frequently wrote on linen, and specimens of  this kind
are  sometimes found inclosed  in the garments or  swathing  clothes  of mum-
mies.
  t Cyperus papyrus. L.
  t The delicate substance now imported from India under the name of rice
paper, is a cellular membrane of the Artocarpus incisifolia, or Bread-fruit-tree.
Brewster's Journal, Hi. 136. 
 56        THE ARTS  OF WRITING AND PRINTING.

 stratum was then laid, with the strips crossing those of the first
 at  right angles.   The whole was moistened  widi  water and
 subjected to pressure  between two polished surfaces.   Upon
 drying, the mass was  found  agglutinated into a smooth and uni-
 form sheet.   The adhesion of the strips  of papyrus to each
 other was doubtless owing  to the glutinous juice of the reed,
 though the Romans, who were ignorant of the  Egyptian mode
 of  manufacturing  it,  attributed  this effect to a  peculiar quality
 in the waters of the  Nile.   The most delicate paper, which
 was made from the inner membranes or tunics of the reed, was
 rendered  extremely white,  and polished  by rubbing it with a
 shell or tooth of an animal.
   Herculaneum Manuscripts.—The papyrus continued in use
 as late as the tenth or twelfth century, when it was superseded by
 parchment and cotton paper.  A few ancient manuscripts writ-
 ten on it are preserved as curiosities in different libraries  of
 Europe, though they are less numerous than those of parchment
 and vellum.   The most interesting collection of papyri is un-
 doubtedly that found at Herculaneum, and was probably buried
 with that city  in  an  eruption of  Vesuvius, which  happened
 during the reign of Titus.   In the excavations which the mod-
 erns have  made into the earth  which covers that city, these
 rolls of papyri, nearly  1700 in number, were found in a house,
 the roof and floors of which had  been  crushed in by the sub-
 stances ejected from the volcano.  The rolls were found in  a
 state so near to decomposition  that the least violence  causes
 them to break and  crumble ;  their color is so nearly black that
 the characters  are distinguishable from the paper only by  a
 slight shade of difference; and  the whole roll is cemented to-
gether so as not to be separable into layers without great difficulty.
 This state has been supposed to be produced  by  the  carbon-
 ization, or converting into coal, of the papyri, by the heat of the
 ashes and lava, in which they were buried. Sir Humphrey Davy,
however, has  given a different opinion  on  the  state -of these
 manuscripts.   He  supposes that their present  condition is not
the  result of carbonization or of heat applied to them, but is the 
          THE ARTS  OF WRITING AND PRINTING.        57

consequence of their remaining for so many ages under ground,
until the vegetable matter of which they are composed, has un-
dergone a spontaneous change, and become  converted  into a
substance analogous to peat, or Bovey  coal.   This conclusion
is  the  result of chemical examination,  and is likewise inferred
from the fact that some specimens of gilding, and of vermillion,
which remained on the walls of the apartment, were not chang-
ed in color, which could not have been the case, had the heat
been sufficient to convert vegetable matter into charcoal.
   About ninety of these manuscripts have been unrolled by a
very tedious process, which consists in glueing pieces of gold
beaters' skin to the outside of the rolls, and  suffering them to
dry on.  They are then gradually raised by means of screws,
lifting  with  them a layer of the papyrus, which is copied and
the process renewed.   Several days, in this way, are requisite
for a single page.  Sir Humphrey Davy thinks a more expedi-
tious way might be adopted by subjecting the rolls to the action
of a chemical  solvent, capable  of destroying the  adhesion of
the folds to each other.   He supposes  that of the manuscripts
which, remain not more than from eighty to one hundred  and
twenty  are  in a state to be unrolled, the  rest being too much
defaced, by crushing or otherwise, to render it probable they will
ever be decyphered.
   Parchment.—Next to the papyrus,  the skins of animals, in
the form of parchment and  vellum, were  extensively used for
writing,  by the  ancients,  from a remote   period.    When
Eumenes, or Attalus, attempted to found a library at Pergamus,
200 years B. C, which should rival the famous Alexandrian li-
brary,  one of the Ptolemies, then king  of Egypt, jealous of his
success, made a decree prohibiting the  exportation of papyrus.
The inhabitants of Pergamus  set about manufacturing parch-
ment as a substitute,  and formed  their library  principally of
manuscripts on this material; whence it was known among the
Latins by the name of Pergamena.  The term membrana  was
also applied by them  to parchment.
   Paper.—Paper like that used at the present day, composed
of flexible  fibres reduced to a  pulp by  minute division,  and
               8 
58'        THE ARTS  OF WRITINU  AND  PRINTING.

cemented into sheets  by means of size or glue, began to be
known  in the  East in the beginning of the  tenth century.   It
was first composed of  cotton or silk and called bombycina, and
was not made  from linen  rags  until  the  fourteenth  century.
Coarse brown paper was first manufactured in England in 1588 ;
writing and printing paper in that country not till 1690, previous-
ly to which, it was imported from the continent.
   Instruments.—While  writing was  practised upon hard  sub-
stances, as stone and metal,  a hard metallic point was the instru-
ment with which letters were  formed.  The stylus, which the
Romans employed for writing on brass tablets covered with wax,
was acute at one end  for writing, and  flattened or blunt at the
other, for erasing what was  written.   For  writing in colored
fluids, or ink, the calamus was used,  a reed  sharpened at the
point, and split like our pens.   Quills  were not introduced till
the fourth or sixth century.  *
   Some of the eastern nations still write with  reeds, canes, and
bamboos, instead of  quills.   The Chinese  write with small
brushes like camel's hair pencils.
   Inks.—The ink of  the ancients consisted of a carbonaceous
substance, such as  lampblack, soot, or pulverized  coal,  united
with a viscid or gummy liquid.   The black liquor of the cuttle
fish (Sepia) was sometimes employed.  Colored inks of Ver-
million, red lead, and  purple, were  also  used.  The eastern
emperors signed their edicts with red  ink, the use of which was
prohibited to others, under  pain of death.
   Modern ink is essentially a tanno-gallate of iron  suspended
by mucilage.   It may be made from salts of iron, and infusions
of various astringent vegetables.   But as many products of
this kind are apt to fade by time, it is not safe to trust to any
which have not had the  testimony of long  experience in their

  * The earliest notice of the use of quills, is by an anonymous author of the
life of Constantius, who says that Theodoric, the Ostrogothic king of Rome,
was so illiterate, and so dull of intellect, that, during the ten years of his reign,
he could not learn four letters to sign at  the bottom of his edicts; so that
they were cut for him in a plate of gold, through which he traced the letters
with a quill.  One of the oldest certain mentions of the use of quills, is by Isi-
dore, who died in 636. 
          THE ARTS OF  WRITING AND  PRINTING.         59

favor.   The best materials are the nutgall and sulphate of iron,
with gum arabic.  Other ingredients are  sometimes  added,
such as logwood,  sulphate  of  copper,  and sugar.  When ink
fades, it is commonly from the fugitive nature of the gallic acid
and tannin ; and it may be revived by moistening the page with
a fresh infusion of galls.   When ink grows thin from freezing,
or dilution, so that its particles subside, they may again be sus-
pended,  by agitating it with sugar, or gum.   If writing with
common ink has been  obliterated  by chlorine, it may be again
rendered legible, by the vapor, or solution, of sulphuret of am-
monia.   Indelible ink is produced by writing with dissolved  ni-
trate of silver on a surface impregnated with carbonate of soda.
   Copying Machines.—Various modes have been devised,  for
making extemporaneous  copies of written pages.  Dr Frank-
lin's method consisted  in covering the writing, while yet moist,
with fine powdered emery ; and  afterwards  passing the sheet
through a press, in contact with a plate of pewter, or  copper;
which thus became marked with the letters, so as to yield im-
pressions, as  in  the common mode  of copperplate  printing.
Mr Watt's copying machine, consists of a  press, in  which a
thin, bibulous paper, previously moistened, is forced into close
contact with  the  page, while newly written.   A part  of  the
ink, sufficient to produce  legible characters, is thus transferred
to the thin  paper.  The writing is of course reversed, but  the
thinness of the paper permits it to be read on the opposite side,
which  restores the  order of  the  letters.   Mr Hawkins' poly-
graph, is a machine carrying two or more pens in different pla-
ces, which are  so connected as to pursue a similar path with
each other, and execute two or  more copies at once.  Lithog-
raphy likewise offers a ready method of multiplying copies.

                          PRINTING.

   The art of printing,  as it is now practised, by the composition
of moveable types, is so simple and  obvious in  its  principles,
that it  is truly wonderful  the  process was  not earlier known. 
60        THE ARTS OF  WRITING  AND  PRINTING.

The ancients many times made near approaches to the discov-
ery, but by some  singular  fatality, they were kept from its prof-
itable use.   Arts  far more curious, and sciences far more diffi-
cult, were known, and carried to perfection,  by the patient in-
dustry of the ingenious and enterprising in former  times.   But
this art, which was to give  permanency to all the rest, and which
now seems to be  at the root of all human knowledge, was nev-
er in useful  operation in Europe  until three  or four centuries
ago.
   Types.—Printing at the present day is executed with move-
able types, which are oblong square pieces of metal, each bear-
ing a letter in relief  at one extremity.   The  metal • of which
they are made, is an alloy,  which consists  essentially of lead
and antimony.   The lead is selected in preference to other
metals,  because it is fusible at a low  temperature, and  retains
accurately the shape it receives from the mould.   But as lead
alone is too soft to sustain  the friction and pressure to which it
is  liable in use, about a fifth part  of antimony is added.  This
gives it  a superior hardness when cast, and as this  alloy has the
property of  shrinking less than most other  metals as it cools,
the type receives all the sharpness and finish, which  it can ac-
quire, by filling every part of the mould.   In  making types, the
letter is first cut by an artist upon  the end of a  steel  punch,
answering to the shape of the intended  type.  This  punch  is
driven into a piece of copper, which forms the matrix or bottom
of the mould intended to produce the letter.  As many vari-
eties of punches must be  made of steel,  as there are sizes  and
species of characters required.  In casting, the types are form-
ed with great rapidity, owing to the quickness with which  the
metal cools.   An expert  operator  will  make  2000  or 3000
types in a day.   Some machines have  been  introduced, for
casing types, which operate with much greater rapidity.   The
characters upon types are 'of course  reversed, so  that  in  ar-
ranging  them for the press, the compositor, or printer who  sets
the types, begins  at the right hand of  each line. 
          THE ARTS  OF WRITING AND PRINTING.         61

   Case.—Before the types are applied to use, they are arranged
in the cells, or compartments, of a long wooden receptacle, call-
ed a case; each  species of  letter, character, or space, by it-
self.   In arranging the compartments, the collections of letters
do not succeed each other in alphabetical order, nor are they
all of  equal size.  Those  letters which  occur most frequently
in printing, are required  in greater numbers.  They are there-
fore made to occupy the largest compartments, and are placed
nearest to the compositor.  Thus  the letter e, which is of fre-
quent occurrence, fills a large compartment, and is nearest the
compositor, while the letter x, which occurs much less frequent-
ly, is  provided in small  numbers,  and placed at the extremity
of the case.  In  a bill or collection of types of the  size called
pica,  weighing in all 800 pounds, the number of the letter e is
12000 ; of t, 9000; of a,  8500; of i, n, o, and s, 8000  each;
of c there  are 3000; of b 1600; k 800; x 400; z 200.   This
is for  the English language.   In  other languages, the compar-
ative frequency must be  different.
  Sizes.—Different names  are given  to  the various sizes of
types, of which the  following are  most employed in common
book  printing.

   Pica.—a bcdefghijklmnopqrstu
   Small Pica.—a bcdefghijklmnopqrstuvw
   Long Primer.—a bcdefghijklmnopqrstuvw
   Bourgeois.—a bcdefghijklmnopqrstuvwxyz
   Brevier.—a bcdefghijklmnopqrstuvwxyz
   Minion.—a bcdefghijklmnopqrstuvwxyz
   Nonpareil.—ab cdefghijklmnopqrstuvwxyz

   Composing.—The  compositor  is first provided  with an in-
strument called the composing stick.   This is a plate, common-
ly of  iron or brass, surrounded with ledges,  one  of which is
moveable, so that the length of the  lines may be adjusted to
the width of the page.  The compositor selects from their pla-
ces the  letters  successively,  to constitute the first word, which 
62        THE  ARTS OF WRITING AND PRINTING.

are arranged in  an inverted order from that in which they are
to appear on the printed  page, beginning at the right.  At the
end of the  word a quadrat is inserted  to  produce a space be-
tween  this  word and the  next  following.  The quadrats, of
which  there are various kinds,  differently named from  their
width,  are blunt types, bearing no letter on their extremities.  In
printing, they do not come up to the surface, and  of course
yield no impression.   As the beauty of the page depends upon
the evenness of the margin produced by the equality of the
lines, these quadrats are used to swell out the shorter lines and
bring them to an equality with the rest.  When one line is finished,
the printer  shifts the rule from below it to the top, and commen-
ces setting  the  types for a second line.  The  rule is a thin
brass  plate used to make the types slide easily and not  catch
upon the line below  them.
   The quickness with which an expert compositor advances in
his work, is greater than would appear possible from a first con-
sideration of the subject.  The familiarity with the situations
of the letters and their arrangement, produced by long habit, is
such, that to select the types and place them, does not require
a thought to be bestowed on the process.   It is only necessary
to perceive the meaning of each word,  and the putting it togeth-
er follows as mechanically as writing.   It is even possible for a
printer  to compose in the dark, for the exact situation of each
letter in the case before  him being known, and the upper side
of each  being  known by notches in the type,  they can be se-
lected  and arranged by the sense of feeling alone.
   Imposing.—When a sufficient  number  of lines,  say  six or
eight, are formed in the composing stick, they are emptied into
another  instrument called  the galley,  which is a flat board or
plate, partly or  wholly surrounded  by a rim   In this  galley,
the types are accumulated, generally in  the form of long col-
umns, which are afterwards divided into pages, each  page be-
ing tied together with a string to prevent  the types from falling
asunder.   When  a  sufficient number of pages are  complet-
ed to  constitute what is called a forme, or in other words, to 
           THE ARTS OF  WRITING AND  PRINTING.        63

fill one side of a  sheet, they are  arranged  upon an imposing
stone, and strongly locked up, or wedged together, in an  iron
frame denominated a chase, to prepare them  for the press.
   Signatures.—A  sheet intended for a folio, has two pages on
a side, and will form two leaves.   A quarto has four;. an octa-
vo, eight; a duodecimo, twelve, he.   These pages areso arrang-
ed in the forme, that in the impression, they  will assume their
true order, after the sheet is folded.   The  sheets are marked
at the bottom of certain pages with successive numbers, or capi-
tal letters ; the object of  which  is to afford  the necessary in-
structions for the order of folding and gathering them.   These
are called signatures.
   Correcting  the Press.—The first impression taken  from the
types is called aproof.  This is carefully read over and  the er-
rors and inaccuracies marked.   To correct them, the wedges
or quoins are  knocked out so as to loosen  the types, the erro-
neous letters  are drawn out, and the  proper ones substituted,
and the whole  is again wedged into the frame.
   Many of the errors of the press, which remain  uncorrected
in books, arise from a want of understanding between  the au-
thor, or corrector,  and the printer, in the  characters used in
correction.   It is not enough  that  the author  should detect
these errors and note them in the margin.  He must express, by
intelligible marks,  how these defects are to be  altered, and un-
less he uses  such marks as are employed by printers themselves,
his attempts at correctness will be  defeated.   Every  person
who  has occasion to appear in print, should  first know  how to
correct the press. *

   * If the error is confined to a letter or word, it is easily corrected.  But if it
involves the addition or erasure of a sentence or a number of lines, the cor-
rection is more difficult.  The whole forme must be deranged, and as the add-
ing or expunging of lines affects the length of the page, it must be adjusted
at the expense of the next  following page ; so that all the subsequent pages
may be disturbed, before the necessary correctness is obtained.  An author
who corrects the  press for his own  works, will very much abridge the labor
of the printer, if, in all cases of an erased word, he will substitute another of
nearly the same length in its neighborhood, or, if a new word is added, by strik-
gn out one in the paragraph which can be better spared. 
64         THE  ARTS OF WRITING AND PRINTING.
   The following signs for correcting the press, are em-
ployed by printers themselves.
   When a  wrong  letter is discovered, a line is  drawn
through it, and the true letter written in the margin, thus;

     To be, or not to be, that iiji the question.                *

   If a letter is found to be  omitted, a caret is placed
under its place, and the letter written in the margin, thus;

     To be, or not  to be, tht is the question.                 a

   If a superfluous letter is detected, it is crossed out,
and a character which  stands  for  dele, introduced in
the margin.

     To be, or not to<{> be, that is the question.            ^

   If two words'are improperly joined together, a char-
acter indicating a space, or quadrat, is used.

     To  be, or not  tobe, that is the question.              4£

  If syllables of the same word are improperly separat-
ed, they  are joined by a horizontal parenthesis.

     To be, or not  to be, that is the ques   tion.

   When words are found to  be transposed,  they are
connected by a curved  line,  and the letters tr. written
in the margin.

     To  be, or not  to be, (TsVjjiaQ the question.           tr.
   When  a letter is inverted, it is expressed by a char-
acter of this sort in  the margin.

   Marks  of punctuation, if  of small size, are inclosed
in circles, thus ;

   A comma is placed after a  short stroke, an apostrophe
before it.
9
0 
THE ARTS  OF WRITING  AND  PRINTING.        65
   Words intended to be printed in Italics, are marked beneath
with a single line; if in small capitals, with two lines ; and if in
large capitals, with three.   Thus a line marked  in this man-
ner,
     Oh thou,  in Hellas deemed of heavenly birth.

would be printed thus;—

     Oh thou in HELLAS  deemed of heavenly birth.

   In correcting with these marks, the abbreviations Ital. Rom.
 Caps. he. should also be written in the margin.
   Corrections  themselves sometimes require to be corrected.
Thus if a word  has  been improperly  altered,  and it is after-
wards thought best to retain it, dots are  placed beneath  and
the word stet written in the margin.
   When lines are crooked, or letters have been  disturbed from
their places, or blemishes  appear, it is sufficient to call the at-
tention  of the printer, by a dash of  the pen, at the place.
   Press Work.—After the sheet is  corrected and revised, it is
then ready for the press, to which it is accordingly transferred.
The ink is first applied  over the whole surface of the types;
the  paper, previously moistened, is  then laid down upon them,
the whole is passed under the press, and the paper being brought
into forcible contact with the types, receives from their surface
the ink necessary for a distinct impression.  Printers'  ink  is
composed chiefly of lampblack and oil inspissated by boiling and
and burning.  Oil is necessary, that the ink may  not dry during
the operation, and it is reduced by  boiling, to prevent it from
spreading on the  paper.   It is  applied to the  types by large
elastic balls made of leather and stuffed with wool, or by elas-
tic rollers, like those used in printing machines.
   Printing Press.—The common or old printing press, derives
its power from  a screw, which is turned  by a lever,  and acts
perpendicularly on the platten, or level part, which transmits the
pressure.   Various improvements have been made in the print-
               9 
66
THE ARTS  OF WRITING  AND  PRINTING.
ing press, by Lord Stanhope, and  other  inventors, in most of
which a cast  iron  frame is substituted for a wooden one, being
more inflexible ; and a combination of levers is used, so arranged
as to cause the platten to descend with decreasing rapidity, and
consequently with  increasing force, till it exerts the greatest
power at the moment of contact of the paper with the types.
   Stereotyping.—In stereotype printing,  instead of moveable
types, blocks or plates are used, each containing all the charac-
ters  requisite to form a  page.   The process of stereotyping is
simple.   A page of any work proposed  to be stereotyped, is
set up in the usual  manner  with moveable types.  From this
page, when corrected, a mould in plaster, is taken off, and from
this  mould a plate of type metal is cast, having all the charac-
ters  in relief, and being  a fac-simile of the original page.  From
this plate the printing is executed, and there must be of course,
as many plates cast, as there are pages in  the book to be print-
ed.  It will thus be seen, from the accounts already given, that
the stereotyped  letter press, constitutes the sixth time that the
character  has been formed, viz.  1, in the steel punch; 2, in
the matrix ; 3, in the moveable type; 4, in  the plaster cast; 5,
in the stereotyped character, and 6, in the printed page.
   The  plaster used for forming the moulds is pulverized gyp-
sum, dried by heat, and mixed with water; to which is  added
a little whiting to diminish the tendency of the plaster to  shrink
and crack.  After the  forme of types has  been  slightly oiled,
and surrounded with a brass frame, fluid plaster is applied over
the surface with a brush or roller, so as to fill every cavity of
the  letters.   A quantity of plaster mixed  with  water to the
consistence of cream, is then  poured on the type, and the su-
perfluous part scraped off.   When the plaster has become hard,
it is  lifted off by the frame  and detached  from it.   It is then
baked  to  dryness in an oven, and when quite hot, it is placed
in an iron box or casting pot, which has also been heated in an
oven.   The box is now plunged into a large pot of melted type
metal, and kept about ten minutes under the surface, in order
that  the weight of  the metal may force it into all the finer parts 
           THE ARTS OF  WRITING AND  PRINTING.        67

of the letters.  The whole is then cooled, the mould broken
and  washed off, and the back of the plate turned smooth in a
lathe, or planed by a machine.   The earlier stereotype found-
ers, as Didot and others, formed their moulds with a soft met-
al, or a  metal  at the point of congelation, instead of plaster.
   Stereotype printing is chiefly useful for standard and classi-
cal works,  for which there is a regular demand, and of which
the successive editions require no alteration.  It is now execut-
ed with such increased  economy, as to be applicable to works
even of less durability.
   Machine Printing.—Printing by machinery, is one of the
latest achievments of art, having had its origin within the pres-
ent century.  It has produced a very great improvement in the
expedition  with which work is executed,  and is now extensive-
ly applied  to the  printing of newspapers and  even of books.
Various  machines  are  already introduced into use,  most of
which perform the processes of inking the types, conveying the
paper, and  giving the impression.  For distributing the ink on
the types, elastic cylinders are employed, called inking rollers,
made of a  composition of glue and treacle,  which  combines
the properties of smoothness, elasticity, and sufficient durability.
These transmit the ink to the types by rolling over their surface.
The impression is performed in most of the English machines,
by large cylinders  which revolve upon  the types, having the
sheet of paper confined to their surface by bands of tape.   The
types are arranged in some machines in the common flat form,
in others, the characters are placed in a convex form upon the
surface of  cylinders.  To produce the latter  effect Mr Nich-
olson proposed to cast the body of the types with a tapering or
wedge form, like  the stones of an arch,  but Mr  Cowper has
produced the same object more expeditiously, by curving stere-
otype plates into the required shape.   Messrs Donkin and Ba-
con placed  their types on the four sides of a  revolving prism,
while the ink was applied by  a roller which rose and  fell with
the irregularities of the prism, and  the sheet  was wrapped on
another  prism so  formed as to meet the  surfaces of the  first 
68        THE ARTS OF  WRITING  AND  PRINTING.

A common printing press, gives about 250 impressions per hour,
whereas of the Times, a London newspaper, printed by Apple-
gath and Cowper's machine, it is stated that 4000 per hour are
printed on one side.  The first working machine which printed
by steam, was erected by  Mr Koenig, in  1814.
  In this country, Treadwell's power press is the machine most
employed.   In this  invention, the types are  inked  by elastic
rollers, and the distribution of the ink rendered equal, by a re-
volving table which passes in  contact with  the rollers.   The
impressions  are  made by  a flat surface or platten, instead of a
cylinder, so that cleaner and better impressions are  supposed
to be obtained from it, than from any other machine.
  History.—The art of printing was first carried into success-
ful operation, a little  before the middle of the fifteenth century.
The honor of having given birth to the invention, is claimed by
the  cities of Haerlem, Mentz, and Strasburgh, in each of which
the  art was successfully practised at an early period.   The best
authors, however, agree in considering that the original inventor
of printing, was Laurentius, otherwise called Coster, of Haer-
lem, who made his first attempt in 1430, with separate wooden
types.   He died ten  years after, having printed the ' Horarium,'
the  ' Speculum Belgicum,'  and two different editions of Dona-
tus, which were the first books.   After his death, printing was
carried  on at  Mentz, by John Gensfleisch, who had possessed
himself of some of Laurentius's types, and who like his master
printed in wood.   This man, with the assistance of his brother,
who is usually called Guttenberg, afterward invented cut metal
types, with which was printed the earliest edition of the bible.
This edition  appeared in  1450, having taken  seven or eight
years for its completion.
  Guttenberg used none but wooden or cut metal types.   The
art  received its consummation soon after, from Peter Schoeffer,
who invented the mode of casting types in matrices.   The cel-
ebrated Faustus, who has often been considered as the inventor
of printing, was in partnership  with the  persons already men-
tioned, and  furnished funds to defray the expenses of the en- 
          THE ARTS OF WRITING  AND  PRINTING.        69

terprise, the processes being  kept  secret.  The well known
tale of the  practice of necromancy, by Faustus, was owing to
his  carrying a parcel of his bibles to Paris,* and offering  them
for sale as manuscripts.  The French finding so great a  num-
ber of books resembling each other exactly, and more so than
it was possible for any chirographer to have made them, conclud-
ed there  was  witchcraft in the case, and by inditing Faustus as
a conjuror, compelled him  to disclose  the secret in his own
defence.
   After the invention of printing with fusible types, it spread
rapidly into many of the cities of Europe, and  was practised
at an early period at Tours, Rome, and  Venice.  It was first
carried on  in England by Caxton  and Corsellis, about 1470,
and the earliest press was established at Oxford.
   It is remarkable that this  important art, after becoming once
established, underwent no essential improvement for a period of
more than  300 years.  Having remained  stationary for  three
centuries, it has received a fresh impulse  within the last few
years, by the invention of stereotyping,  and of printing by ma-
chinery.
   Although printing with moveable types is exclusively a mod-
ern art, yet there are some  steps in the discovery, which have
claim to greater antiquity.   The Chinese have printed with
their  characters, for more  than  900 years, but  as  the nature
of this character requires that much should be expressed by a
single figure, they are obliged to cut each character with all its
complications in a block of  wood, so that their method resem-
bles a limited kind of stereotype printing.
   Among  the  relics of ancient  Rome, there  have been  found
letters cut in brass and raised above the  surface exactly like our
printing types.   Some of these  contain the names of individu-
als, and from their shape and  appendages,  were evidently used
for the purpose of  signature, the letters being  small,  smooth,
and even, while the ground beneath them is unequal, and rough,
so that they must have been employed, not for impressions into
soft substances, but  for printing with colored liquids, on a sur- 
70        THE ARTS  OF WRITING  AND  PRINTING.

face like parchment or paper.   Had the individuals, whose
names were thus printed, been visited with the thought that by
separating  the letters, they might print the name of another, it
is  probable that the art would have been at once  discovered,
and that the dark ages might never have happened.

  Works of Reference.—Astle, Origin and Progress of Writing,
4to. London, 1803;—Fry, Pantographia, 4to. London, 1799;—Towm-
iet, Illustrations of Biblical  Literature, 1821;—Stower, Printer's
Grammar, 8vo. London,  1808;—Thomas, History of Printing, 8vo.
Worcester,  U.  S. 1810;—Meerman, Origines  Typographical  Hagoz
1765;—Cowper, in Brande's Journal of Science, 1828;—Hansard,
Typographia, large 8vo. 1825. 
CHAPTER IT.
           ARTS OF DESIGNING AND PAINTING.

  Designing is the art of delineating or drawing the appear-
ance of natural  objects, by lines on a plane surface.*  Paint-
ing may be considered as the  same art, so extended as to in-
clude coloring, and whatever else is necessary to produce com-
plete or finished resemblances.   It is obvious, that if the art of
painting was carried to perfection, these resemblances could not
be told at sight, from their originals;  since we are supposed to
discern objects by the medium of their pictures painted on the
retina of the eye,  and since a  polished mirror gives us every
appearance of reality, in  the forms  reflected from  it, though
they all proceed from the same plane.
  Divisions.—To produce  perfect  representations  of nature,
three things must receive attention, and the study of  these may
be considered as constituting distinct departments in the art of
painting.  These are, 1. The perspective, by which the outlines
of figures are placed on the picture in situations depending on
their position in regard to the eye.   2. The chiaro  oscuro, or
light and shade, by which the. prominence and depression of
different parts of the piece, are made to appear.   3. The color-
ing, by which the hues and tints of the painting are made  con-
formable to those of the original.
  Perspective.—Perspective is  the art of delineating the  out-
lines of objects on any given surface, as they would  appear to
the eye, if that surface were transparent, and the objects them-
selves were  seen through it from a  fixed position.   It is the
foundation of correctness in painting, and a strict  attention  to
* Rees's Cyclopedia. 
72          ARTS OF DESIGNING AND PAINTING.
its  rules, is  indispensable to perfection in the art.   The first
attempts at drawing, have, in all countries, consisted of diagrams,
and sketches, representing merely the plans, or profiles of ob-
jects, without regard to their perspective relations.   But a con-
tinued attention to their actual appearance or images, combined
with the application of a few geometrical and optical principles,
has furnished the means of fixing the  outlines of objects, in
their true situation on a perspective plane.
   If we look through a window at a mass of buildings, or any
external objects, and  observe  that part of the glass to which
each  object, line, or point, appears opposite, we find that  their
apparent situation is very different from  their real.   We find
that horizontal lines  sometimes appear oblique, or even perpen-
dicular, that circles, in certain  situations, look like ellipses, and
squares, like trapezoids, or parallelograms.   High  objects are
seen beneath low ones, and large bodies are exceeded in appar-
ent magnitude, by small  ones.   The foundation of all these ap-
pearances exists in the  rectilinear motion of the rays of  light
passing from the  object to the eye.
   Field of Vision.—When the  eye is fixed, the rays entering
it from the whole field of vision, constitute a cone  having  its
apex in the eye.   The field presented to the  eye, and occupy-
ing the base  of the cone, cannot well subtend  an angle of more
than 90  degrees, and we cannot have a convenient and agreea-
ble view of  a field  occupying  more than 60 degrees.  Even
the most satisfactory views of objects are obtained at such dis-
tances as cause them to subtend an angle of 30  or 40 degrees.
Panoramic views subtend a larger angle than those which have
been  specified, and of course cannot be taken in by the eye at
a single  view.  It becomes, therefore, necessary to take  suc-
cessive views with the eye, in different directions.
   Distance and  Foreshortening.—Of objects situated  within
the field of vision, those necessarily appear  largest, cateris pa-
ribus,  which are  nearest to  us, because they subtend a larger
angle at  the eye.  Objects or surfaces situated obliquely in re-
gard to the axis of the eye, are  altered in  apparent shape by 
            ARTS OF DESIGNING AND PAINTING.          73

the shortening of their oblique  diameters.   This is what is
technically called foreshortening.  If several objects, for exam-
ple, of equal size, be placed at different distances, and in differ-
ent positions [See Plate III. Fig. 5.],- the one nearest the eye,
as X, will subtend the largest angle, and its comparative length
in the picture  will be  represented by the line A B.  The  ob-
ject Y, being  further off, subtends a smaller angle, and will be
represented by the line A C.  The object Z,  being still further
removed, and also  foreshortened by its  oblique position, will
produce  an image no longer than from A to D.
   A simple instrument may be formed by any person, to rep-
resent the effect of  distance and of  foreshortening in perspec-
tive.   Let four straight, stiff wires [PI. III. Fig.  6.] be connect-
ed at one end, A, by a string or socket, which will allow them
to diverge.  Let a thin,  square  board, or tin plate, be attached
at the other  end, at C, by loops  at  its four  corners, through
which the wires pass.  Let a string of elastic  gum be placed
around the wires at B, about half way between A and C.  The
elastic string  will represent the picture, the  board the object,
and the wires  the rays passing from the object to the eye at A.
If now the board be moved upon the wires toward the eye, the
elastic string  will be extended, or the picture enlarged.  The
reverse will happen, if the board be carried away from the place
of the eye.  The board may also be turned into various oblique
positions, and  the elastic string will represent the figure produc-
ed by the foreshortening.
   Definitions.—There are used in perspective  a certain num-
ber of terms peculiar to the art, definitions of which are neces-
sary to an intelligent use  of them.
   The original object, is that which is made the subject of the
picture.
   Original planes or lines,  are the surfaces or lines of original
objects.
   The point of view is the  situation of the eye.
   The point of sight is the point in the perspective plane, which
is nearest to the eye.   As far as the picture is concerned, these
               10 
74          ARTS OF DESIGNING AND PAINTING.
two points coincide, so that some authors have used them indis-
criminately one for the other.   The point of sight is also call-
ed the centre of the picture.
  A  visual ray is a line from  the object to the eye.   If the
object is a point, there is but one visual ray, if it is a line, the
visual rays form a triangle, if it is a square, they form a pyra-
mid, if  a circle, a cone, he.  The principal visual ray is that
from the nearest point in the picture, or point of sight.
  The  perspective plane is the  surface on which the picture is
delineated ; or, it is the transparent surface through which we
suppose objects to be viewed.
  The directing plane is a plane supposed to pass through the
eye of  the spectator, parallel to the perspective  plane.
  The   ground plane is  the  earth,  or the plane surface on
which the spectator and  objects are situated.
  The  horizon, or horizontal plane, is one parallel to the ground
plane, and at the height of the spectator's  eye.
  The  horizontal line is the intersection of the  picture or per-
spective plane with the horizontal plane.
  The ground line is the intersection of the perspective plane
with  the ground plane ; or, it is the line on which the picture
is supposed to stand-
   The perpendicular is a line on the perspective plane, drawn
through the point of sight, perpendicular to the ground line, and
horizontal line.
   The points of distance  are points on the perspective plane,
set off from the point of sight, sometimes on the horizontal line,
and sometimes on the perpendicular, at the same distance  from
the point of sight, that the eye is supposed to be at, from the
perspective plane.
   To render the foregoing  definitions  more obvious, a diagram
[PI. II. Fig. 2.] is introduced, in which the several planes are
supposed to be  visible, and themselves, or a part of each of
them, seen in perspective.   X is the eye of  a spectator, or
point of view.   S T, the original object.   X T, and X S, visual
rays.   X Y, the principal visual ray.   A B O P, the picture, or 
            ARTS OF DESIGNING  AND  PAINTING.          75

part of the perspective plane.  V W, the image of the original
object in the picture, or perspective plane.  D, the point of sight,
or centre of the picture.   H N R Q, the ground plane.  I K L
M, the horizon or horizontal plane.   AB, the ground line, or
bottom of the picture.   F G, the  horizontal line.   C.E, the
perpendicular.   E, a point of distance.   Other points of dis-
tance  would be at F and G, if equally  distant from D with X
or E.  In Fig.  1, corresponding letters are used.
   The vanishing point of the image of  a right line is the point
in which a line parallel to it, passing through the eye, cuts the
perspective plane.  Lines which in the  original are parallel, in
the picture converge to the same vanishing  point.   Thus the
parallel railings of a bridge, or the parallel rows of windows in
a building, all appear to converge to the same point.  In PI. III.
Fig.  8. c, is the  vanishing point of the lines y x,fk, and of all
lines parallel to them.  All lines which are perpendicular to the
perspective plane, have for their  vanishing point the centre of
the  picture.  Thus D, in PI. II. Fig. 1, is the vanishing point
of  all such lines.
   Plate II.—A  general idea of the nature of perspective may
be derived  from  the  inspection of PI. II.  fig. 1.   In adjusting
this plate  for use, the folded or thick part must be raised per-
pendicularly, the rest being kept level.  The  part thus raised,
will represent the perspective plane, while the rest of the plate
is the ground plane.  The  spectator is supposed to stand upon
Z, with his eye at a height equal to that of D, above the ground
plane.  If now the perpendicular part be supposed to be trans-
parent, so that the lines or objects beyond, can be seen through
it, the appearance which they present on this perpendicular
plane, will be their true perspective representation.  This may
be rendered obvious, by placing  upon Z, a chess man, or any
other object, the  height of which is equal to C  D, representing
the  height of the spectator's eye  from the ground  plane.  If
then  straight wires or threads, representing rays, were carried
from'the top of this object to any  of the large  letters upon the
black lines of the ground plane, they would  pass through the 
76            ARTS  OF DESIGNING  AND PAINTING.
perspective  plane in the points indicated by the "corresponding
small letters.   The lines also which connect these letters, will
assume the situations represented in the diagram.

  Problems.—Since the figures of all objects are contained within defi-
nite lines, it is evident that  the whole art of perspective consists in &
method of finding the situation of all lines upon the perspective plane,
and of cutting  those  lines in any given proportion,  according to the
length required.  The same diagram [PI. II. fig. 1.] will serve to illus-
trate several of the most obvious problems.
  I.  Suppose, for instance, that it is required to find the perspective
situation of straight lines, such as HI and O P, situated on the ground
plane, and parallel to the ground line.  It is first obvious, that if they
are parallel to the  ground line, they are also  parallel to one another,
and  to  the picture.  We then know that the line HI is to be drawn
parallel to A B, and  we only require to know at what distance it must
be drawn from it. *   To ascertain this, we measure the perpendicular
distance C M, of the  given line from the perspective plane, and set off"
this  distance  from C to q.  We then  draw the line G q, cutting the
line C D in m, and the line hi, drawn through  m, parallel to the ground
line A B, is the perspective situation of the line H I, required.
  The reason of this will appear evident, from considering that G be-
ing situated at the height of the eye from the ground line A B, and G
D being equal to the  distance of the eye from the  perspective plane;
the line D C may be  imagined to be the perspective plane seen edge-
ways ; and then any point q,  situated at a given distance beyond  it,
must appear at m, in a straight line drawn from the  eye at G, to it.
Therefore m, is the proper distance from C, at which that point in the
line required, must be drawn.   In like manner, the situation of the point
k, determining the perspective distance of the line op, may be found.
   II. If it is required  to find the perspective place of a line on the ground
plane that is perpendicular to the ground line, we measure its distance
from the  perpendicular C E, and setting it off from C upon the ground
line, we draw a line  from the point, thus set off, to the point of sight
D, which will give the  situation  required.  Thus for example, if we
wish to find the perspective appearance of a line Q, D, which is perpen-
dicular to the ground line AB, and parallel to C D, we take the distance
Q, C, and set it off from C to q, and then D ^ is the line required.  For

   * Such lines are considered parallel by writers on perspective, because a
line parallel to them passing through the eye, can never cut the perspective
plane.  Therefore they can have no vanishing point on the perspective plane. 
ARTS OF  DESIGNING  AND  PAINTING.
77
the same reason, D r represents the line D R; also D s represents D S,
and D t represents D T.  Since all lines perpendicular to the ground
line, when infinitely produced, seem to meet on the perspective plane,
in the point of sight D, it is the vanishing point of those lines.
  III. If it is required to find the perspective situation of a line which
is vertical, i.  e. perpendicular to  the ground plane, having  first ascer-
tained the point upon  which it stands in the ground  plane, we draw
from the  corresponding point in the perspective plane, a line perpen-
dicular to  the ground line.   Thus if we have ascertained that the place
at which a vertical line stands on the ground plane, is at W, we find
the corresponding points,in the perspective plane, and from it raise a
line w x, perpendicular to A B, and  somewhere in that line continued,
will the required line terminate.  The reason of this will appear, when
we recollect that vertical lines are  parallel to the picture, and per-
pendicular to the  ground line.
   IV. If circles or curved  lines are to be put in perspective, this may
be done by  describing squares  about them, and putting these in per-
spective.  This will assist the judgment in completing the curved lines.
Or we may find the perspective  situations of a number of points in the
curve, and join these with a steady hand.
   A great number of problems,  founded on the principles of perspec-
tive, are to be found in works on that  science, and constitute an inter-
esting study.   But  in  practice, artists find it convenient to resort to
some more direct and  compendious method of obtaining the perspec-
tive situation of objects, without the trouble of mensuration.

   Instrumental Perspective.—The rules usually laid down for
 drawing  in perspective, suppose a previous knowledge  of the
real distances, magnitudes, and relative positions of  all the ob-
jects that are introduced into the picture.   But, in many cases,
a person may be so situated, that  this knowledge cannot be ob-
tained, and in many  cases, likewise, the labor, which this meth-
od requires,  is  troublesome  and  discouraging.   Dr Priestley
has described a method of drawing objects in true perspective,
without moving from the place in which they are viewed.  It
consists  simply in taking  observations of the various  points of
 an object, so as to deteimine their elevation above the horizon,
and their declination from a perpendicular.

   To supply the place of actual mensuration, an azimuth quadrant, or
a theodolite, is used, or any instrument by which the elevation of  an ob 
78
ARTS OF DESIGNING AND  PAINTING.
 ject can be found, and likewise its angle of declination from the per-
 pendicular which goes through the point of sight.
   The artist having this instrument, and placing himself at what dis-
 tance he thinks most convenient, from  any objects that he proposes  to
 draw, lays down  upon  the paper of his drawing board, two lines, cross-
 ing each other at right angles ; one of them F G, [PI. III. fig. 8.]  to
 represent the  horizon, and the other C E, the perpendicular,  passing
 through the point of sight D.  He must also choose any distance he
 may think proper to work at, and set it off from D to E.
   Having  thus prepared for the operation, he JJitches upon any point
 in the  object in  sight, as, for instance, that which  corresponds to x;
 and, by the help of the instrument, first of all, finds its declination from
 the perpendicular to the right or left hand.  Supposing it to be 10 de-
 grees to the right, he sets off the angle D E a, equal to 10 degrees, and
 concludes, that the point he wants to fix must  be  somewhere in the
 perpendicular a e.  To find in what part of this line the point  is, he
 must take its elevation above the horizon, and, supposing it to be 20 de-
 grees, he makes  a b equal to a E,  and  the angle a b x,  equal to 20 de-
 grees ;  which finds x the point required.
   In this method may the  situation of any other point be found, and
 these points, being joined by lines, the whole object will be delineated.
   But if the  objects to be represented, contain  many light lines, that
 are parallel to each other, such as occur in buildings,  machines, &c.
 there will be no occasion to take many points ; because the situations
 of the lines may he  determined by vanishing points, found by the help
 of a few of them.  Thus having  found y, in the same manner as we
 found x, and knowing  that  the line x y, is parallel  to the horizon, we
 produce  it till it touches the horizontal line in c, which is, therefore,
 the vanishing  point for that  line, and all that are parallel to it,  several
 of which are represented in the figure.  The distance  at which these
parallels are drawn, may either be guessed by the eye, or be determin-
 ed  with  more accuracy by finding a point at one of their extremities,
in the manner just described.
  Also, if we know the angle that any line, as y z, makes with another
line, as x y, the situation of which is known, there  is no occasion to take
 any point, in order to determine the direction of it.  In  this  figure,
xyz represents a right angle, which is that which most frequently oc-
curs in buildings,  machines, &c.  To determine, therefore, the situa-
tion of the line y z, we consider that c, the vanishing point of y x, makes
the angle DE c, equal to 20 degrees, the complement of which, from
90, is 70.  We therefore make the angle D E H equal to 70 degrees, and
a line E H, produced till it meets the horizontal line in a place without 
ARTS OF DESIGNING  AND PAINTING.
79
 the bounds of this figure, gives the vanishing point of y z, and of every
 other line parallel to it which is at right angles with the line xy.  To
 this point, therefore, we draw the line y z, and all the others  in that
 plane that are parallel to it.
   The point x, is to the right hand of the perpendicular, and it has an
 elevation above the horizon ; but it can require no additional instruc-
 tion, to be able from this, to fix any  point to the left hand of the per-
 pendicular, and one that has a depression below the horizon.
   If we would introduce measures into a drawing made in this manner,
 or find a scale for the picture, we measure some one line in the original,
 as kf. In order  to this, from c, the vanishing point of the line kfwe
 take  c d, equal to c E,  which gives d the measuring point of the line,
 and from this point, we draw two lines, one from each extremity of the
 line kf, to i h, in the line that bounds the picture, or any other line
 drawn parallel to the horizontal line.  Then we divide the line ih, in
 the  same proportion as kf; and by this means get a scale, by which
 we can measure any other line in the picture, or insert in it other ob-
 jects of any given magnitudes.

   Mechanical  Perspective.—To avoid wholly the  delay and
 trouble of computation, artists frequently make use in practice,
 of some mechanical method of perspective drawing, by which
 the  outlines of objects can be obtained with  expedition, and
 sufficient correctness.   Thus the -camera obscura, and camera
 lucida, cast upon paper a perspective  image, which can be im-
 mediately traced.   A method of drawing by  squares  is like-
 wise easily practised.   For this purpose, the paper, or surface
 which is to receive the picture, is divided by pencil lines into a
 certain number of squares.   A  small frame, of corresponding
 size,  is divided into a like number of squares by threads, or by
 lines drawn upon glass.  This frame is placed  perpendicularly
 between the eye and the object, and kept at a stationary distance
 from the eye, which is also fixed.   The outlines and parts of
 objects which  appear in particular squares of the  frame, are
 transferred to corresponding ones on the paper^ and in this way
 the  principal points of the perspective  view may be obtained.
   Perspectographs.—Various instruments  have been invented
 under the name of perspectographs,  to be used  in obtaining the
points and outlines of original  objects.   They commonly con- 
80
ARTS  OF DESIGNING AND  PAINTING.
sist of a fixed part perforated with a small hole in the point of
view, and a moveable  part situated  in the perspective  plane,
and capable of traversing any part of it.   This moveable part
may consist of any minute substance, or which  is better,  a
moveable point may be obtained by the  intersection of two
threads.   Any points  in the perspective  plane may thus be
found, and transferred to the picture by bringing the part of the
instrument which contains them, into contact with the paper.
   A simple and very useful  perspectograph may be made by
erecting a pane of glass upon one end of a board, or short ta-
ble, and a moveable piece with an  aperture for the eye at the
other end. *   The moveable piece is to be fixed at any conve-
nient distance, and the object  is to be viewed from it, through
the pane of glass.   The  outlines, as they appear, are  traced
upon the glass with a stick of wax sharpened like a crayon, and
they may be afterwards rendered very plain, and transferable,
by sprinkling them with any black powder.
   The  geometrical and mechanical  methods which have been
described,  will enable a person not previously conversant with
the art, to obtain correct perspective representations of any ob-
ject.   But  by long practice, in drawing from nature, a  certain
tact is acquired by painters, which enables them by the accura-
cy of the eye and judgment  alone, to make correct views of
objects, without the aid of any  computation or mechanical pro-
cess.  Thus minature painters  produce the nicest resemblance
of the human  countenance, in any position, with no other guide,
than the faculty obtained by experience, of estimating the ex-
act shape and proportion, which each part of the original should
bear upon the picture.
   Projections.—The  projections of a body, are the different
modes by which it may be delineated on a plane surface.   That
which has  already been described, is called the scenographic
projection, and represents objects as they actually appear to the

   * No method fixes the eye so effectually, as to rest the teeth upon a solid,
or fixed body. 
             ARTS OF  DESIGNING AND PAINTING.           81

 eye, at limited distances.   The orthographic projection repre-
 sents objects as they would appear to the eye at an infinite dis
 tance, the rays which proceed from them, being parallel, instead
 of converging.   The  shadow, which a body casts in the rays
 of the sun, may  be considered  as  an  orthographic projection.
 In this projection, lines which  are parallel in the  original, are
 parallel in the picture, and do  not converge to  any vanishing
 point.  Their comparative length, also, is not affected by dif-
 ference of apparent distance.   The orthographic projection is
 much used  in delineating buildings, machinery, &c,  because
 those parts of the drawing which are not foreshortened,  main-
 tain their true relative size, so that  measures can be taken from
 them.  In PI. III. Fig. 7, No. 1 is the scenographic,  and No 2,
 the orthographic projection of a cube.   In  addition to these,
 the term ichnographic projection, is sometimes used to express
 the horizontal delineation,  or  ground plan  of an object.  A
 birds' eye view is a scenographic or orthographic projection, ta-
 ken  from  an elevated point in the air, from which  the eye is
 supposed to look down upon the objects.
   Isometrical Perspective.—This name has been introduced by
 Professor Farrish, to express a  kind of drawing peculiarly con-
 venient in delineations of machinery, and bodies of regular fig-
 ure.  It is a species of orthographic projection, in  which three
 planes, at right angles with each  other, appear similar and equal.
 An idea of it may be formed, by supposing a cube to be  so
 placed, that one of its angles will appear in the  centre, while its
 outline will be a true hexagon.    In this projection, the  sides  of
 the cube appear  equal, and all sections of the  cube parallel  to
 either side, will also be equal.   All right angles  are represent-
 ed by angles of 60 degrees, or  the supplement of  60 degrees.
 All circles  parallel to either of the  three planes,  will  be repre-
 sented by similar  ellipses.   Figures not parallel to either of the
planes, may be calculated by easy  rules.   It is  therefore the
 easiest and most expressive  kind of drawing for the  wheelwork,
axles, and  regular frames of machinery;  for philosophical in-
               11 
S2
ARTS  OF DESIGNING  AND  PAINTING.
struments, and for many architectural designs. *   In PI. III. fig.
9, is an isometrical view of a cube, with circles inscribed on its
sides, and the axes of those circles projecting a short way.

                      CHIARO OSCURO.

  Next to correct perspective, the most important circumstance
in painting, is the correct distribution of light and  shade.   To
the skilful management of these, we are indebted for the strength
and  liveliness of pictures, and what is technically called  their
relief, or the elevation which certain parts  appear to assume
above the plane upon which the picture is.made.
  Light and Shade.—Light and shade, as  they  appear  to us
upon natural objects,  are the consequences of the  rectilinear
motion of the rays cast upon  them by luminous bodies.   If an
object  be exposed to the rays of  the sun, or of a single  lamp
or candle, those parts or surfaces which are  presented directly
to these rays, become strongly illuminated, and acquire a lighter
cast approaching to white.   Those surfaces which  stand ob-
liquely to the light, receive less of the rays,-and of course have
a deeper tinge.   Those lastly, which are averted from the  light,
and  receive no rays but such  as are reflected to them from oth-
er objects, acquire  a very dark shade, approaching, when  con-
trasted with the others, towards black.
  The distribution of light and shade upon  any object, is always
proportionate and  correspondent  to its shape.   An even or
plane surface, exposed to the sun's rays, will be equally illumi-
nated  throughout, since  whatever  be its position, its parts will
all make a similar angle with the rays.   But uneven or irregu-
lar surfaces  will be unequally illuminated, the prominent  parts
receiving most light, and  the depressed portions most shade, an
effect  which will be  increased, if the light falls  obliquely or
sideways.   If the irregularities of surface be sharp and strong,

  * For the principles of isometrical drawing, see the Cambridge Philosophi-
cal Transactions; or Gregory's Mathematics for Practical Men, p. 179. 
             ARTS  OF DESIGNING AND PAINTING.           83

 the  changes from light to shade, will be sudden, and the con-
 trast great.   On the other hand, if they are smooth and round
 ed, the transition will be soft and gradual.
   Association.—As bodies are never seen, except when they
 are illuminated, the manner in which light and shade are distrib-
 uted upon  them, forms by association a part  of our  ideas  of
 their shape.   Painters have learned to imitate this arrangement
 of light and shade, by varying  the  quantity  and  intensity  of
 their coloring substances, so as to produce in the  mind the same
 associations of shape from a plane surface,  as would arise from
 the falling of light on the original object itself.   This  art con-
 stitutes  what is technically  called the chiaro oscuro, from the
 Italian  words signifying clear and obscure.   Next to perspective
 it is the most important part of painting, and there are many
 cases in which perspective alone would wholly fail to convey to
 us a correct idea  of the form of objects, were it not assisted by
 appropriate  insertion of lights and  shades.  Thus a circle,  a
 sphere, and a cone  viewed vertically, may all have  the same
 perspective outline; but their  difference of  figure becomes ap-
 parent, as soon as  we consider their distribution of  light  and
 shade.
   Direction  of Light.—The most, distinct perceptions of shape
 are  produced when the  light falls in  one direction, e. g. when
 it is  received immediately from the sun, or from a single win-
 dow or  candle.  The distinctness of an object is  always  im-
paired,  when it is situated between cross lights, or when it is il-
luminated by .a variety of windows or candles on  different sides
of the room.   An object may even be so surrounded with lights,
that it shall be impossible  to discover  its exact shape.   Its out-
line indeed will be  discernable, but  the  equal illumination on
all sides, will exclude the existence  of shadow, and of course
 we shall lose the  power of appreciating  the comparative dis-
 tance of its  parts from the eye.  In most paintings, we find
that  the principal mass of light falls in one direction.   An  ob-
lique or a sideway direction, is most common,  though  a front,
and  even a  back light, is managed to produce  very striking 
S4
ARTS  OF DESIGNING AND PAINTING.
effects.  Painters also exercise their skill with the introduction
of cross lights, from different windows, or lamps ;  but the suc-
cessful  execution of a piece of this sort is more difficult, than
with a single light.
   Reflected Light.—Owing to the reflection which takes place
from all terrestrial bodies, we find that objects, in most situations,
have  not only a principal or  direct light, but also a secondary
or reflected one.  Hence the darkest part of globular and cy-
lindrical bodies, is not that which is most remote from the orig-
inal  light.   This part  receives from the reflection of objects
beyond it,  a faint illumination,  so that the darkest  part will be
found between it and the part on which the light directly falls.
See the sphere represented PI. III. Fig. 4.
   Sharp lights, or such  as are intense and sudden, indicate pol-
ished surfaces, and are employed to represent them.   Where
they are accompanied by very  deep shades, they express great
elevation  above  the  common  surface.   Faint  lights,  on  the
contrary,  imply a dull surface,  obscure illumination, or  small
elevation.
   Expression of Shape.—Light and shade,  are not adequate, in
all cases, to give us certain indications of the forms of bodies.
Surfaces which  appear concave in one direction of the  light,
may appear convex, if the light is introduced from  the opposite
side.   In contemplating an undulating object, like a curtain, or
its picture upon paper hangings,  we are often at a loss to dis-
tinguish the elevated, from  the depressed  portions; and by a
little effort of the imagination, we can persuade  ourselves that
a particular part is at one  time elevated, and  at another,  de-
pressed.   Cameos and intaglios maybe mistaken for each oth-
er, and any of the figures [PI. III. fig. 4.] may appear promi-
nent or depressed, in the same  part,  by reversing the direction
in which the light is supposed to strike upon them.
   In  cases of this sort, our  final ideas of shape  are derived,
not only from the object  itself, but from its relations with con-
tiguous objects. 
            ARTS  OF DESIGNING AND PAINTING.           85

   Eyes of a Portrait.—The influence which the association of
contiguous objects has upon our ideas, is strikingly exemplified in
the eyes of a portrait.   We estimate the direction of the eyes,
not only from the  position of the ball in regard to the eyelids,
but also from the relative position of the remaining features of
the face.   Dr  Wollaston  has shown, that the  same  eyes in a
picture, which looks at us, may be made to appear averted from
us, if we apply new features to the lower  half of the  face.
[PI. III. Fig. 3.]  The reason, why  the eyes of a portrait ap ;
pear to follow us, in all parts of the  room, is simply, that the
relative position of the features cannot change, so that if the
picture appears to look at us once, it  must appear to look at us
always.   If we move  to one side of a portrait,  the change,
which  happens, is  unlike that which would take place in a bust,
or living face.  The picture is merely foreshortened, so that we
see a narrower image of a face, but it is still that of a face look-
ing at us.  And if the  canvass be transparent, the same effect
takes place from the back of the picture.
   Shadows.—Shadows are cast in the direction opposite to that
by which we suppose  the light to enter, and their  introduction
in pictures, always heightens the effect.   A  painted  object, is
relieved, or raised from the surface, by the expression of light
and shade on itself.   But the relief is greatly increased, if the
shadow which it makes on the ground, or other surface, be also
introduced.   Shadows are commonly softened off at the edges,
or terminate gradually.  When, however, the light is strong, or
the shadow very  near to the  object, its termination  is more
abrupt.
   Aerial Perspective.—This name is given by painters, to the
mode  of producing  the effect of distance, by a diminution in
the distinctness and brightness of objects,  according to their
remoteness  from  the  eye,  and the  condition of the  medium
through which they are seen.   It is well known, that distant
objects appear  indistinct, and of a greyish or bluish tinge, from
the effect produced by the intervening atmosphere.  Their in-
distinctness is increased, if the atmosphere is hazy.  Their ap- 
86           ARTS OF DESIGNING AND  PAINTING.
pearance is also  modified by the degree of their illumination,
and by  the  character of the light  which falls on them.   The
painter,  therefore, finds it necessary to consider the  depth of
atmosphere which is  interposed between him and his object,
the condition of this atmosphere, and the quantity and color of
the light which falls on it, and on the  objects.   A want of at-
tention to these circumstances,  gives  rise to the defect called
hardness in painting.

                          COLORING.

   By the aid of perspective, and the chiaro oscuro alone, very
good representations of objects may be obtained.   All our com-
mon  engravings, wood  cuts, drawings in Indian ink, in black
crayons, he., derive their expressiveness from these only.  But
a still nearer approach to the appearance of nature, is made, by
the employment of colors  analogous to those which  are found
to exist in the objects represented.
   Colors.—From the science of optics, we learn that the solar
beam is  divisible into seven primary colors, white being the mix-
ture, and black the privation of all of them.   These colors,
are violet, indigo, blue, green, yellow, orange, red.*    Three of
these are capable of producing all the rest, by their intermixture
and degree, viz. blue, red, and yellow.
   The color belonging to  different natural objects, was suppos-
ed, by Newton, to be occasioned by a power which  their  sur-
faces possess, to reflect  certain  rays, while they absorb all  the
rest.   This power is so infinitely diversified in nature, that we
find not only every kind of primary ray  reflected, but likewise
every possible  tint, and  intermediate grade, which can be  pro-
duced by the admixture of two  or  more original colors.   To

  * Dr Wollaston found the spectrum formed in looking through a prism at a
narrow line of light, to consist of four colors, red, green, blue, and violet with
a narrow stripe of yellow.  The three  simple  colors, red, green, and violet,
may produce yellow, by the admixture of red and  green; crimson, by red and
violet; blue, by green and violet, and white by the combination of all three 
ARTS OF DESIGNING AND PAINTING.
87
represent  these various hues, it is necessary  that the painter
should possess coloring  substances  analogous to thein all, or
capable of producing them all by mixture, and that he should
apply them in such a manner, that the true color may remain
distinct, independently of the lights and  shades necessary to
place the  objects in relief.
   Shades.—In a colored  painting of an object  which has any
rotundity  of form, there are usually, at least, three tints, or de-
grees of  color.  These are the light, the middle tint, and the
shade.  Of these, the middle tint is the one which represents
the true color of the object, and occupies an intermediate situ-
ation between the light and shade.  Thus in  the painting of a
red fruit,  for instance the cherry, the middle tint is Vermillion,
or some  similar color, being that which the surface of the fruit
would have, if it were perfectly flat.  The  part of the fruit
nearest the light,  has a very bright  color partaking  of white,
while the remote  parts are  shaded  with lake or some darker
red.  In  like manner, a yellow fruit, like the lemon, has not
only the true color of  the rind, but is lightened at the top with
straw color or white, and shaded with brown toward the edges.
It is necessary that the colors used for dark shading, should be
in some degree correspondent with the middle tint, and not di-
ametrically opposite to  it.   Thus, in  single objects, yellow
cannot be shaded  with blue, nor red with green.
   Tone.—Pictures differ from each other in the  respective
depth of  color, which pervades the whole  piece.  The  word
tone, borrowed from the art of music, signifies in painting, the
peculiar  cast, or governing hue, which  a picture, or a  color,
possesses.  Thus  if dark  masses of color, with feeble lights,
predominate,  the  piece has a deep or  low  tone, while if the
reverse exists, a bright or light tone is produced.   It is essen-
tial  to  harmony that a  picture  should  have  the same tone
throughout, or that its  lights  and shades  should  correspond in
their intensity to the tone  which governs the whole.
   Harmony.—When  different objects are grouped together in
the same  view, each one possesses two kinds of color, the  orig- 
88
ARTS OF DESIGNING AND PAINTING.
inal color, and the adventitious.  The original color, often called
among painters the local color, is that which belongs to the object
itself, independent of situation.  The adventitious color, is that
which is reflected upon it from neighboring objects, and which
of course depends upon situation.  For example, the color of
the human face is that which we call flesh color, and, if painted
alone, may be represented  by  the shades of that  color.  If,
however, it is  surrounded  by a purple  drapery, it  receives a
purplish tinge, and requires to be so represented.   In like man-
ner, a yellow  dress  communicates to it a  yellowish cast, &tc.
An attention to this adventitious coloring, combined  with a uni-
formity of tone, constitutes the basis of what is technically called
harmony in painting.  Harmony requires that strong and glaring
colors should never be forcibly contrasted  with each other, but
that each object should  partake at its  edges of a certain portion
of the color which  predominates in  objects near to it.   This
rule not only produces  effects most grateful to the eye, but an
observance of it  gives,  in fact, the only true  representation of
nature.
   Contrast.—Colors are divided by painters, into the warm and
the cold<   Warm colors are  those in which red and yellow pre-
dominate.   Cold colors  are blue, grey, and others  allied to
them.  Neutral colors are intermediate tints, or mixtures.  Of
the various pigments or  coloring substances, which painters em-
ploy,  none have  the genuine brilliancy of the prismatic  rays ;
and all  fall short  of the  hues produced by nature in living ob-
jects.   The petal of a  flower, the feather of a  bird, and  the
wing  of an insect, are  tinged with a  richness  and splendor,
which no factitious  colors can  equal.   Painters can only  ap-
proach, when  necessary, towards the  brightness of  natural col-
ors, by  availing  themselves  of the effect of contrast,  and by
heightening one color by the introduction of others,  which pre-
pare the eye for its more perfect and  favorable reception.
   Remarks.—The power of giving true representations of ob-
jects, is derived, originally, from an attentive study of the colors
and  appearance  which  they actually exhibit in  nature ;  after- 
             ARTS OF DESIGNING AND PAINTING.          89

wards from a comparison of the success of different artists, and
an attention to the means they have employed.  What belongs
to the philosophical part of painting, can hardly be said to extend
beyond the correct imitation of nature.   But the inventive part,
the  design and composition of great pieces,  such as have not
necessarily any originals in nature, requires not only philosophic
accuracy, and practical skill, but also demands original genius,
strength and  fertility of imagination, and a strong perception of
sublimity and beauty, whether natural or  moral.  To paint a
portrait, or a landscape  from nature, requires no more than a
faculty of correct imitation.  But to express on the canvass a
scene of history or of  fiction, to create forms of ideal beauty
exceeding the realities of life, and to express, by attitudes and
lineaments,  passions,  which  tell the  events they  accompa-
ny,—this  excellence is attained by few ;  it is not to be taught  by
any rules of  art, but,  like poetry, and eloquence, it is within the
reach of those only, whom a strong and exclusive interest in the
pursuit, has qualified to feel deeply, and to express powerfully.

  Note.—For the modes of painting in water, oil, fresco- he.,
also for coloring substances, see Chapter XVIII.
  Malton's Treatise on Perspective, fol. 1779;—Priestley's In-
troduction to Perspective, 8vo. 1770;—Wood's Lectures on Perspec-
tive, with an Apparatus, 1809;—Blunt's Essay on Mechanical Draw-
ing, 4to.  1811;—Lucas's  Progressive  Drawing Book, Baltimore,
1827 ;—Burnet, on Light and Shade, 4to. 1827;—Burnet, on Color-
ing, 4to. 1827 ;—Vallee, Traite de la Science du Dessin, 4to. Paris,
1821;—Millin, Dictionnaire de Beaux Arts,  3 torn. 8vo. 180G;—El-
sies's'Dictionary of Fine Arts, 8vo. 1826;—Works of Sir J. Reynolds,
—Oris,—Fusejli,—Barry,—West,—De Piles, &c. &c.   .
12 
CHAPTER V.
         ARTS OF ENGRAVING AND LITHOGRAPHY.

  The arts of engraving and lithography, bear the same rela-
tion to drawing, that the art of printing does to that of writing;
the first being intended for the expression of original designs,
the latter for the multiplication of copies of the  design, when
made.

                        ENGRAVING.

   Origin.—The origin of copperplate engraving, appears to
have been in the fifteenth century, previously to which  time it
was probably unknown.   The first inventors of engraving, were
the goldsmiths, who, from the habit of marking ciphers and lit-
tle devices on their wares, acquired a dexterity and despatch in
the use of the graving tool, and at the same time, a power of
producing subjects of such neatness and  delicacy, that a desire
was naturally excited in them, to preserve and increase the pro-
ducts of the  art, by transfering  them to  paper.   This  object
was  effected by the use of a  suitable  pigment, and the aid of
the rolling press.
   Materials.—Common engraving differs from printing,  in hav-
ing its  subjects or devices cut into, or below, the surface of a
metallic plate, instead of  being  elevated or raised  above it, as
in types, and wood cuts.    For the purpose of engraving, a va-
riety of metals have been employed, and various  combinations
or alloys.  Copper has, however, been  selected  by common
consent, as uniting the  greatest number of desirable qualities ;
having  sufficient softness to permit it to be cut when cold, and
sufficient  hardness and tenacity, to resist the action of the press, 
          ARTS OF ENGRAVING  AND  LITHOGRAPHY.        91

and the wearing of continued  friction.   A plate  of the  best
copper is selected, about one fourth of an inch thick, having one
side finely polished, and its edges rounded, to prevent it from cut-
ting the  paper.   The engraver works opposite to a window,  hav-
ing a screen interposed to soften the light, and the plate placed on
an oblique table in the  most convenient position for  seeing.
   Instruments.—The  instruments employed in the practice of
the art, are the following.   1.  The graver.  This is a small
steel bar,  of a prismatic form, having one end attached to an
oblique handle, and the other  ground off obliquely, so as to
produce a sharp point at one angle.   In working, this  instru-
ment is held in the palm of the  hand, and pushed  forward, so
as  to cut  out  a portion of the copper.  2. The dry point.
This is  a  strong bluntish needle, fixed in a handle, and intend-
ed for drawing the finer lines.   It is held in the fingers, in the
same way as a pen or pencil.   3.  The scraper, a triangular
instrument,  with concave sides, and sharp edges, intended for
removing  or scraping off portions, which  are accidentally raised
above the surface.   4. The burnisher.  This is merely a blunt
smooth tool, for rubbing out blemishes, and smoothing the sur-
face of the copper.   Various  kinds of varnish,  rosin, wax,
charcoal,  and mineral  acids, are also employed in different parts
of  the  operation, according to the subject and  the  style of en-
graving which is adopted.
   Styles.—The principal  varieties, or styles, of engraving on
copper, are the following.   1.  Line engraving.  2. Stippling.
3.  Etching.   4. Mezzo tinto.   5. Aqua tinta.  Lithography,
and some  other modes of  multiplying  designs, are imitations
and substitutes, rather  than  species of engraving. *
   Line Engraving.—Line  engraving, called  by the  French,
Gravure en taille douce, is one of the most common species of
engraying;  and  though  less elaborate than the second mode,

  * Musical characters  are  sometimes  executed in a mode different from all
these, by making impressions with a punch upon  pewter, or some  other soft
metal. 
02       ARTS OF  ENGRAVING AND  LITHOGRAPHY.

has produced most of the finest and boldest specimens of the
art.   In this species, the surfaces  and  figures, the lights and
shades, are produced by the multiplication of minute lines, cut
in by the graver and dry point, approaching each other so near-
ly, that the inequality produced by the admixture of black and
white, does not offend the eye, nor  interrupt the harmony of
the piece.   The effect and beauty of line engravings, depends
much upon the smoothness of the lines, their gradual  swell and
decrease, and their  evenness or parallel situation.
   For engraving in  this manner, the artist transfers the outlines
of his original  drawing, by tracing them with black lead, on an
oiled paper,*  and  afterwards passing this  paper through the
press  in contact with  the copperplate,  which is previously
covered with  a  thin  coating  of wax.   A  sufficient  quantity
of the lead adheres to the copper, to enable  him to  engrave
the outlines with great accuracy.   The graver is then held in
the palm of the  hand, and pushed forward with a strong but
steady and regular motion until a line is completed.   The  gra-
ver by its operation, removes a thread of copper from the  line,
and at the  same time raises the surface on each side of it, form-
ing what is called a  burr.   This burr  is subsequently  removed
by the process of scraping and burnishing.   After the outlines
are finished, the dark surfaces are introduced by means of close
parallel lines cut in,  in the same manner as before.   Gradations
of light and shade are produced by the gradual and simultane-
ous tapering of all the lines which constitute the dark portions,
and the softness and regularity with which this is accomplished,
greatly  affects the beauty of the piece.  Very dark shades are
produced by lines crossing each other, either in squares or lo-
zenges, which are varied according to  the nature of the subject.
Very light shades, on the contrary, are left  untouched, or cov-

  * Paper rendered transparent with spermaceti, is useful in tracing figures
with a lead pencil.  If paper be varnished with a mixture of Canada balsam,
and oil of turpentine, very distinct lines may be traced on it with the dry
point only, and these  may be again transferred, by varnishing the copper, and
tracing them  upon it, through the paper. This method is now much employ-
ed by engravers. 
          ARTS OF  ENGRAVING AND LITHOGRAPHY.       93

ered with broken lines.   Lines which swell or taper, are first
cut of a uniform size, and afterwards deepened by a second or
third stroke of the graver.  Mistakes or blemishes, are erased
from the plate, either by burnishing, with the proper instrument,
or by rubbing with charcoal.
   Stippling.—The  second  mode of engraving, is that called
stippling,  or engraving in  dots.   This  resembles the last men-
tioned method in its processes, except that instead  of lines, it is
finished by minute points or  excavations in the copper.  These
punctures when made  with the  dry point, are circular, when
made with the graver, they are rhomboidalor triangular.   The
variations and  progressive  magnitude of these dots, give the
whole effect to stippled  engraving.   This style of work, is  al-
ways more slow, laborious, and of course more expensive, than
engraving in  lines.    It has, however, some  advantages in the
softness and delicacy of its  lights and shades, and  approaches
nearer to the  effect of painting, than the preceding  method.  A
more expeditious way of multiplying the dots, has been contriv-
ed in the instrument called a roulette, a toothed wheel, fixed to
a handle,  which by  being rolled  forcibly along the copper pro-
duces a  row of indentations.  This  method, however, is less
manageable than  the other, and  generally produces a  stiff
effect.
   Etching.—Etching is  the third  mode of engraving, and is
performed by chemical corrosion.   It is  apparently the easiest
mode of engraving, requiring least practice in the operator.   In
fact, any person who can  draw, may etch coarse designs toler-
ably well, after having acquainted himself with the  theory only.
Hence we find that engineers, naturalists, surgeons, he. some-
times etch their own plates,  especially of light subjects.
   A plate  for etching,  is prepared in the same  manner as for
common  engraving.   It is then  covered throughout its whole
surface, with  a very thin coating of varnish made of wax, mas-
tic, and asphaltum ;  sometimes of rosin, and animal  oil, or of
linseed  oil inspissated  by  boiling.   This  varnish is  black-
ened  by  the  smoke  of a lamp, in order  that the operator 
94       ARTS  OF ENGRAVING AND LITHOGRAPHY.

may see the progress and state of his work.   The instrument
used  in  etching, is a needle, resembling the  dry point, but  of
different sizes, according to the nature of the work.  The plate
being  prepared, the operator  supporting his  hand on a ruler,
begins to make his drawing with the needle in the coat of var-
nish, taking care to penetrate always to the copper.   In the use
of the needle, those  lines which require to be deepest,  must
have the greatest force bestowed on them, but it  is not possible
to produce so perfect  an  effect in this way, as by incisions  of
the graver.  After the design is completed, the  operator  pro-
ceeds to the second part of the process, the corrosion, or as it
technically called biting in.  For this purpose, the plate is sur-
rounded with a wall of  soft wax, to  prevent the escape of fluid
from  its surface.   A quantity of diluted nitric  acid,  is  then
poured upon it, and suffered to remain for some time.   A chemi-
cal action immediately takes place in  all the lines or points where
the copper is denuded by the  strokes of the needle, while the
rest of the surface is defended by the varnish.   In the mean
time, the operator brushes the surface frequently, with a feath-
er, to clear away the bubbles and saturated portions of the met-
al.   After  the first biting is continued for a  sufficient length  of
time in the judgment of the operator, the acid is poured off and
the plate examined.   The light  shades, if found sufficiently
deep, are then covered  wTith varnish, to protect them from fur-
ther  action of the acid, or as it is technically called, stopped
out.   The biting is then continued for the second  shades, which
are next stopped out, and these processes are alternately repeat-
ed till  the piece is finished.   The plate is then freed from var-
nish, by melting and  wiping it, and  cleansed by  washing  with
oil of turpentine.  It must, in this state, be  carefully examined
or proved, and any deficiencies in the linesrowing to the  acci-
dental presence of varnish, must be finished with the graver.
The plate is then ready for the press.
   The productions of the etching needle, can never have the
smoothness and beauty of mechanical engravings.  Notwith-
standing all the care which may be taken, the lines  will  have 
          ARTS OF ENGRAVING AND LITHOGRAPHY.       95

an  irregularity and roughness, owing to the unequal  action of
the acid.   There are, nevertheless, subjects, to which this very
irregularity renders etched work peculiarly suited.  Those ob-
jects which in nature are rough, and  coarse, are well represent-
ed by this species  of engraving.   The trunks  of trees, broken
ground, rocks, walls,  cottages, Sic, especially when  executed
on a large  scale, receive a more natural aspect from the rough
effect of etching than they could  do without great  labor  from
the softer touches  of the  graver.  In landscape  engraving we
commonly find a mixture of methods, the  coarser parts being
etched, while objects of more delicacy are  cut with the graver.
Letters and written characters, are mostly cut, and but seldom
etched.
   Mezzo  Tinto.—Engraving in  mezzo tinto, or mezzotint, is
the fourth species.   This method is the  reverse of all those
hitherto  mentioned, and consists in bringing up lights from a
dark ground.  The mezzo tinto w% invented by Prince Ru-
pert, in 1649.  Since his time, it has been greatly improved,
and though not calculated for  general use, it has been applied
to various subjects with great success.   For engraving in mez-
zo tinto, the whole surface of the copperplate is first roughen-
ed  or covered with minute prominences and excavations, too
small to be obvious to the naked eye;  so that if  an impression
be taken from it in this state,  it has  an  uniform  velvety black
appearance.   This roughness is produced mechanically, by the
operations of a small toothed instrument denominated a cradle.
This instrument by continual turns and  impressions, which oc-
cupy a great length of time, gradually breaks up  and  produces
an uniform roughness on the whole surface of the plate.  That
the ground, as it is called, may be of the requisite fineness, the
operation must be repeated a considerable number  of times,
the position of the plate in regard to the instrument, being va-
ried each time.  This  is the  most  tedious part of the  labor.
When the plate is prepared, the rest of the  process, to a skilful
engraver, is easy,  when compared with cutting or  stippling.
It consists in pressing down or rubbing out the roughness of the 
9G        ARTS  OF ENGRAVING AND LITHOGRAPHY.

plate, by means of the burnisher and  scraper, to the extent of
the intended figure, obliterating the ground for lights, and leav-
ing it for shades.   Where a strong light is required, the whole
ground is erased.   For a medium  light it is moderately burn-
ished, or partially erased.   For the deepest shades, the ground
is left entire.   Care is taken to preserve the insensible grada-
tions of  light  and shade upon which the effect and harmony of
the piece essentially depend.
   Engraving in  mezzo tinto, approaches more nearly to the ef-
fect of oil paintings than any other species.  It is well calculat-
ed for the representation of obscure pieces, such as night scenes,
he.   Some individuals have applied it with good success to the
engraving of portraits.   The principal  objection to the  method
is, that the  plates  wear out  speedily  under  the press, and of
course yield a comparatively small  number of impressions.
   Aqua Tinta.—Engraving in aqua tinta, is  the only remain-
ing mode.   This  is  doneby  a process partly  chemical,  and
partly mechanical.  It consists in producing chemically,  a rough
ground  covering the surface of the figure to be engraved, and
afterwards  introducing  the  lights  and shades by mechanical
means.   It  may, however, be executed  by a process  wholly
chemical.   For engraving in aquatint, the surface of the copper,
after having the  outline  engraved or etched in the usual way, is
covered  throughout with minute particles of resin, invisible  to
the naked eye,  detached from each other and adhering to  the
surface of the metal.   This process, called laying the ground,
is effected in different ways.   One method, is to  inclose a quan-
tity of finely powdered rosin or mastic, in a flannel,  or linen
bag.   This is held at a certain height above the  plate, and  beat
with a stick.  A fine cloud of dust issues from the bag, and set-
tles upon the  surface of the plate, with the same uniformity as
the dust of  the atmosphere settles upon furniture in dry  weath-
er.   This  dust  is fixed to the surface, by heating the plate till
the resin melts.   The ground is thus laid.   A second mode, is
to cover the plate with a coat of very thin spirit varnish  prepar-
ed for the purpose.  This varnish is so  fluid, or contains so little 
           ARTS OF  ENGRAVING AND LITHOGRAPHY.        97

 resin, that when it dries  by the evaporation of the spirit, the
 whole surface breaks up, or cracks into an  infinite number of
 particles, all adhering to the  plate.  After the ground is com-
 pleted, the vacant parts of the plate, or those not intended to
 be occupied by the figure, are stopped out;  i. e. covered  by a
 thick  varnish, impenetrable to acid.  The plate  is now sur-
 rounded by a wall of wax,  as for  etching, and diluted nitric acid
 is poured on.   A  chemical action immediately commences in
 all the interstices between the resinous particles ; and the face of
 the plate, for the desired extent, is converted into a porous sur-
 face, made  up of little prominences  and excavations.   The
 fighter shades  are stopped out at an early stage of  the process,
 and the corrosion continued for the dark ones.  After the plate
 is judged to be sufficiently bitten in,  it is cleaned and proved by
 an impression.  If the  ground is good, i. e. not too faint, too
 coarse, or too  uneven, the work  is then finished by burnishing
 the shadings to give them greater softness, and if necessary, by
 cutting deep lines or dots in the darkest parts.
   Engraving in aqua tinta has the greatest resemblance to paint-
 ings in water colors, or in India ink.   When well executed, the
 white points  which diversify the surface, are nearly invisible to
 the naked eye, so  that a uniform surface  is presented.  The
 art was first invented by a Frenchman, by the name of Leprince,
 who for some time kept his art a secret, and sold  his impres-
 sions for original  drawings.   It is a mode  of engraving well
 adapted to light subjects,  sketches, landscapes, &c, and  for
 subjects of which only a few copies or impressions  are wanted.
 Owing to the fineness of the ground, the plates wear out rapid-
 ly, and seldom yield, when of the ordinary strength, more than
 600 impressions.
   Aqua tinta is the most precarious kind of engraving, and re-
 quires much  experience  and attention on the part of the artist,
 to  succeed well.  If the ground is laid too  thick,  or too thin,
 the result is imperfect.   If the corrosion  by  the  acid  is not
continued long  enough,  the ground is too faint; if continued
loo long, the acid acts laterally, and destroys the whole surface,
               13 
98        ARTS OF ENGRAVING  AND  LITHOGRAPHY.

It is often necessary to repeat the whole  process, and to go
through the operations of laying the  ground, stopping out, and
biting, a number of successive times, before  a ground is obtain-
ed of sufficient strength and regularity to answer for the press.
   Copperplate Printing.—Copperplate printing is performed
by means of a  rolling press,  in which the plate and paper are
strongly compressed together between a cylinder of wood and
a sliding platform.   The ink employed for copperplates, is made
of a carbonaceous substance called Frankfort black, and linseed
oil, inspissated by boiling.   Oil must be used, instead of water,
that the ink may not dry during  the process ; it is boiled till it
becomes thick and viscid, that it may not spread upon the pa-
per.   Previously to  the operation,  the paper is wet, as  for
printing with types.   The printer having warmed his plate over
a bed of coals, proceeds to cover its surface with ink by an in-
strument resembling a printer's roller.   When the cavities of the
engraving are thoroughly charged with ink, the smooth surface
of the plate is wiped as clean from ink as possible.  The latter
part of the wiping is always performed by the palm of the hand,
aided by a little dry  powder,  commonly whiting.   The ink re-
mains only in the crevices of the engraving, into which the hand
does not  penetrate in wiping the surface.  The plate is next
laid on the sliding  plank, with its face upward, and the paper
laid upon it.  An elastic substance, commonly folds of woollen
cloth, is placed above and below.  A turn of the cylinder car-
ries the plate under a very strong pressure, by which  portions
of the paper are forced down into all the cavities of the engrav-
ing.   The ink, or a part of it, leaves the copper and adheres
to the paper, giving an exact representation of the whole en-
graving.
   Colored Engravings.—Colored engravings, are variously
executed.  The  most common, are printed in black  outline,
and afterward painted separately in water colors.   Sometimes
a surface is produced by aqua tinta,  or stippling, and different
colors  applied in printing  to different  parts, care being  taken
to wipe off the colors in opposite directions, that they may not 
          ARTS  OF ENGRAVING  AND  LITHOGRAPHY.       99

interfere with each  other.  But the most perfect, as well as
elaborate productions, are those which are first printed in colors
and afterwards painted by hand.
   Steel Engraving.—The process of steel engraving, intro-
duced by Mr Perkins, depends on the  property, which steel
has, of being softened, by losing a part of its carbon ;  and af-
terwards of being hardened, by regaining it.  If a steel plate,
prepared  for engraving, be inclosed in a box with iron filings,
and  exposed to  a white heat for some hours, the surface loses
a portion of carbon and becomes sufficiently softened to be cut
with the graver.   If then-the plate, after being engraved, is re-
exposed to heat in a box with animal charcoal, the surface be-
comes again carbonated, and an engraved steel plate is thus ob-
tained.
   The great advantage of steel plates, consists in their hard-
ness, by which they last for an indefinite time, and yield an al-
most unlimited number of impressions; whereas a  copperplate
wears out after two or three thousand impressions, and even much
sooner, if the engraving be fine.   An engraving on a steel plate,
may be transferred in relief to a softened steel cylinder, by pres-
sure ; and this cylinder, after being hardened, may again trans-
fer the design, by rolling it upon a fresh  steel plate; and thus
the design may be multiplied at  pleasure.
   Steel engraving is of use, where a great number of impres-
sions are called  for; as it saves the  expense of engraving the
plate anew, and  furnishes  copies more exactly resembling each
other, than can be obtained by any other mode.  Of course il
affords the greatest security against counterfeiting.
   Etching on steel plates, is practised with various chemical
agents, one of which consists of a mixture of six parts of acetic
acid, with one of nitric acid.  Another menstruum is made by
dissolving an ounce of  corrosive sublimate, and a quarter of an
ounce of alum, in half a pint of water.
   Wood Engraving.—Engravings in wood, are differently ex-
ecuted  from those  already  described, the subjects being cut
in  relief; so that they require to  be printed in the same manner 
 100      ARTS  OF ENGRAVING  AND  LITIIOGRArilV.

 as common types, and not with the rolling press.   The material
 used is boxwood, which unites the properties of hardness, fine-
 ness, and density.  It is cut across the grain into pieces of the
 height of common types, in order that  the  engraving may be
 made  upon the end of the grain, for the sake of strength  and
 durability.  The surface being planed very smooth, the design
 is drawn upon it with a black lead pencil.   The lines of this
 design are  left  untouched, but the whole of the intermediate
 spaces between  the lines are  cut away with a common graver,
 or chisel.  Wood engravings have the advantage that the blocks
 may be inserted in a page with  common  types,  and printed
 without separate expense.  They are exceedingly durable, and
 may, if desired, be multiplied by the process of stereotyping.

                      LITHOGRAPHY.

   Lithography is the art of taking impressions from drawings
 or writings made on stone, without engraving.
  Principles.—This art is founded on the property which stone
 possesses, of imbibing fluids by capillary attraction, and on the
 chemical  repulsion  which  oil and water have  for each other.
A drawing is first made on stone  with an ink, or crayon, of an
 oily composition, and the surface is washed over with water,
 which  sinks into all the parts  of the stone, not defended by the
 drawing.   A cylindrical roller, charged with printing ink, is then
 passed over the  surface of the  stone.   The drawing receives
 the ink, which is oily, while the other parts of the stone repel it,
 being defended by the water.   The process, therefore, depends
 entirely on chemical principles, and is thus distinct from letter-
 press or copperplate printing, which are mechanical.  On  this
 account, it has, in Germany, been called chemical printing.
   Origin.—The invention of lithography is generally ascribed
 to Alois Senefelder, the  son of a performer at the  Theatre of
 Munich, who  received his education at the University of In-
 goldstadt.   Having become  an  author, and being too poor to
 publish his works, he tried many plans with  copperplates,  and 
          ARTS OF ENGRAVING AND LITHOGRAPHY.      101

 compositions, and accidentally with stone, as substitutes for let-
 ter-press, in order to be his own  printer.   His  first  essays  to
 print  for publication, were some  pieces of  music, executed in
 1796, after which he attempted various drawings and writings.
 The first productions of the art were rude and of little promise.
 Its progress, however, has  been so rapid, that it now  gives em-
 ployment to a vast number of artists, and works are  produced
 which rival the finest engravings,  and even surpass them in the
 expression of certain subjects.
   Lithographic Stones.—As calcareous stones will all imbibe
 oil and  water,  and receive the  action of acids, they are all
 capable of being used  for  lithography.  Those, however, are
 best adapted to the purpose, which are compact, of a fine and
 equal grain,  and free from veins, or imbedded  fossils or crys-
 tals.  A conchoidal fracture is considered a good characteristic.
   The  quarries of Solenhofen, near Pappenheim, in Bavaria,
 furnished the  first plates,  and  none have as yet been found to
 equal them in quality.   They are of a  uniform, pale yellowish
 or bluish white color,  and the fracture is perfectly  conchoidal.
 Generally, the hardest are considered best, provided they are uni-
 form  in texture.  Such  are necessary for fine chalk  drawings,
 while softer  ones answer for ink, or for coarser drawings  in
 chalk.
   In  France, stones have been found near Chateauroux, of a
 similar color to those of Solenhofen, and even harder, and of a
 finer grain, but they are full of spots of a softer nature, so that
 it is difficult to procure  pieces of the necessary  size.   In Eng-
 land,  a stone has been used for lithography, which is found at
 Corston, near Bath.   It is one of the white lias beds, but not
 so fine in grain, nor so close in texture  as  the  German stone,
 and therefore inferior.   In the  extensive limestone tracts of the
 United  States, there is little doubt that future observation will
 bring to light stones of a suitable  character  for lithography.
   To bear the pressure  used in taking  impressions,  a  stone
twelve inches square, should be an inch or two thick; and the
thickness must increase  with the size of the stone. 
102       ARTS OF  ENGRAVING AND LITHOGRAPHY.

   Preparation.—The stones are first ground to a level surface,
by rubbing two of them face to face with sand  and water.   To
prepare them for ink drawings, they are  next  polished  with
pumice stone.  But when they are intended for chalk drawings,
they are merely ground with fine  sand, which has been passed
through a  sieve, and which produces a smooth  and uniform sur-
face, which is grained and not polished, this surface being best
adapted for holding the chalk.
   Lithographic Ink and  Chalk.—For these materials, the union
of several qualities is required, to obtain which, it is necessary
to combine several substances together.
   For lithographic ink,  a great many  different  receipts have
been  given,  one  of the  most approved of which  is  a com-
position made of equal parts of tallow, wax, shell lac, and com-
mon soap, with about one twentieth part of the whole, of lamp-
black.  These materials are mixed in an  iron vessel.   The
wax and  tallow,  are first put in, and heated till they take fire,
after which, the other ingredients are successively added.  The
burning is allowed to continue until the  composition is reduced
about one third.
   Lithographic chalk should have the qualities of a good draw-
ing crayon;  it should be  even  in texture, and  carry a good
point.  The  following proportions are  among  the best.  Soap,
l^ oz.; tallow,  2 oz.; wax, l|  oz.;  shell lac, 1  oz.; lamp-
black, \ oz.   The manipulation is similar to that for the ink.
   Mode of Drawing.—With these materials, the artist proceeds
to work on the prepared  stone, after wiping it with a dry cloth.
The ink being rubbed with warm water, like Indian  ink, is used
on the polished stone, and a gradation of tints  can be obtained,
only by varying the thickness of the lines,  and the  distance at
which they are placed apart.  It is  necessary to mix the ink to
such a consistency, that,  while it works freely, it  shall  yet be
strong enough to  stand perfect, through the process  of printing.
A consistency, a little greater than that of writing ink, is suffi-
cient for this purpose.  The instruments used for drawing with
ink,  are steel pens,  and fine camel's hair pencils. 
          ARTS  OF ENGRAVING  AND  LITHOGRAPHY.      103

   The  chalk will not hold upon the polished stone.   But the
grained stone prepared for chalk, may be drawn upon with the
chalk crayon, as easily as paper.  The  subject may be traced
on  the  stone, with lead pencil or red  chalk, but it should be
done so lightly, as not to fill up any of the grain of the stone.
In drawing, the  degree of pressure of the hand will  vary the
strength of the  tint, and it is  desirable to give the  requisite
strength at once, as the surface of the  stone is a little  altered,
by receiving the chalk, and hence it does not take any addition-
al lines with the same equality.  Practice is necessary to give
a command of the material, as it does not work quite  like the
common  crayon, there being great difficulty in keeping a good
point.  There is also difficulty in obtaining the finer tints per-
fect in the impression; and for the  light tints, the chalk must
be used in a reed, as the metal  port-crayon is too heavy to draw
them, even without any pressure from the hand.   A scraper is
used to correct  errors, and also to produce lights.
   It is necessary to observe that the grain with which  the stone
is prepared, should vary with the  fineness of the  drawing.
 Several pieces of chalk should be prepared to use in succession,
 as the warmth  of the hand softens it.  It is useful to cut the
 chalk to the form of a  wedge, rather than a point, as it is less
 likely to bend in that form.   Small  portions of the point will
 break off during the drawing; these must be carefully remov-
 ed with a small brush.
   Etching the Stone.—After the drawing is finished on the stone,
 as before described, it is sent  to the lithographic printer, who
 proceeds to etch the drawing, as it is called.   The stone is pla-
 ced obliquely on one edge over a trough, and very dilute nitric
 or sulphuric  acid is poured over it.   The degree of  strength,
 which is little more than one per cent, of acid, should be such as
 to produce a very slight effervesence.   The object of this slight
 etching appears to be to produce a chemical, rather than  a me-
chanical change of surface, and it is by some considered super-
fluous,  except "to discharge the alkali of the soap.
   The  stone is now carefully washed, by pouring clean rain
water over it, and afterwards gum water ; and when not too wet, 
 104      ARTS  OF ENGRAVING  AND LITHOGRAPHY.

 the roller, charged with printing ink, is rolled over it in both di-
 rections, till the  drawing takes the ink.  It is then well covered
 with a solution of gum-arabic in water, of about the consisten-
 cy of oil.   This is allowed to dry,  and preserves the drawing
 from any alteration, as the lines  cannot spread, in consequence
 of the pores of  the stone being filled with gum.
   Printing.—When the stone is ready for the press,'the print-
 ing ink  is  applied to it, by means of an  elastic roller, covered
 with leather.  In the lithographic press, the paper is first brought
 in contact with  the stone, and  protected by a tight cover  of
 strong leather.   The whole is then passed  under the edge of
 a blunt wooden  scraper, which is powerfully pressed down by a
 double lever, and thus every part of the  paper is successively
 brought into forcible  contact with  the stone, and an accurate
 impression received of the drawing.    The ink is then reapplied
 to the stone, and the process repeated for each impression.
   Printing Ink.—This is composed, as other printing inks are,
 of oil-varnish, and fine lamp black.    To prepare the varnish, a
 vessel is  about half filled  with pure linseed oil, and heated till
 it  takes  fire from the flame of a piece of burning paper.   It
 should then be  allowed to burn, till it is reduced to the degree
 of density required.
   Remarks.—The great distinction of lithography  from en-
 graving is, that  it gives  a  fac-simile of the original drawing,
 which  retains the freedom and touch of the artist's own hand,
 while, on the contrary, an engraving must be a  copy.   This
 character in a lithographic print, arises from the  facility with
which  the  drawing is produced, as the process is exactly  that
 which  the  artist would follow, in making a common drawing.
 A further advantage, derived from the same cause, is, that the
 drawing  being made at once on  the  stone, the  whole  expense
of engraving is saved.
   The more  finished drawings in ink, however, have  not the
same advantages, for the  gradations can only be obtained by the
variations in the  breadth and the distance of the lines, which is 
          ARTS OF ENGRAVING  AND  LITHOGRAPHY.       105

the same  principle as that on which the  engraver works;  and
hence the labor is more nearly equal in the two methods.
   The  number of impressions, which can be taken from a li-
thographic chalk drawing, will vary according to the fineness of
the tints.   A fine  drawing, will give 400, or  500;  a strong
one, 1000, or 1500.   Ink drawings, and writings, give consid-
erably more than copperplates.   The finest will yield 6000, or
8000, and strong lines, and writings, many more.  Upwards of
80,000 impressions have been taken at Munich, from one writ-
ing, of a form for  regimental returns.
   A method has been  introduced, by which copies of valuable
engravings may be multiplied indefinitely.   An impression on
paper, is taken, in  the  usual manner, from the copperplate, and
immediately laid with its surface upon  water.  When sufficient-
ly wet,  it is carefully  applied to  the surface of a stone,  pre-
pared in the usual  manner,  and pressed  down  upon it by the
application of a roller, till the ink leaves the paper, and adheres
to the stone.   It is then printed in the common  way.  Auto-
graphic  writings may be transferred  from paper to stone, and
printed in a manner nearly similar.
  Land seer's Lectures on Engraving, 8vo. London, 1807;—Meadows,
Lectures on Engraving,  London, 1811;—Partington's Mechanic's
Gallery, 8vo. 1825;—Rees's Cyclopaedia, under the various heads ;—
Hclmandel's Treatise on Lithography, 8vo. 1817;—Senefelder's
Complete Course of Lithography, 4to. ;—London Journal of Arts, pas-
sim ;—De Lasteyrie, Journal de Connaisances  usuelles, translated
Franklin Journal, vol. iv.
14 
CHAPTER VI.
        OF SCULPTURE, MODELLING, AND CASTING.

   Subjects.—Sculpture in its most general sense, is the art of
producing resemblances of visible forms, out of solid materials.
The required shapes are produced by carving, when the mate-
rial is solid  and  brittle; and to this sense the term sculpture is
sometimes limited.   They are  also formed by modelling, when
the material is soft; and by  casting, when it is liquid, or fusi-
ble.   The productions of this art are known under various de-
nominations, according to their character and  subject.   Of
these, the most important are statues, which are entire  resem-
blances of living  objects.  Busts  consist of the upper portions
of statues.   Bas-reliefs, in the common acceptation of the term,
are partial sculptures, or lateral views of figures, raised upon a
plane surface.   Their different degrees of prominence are dis-
tinguished by the Italians, under different  names.   These  are,
alto relievo, or high relief, when the figures are nearly complete,
or appear to issue from the  back • ground;  mezzo  relievo,  or
middle  relief, in which they are half raised  from  the surface;
and  basso  relievo, low relief, or bas-relief properly  so  called,
when the figures have  not the prominence  which their  outline
requires, but appear as if compressed.  The principal remain-
ing objects of sculpture, are vases, armatures, or trophies, and
the decorative parts of architecture.
   Modelling.—Before any object is executed in stone,  it is the
practice of sculptors, to complete  a representation of their de-
sign, by modelling it in clay, or  some other soft material.   The
genius of the artist is displayed altogether in the model, for the
process of  afterwards  copying  the model  in  stone, is  chiefly
mechanical, and may often be executed by another  person, as 
        OF  SCULPTURE, MODELLING, AND CASTING.      107

well as by the sculptor himself.   When a clay model is under-
taken, if the proposed figure be large, a frame of wood or iron
is erected to give support to the limbs and different parts of the
figure.  Upon this frame, a proper quantity of wet clay is dis-
tributed, and  wrought  into the  form of the intended statue.
The moulding of the  clay is performed with  the  hands, and
with various instruments of wood and ivory.   When the mod-
el is completed,  copies may be taken from it, either by casting
them in plaster,  or in metal; or by chiseling them in marble.
   Casting in Plaster.—Copies are most frequently taken, both
from new models, and  from old  statues, by casting  them in
plaster.   For this purpose a mould in plaster is first made from
the surface of the statue, or figure, itself; and this mould is af-
terwards  used to reproduce the  figure by casting.   Plaster  is
prepared for use by pulverizing  common gypsum,  and expos-
ing it to the heat  of a fire until its moisture  is wholly expelled. *
While  in this dry state, if it  be mixed with water to the consis-
tence of cream or paste, it has the property of hardening in a
few  minutes, and takes a very sharp impression.  The hard-
ness afterwards  increases  by keeping,  till it  approaches the
character of stone.
   Moulds are formed in the following manner.   The statue or
figure  to be copied, is first oiled, to prevent it from cohering
with the gypsum.  A quantity of liquid plaster sufficient for the
mould, is then poured on, immediately after being mixed, and
is suffered to harden.   If  the  subject be a bas-relief, or any
figure  which can be withdrawn without injury, the mould may
be considered as finished, requiring only to be surrounded with
an edging.  But if it be a statue, it cannot be withdrawn, with-
out breaking the mould, and on this account it becomes neces-
sary to divide the mould into such a number of pieces, as will
separate perfectly from the original.   These are taken off from

  * The heat requisite for this purpose must be greater than that of boiling
water.  Care must be taken not to raise the heat too high, as in that case the
sulphate of lime would be decomposed. 
108      OF  SCULPTURE,  MODELLING, AND CASTING.

the statue, and when afterwards replaced, or put together, with-
out the statue, they constitute  a  perfect mould.  This mould,
its parts having been oiled to prevent  adhesion, is made to re-
ceive a quantity of plaster,  by pouring it in at a small  orifice.
The mould is then  turned in every direction, in order that  the
plaster may fill every part of the surface; and when a sufficient
quantity is poured in to produce  the  strength  required  in  the
cast, the remainder is often left hollow, for the  sake of lightness,
and economy of the  material.   When the  cast is  dry, it is  ex-
tricated by separating the pieces  of the mould, and finished by
removing the seams and blemishes with the proper tools. *  If
the  form or  position require it,  the limbs are cast separately,
and afterwards cemented on.
   Moulds and busts are obtained in a similar manner from liv-
ing faces, by covering them with new plaster, and  removing it
in pieces as soon as  it becomes hard.   It is necessary that the
skin of the  face should be oiled, and  during the operation, the
eyes are closed, and the person breathes through tubes inserted
in the nostrils.
   Elastic moulds have been formed by pouring upon the figure
to  be  copied, a strong  solution of glue.   This hardens upon
cooling, and  takes a fine impression.   It is then cut into suita-
ble pieces and removed.   The  advantage of  the elastic mould
is that it separates more easily from irregular surfaces, or those
with uneven  projections and under cuttings, from which a com-
mon mould could not be removed without violence, f

   * Plaster casts are varnished by a mixture of soap and white wax in boiling
 water.  A quarter of an ounce of soap is dissolved in a pint of water, and an
 equal  quantity of wax afterwards incorporated.  The cast is dipped in this
 liquid, and after drying  a week, is polished by rubbing with soft linen.  The
 surface produced in this manner approaches to the polish of marble.
   When plaster casts are to be exposed to the weather, their durability is great-
 ly increased by saturating them with linseed oil, with which wax or rosin may
 be combined.  When intended to resemble bronze, a soap  is used, made of
linseed oil and  soda  colored by the sulphates of copper and iron.  Walls and
 ceilings are rendered water proof in the same way.   See  an abstract of a
 memoir of D'Arcet and Thenard,in  Brande's Journal, vol. xxii.  184, and
 Franklin Journal, ii. 276.
   t See a paper by Mr Fox, republished in the Franklin Journal, vol. iii. 
        OF SCULPTURE,  MODELLING, AND CASTING.      109

  For small and delicate impressions, which are merely in re-
lief, melted sulphur is sometimes used, also a strong solution of
isinglass in proof spirit.   The latter material has the advantage
that it is not brittle when dry, but  possesses a consistence like
that of horn.  Both substances yield very accurate and  sharp
impressions.
  Bronze Casting.—Statues  intended to occupy situations in
which  they may be exposed to violence, are commonly  made
of bronze.  This material resists both mechanical injuries, and
decay  from  the influence of the atmosphere.   The  moulds in
which  bronze statues are cast, are made on the pattern, out of
plaster and brick dust, the latter material being added to resist
the heat of the melted metal.   The parts of this mould are
covered on their inside with a  coating of clay, as thick as the
bronze is  intended to be.   The mould is then closed, and  filled
on its inside with a nucleus or  core of plaster and brick  dust,
mixed with water.   When  this is done,  the mould is opened,
and the clay carefully removed.  The mould with its core, are
then thoroughly  dried, and the  core secured in its  central posi-
tion by short bars of bronze  which pass into it through the ex-
ternal part of  the  mould.   The whole is then bound with iron
hoops, and  when  placed in a proper situation  for casting, the
melted bronze is poured in through an aperture left for the pur-
pose.   Of course  the bronze fills the same cavity which was
previously occupied by the clay, and forms a metallic  covering
to the  core.  This is afterwards  made  smooth by mechanical
means.
   Practice of Sculpture.—To execute a statue in marble, which
shall exactly correspond to a pattern or model, is a work of me-
chanical,  rather than of inventive skill.  It is performed by find-
ing, in the  block of marble, the  exact  situation of numerous
 points corresponding to the chief  elevations and cavities in the
 figure to  be imitated, and  joining these   by the proper curves
 and surfaces  at the judgment of  the  eye.  These  points are
 found, by measuring the height, depth, and lateral deviation of
the  corresponding points in the model;  after which, those  in 
 110     OF SCULPTURE, MODELLING,  AND  CASTING.

 the block are found by similar measurements.  Sometimes the
 points are ascertained, by placing the model horizontally under
 a frame, and suspending  a plumb line successively from differ-
 ent parts of the frame, till it reaches the parts of the figure be-
 neath it.   Sometimes an instrument is used  consisting of a
 moveable point, attached by various joints to an  upright post, so
 that it may be  carried to any part of the  statue, and  indicate
 the relative position of that part in regard to the post.   Ma-
 chines have also been contrived for cutting any required  figure
 from a block, the cutting instrument being directed by a guage
 which rests upon the model in another part of the machine.
   Marble is wrought to the rough outline of the statue, by the
 chisel and hammer, aided by the  occasional use of drills and
 other perforating tools.   It is then smoothed with rasps and files,
 and when  required, is polished with pumice stone and putty.
 The hair of statues is always  finished with the chisel, and for
 this object, very  sharp instruments with  different  points and
 edges are necessary.  The ancient sculptors appear to have re-
 lied almost wholly upon the chisel, and to have used that instru-
 ment with great boldness and freedom, such as could have been
justified only by consummate skill in the art.  The moderns, on
 the contrary, approach the surface of the statue  with great cau-
 tion, and employ safer means for giving the last finish.   Some
 of the most celebrated  antique statues, such as the Laocoon,
 the Apollo  Belvidere, and Venus  de  Medicis, are thought to
 have been finished with the chisel alone.
   Materials.—Although marble has been the common material
 of sculpture, both in  ancient and modern times, yet other sub-
 stances  have been occasionally made  subjects of  the  chisel.
 Statues of porphyry, granite,  serpentine,  and alabaster,  are
 found among the remains of antiquity.  Other materials of a
 less durable kind, were also employed.  Some of the principal
 works of Phidias were  made of ivory  and gold, particularly
 his colossal  statues  of  Jupiter  Olympius,  and Minerva,  at
 Athens. 
         OF SCULPTURE, MODELLING,  AND CASTING.      Ill

   Objects of Sculpture.—In sculpture, as in the other imitative
 arts, two ends  propose themselves to the skill of the artisL
 One consists in the imitation of a particular object, in which
 case the art of the sculptor can be expected only to equal, but
 not to surpass, his original.  The other consists in new combi-
 nations of excellence,  and in  the invention of forms and  ex-
 pressions, which  are not known to exist* together in nature, but
 are embodied in  the imagination of the artist.   Beauty in ob-
jects thus  conceived, constitutes the beau ideal in  art, to attain
 which,  has ever been the ambition of cultivators of the fine
 arts.   In statuary, the specimens which have  descended to us
 from the ancient  Greeks, are by universal  consent admitted to
 be the most perfect designs of beauty, and furnish the common
 models for study  and imitation, at the present, as in all former
 ages.
   Gem Engraving.—The  art of cutting  precious stones, is
 more properly a species of sculpture, than of engraving.   The
 hardness of these stones renders it  impossible to  operate on
 them by the strongest steel instruments.   They are therefore
 wrought in a slow manner, by grinding them away upon  the
 surface of a wheel, commonly made of metal, and covered with
 the grit, or fine powder of some hard substance.  The diamond
 can only be ground, or cut, with its own dust.  Rubies, agates,
 emeralds, &c, are cut and polished with emery  or tripoli, in
fine powder.  Lapidaries make use of small wheels, balls, and
 drills, of various forms, made of iron, or copper, which revolve
with great rapidity, and act upon the stone through  the medium
of the  pulverized material on their  surface.   They  also  use
wires covered  with emery, for the purpose of sawing plates.
   The imitative designs, which are cut upon  hard stones, are
 chiefly of two kinds.   The first of these are cameos, which are
 little bas-reliefs or figures, raised above the surface.  They are
 commonly made from stones, the  strata of which are of differ-
 ent colors,  so that the raised figure is of a different color from
the ground to which it is attached.  Varieties  of agate, carne-
lian, onyx,  he., are made use of for this purpose.   Sometimes 
1 12      OF SCULPTURE, MODELLING, AND CASTING.

several  successive strata  of different colors, are so wrought as
to produce the appearance of painting.   A cheaper kind of ca-
meos are made from  marine shells.  These  having lime for
their basis, may be scratched with steel, or corroded with acids.
Intaglios are the second  kind of engraved gems.   They differ
from cameos in having the figure cut into, or below, the surface,
so that they serve as seals to produce impressions in relief upon
soft substances.
  Mosaic.—Mosaics  are imitations of paintings made by com-
bining together an infinite number of minute stones of different
colors, and cementing them on a plane surface.  In the most cost-
ly mosaics, precious stones have been cut, and arranged to  pro-
duce this effect.   But in common works of this art, enamels of
different colors, manufactured for the purpose, are the material
employed.  The  enamel is first formed  into  sticks,  from  the
ends of vwhich pieces  of the requisite size are cut, or broken off.
These are confined in their proper places upon a plate of met-
al or stone, by a cement made  of  quicklime, pulverized lime-
stone, and linseed  oil.   After  the whole  has  adhered, it is al-
lowed to dry two months, and is then polished with a flat stone
and emery. *   Inlaid works of agate, and other costly stones,
are executed on the same principle as mosaic ; except that the
stones are larger and cut to the shape of different parts of the
object to be represented,  whereas in mosaic, the  pieces  are of
the same size and shape.   The opus reticulatum of the ancients,
with  which columns  and walls were sometimes  incrusted, is
found to consist of  small stones of a pyramidal form, the apex
of which  is imbedded in  mortar, while the base, which is  pol-
ished, forms the outer surface.
   Scagliola.—This name is given at Rome, to a sort of artifi-
cial  inlaid work, composed of plaster, but resembling stone.
For works of this kind, gypsum, dried and powdered, is mixed

  * One of the largest mosaics which has been executed, is a copy of Leonar-
do da Vinci's celebrated picture of the last supper.   It measures 21 feet by 12,
and employed eight or ten artists for eight years.  It was executed under the
direction of Raffaelli, at Milan, by order of the French government.  Cadell. 
         OF  SCULPTURE, MODELLING, AND  CASTING.     113

with a solution of glue, and spread on a tablet for the ground
of the picture.   Cavities of the form  intended  in the design,
are then made in it with an engraving tool.   These are succes-
sively filled  up with  portions of plaster of different  colors, so
managed  as  to produce the  effect of painting.   In  this  way
buildings, and various natural objects are represented.   The
surface is finely polished, by rubbing it with different powders,
and where the ground is white, with rushes.
  Winckelmann, Histoire de V Art chez les Anciens, 3 vols,  4to. tr.
1802;—Mielin, Dictionnaire des Beaux Arts, 3 vols, 8vo. 1806;—
Rees's Cyclopaedia;—Works of Vasari;—Qxtatremere de  Q,uin-
cy—Cicognara—Visconti, &c.;—Travels, and works of Cearke—
Eustace—Cadeee—Dodwell—Stuart—Elgin, fyc. &c.
15 
CHAPTER VII.
            OF ARCHITECTURE AND BUILDING.

  Architecture.—Architecture, in its most general sense, is the
art  of erecting buildings, of any kind.  In  modern use,  this
name is sometimes restricted to the external forms, or styles, of
building, in which  sense,  architecture is one of the fine arts.
It appears  to  have been among the earliest inventions,  and its
works have been commonly regulated  by some  principle of
hereditary imitation.   Whatever rude structure the climate and
materials of any country have  obliged its early inhabitants to
adopt for their temporary shelter, the same structure, with all
its prominent features, has been afterwards kept up by their refin-
ed,  and opulent posterity.   Thus, the Egyptian style of building
has its origin in the cavern and mound ; * the Chinese architec-
ture is modelled from the tent; the Grecian, is derived from the
wooden cabin, and the Gothic, from the bower of trees.
  Elements.—The essential  elementary parts of a building, are
those which contribute to its support, inclosure, and covering.
Of  these, the  most important are the foundation, the column,
the wall, the lintel, the arch,  the vault, the dome, and the roof.
  Foundations.—In laying the foundation of any building, it is
necessary to dig to a certain depth in the earth, to secure a sol-
id basis, below the reach of frost and common accidents.  The
most solid basis is rock, or gravel  which has not been  moved.
Next to these, are clay and sand, provided no other excavations
have been  made in the immediate  neighborhood.   From this
basis, a stone  wall is carried  up to  the surface of the  ground,
and constitutes the foundation.  Where  it is intended  that the
* Wilkins' Vitruvius. p. xvii. 
OF ARCHITECTURE AND  BUILDING.          115
 superstructure shall press unequally, as at its piers, chimnies, or
 columns, it is sometimes of use to  occupy the space  between
 the points of pressure, by an inverted arch.  This distributes
 the pressure equally, and prevents the foundation from spring-
 ing between  the different points.   In loose or muddy situations,
 it is always unsafe to build, unless  we can reach the solid  bot-
 tom below.  In salt marshes and flats, this is done by deposit-
 ing timbers, or driving wooden piles,  into the earth, and raising
 walls upon  them.   The preservative quality of the salt, will
 keep these timbers  unimpaired for a great length of time, and
 makes  the   foundation equally secure  with  one of brick or
 stone.
   Column.—The simplest member in any building, though by
 no  means  an essential one  to all, is the  column, or pillar.
 This is a perpendicular part, commonly  of equal breadth and
 thickness, not intended for the  purpose of inclosure, but simply
 for the support of some part of the superstructure.   The prin-
 cipal force which a column has to resist, is that of perpendicular
 pressure.   In its shape, the shaft of a column  should not be
 exactly cylindrical, but since the lower part must support the
 weight of the superior part, in addition  to the weight which
 presses equally on the whole  column, the thickness should grad-
 ually decrease  from  bottom to top.  The outline of columns,
 should be a little curved, so as  to represent a portion of a very
 long spheroid, or paraboloid, rather than  of a cone.  This fig-
 ure  is the joint result of two calculations, independent of beauty
of appearance.   One of these  is, that the form  best adapted
 for stability of base, is that of a cone.  The other is, that the
figure which  would be of equal  strength throughout for sup-
 porting a superincumbent weight,  would  be generated  by the
 revolution of  two parabolas round the axis of the column, the
 vertices of the curves being at its extremities. *
*See Tredgold's Principles of Carpentry, p. 50. 
116
OF ARCHITECTURE AND BUILDING.
                    12        3
  In the  accompanying wood cut, No. 1 is the figure having
the greatest  stability of base; 2, the figure which is of equal
strength throughout for  resisting vertical pressure, and 3, the in-
termediate, or common  form of the column, a little more curv-
ed than is usual in practice, and having its top truncated to  give
stability to the entablature.
   The  swell of the  shafts of columns, was called the entasis,
by the ancients.  It has  been lately found, * that the columns
of the Parthenon, at Athens, which  have been commonly sup-
posed  straight, deviate  about an  inch from a straight line, and
that their greatest swell  is at  about one third of their height.
   Columns in the antique orders, are usually made to diminish
one sixth, or one seventh, of their  diameter, and sometimes even
one fourth.   The Gothic pillar  is commonly of equal thick-
ness throughout.
   Wall.—The wall, another elementary part of a  building,
may be considered  as the lateral continuation of a column, an-
swering  the  purpose both of inclosure and  support.   A  wall
must diminish as it  rises, for the same reasons, and in the same
proportion, as the column.   It must diminish still more rapidly
if it extends through several  stories, supporting weights at dif-
ferent heights.   A wall, to possess the greatest strength, must
also consist  of pieces,  the upper and lower surfaces of which
are  horizontal and  regular, not rounded nor oblique.   The
walls of most of the ancient structures, which have  stood  to
the present time, are constructed in this manner, and frequent-
ly have their  stones bound  together  with  bolts and cramps

  * By Messrs Allason and Cockerel. See Brande's Journal, vol. x. p. 204.
« 
OF ARCHITECTURE  AND BUILDING.
117
 of iron.   The  same method is adopted in such modern struc-
 tures as are intended to possess great strength and durability,
 and in some cases the stones are even dovetailed together, as in
 the light houses at Eddystone, and Bell Rock.   But  many of
 our modern stone walls, for the sake of cheapness, have only
 one face of the stones squared, the inner half of the wall being
 completed with brick; so that they can in reality be considered
 only as brick walls faced with stone.   Such walls are said to be
 liable to become convex outwardly, from the difference in  the
 shrinking  of the cement.
   Rubble walls,  are made of  rough, irregular stones laid  in
 mortar.   The  stones  should  be  broken, if possible,  so as to
 produce horizontal surfaces.  The coffer walls of the ancient Ro-
 mans were made by inclosing successive portions of the intend-
 ed  wall in a box, and  filling it with  stones, sand, and  mortar,
 promiscuously.   This  kind of structure must have been   ex-
 tremely insecure.   The Pantheon, and various other Roman
 buildings, are surrounded with a  double brick wall, having  its
 vacancy filled up with  loose bricks and cement.   The whole
 has gradually consolidated  into a mass of great firmness.  The
 reticulated walls of the Romans, having bricks with oblique sur-
 faces, would at the present day be thought highly unphilosophi-
 eal.   Indeed they could not long have stood, had it not been
 for the great strength of their cement.
   Modern brick walls  are  laid with great precision, and  de-
 pend for  firmness  more upon their position than upon  the
 strength of their  cement.   The bricks being laid in horizontal
 courses, and continually 0"erlaying  each  other,  or  breaking
joints, the whole  mass is strongly interwoven, and bound  to-
 gether.  Wooden walls, composed  of  timbers covered with
 boards, are a common, but  more  perishable kind.  They re-
 quire to be constantly covered with a coating of a foreign sub-
 stance, as paint or plaster, to preserve them from  spontaneous
 decomposition.
   In  some parts of France, and  elsewhere, a kind of wall is
 made of  earth, rendered compact by ramming it in moulds or 
 118         OF  ARCHITECTURE AND BUILDING.

 cases.  This  method is called building in  Pise,  and is much
 more durable  than the nature of the  material would lead us to
 suppose.
   Walls of all kinds are greatly  strengthened by angles and
 curves, also by projections, such  as  pillasters, chimnies, and
 buttresses.  These projections serve to increase the breadth of
 the foundation, and are always to be made use of in large build-
 ings, and in walls of considerable length.
   Lintel.—The  lintel, or beam, extends in  a right  line over a
 vacant  space,  from  one  column  or  wall,  to  another.   The
 strength of the lintel will be greater in proportion  as its trans-
 verse vertical  diameter  exceeds the horizontal, the strength be-
 ing always as  the square of the depth.  [See page 46].  The
floor is the lateral continuation or connexion  of beams by means
 of a covering of boards.
   Arch.—The arch is a transverse member of a building an-
 swering the same purpose as the lintel, but vastly exceeding it in
 strength.   The arch, unlike the lintel, may consist of any num-
 ber of constituent pieces, without impairing  its strength.   It is,
 however, necessary that all the pieces should possess a uniform
 shape, the  shape  of a portion of a wedge ;  and that the joints,
 formed by the contact of their surfaces, should point towards a
 common centre.   In this case, no one portion of the arch can
 be displaced or forced inward ; and the arch cannot be broken
 by any force  which is not  sufficient to crush the  materials of
 which it is  made.  In arches made of common bricks, the sides
 of which are parallel, any one of the bricks  might be forced in-
 ward, were it  not for the adhesion of the cement.   Any two of
 the bricks however,  constitute a wedge, by the disposition of
 their mortar, and cannot collectively be  forced  inward.  An
 arch of the proper form, when complete, is rendered stronger,
 instead of weaker, by the  pressure of a  considerable  weight,
 provided this  pressure  be uniform.  [PL I. Fig. k~\.  While
 building, however, it requires to be supported by a centring of
 the shape of its internal surface, until'it  is complete.  The up-
 per stone of an arch is called the key  stone,  but is not more  es-
 sential than any other. 
             OF ARCHITECTURE  AND  BUILDING.          119

  In regard to the shape of the arch, its most simple form is that
of the semi-circle.  [PI. I. Fig. k~\.   It is, however,  very fre-
quently a smaller arc of a circle, and still more frequently a por-
tion of an ellipse.   The simplest theory of an arch supporting it-
self only, is that of Dr Hooke.  The arch, when it has only its
own weight to bear, may be considered as the inversion of a chain,
suspended at each end.  The chain hangs in such a form, that
the  weight of each  link or portion is held in equilibrium by the
result of two forces acting at its extremities ; and these forces,
or tensions, are produced, the one by the weight of the portion
of the chain below the link, the other by the same weight  in-
creased by that of the link itself, both of them acting originally
in a vertical  direction.   Now  supposing the chain inverted, so
as to constitute an arch of the same form and weight, the rela-
tive situations of  the forces will be the same, only they will act
in contrary directions, so that they are compounded in a similar
manner,  and  balance each other on the same conditions.  The
arch thus formed,is denominated a catenary arch. [PI. 1. Fig. T],
In common cases it differs but little from a circular arch of the
extent of about one third of a whole circle, and rising from the
abutments with an  obliquity of about 30 degrees from a per-
pendicular.
  But though the catenary arch is the best form for supporting
its  own  weight, and also all additional weight which presses in
a vertical direction, it is not the best form to resist lateral  pres-
sure, or pressure  like that of fluids,  acting equally in all direc-
tions.  Thus the  arches  of bridges  and  similar structures,
when  covered  with loose  stones  and earth, are pressed side-
ways, as well as vertically, in the same manner as if they sup-
ported a weight of  fluid.  In this  case, it is necessary that the
arch should arise more perpendicularly from the abutment, and
that its general figure should be that of the longitudinal segment
of an ellipse.  [PI. I.  Fig. m].   In small arches in  common
buildings, where  the  disturbing force is not great, it is of little
consequence what  is the shape  of  the  curve.   The  outlines
may even be perfectly straight, as in the tier of bricks which 
120         OF ARCHITECTURE  AND  BUILDING.

we  frequently see over a window.   This is, strictly speaking, a
real arch, provided the  surfaces of the bricks tend  towards a
common centre.   [PI. I. Fig. s].  It is the weakest kind of
arch, and a part of it is necessarily superfluous, since no great-
er  portion can  act in supporting a weight  above it,  than  can
be included between two curved or arched  lines.
  Besides the arches already mentioned, various others are in
use.  The acute  or lancet  arch,  [PI. I. Fig. o] much used in
Gothic architecture, is described  usually from two centres out-
side the  arch.  It is a strong arch for supporting vertical pres-
sure.  The rampant arch [Fig. n\  is one, in which the two ends
spring from unequal heights.   The horse shoe or Moorish arch
[Fig. p and q] is described from one or more centres placed
above the base line.   In this arch, the lower parts are in  dan-
ger of being  forced inward.  The ogee arch [Fig. r] is conca-
vo-convex, and therefore fit only for ornament.
  In describing arches, the upper surface is called the extrados,
and the  inner, the intrados.   The springing lines are those
where  the intrados' meets the abutments,  or  supporting walls.
The span is the distance from one  springing  line to the other.
The wedge-shaped  stones which form an  arch, are sometimes
called  voussoirs, the  uppermost  being the key stone.  [PI. I.
Fig. k~].  The part of a pier from which an arch springs, is
called the impost,  and the  curve  formed by the upper side of
the voussoirs, the archivolt.
  Abutments.—It is  necessary that the  walls, abutments,  and
piers, on which arches are supported, should be so  firm  as to
resist the lateral thrust, as well as vertical pressure, of the arch.
It will at once be seen that the lateral or sideway pressure of
an arch is very considerable, when we recollect that every stone,
or  portion of the  arch, is a wedge, a part  of whose force  acts
to  separate the abutments.   For want of  attention to this cir-
cumstance,   important  mistakes  have  been  committed,   the
strength of buildings  materially impaired, and their ruin accel-
erated.   In  some cases, the want of lateral firmness in  the
walls, is compensated by a bar of iron stretched across the span 
             OF ARCHITECTURE  AND  BUILDING.          121

of the arch and connecting the abutments, like the tie beam of
a roof.  This is the case in the cathedral of Milan, and some
other Gothic  buildings. *
  Arcade.—In an arcade, or continuation of arches, it is only
necessary that the outer supports  of the terminal arches should
be strong enough to resist horizontal  pressure.   In the inter-
mediate arches, the lateral force  of each arch is counteracted
by the opposing  lateral  force of the one contiguous to it.   In
bridges, however, where individual arches are liable to be de-
stroyed by accident, it is desirable, that each of the piers should
possess sufficient horizontal  strength,  to resist the lateral pres-
sure of the adjoining arches.
   Vault.—The  vault  is the lateral  continuation of an arch,
serving to cover an area, or passage, and bearing the same rela-
tion  to the arch, that the wall does to  the  column.   A simple
vault is constructed on the principles  of the arch, and distrib-
utes  its pressure equally along the walls, or abutments.  A com-
plex or groined vault is made by two vaults  intersecting each
other, in which case, the  pressure is  thrown upon springing
points, and is greatly increased at those points.  The groined
vault is common  in Gothic architecture.   [PI. VI. Fig. 6].
   Dome.—The  dome,  sometimes called cupola, is a concave
covering to a building, or part of it, and  may be either a  seg-
ment of a sphere, of a  spheroid,  or of any similar figure.
When built of  stone, it is a very  strong kind  of structure, even
more so than the arch, since the  tendency of each part to fall,
is counteracted, not only by those above and below  it, but  also
by those on each side.   It is only necessary that the  constituent
pieces should have a common form, and that this form should
be somewhat like the frustum of a pyramid, so that when placed
in its situation,  its four angles may point toward the centre, or
axis, of the  dome.  During the  erection of a dome, it is  not
necessary that it should be supported by a centring, until com-
plete, as is done in the arch.   Each circle of stones, when

       * Cadell's Journey through Carniola and Italy, vol. ii. p. 77.
               16 
 122         OF  ARCHITECTURE  AND  BUILDING.

 laid,  is capable  of supporting itself, without aid from  those
 above it.  It follows that the dome may be left open at top,
 without a key stone, and yet be perfectly secure,  in this respect,
 being the reverse of the  arch.  The dome of the Pantheon,
 at Rome, has been always open at top, and yet has stood-unim-
 paired for nearly 2000  years.   The  upper circle of stones,
 though  apparently the  weakest, is nevertheless often  made to
 support the additional weight of a lantern or tower above it.
 In several of the largest  cathedrals, there are two  domes, one
 within the other, which contribute their joint support to the lan-
 tern which rests upon the top.  In  these  buildings, the dome
 rests  upon a circular  wall, which is supported  in its turn by
 arches upon massive pillars or piers.  This construction is cal-
 led building upon pendentives, and gives open space and room
 for passage, beneath the dome.
   The  remarks which have been made in regard to the abut-
 ments of the arch, apply  equally to  the walls immediately sup-
porting  a  dome.   They  must  be of sufficient thickness  and
solidity to resist the lateral pressure of the dome,  which is very
 great.   The walls of the Roman  Pantheon are of  great depth
and solidity.   In  order that a dome  in itself should be perfect-
ly secure, its lower parts must not be too nearly  vertical,  since
in this case, they  partake of the nature of perpendicular walls,
and are acted upon by the spreading force of the parts above
them.   The  dome of St Paul's church, in London, and some
others of similar construction, are bound with chains or hoops
of iron  to prevent them  from  spreading at bottom.  Domes
which  are made of wood,  depend  in part for their strength,
on their internal  carpentry.  The  Halle du Bled, in Paris,
had, originally, a wooden dome more than 200  feet in diam-
eter, and  only one  foot  in thickness.   This has  since  been
replaced by a  dome of iron.
   Plate I.—In the first  plate is given a comparative  view in
outline of  some of the  most remarkable domes in  ancient and
modern buildings, together  with the edifices to which they be-
long, likewise various other structures reduced to the same scale. 
            OF  ARCHITECTURE  AND  BUILDING.         123

   The highest dome, [No. 3] is that of St Peter's church, at
Rome, generally considered the most  splendid building  in the
world, and one of the largest in size.   This edifice was  a cen-
tury in building, from about 1510 to 1610.  It was begun by
Bramante, and finished by Michael Angelo, and Vignola.   The
dome is of an ellipsoidal form, solid at bottom, but divided into
two thin, concentric domes at top, between which is the stair
leading  to the lantern.   The whole height from the ground to
the cross at top, is about 470 feet.   The base of the dome rests
upon arches, supported by massive stone piers.  Within the last
century, some fissures of dangerous appearance were discovered
in this  dome, to remedy which, it was surrounded with  iron
chains by the artist Zabaglia.
   The next dome in height, [No. 4] is that of the church of St
Maria  del Fiore, at Florence.   Its vertical section is an elon-
gated ellipsoid, its horizontal section octagonal.   This church
is about 380 feet high, and was built between 1298 and 1472.
The dome was erected by Bruneleschi, one of the earliest re-
vivers of antique architecture.
   St Paul's cathedral, London,  [No. 5] was erected  by Sir
Christopher Wren, between 1685 and 1710.   It has two domes
at different heights, the inner being made of brick, and the out-
er of wood.   Between the two, is a hollow, truncated cone of
brick work, which furnishes the  support of the  lantern  at top.
The outline of the dome is somewhat more  than a semicircle,
and  is prevented from  spreading  at bottom, by a strong  iron
hoop.
   The church of St Genevieve, in Paris,  [No. 6] which, dur-
ing the absence of the Bourbon family, was called the Panthe-
on, was begun by Soufflot, in  1757.    This  edifice  has been
threatened with ruin in consequence of the piers, which support
the dome, being made too small for the nature of the ,material,
and  the  superincumbent weight.  It became necessary to re-
place a part of the stones which were crushed, and to increase
the amount of support, to obtain present security. 
124        OF ARCHITECTURE AND  BUILDING.

   The  Mosque of St Sophia, at Constantinople, [No. 7] pre-
sents a specimen of the  kind of dome used by the  ancients,
which was more flat than any of the preceding  examples, and
was usually a small segment of a sphere.  This edifice was
erected  during the reign of Justinian, in the  sixth century.
Owing to the want of sufficient  solidity in the supporting wall,
the dome fell down at two successive times, and the architect
was under the necessity of filling up the subjacent arcades, and
of building large buttresses on the outside of the wall, to resist
the pressure, and give to the dome eventual  stability.   The
span of  this dome is 112 feet.
   The  Pantheon, at Rome, [No. 8] is probably the  oldest
dome now  standing, and is  one of the best  constructed.  Its
outer and inner surfaces are  of different curvatures, so that the
thickness increases downward, the inner surface being a  hemi-
sphere.   The  walls of this edifice are of great solidity, and to
this circumstance  the security of the  superstructure is in part
owing.   This dome is open at the top.   It was built by Agrip-
pa, in the reign of Augustus  Caesar.   A more  perfect view of
the Pantheon, is given in Plate V.
   The outline of  St Mark's  church, at Venice, which has -sev-
eral domes; that of the front  of the Parthenon,  at Athens,
which shows the lowness of the Grecian pediment; that of the
restored temple of Vesta, at Tivoli, and lastly that of the small
Ionic temple which stood upon the Ilissus, are added merely
to give an idea of their comparative size.   The column erected
to the memory of the emperor Trajan, also one of the obelisks
brought  from  Egypt by the  ancient Romans, are  introduced
upon the same scale.
   No. 1, in  the same plate, represents the outline of the largest
of the Egyptian Pyramids, respecting the dimensions of which,
travellers vary  greatly  in their accounts.   One of the  more
moderate of their  estimates  is here taken, which  makes  the
height a little less than 500 feet.
   No. 2, shows the length and height of the Coliseum, at Rome
a vast elliptical  amphitheatre, which 15,000 men were occupied 
             OF ARCHITECTURE AND BUILDING.         125

ten years in completing.  It was built in the reign of Vespasian
and Titus, and its walls are standing at the present  day.
   No. 15, represents  the  celebrated  leaning  tower of Pisa.
The several stories of this structure, are supported by arcades
upon  columns, in the Greco-gothic  style.   The height  of the
whole is 180  feet.   This tower leans over about 14 feet from
a perpendicular. The view here taken of it, does not represent its
greatest inclination.  Whether the obliquity was the effect of
design, or of  the  settling of the foundation on  one side, is a
point  upon which writers are  not agreed.   It was  built  in the
twelfth century.
   No. 16, is the steeple of the Gothic Cathedral, at Strasburg.
It is among  the highest steeples in Europe,  and is introduced
to show its comparative elevation.  No.  17, is the centre steeple
of the Duomo or Cathedral of Milan,  about  350 feet high.
This edifice is of white marble.  Its general character is Goth-
ic, intermixed with details in the later Roman style.
   The proportions of most of the foregoing buildings are taken
from  Durand, who has reduced  them to a scale.  The same
scale  applies to the other architectural  plates in this volume,
with the exception of perspective representations, in which more
than one side is seen.
   The outlines of several American edifices,  reduced to the
same  scale,  are  added in  this plate  for  the   convenience
of comparison.   No. 18, is that of the Capitol, at Washington,
built of freestone, the  length of which is 350 feet, the  height
of the front 70 feet, and the  height of the  centre dome  120
feet.   No. 19, is the City  Hall, at New York,  built  chiefly of
marble, its length 220 feet, and the height of the statue at top,
120 feet.  No. 20, is  the State House, Boston, 173 feet in
length,  built of brick,  and  painted.   No.  21, is  the  Bank
of the United States, at Philadelphia, a marble building, having
its front 86 feet wide, copied in most respects from the Parthe-
non at Athens.  No. 22, the  monument erected at Baltimore,
in commemoration of the battle and  victory  at that place.
Height about 55 feet. 
126
OF ARCHITECTURE  AND  BUILDING.
   Roof—The roof is the most common and cheap method of
 covering buildings, to protect them from rain and other effects
 of the  weather.  It is sometimes flat, but more frequently ob-
 lique in its shape.   The flat or platform roof is the least advan-
 tageous for shedding rain, and is seldom used in northern coun-
 tries.   The pent roof, consisting of two oblique sides meeting
 at top,  is the most common form  [PI. I. Fig. w~\.   These roofs
 are  made  steepest in  cold climates,  where  they  are liable
 to be  loaded  with  snow.   Where  the  four  sides  of the
 roof are all oblique, it is denominated a hipped roof, [Fig. x]
 and where there are two portions to the roof, of different obli-
 quity,  it is a curb,  or mansard roof.   [Fig. y].  In modern
 times, roofs are made almost exclusively of wood, though fre-
 quently covered with incombustible materials.  The internal
 structure or carpentry of roofs, is a subject of considerable me-
 chanical contrivance.   The roof is supported by rafters which
 abut on the walls on each side, like the extremities of an arch.
 If no other timbers existed, except the rafters, they would exert
 astrong.lateral pressure on the walls, tending to separate and over-
 throw them. *   To counteract this lateral force, a tie beam, as it
 is called, extends across, receiving the ends of the rafters, and pro-
 tecting  the wall from their horizontal thrust.   To prevent the tie
 beam from sagging, or bending downward with its own weight, a
 king post is erected  from this beam, to the upper angle of the
 rafters,  serving to connect the whole, and to suspend the weight
 of the beam.   This is called trussing.    Queen posts  are some-
 times added, parallel to  the king post, in large roofs,  also  vari-
 ous other connecting timbers.   In Gothic buildings, where the
 vaults do not  admit of the  use of a tie  beam, the rafters  are
 prevented from spreading, as in an arch, by the strength of the
 buttresses.

  * The largest roof that has hitherto been built, is supposed to have been that
 of the riding house, at Moscow.  Its span was 235 feet, and the slope of the
 roof, about 19 degrees.  The principal support of this immense truss, consist-
 ed in an arch of timber in three thicknesses, indented together, and strapped
 and bolted with iron.  The principal rafters and tie beams, were supported by
 several vertical pieces, notched to this arch, and the whole stiffened by diago-
nal braces.  Tredgold's Carpentry, p. 87. 
              OF ARCHITECTURE  AND  BUILDING.          127

   In  comparing the lateral pressure of a high roof, with  that
 of a low one, the length of the tie beam being the same, it will
 be seen thajt a high roof, from its containing most materials, will
 produce the  greatest pressure, as far  as weight is concerned.
 On  the other hand, if the weight of both  be equal,  then the
 low roof will exert the greater pressure, and this will increase in
 proportion to the distance of the point at which perpendiculars
 drawn from the end of each rafter, would meet.
   In roofs, as well as in wooden domes, and bridges, the mate-
 rials are subjected  to an internal strain, to resist which, the co-
 hesive strength of  the material is relied on.   On this account,
 beams should, when possible, be of one piece.   Where  this
 cannot be effected, two or more beams are connected together
 by splicing.  Spliced beams are never so strong  as whole ones,
 yet  they may be made to  approach the same strength, by affix-
 ing  lateral pieces,  or by making  the ends overlay each  other,
 and connecting them  with bolts  and straps of iron.  The ten-
 dency to separate is  also resisted, by letting the two pieces  into
 each other, by the process called scarfing.  Mortises, intended
 to truss or suspend  one piece by another, should be formed
 upon similar principles.
   Roofs in this country, after being boarded, receive a second-
 ary  covering of shingles.   When intended to be incombustible,
 they are covered with slates or earthen tiles, or with sheets of
 lead, copper, or tinned iron.   Slates are preferable to tiles, be-
 ing lighter, and absorbing  less moisture.  Metallic sheets  are
 chiefly used for  flat roofs, wooden domes, and curved and an-
 gular surfaces, which require a flexible  material to cover them,
 or have not a sufficient pitch to shed the rain from  slates or
 shingles.  Various  artificial compositions are occasionally used
 to cover roofs, the most common of which, are mixtures of tar
 with lime, and sometimes with sand  and gravel.
   Styles of Building.—The architecture of different countries,
 has been characterized by peculiarities in external form,  and in
 modes  of  construction.   These  peculiarities, among  ancient
nations, were so distinct, that their structures may be identified 
128         OF ARCHITECTURE  AND  BUILDING.
even in the state of ruins ;  and the origin and era of each may
be conjectured with tolerable  accuracy.  Before we proceed
to describe architectural objects, it  is  necessary .to  explain
certain terms,  which  are  used to  denote  their   different
constituent portions.  The architectural orders will be spoken
of under the head of the Grecian and Roman styles, but their
component parts ought previously to be understood.
  Definitions.—The front or facade of a building, made after
the ancient models, or any portion of it, may present three parts,
occupying different heights.
  The pedestal is the lower  part, usually supporting a column.
The  single pedestal is wanting in most antique structures, and
its place  supplied by a  stylobate.   The stylobate is either  a
platform with steps, or a continuous pedestal, supporting a row of
columns.   The lower part of a finished pedestal is called the
plinth, * the middle part is the die, and the upper part the cornice
of the pedestal, or surbase.
  The column, is the middle part, situated upon the pedestal or
stylobate.  It is commonly detached from the wall, but is  some-
times  buried in it for half its  diameter, and is then said to be
engaged.   Pilasters are square  or  flat columns, attached to
walls.  The lower  part of a  column,  when  distinct, is called
the base;  the middle, or longest part, is the shaft, and the upper,
or ornamented part, is the capital.   The height of columns  is
measured in diameters  of the column  itself,  taken  always at
the base.
   The entablature,  is the horizontal, continuous portion, which
rests upon  the top of a row of  columns.  The lower part of
the  entablature is called  the architrave, or epistylium.   The
middle part is the frieze,  which, from its usually  containing
sculpture, was called zophorus by the ancients.  The upper, or
projecting part, is the cornice.

  * The name plinth, in its general sense, is applied to any square projecting
 basis, such as those at the bottom of walls, and under the base of columns. 
OF ARCHITECTURE AND BUILDING.
129
Cornice,
Entablature
Column<
Stylobate or
  Pedestal
Base.
Cornice.
Plinth.
   A pediment, is the triangular face, produced by the extremi-
ty of a roof.   The middle, or flat portion, inclosed by the cor-
nice of the pediment, is called the  tympanum.   Pedestals for
statues, erected on the summit and  extremities of  a pediment,
are called  acroteria [PI.  V. Fig. 2].   An attic, is an upper
part of a building, terminated at  top by a horizontal  line, in-
stead of a pediment.
   The different mouldings in architecture are described from
their sections, or from the  profile which they present, when cut
across.  Of these  the  torus is a convex  moulding, the section
of which  is a  semicircle  or nearly so  [PI. I. Fig. a].  The
astragal, is like  the  torus, but smaller  [Fig. b~\.   The ovolo
               17 
 130         OF ARCHITECTURE  AND  BUILDING.

 is convex, but its outline is only the quarter of a  circle [Fig.
 c].  The  echinus resembles the ovolo, but its outline is spiral,
 not circular  [Fig. d].   The scotia is a deep, concave  mould-
 ing [Fig.  e].   The cavetto is also concave,  and occupying
 but a quarter of a  circle [Fig. /].   The cymatium is an un-
 dulated moulding, of which the upper  part is concave, and the
 lower  convex [Fig. g~\.  The ogee  or  talon, is an inverted
 cymatium  [Fig.  h].    The fillet is  a  small  square or flat
 moulding [Fig.  i]. *
   Measures.—In architectural measurement, a diameter means
 the width  of a column at the base.   A module is half a diam-
 eter.   A minute is a sixtieth part  of  a  diameter.
   Drawings.—In representing edifices by drawings, architects
 make  use  of the plan, elevation, section, and perspective.  The
plan is a map, or design, of a horizontal surface, showing the
 ichnographic projection, or ground work, with the relative po-
 sition of walls, columns, doors, he. f   The elevation is the or-
 thographic projection of a front, or vertical surface; this being
 represented,  not as it is actually seen  in  perspective, but as  it
 would appear if seen  from an infinite  distance.  The  section
 shows the  interior of a  building, supposing the part in front of
 an intersecting plane, to be removed.   The perspective  shows
 the building  as it actually appears to the eye, subject to the laws
 of scenographic perspective.   The three former are used by
 architects,  for purposes of admeasurement, the latter is  used
 also by painters, and is capable of bringing more than one side
 into the same view, as the eye actually perceives them.
   Restorations.—As the most approved features in  modern
 architecture, are derived from buildings which are more or less
 ancient, and  as many of these buildings are now in too dilapi-
 dated  a state to  be easily copied,  recourse is had to such imi-
 tative restorations in drawings and models, as can be made out

  * By  a singular  mixture of derivations, the Greek, Latin, Italian, French,
 and English  languages are laid under contribution for the technical terms  of
 Architecture.
  t See various plans of temples on pages 136,137. 
             OF ARCHITECTURE AND BUILDING.          131

from the fragments and ruins which remain.  In consequence
of the known simplicity and regularity of most antique edifices,
the task of restoration is  less difficult than might be supposed.
The ground work, which  is commonly extant, shows the length
and breadth of the building, with the position of its walls, doors,
and  columns.  A single  column, whether  standing or  fallen,
and a fragment of the entablature,  furnish data from which the
remainder of the colonnade, and the height of the main body,
can be made out.   A single stone from the  cornice of the pedi-
ment, is often sufficient  to give the angle of inclination, and
consequently the height  of the roof.   In  this  way, beautiful
restorations are obtained of structures, when in  so  ruinous a
state, as scarcely to have left one stone upon another.

                     EGYPTIAN STYLE.

   In ancient Egypt, a style of building prevailed, more mas-
sive and substantial than  any  which has succeeded it.   The
elementary features of Egyptian architecture, were chiefly  as
follows.   1.  Their walls were of  great thickness, and sloping
on the outside.   This feature is supposed to have been derived
from the mud  walls, mounds, and  caverns of their  ancestors.
2. The  roofs  and covered ways were flat, or without pedi-
ments, and  composed of blocks  of stone, reaching  from one
wall or column to another.  The principle of the arch, although
known to them, was seldom, if ever, employed by them.   3.
Their  columns  were numerous, close,  short,  and very  large,
being sometimes 10 or 12 feet in diameter.  They were gener-
ally without bases, and had a great variety of capitals, from a
simple square block, ornamented with hieroglyphics, or faces,
to an elaborate composition of palm leaves not unlike the Co-
rinthian capital.  4. They used a  sort of concave entablature,
or cornice, composed of vertical flutings, or leaves, and a wing-
ed globe  in the  centre.   5. Pyramids, well known  for  their
prodigious size, and obelisks composed  of a single stone, often
exceeding 70 feet in height, are structures peculiarly Egyptian. 
 1-32         OF ARCHITECTURE AND BUILDING.

6. Statues of enormous  size, sphinxes carved in stone, and
sculptures in outline of fabulous deities and animals, with  innu-
merable hieroglyphics,  are the decorative objects which belong
to this style of architecture.
  For Egyptian  specimens, see PI. I. Fig.  1.; PI. VI. Fig.
I, and PL VII. Fig. 1, 2, and 3.
  The architecture of the ancient  Hindoos, appears to have
been  derived from the same original ideas as the Egyptian.
The  most  remarkable relics of this people,  are their subterra-
neous temples, of vast  size and elaborate workmanship, carved
out of the solid rock, at Elephanta, Ellora, and Salsette.  One
of their columns is shown in Plate VII. Fig. 4.

                   THE CHINESE  STYLE.

   The ancient Tartars, and wandering shepherds of Asia, ap-
pear to have  lived  from time  immemorial  in tents, a kind of
habitation adapted  to  their erratic life.  The Chinese  have
made the tent, the elementary feature of their architecture, and
of their style any one  may form an idea, by inspecting the fig-
ures which are depicted upon common  china ware.   Chinese
roofs are concave on the upper side, as  if made of canvass in-
stead of  wood.   A Chinese portico,  is  not unlike  the awnings
spread over our shop windows in summer time.   The  verandah,
sometimes copied in dwelling houses here, is a structure of this
sort.   The Chinese towers and pagodas, have concave  roofs,
 like awnings, projecting over their several stories.   The light-
 ness  of the style used  by the Chinese, leads them to build with
 wood, sometimes with  brick, and seldom with stone [PL VI.,
 Fig.  2, and VII.  Fig.  18].

                   THE  GRECIAN  STYLE.

   Grecian architecture, from which have been derived the most
 splendid  structures of later  ages, has its origin in the  wooden
 hut or cabin, formed of posts set in the earth, and covered with 
             OF ARCHITECTURE AND BUILDING.         133^

transverse poles and rafters.   Its beginnings were very simple,
being little more than imitations in stone, of the original posts
and beams.  By degrees these were modified and decorated,
so as to give rise to the distinction of what are now called the
orders of architecture.
   Orders of Architecture.—By the architectural  orders, are
understood certain modes of proportioning  and decorating the
column and its entablature.   They were in use during the best
days of Greece and Rome, for a period of six or seven centu-
ries.  They were lost sight of" in the dark ages, and again re-
vived by the Italians at the time of the restoration of letters.
The Greeks had three orders, called the Doric, Ionic, and Co-
rinthian.   These were adopted and modified by the Romans,
who also added two others, called  the Tuscan and Composite.
   Doric Order.—The Doric is the earliest and most massive
order of the ' Greeks.   It is known by its large columns with
plain capitals; its triglyphs resembling the ends of beams, and
its mutules corresponding to those of rafters.   The column,  in
the examples at Athens,  is about  six  diameters in height.  In
the older examples, as those at Paestum, it is but four or five.
The shaft had no base, but stood directly on the stylobate.   It
had 20 flutings, which were superficial,  and separated by angu-
lar edges.   The perpendicular outline was nearly straight.
The Doric capital was plain, being formed of a few annulets  or
rings, a large echinus, and a flat stone at top called the abacus.
The architrave was plain ; the frieze was intersected by oblong
projections called triglyphs, divided into three parts by vertical
furrows,  and ornamented beneath, by guttce or drops.   The
spaces between the  triglyphs were called metopes,  and com-
monly contained sculptures.  The sculptures representing Cen-
taurs andLapithae, carried by Lord Elgin to London, were me-
topes of the Parthenon, or temple of Minerva, at Athens.   The
cornice of the Doric order consisted of a few large mouldings,
having on their under side  a series of square, sloping projec-
tions,  resembling the ends of  rafters, and  called  mutules.
These were placed over  both triglyphs and metopes, and were 
134         OF ARCHITECTURE  AND BUILDING.
 ornamented, on  their under  side, with circular guttce.   The
 best specimens of the Doric order, are found in the Parthenon,
 the  Propylaea, and the Temple  of Theseus, at Athens [PL
 VI.  Fig. 7. PL IV. Fig. 1, 2, 3,  4, 5, and 6].
   Ionic Order.—The Ionic is a  lighter order than the Doric,
 its column being  eight or nine  diameters  in  height.   It  had a
 base  often  composed of a torus,  a scotia, and a second  torus,
 with  intervening fillets.  This is called  the  Attic base [PI.
 VII. Fig. 9].   Others were used  in different parts of Greece.
 The  shaft  had 24, or more, flutings, which  were  narrow, as
 deep as a semicircle, and separated by a fillet  or square  edge.
 The capital of this order consisted  of two parallel double scrolls,
 called volutes, occupying opposite  sides, and supporting an  ab-
 acus,  which was nearly square,  but moulded  at  its edges.
 These volutes have been considered as copied  from ringlets of
 hair, or perhaps  from  the horns  6f Jupiter Ammon.  When
 a column made the angle of an edifice, its volutes were placed,
 not upon opposite, but on contiguous sides ; each  fronting out-
 ward.  In  this case  the volutes interfered with each other at
 the  corner, and  were  obliged to  assume a diagonal  direction.
 The  Ionic  entablature  consisted  of an  architrave and frieze,
 which were continuous or unbroken, and  a cornice of various
 successive mouldings, at the lower part of which was often a
 row of dentels or square teeth.   The examples at Athens, of
 the Ionic order,  are the temple of Erectheus, and the temple
 on the Ilissus, which  was standing in Stuart's time  70  years
 since, but is now extinct [PL  VII. Fig. 9.  PL IV. Fig. 8,
 9, 10, and 11.
   Corinthian  Order.—The  Corinthian was the lightest and
 most decorated of the.  Grecian orders.   Its base  resembled
 that of the Ionic, but was more complicated.   The shaft was
 often ten diameters in height, and was fluted  like  the Ionic.
 The capital was  shaped like an inverted  bell,  and covered on
 the outside with two  rows of leaves of the plant acanthus, *

  * The origin of the Corinthian capital has been ascribed to the sculptor Cal-
limachus, who is 6aid to have copied it from a basket accidentally  enveloped 
OF ARCHITECTURE  AND  BUILDING.
135
 above which were eight pairs of small volutes.   Its abacus was
 moulded and concave on its sides, and truncated at the corners,
 with a flower on the centre of each  side.  The entablature of
 the Corinthian  order, resembled that of the Ionic, but was more
 complicated  and ornamented,  and  had, under the cornice, a
 row of large  oblong projections, bearing a leaf or scroll on their
 under side, and called modillions.  No vestiges  of this order are
 now found in the remains of Corinth, and  the  most legitimate
 example at Athens, is in the choragic monument of Lysicrates.
 The  Corinthian order was much employed in the subsequent
 structures  of Rome, and  its colonies  [PL VII. Fig.  10.  PL
 V. Fig. 1, 2, 3, &c].
   Caryatides.—The Greeks  sometimes departed so far from
 the strict use of the orders, as to introduce statues, in the place
 of columns,  to  support the entablature.   Statues of slaves, he-
 roes, and gods, appear to have been employed,  occasionally for
 this purpose.  The principal specimen of this kind of architecture,
 which remains, is in  a portico, called Pandroseum,  attached to
 the temple of Erectheus, at Athens,  in which statues of Carian
 females, called  Caryatides, are  substituted for columns [PL
 IV. Fig. 9].  One of these statues has been carried to London.
   Grecian Temple.—The most remarkable public edifices of
 the Greeks, were their temples.   These being intended as pla-
 ces of resort for the priests, rather  than for the convening of
 assemblies  within, were in general  obscurely lighted.   Their
 form  was commonly that of an oblong square,  having a colon-
 nade  without, and a  walled cell within.  The cell, was usually
 without windows, receiving its light only from a door at the end,
 and sometimes from an opening in the  roof.  The part of the
 colonnade which formed the front portico, was called the pro-
 naos, and that which formed the back part, the  posticus.   The
 colonnade was  subject to great variety in the number and dis-
position of its columns, from which Vitruvius has described sev-

in leaves  of acanthus.  A more probable supposition traces its origin to some
of the Egyptian capitals, which it certainly resembles. 
136
OF ARCHITECTURE AND BUILDING.
en different species of temples.   These were,  1. The temple
with antce.   In this  the  front was composed of pilasters, call-
ed antae, on the sides, and two columns in the middle.
  2. The Prostyle.   This had a row of columns at one end
only.
3. The Amphiprostyle,  having  a row of columns  at  each
end.
  4. The Peripteral temple.  This was surrounded by a sin-
gle row of columns, having six in front, and in rear, and eleven
counting the angular columns, on each side.
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o o   '           '   o o
0 O   |           |   o o
o ------------------ o
ooooooooooo
  5.  The  Dipteral, with a double row of columns all  round
the cell, the front consisting of eight.
000000000000000
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 o     ,      ■   |     O 0
0 o o   '         '    0 0 0
0 0 O   |         |    0 0 0
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000000000000000
000000000000000 
OF ARCHITECTURE AND BUILDING.          137
   6.  The  Pseudo-dipteral differs from the dipteral, in having
a single row of columns on the sides, at the same distance from
the cell, as if the temple had been dipteral.
000000000000000
0                       0
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0 0                .00
o    I              I     o
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000000000000000
   7. The Hypceihral temple had the centre of its roof open to
the sky.   It was colonnaded without, like the dipteral, but had
ten columns in front.   It had also an internal colonnade, called
peristyle, on both sides of the open space, and composed of two
stories or colonnades, one above the  other.
ooooooooooooooooooo
o o ooooooooooooooooo
0 o —"—"——""■——'—"———■^— 0 0
000 |  OOOOOOOOO  I  O 0J>
ooo                   ooo
o o o                   ooo
ooo I  ooooooooo  I  ooo
o o                   '   o o
ooooooooooooooooooo
ooooooooooooooooooo
   Temples, especially small ones, were sometimes made of a cir-
cular form.  When these were wholly open, or without a cell,
they were  called Monopteral temples.  When there was a cir-
cular cell within the colonnade, they were called Peripteral. *
   Grecian Theatte.—The theatre of the  Greeks, which was
afterwards  copied by the  Romans, was built in the form of a
horse shoe, being semicircular on one side, and square on the
other.   The semicircular part, which contained the audience,
was  filled  with concentric seats, ascending from the centre, to

   The intercolumniation, or distance between the columns, according to
Vitruvius, was differently arranged under the following names.  In the pyc-
nostyle, the columns were a diameter and a half apart.  In the systyle they
were two diameters apart.  In the diastyle, three.  In the amostyle, more
than three.  In the eustyle, two and a quarter.
               18 
138
OF ARCHITECTURE  AND  BUILDING.
 the outside.   In the middle, or bottom, was a semicircular floor
 called the orchestra.  The opposite, or square part, contained
 the actors.  Within this was erected, in front of the audience,
 a wall ornamented with columns and sculpture, called the scena.
 The  stage,  or floor, between  this part and the orchestra, was
 called the proscenium.  Upon this floor was often erected a
 moveable wooden  stage, called, by the  Romans, pulpitum.
 The ancient theatre was open to the sky, but  a temporary awn-
 ing was erected to  shelter the audience from the sun and  rain.
   Remarks.—Grecian architecture is considered to have been
 in its greatest  perfection in  the age of Pericles  and Phidias.
 The sculpture of this period, is admitted to have been superior
 to that of any other age; and although architecture is a more
 arbitrary art, than sculpture,  yet it is natural  to conclude, that
 the state of things which gave birth to excellence in the  one,
must have produced a corresponding power of conceiving sub-
limity and beauty in the  other.  Grecian  architecture  was  in
 general, distinguished  by simplicity of structure, fewness  of
parts, absence of arches, lowness of pediments  and roofs, and
 by decorative  curves, the outline of which was a spiral line,  or
 conic section, and not a  circular arc, as afterwards adopted by
 the Romans.

   Plate  IV.—This plate is intended to give a  view, upon the
 same scale as  PL 1, of various examples of Grecian architec-
 ture, the remains of which are extant at the present  day.   The
 limits of  the plate  permit only the front  elevation to be given,
 which, in the oblong Grecian  temples, was the end of the build-
 ing.
   No. 1, represents the principal temple at Paestum, in Italy.
 At this place  are now  standing, the walls and colonnades of
 three temples, built in the  ancient Doric  style, and undoubt-
 edly  erected  by a Grecian  colony in that country.   The
 characters of  this early  Doric, are  short  and heavy columns
 much diminished upwards, large capitals, and a massive entab-
 lature, nearly  half as high as  the columns.   The  outline of the 
             OK  ARCHITECTURE AND BUILDING.         139

columns in this building is straight, or  without entasis.  The
temple  appears to have been hypasthral, though the number of
columns is less than in the rule prescribed by Vjtruvius.
   No.  2, is  the  Temple of Concord,  commonly so called, at
Agrigentum,  now Girgenti, in Sicily.  It is erected in the mas-
sive style of  the older Doric, on a stylobate of four steps, and,
with the exception of the roof, is in a state of good preservation
at the present day.   Other  Doric ruins are found in the  same
place,  also  at  Segesta,  Selinus, and other parts of Sicily.
Views of these structures are given in Wilkins's Magna Gracia.
   No.  3, is the Temple of  Theseus, at Athens, situated in the
lower part of that city, some way from the Acropolis.   It is the
most perfectly  preserved of any of the Athenian edifices, its
columns and walls having suffered scarce any dilapidation.   At
the top of  its stone platform, or stylobate, it measures 104 feet
in length, by 45 in breadth, and has six columns on each front,
with  thirteen on each side, counting those at the angles.  The
temple of Theseus was erected by Cimon, the son ofMiltiades,
about 450  years before Christ.   The sculptures upon the frieze
of this building, are supposed by Stuart, and others, to refer to
the  exploits  of Theseus, but according to Mr Wilkins, *  they
represent the labors of Hercules.
   No.  4,  is the Propylasa, at Athens, a  structure of much
beauty,  which commanded  the  entrance to the Acropolis, or
citadel.  Besides a portico of six Doric columns on each front,
it had an Ionic colonnade within, and a separate quadrangular
building attached to each  side.   Before the entrance, are two
large pedestals, supposed to have supported  equestrian statues.
The  Propylaea were ascended by steps at different stages, and
had also an inclined plane for  carriages.  This building was
erected in  the time of Pericles, and is now in a ruinous state,
a great portion of what  remains being  hidden by the  walls of
the Turks.  No.  5, is a transverse  section of the  Propylasa,
made at right angles with the former veiw, and showing the dif-
ferent ascents.
Topography and Buildings of Athens, 8vo. 1816'. 
140
OF ARCHITECTURE  AND  BUILDING.
   No. 6, is the fagade of the  Parthenon, or temple of Miner-
va, situated on the summit of the Acropolis, at Athens.   This
building is now considered the best model for the Doric order,
and no edifice, ancient or modern, commands such general ap-
plause at the present day.  It was built by the architect Ictinus,
during the  administration of Pericles, about 440 years  before
Christ.   Its  decorative sculptures  are  supposed to have been
executed under the  direction of  Phidias.  The platform  or
stylobate, consists of  three steps,  the  uppermost of which is
227 feet in length, and 101 in breadth.   The  number of col-
umns is  eight in the  portico of each  front, and seventeen on
each flank, besides which there is an inner row of six columns
at each end of the cell.   The  proportional height of the col-
umns is five diameters and 33 minutes, and they diminish  thir-
teen minutes in diameter from bottom to top.    The sculptures
on the frieze represent the  combats of the Centaurs and La-
pithae.  Those on the eastern pediment, represented the fabu-
lous  birth of Minerva, and those on the western,  the contests
between  that  goddess and Neptune, for the right of presiding
over the city.  When Athens was  visited  by Wheler, in 1676,
the Parthenon remained entire, with the exception of its roof.
But  during the siege of  the city by the Venetians, in 1687, a
shell  which  exploded in the midst of the  cell, destroyed  the
whole central part of the wall, together with  nineteen of the
columns.   Most of the  sculpture of both  pediments has also
disappeared.
   No. 7,  is  the choragic monument of Thrasyllus, situated
without the Acropolis, and constituting the front of a grotto.  It
is not, strictly speaking, of any architectural order, but departs
from the Doric in having a row of circular wreaths, instead of
triglyphs, and a continuous  row of guttae at the bottom  of the
frieze.
   No. 8, is the small Ionic amphiprostyle temple on the banks
of the Ilissus, which was standing in Stuart's time, but has now
wholly  disappeared.    The  delineations  obtained  from  this
building by Stuart, have since furnished the  most popular models
of the Ionic order. 
OF ARCHITECTURE  AND  BUILDING.
141
   No. 9, is the Erectheum, an Ionic  building, much admired,
in the Acropolis, at Athens.   It comprises  two temples, one
dedicated to Minerva  Pofias, the other to the nymph  Pandro-
sus.   The  smaller portico of the  Pandroseum, is remarkable
for a row of Caryatides, or female statues, which perform the
office of columns in supporting the entablature.*   No.  10, is
an Ionic capital from  the temple on the Ilissus.  Those of the
temple of Minerva Polias, were similar in the general form of
the volutes, but  had  also  an ornamented  neck  above the
flutings.
   No. 11. represents the fagade  of the Temple of Apollo
Didymaeus, near Miletus.  It was among the most celebrated
Grecian  structures.   It was termed by Strabo,  the greatest of
all temples, and was ranked by Vitruvius, with that of Diana,
at Ephesus.   Although few of its columns  are  now standing,
the ruins give evidence of its original size and  magnificence.
It appears to have been a dipteral  temple, surrounded with a
double row of columns, triple in front, and in all 112.   Views
of this building are given in the Ionian Antiquities, and  in the
Voyage Pittoresque of  Choiseul Gouffier.
   No. 12, is the choragic monument of Lysicrates, at Athens,
sometimes  improperly  called the   Lantern  of  Demosthenes.
This  elegant little structure has a circular ornamented roof of
one stone,  and  six Corinthian columns  engaged in a circular
wall, the whole supported,  on a square basis.   It is now half
inclosed in  a modern convent. »
   No. 13,  is the  Octagon tower, at Athens, commonly called
the Toiver of  the winds, from  the emblematic  sculptures  on its
sides.  Its  sides are marked  with lines for indicating the hour
of the day by the shadows of  gnomons.

  * One of these  statues was carried off by Lord Elgin, and is placed with
other Athenian marbles in the British Museum.  Stuart makes this building
to consist of three temples, viz. those of Erectheus, Minerva Polias, and Pan-
drosus.  Mr Wilkins divides it into two. 
112
OF ARCHITECTURE AND BUILD INC.
                      ROMAN  STYLE.

   Roman  architecture had its origin in copies of the Greek
 models.   All the Grecian orders  were introduced into  Rome,
 and variously modified.   Their number was augmented by the
 addition of two new orders, the Tuscan and the Composite.
   Tuscan Order.—This order, derived from the ancient Etrus-
 cans, is not unlike the Doric deprived of its triglyphs and mutu-
 les.   It had a simple base containing one torus.  Its column was
 seven  diameters in  height, with an astragal below the capital.
 Its entablature,  somewhat like the Ionic, consisted  of plain,
 running surfaces.  There is no vestige of this order among an-
 cient ruins, and  the modern examples of it are taken from the
 descriptions of Vitruvius  [PL VII. Fig. 6].
   Roman Doric.—The Romans modified the Doric order by
 increasing the height of its column to eight diameters.   Instead
 of the echinus which formed the Grecian capital, they employ-
 ed the ovolo, with an astragal and neck below it.   They placed
 triglyphs over the centre of columns, not at the corners, and used
 horizontal mutules, or introduced foreign ornaments in their stead.
 The Theatre of Marcellus has examples of the Roman Doric
 [PL VII. Fig. 8].
   Roman Ionic.—The Romans diminished- the size of the vo-
 lutes in the Ionic order.   They also introduced a kind of Ionic
 capital in which  there were four pairs of diagonal volutes, in-
 stead of two pairs of parallel  ones.   This  they usually added
 to parts of some other capital, but at the present day it is often
 used alone, under the name of modern Ionic.
   Composite Order.—This fifth  order was made by the Ro-
 mans out of the Corinthian, simply by combining its capital with
that  of the  diagonal, or modern  Ionic  [PL VII.  Fig.  11].
Its best example is found in the arch of Titus.  The  favorite
order, however, in Rome  and its colonies, was the Corinthian,
and it is this order which  prevails among the ruins, not only of
Rome, but  of Nismes, Pola, Palmyra, and Balbec. 
            OF  ARCHITECTURE AND  BUILDING.         143

   Roman Structures.—The temples of the Romans, sometimes
resembled those of the Greeks, but often  differed from  them.
The Pantheon, which is the most  perfectly preserved  temple
of the Augustan age, is a circular budding, lighted only from an
aperture in the dome, and having a Corinthian portico in front.
The amphitheatre differed from the theatre, in being a complete
circular, or rather elliptical building, filled on all sides with as-
cending seats for spectators, and leaving only the central space,
called the arena, for the combatants and public shows.   The
Coliseum is a stupendous  structure of this kind.   The aque-
ducts were stone  canals, supported on massive arcades, and
conveying large streams of water, for the supply of cities.  The
triumphal arches, were commonly solid oblong structures, orna-
mented with sculptures, and open with lofty arches for passen-
gers below [PL VI. Fig. 8].   The Basilica of the  Romans,
was a Hall of Justice, used  also as an exchange, or place of
meeting for merchants.  It was lined on the inside with  colon-
nades of two stories, or with two tiers  of columns one over the
other.   The  earliest  christian churches at Rome, were some-
times called basilicae, from  their possessing an internal  colon-
nade.   The  monumental pillars,  were towers in the shape of
a  column on a pedestal, bearing a  statue on the summit, which
was approached by a spiral staircase within.   Sometimes, how-
ever, the column was solid.   The  Thermce, or baths, were vast
structures, in which multitudes of people could bathe at once.
They were supplied with  warm and  cold water, and fitted up
with numerous rooms for purposes of exercise and recreation.
   Remarks.—In several particulars, the Roman copies differed
from  the  Greek models on which they were founded.   The
stylobate or substructure, among the Greeks, was usually a plain
succession of platforms, constituting an equal access  of steps,
to all sides of the building.   Among  the  Romans, it became
an elevated structure, like a continued pedestal, accessible by
steps only at one end.  The spiral curve of the Greeks, was
exchanged for the geometrical  circular arc, as exemplified in
the substitution of the ovolo for the  echinus in the Doric capital. 
J 44
OF ARCHITECTURE AND BUILDING.
The  changes  in  the orders, have been already mentioned.
After the period of Hadrian, Roman architecture is considered
to have been on the decline.  Among the marks of a deterior-
ated style introduced in the later periods, were columns with
pedestals, columns supporting arches, convex  friezes,  entab-
latures squared so as to represent  the  continuation of the col-
umns,  pedestals for statues projecting  from the sides of col-
umns,  niches  covered with little pediments, he.   See Plates
VI. and VII.

   Plate V.—In this plate, is  represented a series of buildings
in the  Roman style, reduced  to a scale after Durand.  They
are all of the  Corinthian  order.  No. 1, is  the  l*untheon, al-
ready  mentioned, of which the portico is of stone, while the
body, or circular part covered by the dome,  is of brick.  The
occurrence  in this building, of two pediments, one above the
other, is considered a defect, and probably  indicates  that the
parts of the edifice were  erected at different times.   The en-
tablature consists  only of a cornice.   In most  other  respects,
the symmetry of this building is much admired.
   No.  2, is the Temple of Antoninus and Faustina, at Rome.
The walls  and columns are raised upon an  elevated  stylobate
and are approached by steps in front only,  differing in this re-
spect  from the Grecian temples, which were accessible on all
sides.
   No. 3, is the Maison carree at Nismes,  in  France.  It is
pseudo-peripteral, having its columns engaged in the wall, with
the  exception of  ten, which  form the portico in front.  It has
been lately discovered that this building, which remains in ex-
cellent preservation, was  erected to the memory of Caius and
Lucius Caesar, sons of Agrippa, and grandsons  of Augustus. *

   * The origin and date of this beautiful  temple were unknown, until an ar-
tist, named Seguier, made out the inscription on the frieze, by connecting to-
gether the holes in which the nails were driven, that formerly confined bronze
letters upon the wall. 
             OF ARCHITECTURE  AND  BUILDING.          145

  No. 4, is the circular, peripteral temple of Vesta, at Rome.
The temple of Vesta, at Tivoli, outlined in Plate I, differs from
this, in  having a raised stylobate.  The  dome, in both  these
buildings, is an imaginary  restoration, made after  the  rules of
Vitruvius.  Messrs Taylor and Cresy have given to the temple
at Tivoli, a conical roof like  that of the monument of  Lysi-
crates.
  No. 5, is a temple at Pola, in Istria, dedicated to Rome  and
Augustus.   At this place  are  many  interesting  antiquities,
among which are an amphitheatre and triumphal arch.
   No. 6, is the structure commonly called the Arch of Theseus,
at Athens.  It was erected probably by the Roman emperor Ha-
drian, to divide the new city from the old, and bears an inscrip-
tion on each  side, indicating that on one side is seen the city of
Theseus, and on the other the city of Hadrian.
  No. 7, is a sepulchre at Mylassa, in Asia Minor, apparently
of Roman  origin,  and  described in the  Ionian antiquities.  Its
angular pillars are square, but the intermediate columns have
a form  very  unusual in ancient or modern architecture,  being
compressed,  so that a section of the shaft represents an ellipse.
They are fluted for half their length.
   No. 8, is the triumphal  arch of Constantine, at Rome, which,
with  the exception of a part of  its  sculptures, is entire  at the
present day.   This arch was built after the arts had begun to
decline, and  is constructed chiefly of materials taken from  the
arch  of Trajan, erected  two centuries before.  Its columns
stand upon separate, projecting pedestals, and have a part of
the entablature squared upon the top of each.
  No. 9, is the external portico of the  Temple of the Sun, at
Palmyra.   The ruins of this city exceed in extent and magnifi-
cence anything else which remains of  antiquity in Europe, or
Asia.  It is built in the Corinthian order, and in the later style
of Roman architecture, characterized by niches in the walls at
different heights containing statues, by numerous  small  pedi-
ments and entablatures, also in some cases by statues  support-
ed on brackets, or pedestals projecting from the sides of columns.
               19 
146         OF ARCHITECTURE AND BUILDING.

In  this  portico, an example occurs of double columns, a fea-
ture rarely met with, in antique architecture, but sometimes used
by the moderns, upon an extensive scale. *
  No. 10, is the circular temple at Balbec, a place distinguish-
ed  by the  magnificence  and colossal size of its ruins.   This
temple is singular in the form of its outline, which is circular,
with large concave recesses between all the columns, as shown
more  distinctly in the ground plan, No. 11, of the same build-
ing.  In other respects it partakes of the later Roman style.
  No. 12, is the  octagonal temple of Jupiter, forming part  of
the palace erected by the Roman emperor Diocletian, at Salo-
na, now Spalatro, in  Dalmatia, where its  extensive  ruins are
still extant.

                  GRECO-GOTHIC STYLE.

   After the dismemberment of the Roman empire, the arts
degenerated so far, that a custom became prevalent of erecting
new buildings with the fragments of old ones, which were di-
lapidated and torn down for the purpose.   This gave rise to an
irregular style of  building, which continued to be imitated, es-
pecially in Italy, during the dark ages.   It consisted of Grecian
and Roman details,  combined  under new forms, and piled  up
into structures  wholly unlike the antique originals.   Hence the
names  Greco-gothic and Romanesque architecture have been
given to it.  It frequently contained arches upon columns, form-
ing successive arcades, which were accumulated  above each
other to a great height.   The  effect was. sometimes  imposing.
The Cathedral and Leaning Tower at Pisa, and the Church of
St  Mark, at Venice, are cited as the best specimens of this
style  [PL  1.  Fig.  15.  and PL  VII. Fig.  13].   The  Sax-
on architecture, used anciently in England, has some things in
common with this style [PL VII. Fig.  14].

  * To the regular duplicature of columns introduced in the colonnade of the
Louvre, in Paris, Perrault has given the name of arceo-systyle. See note p. 137. 
OF ARCHITECTURE  AND  BUILDING.         147
                     SARACENIC STYLE.

   The edifices erected by the Moors and Saracens in Spain,
 Egypt, and Turkey, are  distinguished, among other things, by
 a peculiar form of the  arch.   This is a curve, constituting more
 than half of a circle, or ellipse.   This  construction of  this
 arch, is unphilosophical, and comparatively insecure.   A simi-
 lar  peculiarity exists  in  the  domes of the oriental Mosques,
 which are sometimes large  segments of  a sphere, appearing as
 if inflated; and at other times concavo-convex in their outline,
 as in  the mosque  of  Achmet.   The  minaret is a tall slender
 tower, peculiar to  Turkish  architecture.  A peculiar flowery
 decoration called arabesque, is common in the Moorish  build-
 ings of  Europe,  and Africa [PL  VI.  Fig.  3.—PL   VII.
 Fig. 16.  PL I. Fig.;? and?].

                      GOTHIC STYLE.

   The Goths, who plundered Rome, had nothing to do with
 the invention of Gothic architecture.  The name was introduc-
 ed by Sir Christopher  Wren, and others, as a term of reproach,
 to stigmatize  the edifices of the middle  ages, which  departed
 from the purity of the antique models.   The term was, at first,
 very extensive in its application, but it is now confined chiefly,
 to what may  be called  the modern Gothic,—the style  of build-
 ing cathedrals, churches, abbeys,  &c. which was  introduced in
 England six or eight centuries ago, and adopted, nearly at  the
 same time, in  France, Germany, and other  parts of  Europe.
 The Gothic style is peculiar and strongly marked.  Its princi-
 ple seems to have  originated  in  the imitation of groves, and
 bowers, under which the Druids performed their sacred  rites.
 Its characteristics, at sight, are, its pointed arches, its pinnacles
 and  spires, its large  buttresses, clustered pillars, vaulted roofs,
profusion of ornaments, and  the general  predominance of the
perpendicular over the  horizontal. 
148         OF ARCHITECTURE  AND  BUILDING.

  Definitions.—As the common place for the display of Goth-
ic architecture, has been in ecclesiastical edifices, it is necessa-
ry to understand the usual plan and construction of these build-
ings.   A church or cathedral is commonly built in the form of
a cross, having a tower, lantern, or spire, erected  at the place
of intersection.  The  part of  the cross, situated toward  the
west, is called the nave.  The opposite or eastern part is called
the  choir, and within this is the chancel.   The transverse por-
tion, forming the  arms  of the cross, is called the  transept.
Nave      g      Choir
   Any high building erected above the roof, is called a steeple;
if square topped, it is a tower; if long  and acute a spire, and
if short  and light, a lantern.  Towers of great height, in pro-
portion to their  diameter,  are  called  turrets.   The  walls  of
Gothic churches, are supported on the outside, by lateral pro-
jections, extending from top to bottom, at the corners, and be-
tween the windows.  These are called buttresses, and they are
rendered necessary to prevent the walls from spreading  under
the enormous weight of the roofs [PL VI. Fig. 4,  and 5].
On the tops of the buttresses, and elsewhere, are slender pyra-
midal structures,  or spires, called pinnacles.   These are orna-
mented on their sides, with  rows of projections, appearing like
leaves or buds, which are  named crockets.   The  summit,  or
upper edge of a wall, if straight, is called a parapet; if indent-
ed, a battlement.   Gothic windows were commonly  crowned
with an acute arch.  They  were long and narrow, or if wide,
were divided into perpendicular lights by mullions.   The lateral 
OF ARCHITECTURE AND BUILDING.
149
 spaces on the upper and  outer  side of the  arch, are called
 spandrells; and  the ornaments in the top, collectively taken,
 are the tracery.  An oriel,  or bay window, is a projecting win-
 dow.  A wheel, or rose window, is large and circular.  A cor-
 bel, is a bracket or short projection from a wall, serving to sus-
 tain a statue, or the springing of  an arch.
   Gothic pillars or columns, are  usually clustered,  appearing
 as if  a number were bound together.  The  single shafts  thus
 connected, are called boltels.  They are confined chiefly to the
 inside of buildings, and  never support anything like an entab-
 lature.  Their use is to aid in sustaining the  vaults under the
 roof, which rest upon them at springing points [PL VI. Fig.
 6].   Gothic vaults intersect each other, forming angles called
 groins.   The parts which are thrown out of the perpendicular
 to assist in forming them, are the pendentives.  The ornament-
 ed  edge of the groined  vault, extending diagonally,  like an
 arch, from one support to  another, is called the ogyve.   The
 gothic term gable,  indicates the erect end of a roof, and  an-
 swers to the Grecian pediment, but is more acute.
   The Gothic style of building  is more  imposing,  and more
 difficult to execute,  than  the  Grecian.  This is  because  the
 weight of its vaults  and  roofs is upheld  at a great  height, by
 supporters acting at single  points,  and apparently but barely
 sufficient to effect their object.  Great mechanical  skill is ne-
 cessary, in balancing and sustaining  the pressures, and archi-
 tects  at the present day, find it difficult to accomplish what was
 achieved by the builders of the middle ages.

  Plate  VI.—No. 1, is the front of  an ancient Egyptian tem-
 ple, at Essenay.  It has the sloping walls, concave entablature,
 crowded columns, and hieroglyphic sculptures, peculiar to the
 edifices of that country.  The roof is flat, and  supported on
 twentyfour columns inside.—No. 2, represents  an  octagonal
 pagoda, at Sinkicien, in  China.  It  gives an  example of the
 curved  Chinese roof, formed in imitation of the tent.—No. 3,
is the Mosque of Achmet,  at  Constantinople, built  in 1610. 
 150         OF ARCHITECTURE AND  BUILDING.

 It has a central  dome, surrounded by four half domes, which
 cover vast recesses resembling niches.   Its court is surrounded
 by a  sort of cloister, covered by numerous small  cupolas, and
 having tall minarets at the angles and  sides.—No. 4, is a per-
 spective  view of York  Cathedral,  one of the most admired
 specimens of Gothic architecture.  It is built in the form of a
 cross, and has three  towers, of which the  two front ones are
 surmounted by pinnacles, and  the central one by battlements.
 It was built between the years 1171  and  1426.—No. 5, is a
 Gothic exterior,  from the wall of Westminster Abbey, showing
 the buttresses, which support the walls, also the short pinnacles
 and battlements.  The slanting braces at top are called flying
 buttresses.—No. 6, is a Gothic interior, from  the nave of York
 Cathedral.  It shows the clustered pillars, pointed arches, groin-
 ed vaulting, and tracery, which belong to the Gothic style.
   Plate  VII.—In this plate  is  presented a series of columns
with some of their entablatures, arches, he,  illustrative of the
styles of building which have prevailed  in different epochs, and
countries.  The three first figures are those  of Egyptian col-
umns, all  serving to show the  massiveness of structure which
prevailed  in the buildings of  that nation.   A great variety  of
these  columns exist at the present day  in, Upper Egypt, partic-
ularly at Karnac and  Luxor,  the remains of ancient Thebes.
No. 1, is from a tomb of Silsifis, and  has an outline which  is
common  among the  Egyptian ruins.—No. 2, likewise a com-
mon form, has a capital composed of faces.—No. 3, is a column
from  Komonbu.   The idea of the Corinthian capital, seems
to have been borrowed from Egyptian specimens  of this kind.
The  column No. 4, is from the  great cave at Elephanta, near
Bombay, one of the wonderful  subterranean  structures exca-
vated by the ancient inhabitants of Hindostan out of solid rock.
 No. 5, is a column from the ruins of Persepolis.  At this place,
which contains the most remarkable  relics of the ancient arts
 of Persia, the style of architecture partakes of the Egyptian
 and Hindoo characteristics, the columns, however, being  more
 slender.—No. 6, represents the Tuscan order, used by the an-
                                                 i 
            OF  ARCHITECTURE AND BUILDING.          151

cient  inhabitants of Etruria.—No. 7, is the  Grecian Doric, of
the age of Pericles, at which time it is considered to have been
in greatest perfection.—No. 8, is the Roman Doric, represent-
ed  with a base, after the restorations of the moderns.—No. 9,
is the Grecian Ionic.   The base represented in this figure, and
the next, is called the Attic base.—No. 10,  the Corinthian or-
der.—No.  11, the Composite Order, in which the volutes are
larger than  in  the Corinthian.   The  modern  Ionic is taken
from the upper part of this capital.  The frieze is represented
as convex, a feature which is considered  peculiar to the later
or declining period of  Roman architecture.—No. 12, is a com-
bination of the column with a pedestal, and a squared portion
of the  entablature, usually attached to  the main  edifice, by
one side.   This peculiarity was introduced after the arts had
begun to decline, and appears in many of the later Roman edi-
fices.   It has been absurdly imitated in more modern times, by
making a squared  entablature to constitute a portion of the col-
umn, and placing another  entablature above  it.—No. 13, shows
a mode of building with  arches between the columns and the
entablature.  It is taken from the remains of Diocletian's pal-
ace at Spalatro, and seems to have  given rise to the Greco-
gothic style.—No. 14, which also exhibits arches upon columns,
is a specimen of Saxon architecture from the Cathedral at Ely.
No. 15, is a twisted  column  from % cloister belonging to St
Paul's  church,  without the walls, at Rome, rebuilt about the
year 800.   Columns of this sort occur in various Italian struc-
tures, but it is difficult to conceive of a form more at variance
with architectural fitness or security.—No. 16, Moorish double
columns, arches, and arabesques, from the Alhambra, at Gren-
ada.  In the same building, the true  Saracenic or horse-shoe
 arch, also occurs.—No.   17, a Gothic  pillar  from Salisbury
 Cathedral.  Other Gothic forms are seen in Plate VI. Fig. 6.
No. 18, a Chinese column from the viceroy's palace, at Canton.
No. 19, section of  a reeded Egyptian column.—No. 20, sec-
tion of  a  fluted Doric column.—No. 21,  section of  a fluted 
152         OF  ARCHITECTURE  AND  BUILDING.

Ionic column.—No's  22, 23,  and  24, sections  of different
Gothic columns.

   Application.—In edifices  erected at the present day, the
Grecian  and  Gothic outlines, are commonly employed  to the
exclusion of the rest.   In choosing between them, the fancy of
the builder, more than any positive rule of fitness, must  direct
the decision.  Modern dwelling houses have necessarily a style
of their own, as far as stories and  apartments, and windows and
chimnies, can give them one.   No more of the-styles of former
ages  can be applied to them, than what may be called the un-
essential and decorative parts.  In general, the Grecian style,
from its right angles and straight entablatures, is more conveni-
ent and fits better with the distribution of our common edifices,
than the pointed  and  irregular Gothic.   The  expense  also is
generally less, especially if anything  like thorough and genuine
Gothic  is  attempted;  a thing, however, rarely undertaken as
yet, in this country.   But the occasional introduction  of the
Gothic  outline, and the partial employment of its  ornaments,
has undoubtedly an agreeable effect,  both in public and private
edifices; and we  are indebted to it, among other things, for the
spire, a structure exclusively Gothic, which, though often mis-
placed, has become  an object of general  approbation, and a
pleasing landmark to our otties and villages.
  Wilkins'  Translation of Vitruvius, 4to. 1817;—Elmes' Lectures
on Architecture, 8vo. 1823;—Stuart's Antiquities of Athens, 4 vols,
fol. 1762, &c.;—Antiquities of Ionia, by the Dilettanti Society, 2
vols, fol. 18J.7-21;—Antiquities of Attica, by the same, fol. 1817;—
Wilkin s' Magna Grsecia, fol. 1807;—Desgodetz's Buildings of Rome,
2 vols, fol. tra. 1771;—Taylor and Cresys' Antiquities of Rome, 2 vols,
fol. 1821-2;—Durand, Recueildes Edifices, oblong fol. 1801;—Pugins'
Specimens of Gothic Architecture, 2 vols,  4to. 1823;—Brittons'
Architectural Antiquities of Great Britain, 4 vols, 4to. 1815, &c. ;—
Tredgold's Elements of Carpentry, 4to. 1821;—Nicholsons'Archi-
tectural Dictionary, 3 vols, 4to. 1821. 
CHAPTER VIII.
          ARTS OF HEATING AND VENTILATION.

 * In  cold  and temperate climates, a large portion of human
labor  is devoted to procure and sustain such a degree of heat,
as is necessary to a comfortable existence.  The means of ef-
fecting  this object, as far as the economy of fires and dwelling
houses is concerned, will be considered in the present chapter.
To procure heat, to distribute it,  to retain it, and to obviate its
inconvienences by ventilation, are  the  principal  objects that
present themselves in a survey of  the subject.

                  PRODUCTION OF HEAT.

   Fuel.—Heat is artificially obtained for common purposes, by
the combustion of fuel.   Fuel may be usefully considered with
regard to its compactness or weight, its quantity of combustible
matter, and its quantity of water.
   Weight of Fuel.—In  regard  to the first  consideration, if
other  things be equal, the more compact and heavy any fuel is,
the more difficult it is to kindle, but the more permanent will it
be found when once on fire.  Coal, for example, is a compact
fuel, when compared with light dry wood.   Coal cannot so well
be kindled by a small blaze, nor by a very small quantity of oth-
er  combustible  matter on fire, because  its density  renders it a
rapid  conductor, and it carries off the heat of the kindling sub-
stance, so as to extinguish  it, before it is itself raised to  the
temperature necessary for its combustion. But if the heat of oth-
er fuel be  applied to it in sufficient quantity, and long enough,
to  ignite it, it then  produces a powerful fire, and a  much more
durable one than lighter  fuel.  Light fuel, on  the other  hand,
               20 
154        ARTS OF HEATING AND VENTILATION.

being a slow  conductor of heat, kindles easily; and, from the
admixture of atmospheric air in its pores  and  crevices, burns
out rapidly, producing a comparatively temporary, though often
a strong,  heat.
   Combustible  matter of Fuel.—The  quantity of  combustible
matter of fuel, if the weight and other circumstances be equal,
may be learnt from  the  ashes, or residuum, left after the com-
bustion.  For example, good Newcastle coal, contains a great-
er portion of combustible  matter, than Nova  Scotia coal, and
leaves behind a smaller amount of earthy  and incombustible
substance.   The heating power, and consequent value, of dif-
ferent kinds of fuel,  is affected by this circumstance, though by
no means dependent on it.   The fitness of fuel for various pur-
poses, is furthermore affected by the facility, with which it gives
off a part of its combustible matter in the form of vapor, or
gas ; which, being burnt in that state, producesj^awe. *  For ex-
ample, the bituminous coals abound in volatile matter, which,
when ignited, supports a powerful blaze.  On the other hand,
the Lehigh and Rhode, Island coals are destitute  of bitumen,
and  yield but little  flame.   It is from similar causes, that dry
pine wood produces a powerful blaze, while its charcoal yields
comparatively little.   A blaze is  of great service, where heat is
required  to be applied to an extensive surface, as in reverberat-
ing furnaces, ovens, glass houses, he.   But  when an equable,
condensed, or lasting fire is wanted, the more solid fuels, which
blaze less, are to be preferred.
   Water in Fuel.—The quantity of watery fluid contained in
fuel, greatly affects  the amount of heat it produces, much more
indeed, than is commonly admitted in  practice.   It is a well
known law  of  chemistry, that the evaporation of liquids, or
their  conversion  into steam, consumes, and renders latent, a
great amount of caloric.  When green wood, or wet coal, are
added to the fire, they abstract from it by degrees, a sufficient
part of its heat, to convert their own sap or moisture into steam,
before they are capable of being burnt.   And as long as any
See Chapter IX. Art. Flame. 
ARTS  OF HEATING AND VENTILATION.        155
considerable part of this fluid remains unevaporated, the com-
bustion  goes on slowly, the fire is dull, and  the  heat* feeble.
Green wood commonly contains a third, or more,  of its weight
of watery fluid, the quantity varying according to the  greater
or less porosity of different trees.  Nothing is further from true
economy than to burn green wood, or wet coal, on the suppo-
sition that because they are more durable, they will in the  end
prove more  cheap.   It is true, their consumption is less rapid ;
but to produce a given amount of heat, a far greater amount of
fuel must be consumed.   Wood that is dried under cover is bet-
ter than wood dried in the open air, being more free from de-
composition.
   Not only the production of steam, but likewise the formation
of different  gases,  which are evolved during combustion, af-
fect the usefulness of fuel, according to their quantity and  ca-
pacity for heat.  It is difficult, however, to estimate with accu-
racy the amount of their practical effect.
   Charcoal.—Charcoal is prepared from wood, and coke in a
similar  manner from pitcoal; by raising  those substances to a
high temperature, sufficient to deprive  them of their moisture
and volatile  matter.   When intended for chemical uses, char-
coal is made by exposing wood to  heat in  iron  cylinders, or
other close vessels.  But for the common purposes of fuel, it
is made by a sort of smothered combustion, in which masses of
wood, when set on fire, are covered with earth, so as nearly to
exclude the  atmospheric  air.  This exclusion of air prevents
the wood from being consumed, while the red heat, which is
kept up for some time, dissipates the moisture  from its pores.
Charcoal  is generated in a small way,  every night, in  fires
which are raked up; the brands and half burnt coals, are kept
from consuming, by the  partial exclusion of the air, while the
light ashes, being a slow conductor of caloric, prevent them from
cooling  below a red heat.   Charcoal, when newly made  from
the heavier kinds of wood, such as oak and walnut, is a power-
ful, and for some purposes, an economical kind of fuel.  Coke,
a kind of fuel used for certain  purposes in England, is charred
pitcoal.   It  produces a strong and  steady heat, but  does  not 
156        ARTS OF  HEATING AND VENTILATION.

blaze.   Large quantities of coke are formed in the manufacto-
ries of coal gas.

                COMMUNICATION OF  HEAT.

  Radiated and conducted Heat.—Caloric, or heat,  is com-
municated to apartments, by fires kept in  them, in two ways.
A part of it is radiated, the rest is conducted.   The first por-
tion passes through the air with great velocity, in diverging rays.
The  second, penetrates  slowly through  the  densest bodies,
whether transparent, or opaque.  In a fire place or open stove,
the heat which is felt by holding the hand before the fire, is
radiated  caloric.   That  which is felt by placing the  hand on
the iron or bricks, is conducted caloric.   To enjoy the full ef-
fect of radiated caloric, we must be  in presence, or  sight of
the radiating object.   To receive  conducted heat, we must be
in contact with the substance which imparts it.   Since, however,
we cannot remain in contact with the fire itself, we derive our
conducted heat from the air, a fluid, which constantly touches,
and envelopes our persons; and which, when heated in itself,
becomes a source of warmth to us.  The object of the various
contrivances, known under the names of stoves and fire places,
is to enable  us to use  fire with  safety, and to obtain  from it a
due supply of radiated caloric, and heated air.
   In common  cases, radiant heat is more agreeable, than con-
ducted heat, when we wish to obtain  a sudden warmth ; since
its degree may be increased at pleasure, by altering our proxi-
mity to the fire; the effect of the radiation being inversely pro-
portionate to the square of the distance.   But as only one half
of the recipient body can be warmed at a time by radiation, no
person surrounded by a cold atmosphere, can be  made uniform-
ly warm, by the radiated heat of a fire.   It  is  only when the
surrounding atmospheric air has become warm, that we obtain
all the advantage which fire is capable of affording.
   Fire  in  the open  Air.—The simplest, and least effectual
mode, by which heat can be obtained, is from a fire in the open 
           ARTS OF HEATING AND VENTILATION.         157

air.   The hunter,  or backwoodsman,  when he encamps for the
night, builds a fire of logs, and lays down to sleep, with his feet
extended towards it.  In this situation he "can enjoy only a small
portion of the radiated  heat of the fire, this heat being thrown
off equally in  all  other directions.   Of the conducted heat
he  obtains  none;  for the  air  which  surrounds   the  fire
having 'nothing to confine it, ascends by its diminished spe-
cific gravity, as fast as it is warmed, and its place is immediately
supplied by strata  of colder air  from beneath.   Hence  a cur-
rent of  cold  air will take place from  the atmosphere  on all
sides, towards the  fire, so that the person who derives warmth
from the fire on one side, will on the other be exposed to addi-
tional cold.  The first  step towards remedying this  inconve-
nience,  is to  build up a barrier, or imperfect wall, on  the out-
side of  the place   occupied by the tenant.   This will intercept
the current of cold air, and oblige it to approach the fire by oth-
er directions, at the same time that it will gradually become heat-
ed itself, and radiate back a portion of its warmth.   The next
improvement consists in extending the  wall, so  as completely
to surround the fire, thus obliging the  air to approach it from
above, or from doors and avenues purposely left for its entrance.
This is, in fact, the commencement of  a  dwelling house.   A
roof with an  aperture for the escape of  the smoke, is a further
improvement on the plan, and lastly the introduction of a  chim-
ney, at once renders the mansion convenient and tenantable. *
   Fire places.—Chimnies  from their usual situation in regard
to rooms, and also  for the sake of a more perfect draught, have
an opening on one side of their base, to which  we give the name
of fire place.   The fire place in former times was  an oblong
or cubical cavity,  having its sides  nearly  at right angles with
the back.  In a cavity of this description, the greater part of
the heat generated  by the fire, was totally lost to the apartment,
nearly all the conducted heat being carried, with the air, up the
chimney; while of the  radiated heat, but a small part  could
directly enter the room,  viz. the part radiated from the front of
* See Sylvester's account of the Derbyshire Infirmary. 
 158        ARTS OF HEATING  AND  VENTILATION.

 the  fire ; the  heat of the other  sides being chiefly thrown into
 the hearth, back, and sides, or up the chimney.   In the old fire
 places, the inconvenience was still further  augmented by in-
 creasing their dimensions to an enormous size, so that seats or
 benches could be  placed on each  side, on the inside of the
jambs.   The consequence was,  that a prodigious current of air
 was constantly carried  up the chimney, and the seats, on the
 inside of the fire place, became the only comfortable  ones  in
 the room.
   Admission of cold Air.—It  is  obvious, that in apartments
 with  open fire places, the air must be continually shifting, and
 that cold air must enter at the crevices of the doors and win-
 dows, to supply the place of that which maintains the combus-
 tion, or escapes up the chimney.  In moderate weather this
 change of air is an advantage, since it freshens and ventilates
 the room, the air of which would otherwise become close and
 impure.   In moderate weather also, the radiant heat is adequate
to warm the walls of the room,  which  in  their turn become
 sources of radiant heat, and  likewise contribute to warm the
 air by their contact.  But in very cold weather, it is nearly or
 quite impossible to render a large apartment warm by means of
 a common open fire place, for, in proportion to the briskness of
the fire itself, will be the rapidity with which the cold air press-
 es into the room, and a  person near the hearth feels perhaps as
much cold on one side of his body, as heat on the other.
   Open Fires.—The  cheerful  sight of an open fire, to which
habit and association have attached us, has created a strong and
 almost genera] preference to the open fire place over the close
 stove,  and a desire, by  remedying its  defects, to make it  more
 effectual and useful.  Of various philosophers who have exer-
 cised their ingenuity on this  subject,  the  two  who  appear to
have labored with most  success, are our countrymen, Dr Frank-
lin, and Count Rumford.
   Franklin Stove.—Dr Franklin, whose writings on the econ-
omy of fire  contain the basis of many of the  improvements
which  have  since oeen introduced, invented an apparatus of 
ARTS  OF HEATING AND VENTILATION.         159
 cast iron, to which he gave the name of the Pennsylvania Fire
 place, but which is now often known by the name of Franklin
 Stove.   This fire place, when executed agreeably to the au-
 thor's instructions, is one of the most effective and economical
 modes in which an open fire  can be managed.  By means of
 a narrow and circuitous smoke flue, which is surrounded  and
 intersected with  air passages, a  great part of the heat of the
 fire is retained in the  room, and  at the same  time a current of
 fresh air,  warmed by the fire place, is  introduced  into  the
 apartment.  In  Plate  VIII.  Fig.  1. is  seen a section of the
 Pennsylvania fire place.   A, is  the place of the fuel and fire,
 BCD, the smoke  flue, passing  first  upward, then  downward
 to the floor, and escaping by the  chimney D, next the wall, K.
 E H, is the air  chamber  into which  the air is admitted from
 without the house through the passage I.   After being heated,
 it is discharged  into  the apartment by lateral openings at the
 topG.*
   Fire places which stand  out into the room, also fire places
 with hollow backs or pipes for hot air, are to be viewed in most
 instances, as simplifications only,  of Franklin's plan.
   Rumford Fire Place.—Count Rumford's fire place forms a
 pleasant and effectual mode of enconomizing the heat of an open
 fire, besides which, its cheapness  and  simplicity give it the  ad-
 vantage  over more complicated plans, and have  occasioned its
 very general introduction.   The  peculiarities of  this fire place
 consist, 1st, in an  advanced back, which brings the fire nearer
 into the room, and at the same time by narrowing the throat of
 the chimney diminishes the current of air which escapes through
 it; 2dly, in the  oblique sides or covings of  the fire place,

  * Most of the articles now sold as Franklin Stoves, are very different from
 the original Pennsylvania fire place.  If any defect existed in the plan of the
 inventor, it was in the small quantity of air admitted through a circuitous and
 obstructed channel, and in the bad character of the material, cast iron being lia-
 ble to warp and crack if exposed to great  heat and cold on opposite sides.
  The first person  who suggested the  introduction of heated air, through
hollow passages, appears to have been  M. Gauger, in a work entitled La
Me.chanique de Feu, published in 1709. 
160        ARTS  OF HEATING  AND VENTILATION.

which are enabled, when heated, to radiate their warmth into
the room.  Count Rumford recommends that the angle, made by
the sides with the back, should  be  one of 135 degrees.   He
also advises  that  the color of the covings should be  white,
this color being best  adapted for radiation.
   Double Fire Place.—For parlours, and common apartments,
no contrivance appears so pleasant and effectual, as the double
fire place, which has of late years been extensively introduced
in this city and  vicinity.  It  is a  modification of Franklin's
plan, and is  made from  any common fire place, by inserting
within it  another fire place made of soapstone, leaving an empty
space, of about an inch in  depth, between  the two, so that when
finished, the back and sides  maybe hollow.   This hollow space
does not communicate with the fire, but has two openings, one
at bottom, communicating with the external atmosphere by a
perforation in the wall, or by a tin pipe laid in the floor;  the
other opening into the apartment, at a point higher than the  fire
place, and  commonly at the side of the  chimney.   In this  fire
place, an open fire, of wood or coal, may be used with the full
advantage, ever obtained, of its  radiant heat.   A large part of
the conducted  heat  is also saved, since the air which enters
from without, becomes heated  in the hollow space, and ascends
by it in consequence of its  diminished specific gravity, entering
the room in a strong warm current.  This air serves the pur-
pose of ventilation, it  supersedes the  entrance of cold air through
the crevices and key holes,  and is also a  preventive against
smoking.   The circumstances to be attended to in the construc-
tion, are as follows.   1.  The  openings for  the air should be
large, in common cases from four to seven  inches in diameter,
since it is better to introduce a large quantity of air moderately
warmed, than a small quantity  made very hot.   More heat will
in this case be conducted from  the  stone,  and the  unpleasant
effects of burnt  air  will  be avoided.  2.  The openings into
the room should be made, when practicable, at least a foot high-
er than the top of the fire  place, for when they are on a level
with it,  or lower, the warm air is liable to be drawn up  the 
          <^RTS  OF HEATING AND VENTILATION.        161

chimney, and the main object defeated.   But if the opening is
above the fire place, then the warm air will ascend and  be dif-
fused through the upper parts of the room, till the whole is
gradually warmed.   3.  The cold air  should be taken  from
without  the  house, and  not from an entry or cellar, because
changing the  air of those places in winter, is apt to reduce them
to a freezing temperature.   The external  opening  should  be
guarded with a wire net, to exclude leaves and light substances,
and  the  internal, should be commanded by a shutter, to regu-
late  the  heat.   For safety it is best, though not always neces-
sary, that the hot air passage should not be in contact with the
woodwork of the house.  4. Good soapstone is the best mate-
rial for these fire places, and with careful use will last many years.
See Soapstone.  For wood fires, the stone should be an inch
and  a half thick, and for coal fires, two  or three inches.
   In Plate VIII. Fig. 2, is a section of a double fire place.  A,
is the place of the fire,  H,  the  soapstone back, B, the throat,
C, the chimney, E, the external  opening, D G G, the  hollow,
or passage for heated air, M, a pipe for conveying the hot air
to N, a lateral  opening  into the room.   P, the  mantel piece.
A soapstone fire place may be rendered  very effectual, by caus-
ing it to project a little into the room, and by adding an air box
to the top, as seen in PL VIII. Fig. 3 and 4.  In the  section,
Fig. 3, A, is the fire, B B, the smoke  passage,  Cec, the air
passage, D,  a box for heated air covering the fire place, and
communicating with the hollow back c c, by a side passage at
the  dotted lines, E, a side  opening  for  discharging the hot air
into  the  room, G, the mantel piece.  In fire places of cheap
construction,  a simple hollow back, made by one slab of soap-
stone, with openings  as have  been  described, will contribute
much to increase the warmth of the  room.
   Coal Grate.—When  coals are used for fuel, it is necessary,
on account of their small size, to confine them together with a
grate.   As they contain more combustible matter, in the  same
space, than  wood, and  produce a greater  degree of heat; a
much smaller fire place  answers for them.  A very small  throat
               21 
 162        ARTS  OF HEATING  AND VENTILATION.

 also in the chimney, is sufficient to carry off the smoke from a
 common  coal  grate.   With  this exception it  has  the  same
 characteristics as a common fire place.
   Anthracite  Grate.—Grates  for. burning anthracite, require
 more perpendicular height, than others, and should be of such
 a proportionate  depth as will  keep the coal together, and not
 offer too great a surface to the atmosphere.  In extremely cold
 weather, it is observed that the front surface of anthracite grows
 black and burns feebly in an open grate, while it does not in a
 furnace or  stove.   In this  case, the cold air  conducts off the
 heat of the  surface, faster than the combustion renews it; and
 if the  amount of surface be too  great in proportion for that of
 the  solid  contents, the fire will go out.   Anthracite grates  are
 usually provided with a very narrow  throat,  to  carry off the
 gases which result from the combustion;  there being  no visible
 smoke.   The throat, however, should  always  be large enough
 to transmit the smoke of any other fuel; for otherwise, a part
 of the carbonic acid which is  formed, will escape into the room,
 and  contaminate the atmosphere, in the same way as burning
 charcoal.   See Chap. I. art. Anthracite.
   Burns' Grate.—Mr Burns, of Glasgow, has made  an altera-
 tion  in the coal grate, by introducing the external air  through
 on opening immediately under the grate.  This air supplies the
 fuel  with oxygen, and furnishes most of the current which pass-
 es up the  chimney.   The  air of the room of course  remains
 comparatively stationary, and is sooner heated.  This plan, when
 combined with the  double  fire place, already  mentioned,  [PL
 VIII. Fig. 3 and 4] is a powerful mode of obtaining  heat.   A
 moveable stone screen should be placed in front of the ash pit,
 to prevent the ashes from being blown into the room.   The ex-
 ternal opening which admits the air, should not be  near any
 wood work,  as sometimes the current is reversed by winds, and
 sparks and smoke are driven out at the  opening.
   Building a Fire.—In building and maintaining an open fire,
whether of wood or coal, certain circumstances  deserve atten-
tion, in the common fire places.  Tt is advantageous to  make 
           ARTS OF  HEATING* AND VENTILATION.        163

the perpendicular height of the fuel, as great as is  consistent
with safety.  A stratum of coals, or ignited wood, will radiate
more  heat into the lower part of the room, if placed  vertically,
than if laid horizontally.  Fuel, for economy, should be so sub-
divided, as to be easy of ignition, and so placed as to give free
access for the air to its different surfaces.   In this way the smoke
is more likely to be burnt.  To secure the greatest effect of ra-
diation, the combustion should be kept,  as much as possible, to
the front surface.  In kindling a fire, the live coals should be kept
together, and placed near the bottom.   A blower, added to a
common grate, converts it for the time being, into a wind furnace.
   Furnaces.—The  object of the furnaces used by artists and
manufacturers, is the reverse of that intended to be produced
by stoves and fire places ; furnaces being  required to produce
an intense  heat, and to  confine it to a limited space.   Hence
furnaces and their chimneys  are surrounded with nonconduc-
tors, that they may expend as little of their heat, as possible, on
the air, and  surrounding objects.   They are commonly made
of fire  proof bricks, and when small, are inclosed in  iron.
Their most  simple form is that of an upright, hollow cylinder,
with a grate  at bottom.  Air or wind furnaces, have their com-
bustion supported by  a draught of air,  which ascends rapidly
because it is strongly heated and rarified.   Blastfurnaces have
the air driven through their fuel with bellows.  Reverberating
furnaces are provided with a concave covering, which reverbe-
rates, or throws back the flame, upon the substances to be heat-
ed or melted.  There are some cases in which  furnaces are
used for warming dwelling houses, particularly when fuel is used
which requires strong ignition, such as the Anthracites.
   Stoves.—Stoves differ from fire places by inclosing the fire
so as to exclude it from sight, the heat being given out through
the material of which the  stove is composed.  The common
Holland stove, of which we  have an almost infinite variety of
modifications, is an iron box of an oblong square form, intend-
ed to stand in the  middle of a  room.   The air is admitted  to
the fire  through a small opening in the door, and  the  smoke 
164        ARTS OF HEATING  AND  VENTILATION.
passes off through a narrow  funnel.  The advantages of this
stove are—1.   That being  insulated  and detached from the
walls of the room, a greater part of the heat produced by the com-
bustion is saved.   The radiated heat being thrown into the walls
of the stove, they become hot, and in  their turn radiate heat
on all sides to the room.   The conducted heat is also received
by successive  portions of the air of the  room  which pass  in
contact with the  stove.  2. The air being made, as in furnaces,
to pass through the fuel, a very small supply is sufficient to keep
up the combustion, so that little need be taken out of the room.
3. The smoke being  confined by the cavity of the stove, can-
not easily escape into the room, and may be made to pass off
by a  small funnel, which, if sufficiently thin and circuitous,
may cause the smoke to part with  a great  portion of its  heat,
before it leaves the apartment.  These circumstances render
the Holland stove one of the most powerful means we can em-
ploy for keeping up a regular and effectual heat, with a small
expense of fuel.
  The  disadvantages of these stoves are, that houses contain-
ing them are never well ventilated, but that the same air remains
stagnant in a room for a  great length of time.   Hence it neces-
sarily becomes impure by the breath of persons who  remain  in
it, and by the  burning of dust and other substances  which settle
on the heated iron of the stove.   A dryness of the air is also pro-
duced, which  is  oppressive to most persons, so that it often be-
comes necessary to place an open vessel of water on the stove,
the evaporation  of which, may supply  moisture to the  atmos-
phere.  Where  rooms are kept very warm by stoves,  it is found
advantageous  even to cause the water to boil, in order to insure
a sufficient supply of vapor.   Stoves are very useful in large
rooms,  which are frequented occasionally, but not  inhabited
constantly ; as halls, churches, he   But for common rooms,
which are occupied at all times,  they are objectionable, for the
reasons which have been stated.
   Russian Stove.—In  cold  countries, where it is desirable  to
obtain a comfortable warmth, even at  the sacrifice of other 
          ARTS  OF HEATING AND VENTILATION.        165

conveniences, various modifications of the common stoves have
been introduced, to render them more powerful, and their heat
more  effectual.  The Swedish and Russian staves  are small
furnaces, with a very circuitous smoke flue.   In principle, they
resemble a common stove with a funnel bent round and round,
until it has performed a great number of turns or revolutions
before it enters  the  chimney.  It differs,  however, in being
wholly enclosed in a large box of  stone or  brick work, which
is  intersected  with air pipes.  In  operation it communicates
heat more slowly, being longer in becoming hot, and also slow-
er in becoming cold, than the common stove.  Russian stoves
are usually provided  with a damper, or valve, at top, which is
used to close the funnel or passage, when the smoke has ceas-
ed  to  ascend.   Its operation, however,  is highly  pernicious,
since  burning  coals when they have ceased to smoke, always
gives out carbonic acid in large quantities, which, if it does not
escape up chimney, must  deteriorate the air of the apartment,
and render it unsafe.
   Cockle.—The  name  of cockle  is  given to an upper part of
a stove or furnace, resembling an inverted vessel.   A large
cockle saves much heat, since its extensive surface conveys the
heat from the flame and smoke, and communicates it to the  at-
mosphere.  In some stoves, the cockle is filled with  a  chequer
work of bricks, among  which the  smoke and flame circulate.
After  becoming once  heated, these  bricks are  slow in cooling,
and continue to yield warmth to the apartment, like the Russian
stoves, for some time after the fire is extinguished.
   Cellar  Stoves and Air Flues.—Such  is the tendency of
heated or rarified air to ascend, that buildings may be effectu-
ally warmed by air flues communicating with stoves in the cel-
lar, or any part of the building below that to be warmed.   A
large suite of apartments may be sufficiently heated in this way
by a single stove.  The stove for this purpose, should be large
and of a kind best adapted to communicate heat.   It should be
entirely enclosed in a detached brick chamber, the wall of which
should be double, that it may be a better nonconductor of heat. 
166        ARTS OF HEATING  AND  VENTILATION.
The space between the  brick  chamber  and stove should not
exceed  an inch.  In the  apparatus  of  the Derbyshire  and
Wakefield Infirmaries, which has been imitated in this country,
the whole of the air is repeatedly conducted by numerous pipes
within half an inch of the stove and its  cockle.  For the supply
of fuel, the same door which opens into the chamber, should
open also into the stove, that there may never be any commu-
nication with the air of the cellar.  A current of external  air
should be brought down  by a separate passage  and delivered
under the stove.  A part of this air is admitted  to  supply the
combustion ;  the rest passes upward in the cavity between the
hot stove and the wall of the brick chamber, and after becom-
ing  thoroughly  heated,  is conducted   through passages  in
which its levity causes it to ascend,  and be delivered into  any
apartment of the house.   Different branches being established
from the main pipe, and commanded by valves or shutters, the
hot air can be distributed at pleasure, to any one or more rooms
at a time.  This plan is very useful in large buildings, such  as
manufactories,  hospitals, he on account of the facility with
which the same stove may be made to warm the whole, or any
part of them.  The advantage of a long vertical draught ena-
bles us to establish a more forcible current of warm air.   See
page 173.  The rooms, while they are heated, are  also ventilated,
for the air which is continually brought in by the warm pipes,
displaces  that which was previously  in the  room, and the  air
blows out at the crevices and key holes,  instead  of blowing in,
as it does in rooms with common  fire places.
   Heating by Steam.—Steam is found to  be  a  useful  me-
dium  for  communicating heat to large buildings.   It  has the
advantage that it conveys heat  in any direction, horizontally,
upward, or downward, and to the most  remote  apartments of
the largest buildings.  In  green-houses  it has been made  to
yield  a sufficient supply of heat, at the distance of 800 feet
from the boiler in which it  is produced. *  When steam of low

  ~ At Messrs Loddiges, at Hackney.  Tredgold, on Warming, &c. p. 19. 
           ARTS OF  HEATING AND VENTILATION.         167

 pressure is employed, the  heat  never exceeds  212  degrees
 of Fahrenheit, so that the air in contact with the apparatus, is
 never contaminated by the burning of dust.
   In constructions for heating by steam, a strong boiler is made
 use of, provided with a safety valve, and the other appendages
 common to the boilers of steam engines.  From this boiler a
 steam  pipe is carried in any required direction, and distributes
 branches to the different apartments which are to be warmed.
 Whenever the water in the boiler is heated to the point of
 ebullition, steam passes into  the pipes and drives out the atmos-
 pheric  air through valves provided for the purpose.  As long
 as the surface of the pipes remains of  a  less heat than 212 de-
 grees, a part of the steam continually condenses, and is imme-
 diately  succeeded by fresh  steam from the boiler.   In the  act
 of condensing, its gives out its latent heat to the  material of
 which the pipe is made, and this material, in turn, imparts it to
 the air of the room.   In this manner the steam will continue to be
 condensed, and to give out heat, as long as the air of the room is at
 any point below 212 degrees.  By the condensation, a quantity of
 water is constantly formed, which, for  economy of  heat, is re-
 turned  by a separate pipe, while  it is yet warm, to  the boiler.
 Inverted syphons containing water, are used to prevent the  air
 and steam from communicating.  If the  steam pipes are made
 of thin, or weak materials, it is necessary to provide them with
safety valves opening inward;  otherwise  they  would be crush-
ed by the pressure of the atmosphere, when the fire is extin-
guished.
   In calculating the  effect of this method, it has been ascer-
tained  that under favorable  circumstances, one cubic foot of
boiler will heat about 2000 cubic feet of space in  a  cotton mill,
where  the  required  temperature is from 70 to 80  degrees of
Fahrenheit.*   And if we allow 25 cubic feet of a  boiler for
one horse's power, in a steam engine supplied  by it, it will fol-
low, that such a boiler is adequate to warm 50,000  cubic feet
■" Buchanan on Heat and Fuel, p. 160. 
 168        ARTS  OF HEATING AND VENTILATION.

 of space for every horse's  power.  It is said also  that every
 square foot of surface  in a steam pipe,  will warm 200  cubic
 feet of space.   These calculations, however, do not apply to
 buildings unfavorably arranged, nor to very cold weather.   The
 pipes,  employed to  distribute the steam, should be made of
 materials, which cool most  rapidly.   Iron, of which the surface
 is tarnished  with rust, is found to  exceed tinned iron, in the ra-
 pidity of cooling, in the proportion of about 18 to 10. *  Room
 must be allowed for the expansion of the pipes, which in cast
 iron may be taken at a tenth of  an  inch for every ten feet in
 length.   In  cotton and calico manufactories, steam is  found
 very advantageous in drying cloths quickly and well.
   In comparing the effect of steam heat, with that of smoke flues,
 different representations have been made by writers on the sub-
ject.   Mr Tredgold observes that 'he must be a novice in the
 science of heat, who cannot produce nearly the  same effect by
the one, as by the other, all other circumstances being the same.'
 The steam apparatus, however, requires more careful manage-
ment, and does not admit of neglect.   Although easily kept in
order by a skilful attendant, yet it cannot, in common cases, be
 entrusted to ordinary or careless persons.

                   RETENTION OF HEAT.

   Causes of Loss.—However advantageously  heat may be
produced and  distributed,  it will fail in producing  its desired
 effect, unless suitable provision is made for  retaining it, where
 it is wanted.   Heat constantly tends to an equilibrium, and, un-
less this tendency be retarded, dwellingjiouses and their apart-
ments will cool, as fast as they are warmed.   The chief causes
which operate to cool apartments, are—1. The  escape of the
warm air upward, through crevices, apertures, and chimnies.
2.  The power of  conducting  and of radiating heat, which all
substances possess in a greater or less degree,  and by which
Tredgold, p. 58. 
           ARTS OF  HEATING AND VENTILATION.         169

 the internal heat of houses is gradually conveyed to the exter-
 nal atmosphere.  To obviate the first of these causes, apart-
 ments should be made as  tight as possible;  and to prevent the
 second, at least in part, their walls should be made  thick, and
 of materials which are slow conductors of heat.
    Crevices.—As crevices in rooms commonly occur from the
 shrinking of their materials, care  should be taken to  employ, in
 building, wood which is  thoroughly  seasoned,  and  which is
 known to be permanent  in its dimensions.   Of the kinds of
 wood employed for doors and windows,  mahogany is the  most
 permanent, and next to this is pine.  Oak, and some other hard
 woods, are very liable to shrink and crack.
    Chimnies.—Chimnies occasion less expenditure of warm  air
 from rooms, than their  size would lead us to expect, because
 they open at the bottom,  or near the  floor.   If, therefore, the
 room be tight,  and  the chimney cold, the  warm air, while at
 rest, will be retained  in the upper portion of the room, or that
 which is above the fire place, as effectually  as in a gasometer.
 But  if a chimney is heated, and a  current thus established
 through it, it may then drain off the air of the apartment; and
 hence the foundation for the common belief that a room becomes
 colder in the night, for having had a fire in the day.   The warm
 air  may be retained, if the throat of the fire place be closed
 with a damper.
   Entries and Skylights.—Entries, as they are commonly con-
 structed,  extending  from the bottom  of  a  house to  the  top,
 have a bad influence on the retention of heat.   The  evil is in-
 creased, when they are surmounted with a skylight, the panes
 of which are arranged like tiles, and not  air tight.   Such  en-
 tries are difficult to warm, and serve to  drain off the warm air
 of apartments, whenever the communicating  doors  are  left
 open; find to transmit it to the roof. *   To prevent this effect,

  * The opposite currents in an open door, by which cold air enters at bottom,
and warm air escapes at top, may be made obvious, in the familiar experiment
of holding a lighted  candle at the bottom  and top of the door.  In one  case
the flame will point  into the room, and in the other out of it.
              22 
170        ARTS OF HEATING AND VENTILATION.

entries should be commanded with doors in different stories;
and  skylights  should  be made sufficiently erect, to have their
sashes complete, or else a tight horizontal  window should be.
added underneath the skylight.
   Windows.—The heat conducted off by the external atmos-
phere, passes,  most readily, through the  windows; since, the
walls of houses, especially when thick, are slow in conducting
caloric, while  a pane of glass interposes but a slight barrier
against its escape.   On this account the  unnecessary  multipli-
cation of windows should be avoided.   In cold climates, a great
advantage is obtained from  using  double windows in winter,
which, by confining between them  a stratum of air, interpose a
powerful nonconductor between the room and the atmosphere.
To secure the full benefit of the double  window, it Should be
made as tight as possible, so that  the included stratum of air
may not easily change; otherwise the expected benefit will not
be obtained.

                       VENTILATION.

   Objects.—If the  only object of  human habitations  were to
procure heat, it would be best obtained by keeping the air in a
state  of  stagnation,   and  employing  those means to create
warmth, which are attended with the least  circulation, or change.
But since the  air of inhabited rooms would  become in time un-
fit for respiration, it is necessary that it should be removed, as
fast as deteriorated, and be replaced by fresh air from abroad.
   Rooms which are  heated  with  stoves are  never well ven-
tilated.   Those  heated by  common  fire  places, are  ven-
tilated, at the expense of losing much of their  warmth by the
admission of cold air.   Those heated by the double fire place
[p. 160], are  sufficiently ventilated, with air at an agreeable
temperature.   Rooms heated by steam are  not at all ventilated,
unless it be by additional  arrangements.   Those  warmed by
hot air flues are apparently well ventilated,  yet in hospitals and 
          ARTS OF HEATING AND VENTILATION.         171

crowded buildings, it is sometimes necessary to add fire places,
or other openings, for discharging the air.
   Ventilators.—The principal  gases, which it  is the  object
of ventilation  to remove,  are  carbonic acid and nitrogen;
these being  produced in excess by the  process of respiration,
by the  combustion of lamps, and by fires  with  an imperfect
draught.  The  specific  gravity of  carbonic  acid is  greater
than  that of common   air.  That  of nitrogen  is  somewhat
less.   These  gases when evolved,  are at  an higher  tempe-
rature than  the surrounding air, and  are mixed  with  steam ;
therefore, while rarified by heat, they ascend to the top of the
apartment.  On this account the  ventilators intended to dis-
charge  them, are made to consist of openings, commanded by
shutters, at the  upper part of  the room.  In rooms which are
liable to be crowded with people, these ventilators have a good
effect, especially in warm weather, and the larger they are, the
greater is the advantage derived from them.   In cold weather,
however, they  have the disadvantage that they discharge the
pure heated  air, in  common with the noxious vapors, and thus
defeat our  efforts  to  obtain  warmth.   In  common  dwelling
houses, no more ventilation is necessary, than can be obtained
from doors,  open fire places,  and windows which  open at top,
as well  as at bottom.
   Culverts.—In the Derbyshire Infirmary an ingenious mode
of ventilation is adopted, by means of an empty culvert, or sub-
terranean  passage; one end of which opens into the building,
while the  other end is provided with a turncap  presenting  its
open mouth  to the wind.   The  air, in passing this  culvert, par-
takes of the  temperature of the earth, and  is thus warmed in
winter, and  cooled in summer.  The  effect, however, is obvi-
ously of a limited kind, since the continual transmission of air
must bring  the surface  of  the  culvert,  to a  temperature ap-
proaching that of the surface of the ground.
   Smoky  Rooms.—Under  the  head of ventilation  may be
placed the art of remedying smoky apartments.   Smoke is a
heterogeneous  vapor, composed of  the gases which result 
J 72        ARTS OF  HEATING AND  VENTILATION.

from  combustion, together with a quantity of opaque matter,
which escapes from the  fuel without being burnt.   Smoke is
specifically heavier than the atmosphere, and  always  descends
after it is cooled, as may be  seen by  observing  the  current of
smoke from a chimney in a cold morning.   At  the time how-
ever of its disengagement from the  fire, it is rarified by heat,
and will always ascend through a chimney properly  construct-
ed, if it is not  prevented  by  some opposing  influence.   The
causes which  produce smoky apartments  are  principally  the
following.
   Damp  Chimnies.—When a fire is first made in a chimney,
which has not  been  used for many months, it is apt to smoke.
This is because  the  chimney  is  cold, and the  column of air
which it contains is not lighter than the surrounding atmosphere.
The  difficulty of remedying  this evil is greater, if the  bricks
have  absorbed much moisture, or the chimney  be new; as in
this case the chimney will not be well heated, till the moisture
is evaporated.  To  expedite  the drying  and heating  of the
chimney, a window should be kept open  on the side against
which the wind blows, and the communication with the rest of
the house, at the  same time, closed.   This will mechanically
assist the smoke and hot air in ascending the chimney.
   Large Fire Places.—If a fire place be made  too high, it will
be liable to smoke, for, since the throat of the chimney takes in
air from all directions, if the fire be too remote from this point,
its  smoke  will be less likely to find  its proper  way.  On the
other hand, the lower the mantel piece is brought, the nearer
will the fire place approach to the character of a wind furnace.
In like manner if the throat of the fire place be too large, the
air of the room, as well as that of the  fire, will pass freely up
the chimney, and thus the whole included air being  colder, its
current will be  more  sluggish.   The advanced  back of the
Rumford  fire  place, by contracting the throat, remedies this
difficulty; and at the same time presents a mechanical obstacle
against sudden counter currents, 
ARTS  OF HEATING AND VENTILATION.
173
   Close Rooms.—Closeness of a  room is a cause of its being
smoky.   If the walls, doors, and windows, are air tight, or near-
ly so, the outer air cannot enter to  take the place of that which
passes up the chimney.   The  current of heated air and smoke
will therefore be interrupted and  expand into the room.   In
most rooms it happens that the  crevices occasioned by  the
shrinking of the wood, or by the want of exactness in finishing,
admit air enough, and more than enough, to supply the chimney.
In new  apartments, however, where all the joinings have been
made with great accuracy, it has been found necessary to make
perforations in the walls to admit air sufficient  to  keep up a
current.   These should always be made behind  the back of
the fire place, when possible, for reasons already explained.
   Contiguous Doors.—The doors of a room, if placed very
near a fire place, or on the same side of the room with it, are apt
to occasion a smoke, as often  as they are opened.  The gust
of air which enters at  an open door so situated,  blows across
the chimney.  A part of it ascends the flue, while the rest ex-
tends into the room carrying with  it a part of  the smoke.
   Short Chimnies.—The longer a chimney is, the more per-
fect is its draught, since  the upward tendency is proportionate
to the difference of weight between the column of air included
in the chimney, and a similar  column of external  air.   Short
chimnies or flues are liable to smoke from the heated  passage
not being long enough to establish a strong  current.  The fire
places in upper stories  are more apt to smoke than those in the
lower  apartments.  In low houses, outhouses, he, the  chim-
ney should always be carried to the greatest practicable height.
Two flues in the same  chimney or stack  should not communi-
cate at any point short  of the top.
   Opposite Fire Places.—When two chimnies exist in differ-
 ent parts of the  same room, or in rooms which  communicate
by doors, it is difficult to kindle a fire in one, while the other is
burning, especially if the  room be tight; because in this  case
the fire which is first established, feeds itself by a current brought
down the  vacant  chimney.    After both fires are kindled, it is 
 474        ARTS OF HEATING  AND  VENTILATION.

 necessary to keep up a  certain equilibrium between them, oth-
 erwise the  stronger will overpower the latter, and draw down
 its smoke into the room.  If doors or windows be opened, the
 evil  is obviated.   If the fires are  in different rooms, the com-
 municating doors between them should be shut.
   Neighboring Eminences.—The  vicinity of elevated objects,
 such as hills, precipices, or  very high buildings,  is productive
 of smoky rooms to houses in their neighborhood.  When the
 wind blows in a direction from the elevated object  to the house,
 it falls down in an oblique direction upon the roof; a part  of it
 enters the chimney, and beats down the smoke, by overpower-
 ing its current.  On the other hand when the wind sets towards
 the hill or elevated object, its passage becomes obstructed, and
 it presses in every direction to escape; and while its upper  por-
 tions pass off by the top of the opposing body, the lower por-
tions  press  downward through any passages which may afford
them  an escape.   Chimnies in houses thus situated should be
carried up to a great height, so as, if possible, to  overtop the
eminence, their sides being secured by iron braces.
   Turncap, fyc.—In many instances a turncap, which is a  cur-
ved tube regulated by a weathercock, so as  always to turn its
mouth in a direction from the wind,  will prevent smoking, in the
case last stated.  The  turncap  offers, also, a  security  against
the influence of  strong  winds, which in common  cases and in
houses most favorably situated, often invert the course of the
smoke by the strong  pressure  they exert on the tops of chim-
nies, and by impinging against their inner side.   In like man-
ner the pots, which are frusta of  cones or pyramids, placed on
the tops of chimnies, assist  the  escape of smoke, by causing
the wind to glance upward from their sides.
   Contiguous Flues.—When two chimnies are contiguous to
each  other, or in the  same stack,  one is frequently liable to
smoke, when  the other contains a fire, from a variety  of  cir-
cumstances.   Not only the effect of high winds,  but also  any
circumstance, which tends to produce an inverted current, may
bring  down the smoke  from one chimney into the apartment 
          ARTS  OF HEATING AND VENTILATION.         175

which contains the other.  To prevent this evil, the fire places
should be furnished with dampers which can be closed when
the flue is not in use.
  Burning of Smoke.—This subject has excited great atten-
tion, owing to the  nuisance produced by smoke in large cities
and manufacturing towns, chiefly where coal is burnt.   In an
economical view it deserves attention, since it renders the same
fuel more effective.  Several methods of getting rid of smoke
have been  proposed and executed with some success.  The
first mode is to cause the smoke to pass through a portion of fuel
which is perfectly ignited and does not smoke, and which if ac-
curately managed, burns it up.   This has been  effected by an
inverted draught, in a syphon chimney, and also by a revolving
grate, which places the ignited fuel between the fresh fuel  and
the chimney.   Another mode is to mix a current  of fresh air
with the smoke, which  causes  it  to burn  upon passing in
contact  with a  clear fire.  A third  method  which has been
adopted  for disposing  of smoke,  consists  in  building chim-
nies of an extraordinary height, so that most of the smoke may
be deposited in soot upon their sides.   It has also been propos-
ed to build circuitous chimnies, in one part of which the smoke
should pursue a descending course, and that in this part a shower
of water should be kept up, to precipitate the denser particles of
the smoke.   The expense of this method will probably pre-
vent its  use, unless in some cases to get rid of dangerous me-
tallic fumes in manufactories.
  Franklin's Works;—Rumford's Works;—Tredgold, on Warm-
 ing and Ventilating Buildings, 8vo. 1824 ;—Buchanan, on the Econo-
 my of Fuel  and Management of Heat, 8vo. 1810;—Sylvester's
 Philosophy of Domestic Economy, and Account of the Derbyshire In-
 firmary,  4to.;—Account of the Wakefield Asylum,  fol.;—Brande's
Quarterly Journal, No's 22, 24, 27, 37, &c. 
CHAPTER IX.
                  ARTS OF ILLUMINATION.

   Flame.—Artificial light is obtained for common purposes, by
 the  combustion of substances,  which afford a permanent and
 luminous flame.   All flames are not equally luminous.  Those
 substances which, during combustion, produce chiefly gaseous
 or volatile  matter, emit from their flame a very feeble light, as
 is seen in burning hydrogen, or sulphur.   Those, on the other
 hand, which produce particles of solid matter during their com-
 bustion, yield a whiter flame, and a greater  illumination.   Sir
 Humphrey Davy is of opinion that the brilliancy of the flames,
 used for  illumination, is owing to the decomposition of the gas-
 eous matter towards the interior of the flame, by which  solid
 charcoal is produced, and strongly ignited, before it is burnt.
 In a conical flame, like that of a candle, the combustion takes
 place most rapidly toward the surface, where the  inflammable
 gas mixes with the atmospheric air.  At the  centre of the base,
 there is a darker portion, which consists of  the matter, which
 is volatilized, but not yet fully on fire.   In the interior, or most
 luminous part, the solid particles are brought to a white heat,
just  before they are burnt.   The degree of their  ignition is
 very powerful, since it is found that the flame of a common
 candle is hot enough to melt a small filament of platinum.
  Support of Flame.—That a flame may burn steadily,  and
 produce a uniform light, it is necessary that the supply of com-
bustible matter should be constant and uniform.   For this pur-
pose the combustible  must  be in a liquid,  or gaseous state,
when it approaches the flame, so that it may flow in an uninter-
rupted  current.  This current is commonly sustained either by 
ARTS  OF ILLUMINATION.
177
capillary attraction, or by mechanical pressure, operating on the
reservoir which contains the combustible.
   Torches and Candles.^-The rudest material  used for afford-
ing light, is the torch, composed of the  resinous part of wood
of the  pine or fir.   In  such torches, the turpentine, or  melted
resin, oozes out through the pores of the wood, and is gradually
burnt, the wood interposing a vehicle, which regulates the sup-
ply and prevents  it from  being   consumed at once;  thus
sustaining a dull and  irregular light, with much smoke, for some
time.  A common candle is an improvement upon  this  natural
mechanism.  It consists, as is well known, of  a  fusible solid,
as tallow, wax, or spermaceti, formed into a  cylinder, having a
wick of cotton, or  some other porous  substance, for its  axis.
As the tallow melts by the radiated heat of the  flame, it is car-
ried upward by the capillary attraction of  the wick, and is con-
verted  into vapor as fast as it reaches  the surface.   The end
of the wick  although it is blackened by the heat, is prevented
from consuming, merely because it is surrounded by inflamma-
ble vapor, so that the oxygen of the atmosphere has no access
to it.   If the wick be turned to one side, so as  to project from
the blaze into the  atmospheric air, it is immediately burnt off.
Tallow being more fusible than  wax, requires to be burnt with
a larger wick.  The reason why  this wick requires continual
snuffing is, that if it is suffered to  become long it  divides the
blaze and intercepts a part of the light, it also  cools the flame
by its radiation, obstructs the combustion, and thus causes the
escape  of smoke and the deposition of charcoal.  Wax and
spermaceti, being less fusible, maybe burnt with a smaller wick,
which,  if made sufficiently slender, bends  out of the flame and
burns off, so as  not to require snuffing.
   Lamps.—When  the  combustible used  is  fluid at  common
temperatures, a  vessel is necessary  to contain this fluid and sup-
ply it to the flame.    In this country, and in England,  whale oil
is the principal  fluid which is burnt in lamps. *  In  France and

  * The  oil which is extracted in cold weather, and called winter  strained
oil, remains fluid at low temperatures.  The summer strained oil is liable to 
178
ARTS  OF ILLUMINATION.
the south of Europe, the oil of poppies, of nuts, rape seed, and
the inferior kinds of olive oil, are used for this purpose.   The
volatile oils,  are but seldom  burnt,  since they exhale a strong
odor  and throw off  soot during their  combustion.  They are
also liable to  take fire over their whole surface, unless guarded
with great care.  Naptha, however, as it is found native, or as
it is distilled from pitcoal, is used  for supplying street lamps in
some of the cities of Europe.
   Reservoirs.—As  the flame of a lamp is intended to consume
no  more oil than is attracted upward by the capillary action of
the wick, it is necessary that a sufficient  body of oil should be
so placed, as to keep its surface permanently at a small distance
below the level of the flame.  The Greeks and Romans em-
ployed lamps of various forms, having the wick projecting from
a sort of beak  at the side, nearly on a level with the surface of
the oil.  A  similar plan is now practised in our street  lamps.
At  the present day, portable  lamps of small size, are made
with a central wick, having the reservoir of oil immediately be-
low the flame.   These  reservoirs, if small, require frequent fill-
ing, and if large,  cast  an  inconvenient  shadow.   All closed
lamps require a minute  hole for the admission of air, otherwise
the pressure of the atmosphere will prevent the oil from ascend-
ing the wick.   If this hole be obstructed, the oil will also some-
times  overflow, from the expansion of the  confined air, when
heated.
   Astral Lamp.—With a view to get rid of  the  effect of shad-
ow, various  contrivances have been introduced, in which the
reservoir is placed at a  distance from the flame.   In the Astral
and Sinumbral lamps,  the principle of which was invented by
Count Rumford, the oil is contained in a large horizontal  ring,
having a burner at the centre, communicating with the ring by
two or more  tubes placed like rays.   The ring is placed a little

congeal in winter. To obviate this inconvenience, lamps have been contriv-
ed for melting the summer oil by the heat of the blaze.  This is done either
by placing the  reservoir of oil immediately over the blaze, or by conducting
the heat by a metallic bar which extends from the flame into the reservoir. 
ARTS  OF ILLUMINATION.
179
 below the level of the flame, and  from its  large  surface  af-
 fords a supply of oil for many hours.   A small aperture is left
 for the admission or escape of air, in the upper part of the
 ring.   When these  lamps  overflow, it is usually because the
 ring is not kept perfectly horizontal, or else because the air hole
 is obstructed, a  circumstance which may even happen from fill-
 ing the lamp too high with oil.
   Hydrostatic Lamps.—In several cases, the laws of hydros-
 tatics have been  applied to raise oil to the flame  from a reser-
 voir placed  so  far below  the  wick as to be  out of  the
 reach  of  its  effective  capillary  attraction.  One  of these
 hydrostatic  lamps is constructed on  the  principle of  Hero's
 fountain.   It is composed of three  vessels or
 cavities occupying  different heights and com-
 municating by tubes or syphons.   One por-
 tion of oil by descending gradually from  the
 middle vessel A, to the lower vessel B, causes
 another portion of oil to  ascend from the upper
 vessel  C, to the flame at D, the hydrostatic
 equilibrium   being kept up  by the interven-
 tion of the column of air B C.
   The lamps of Girard de Marselle,  and of King, are on this
 principle, though the form of their apparatus is that of a cylin-
 der, with internal tubes opening into different cavities.
   Other hydrostatic lamps are constructed, so as to contain, in
one part, a column of some  fluid, the specific  gravity of which,
is considerably greater  than that of oil,  such for  example  as
water saturated with salt.   This fluid acts in  such a manner as
to raise the oil, by its greater weight.  Thus if an
inverted syphon  contain oil in one part, and salt
 water  in another, the  surfaces "of the two fluids
will stand at different heights, inversely proportion-
ate to their specific gravities.   In the diagram, A,
represents the surface of the heavier fluid, and B,
that of the oil.  The bulbs serve as reservoirs to prolong the
action.   Mr Kiers'  lamp  is  constructed  on  this principle.
 
180
ARTS  OF ILLUMINATION.
Those of Barton  and Edelkrantz depend on the same princi-
ple, but in  their construction, an  open tube of oil is made to
float in an upright vessel containing a heavier fluid, which  in
some  cases is salt water, in  others mercury.   As the oil con-
sumes, the  tube, with the  wick and light, descend in the sup-
porting fluid, and follow the surface of the oil, as it lowers.
  Automaton  Lamp.—The automaton lamp of Porter, is a
simple and  effectual contrivance for keeping the surface of  the
oil near the level of the blaze.   It  consists  of an oblong tin
box, having the wick tubes at one end,  this end being thus ren-
dered heavier than the other.   The box is suspended on piv-
ots placed  a little out of the centre,  and  toward the tubes, so
that when the lamp is full of oil, the box will hang level.  As
the oil burns  out, however, the end containing the tubes will
preponderate,  so as to keep  the flame always near the surface
of the oil.  The annexed figures show the position of the lamp
when full,  and when half exhausted.  This lamp  is of  cheap
construction, and is  said to be extensively  used  in cotton mills
and other manufactories in the  north of England.
   Mechanical  Lamps.—Some  lamps  are  manufactured  in
France, in which the oil is raised from a large reservoir below,
to a small one near the flame, by means of a pump.   This in
some  instances is worked by hand, and in others is carried by
clock work, the motion being derived from a spring, which is
wound up as often as necessary.
   Fountain Lamp.—The most common mode of disposing of
the oil in large  lamps, is to place the reservoir  above the level
of the flame, so that the burner, or part  containing the wick, 
                 ARTS OF ILLUMINATION.               181

may be supplied in small quantities, as fast as its oil is consum-
ed.  These reservoirs are constructed on the principle of the
bird fountain.   They are  open at bottom, but the oil is kept
from running out at once,  by the  pressure of the  atmosphere.
The reservoir commonly  terminates in a neck at  bottom, with
an opening on one side.   This neck is immersed beyond the
opening, in a small cavity, which  contains oil nearly on a level
with the burners, and communicates with them by tubes.   So
long as the whole of the  opening is immersed, no oil  can de-
scend from the  reservoir,  because no air can enter to take its
place.   But  whenever the oil in the lower  cavity is consumed
so far, as to sink below the upper edge of the opening, a bub-
ble of  air will enter the neck and ascend into the reservoir;  at
the same time displacing an equal bulk of oil, which descends
to feed the lamp.   For convenience, the opening  is command-
ed by a sliding valve, and  when the reservoir  is to be filled, it
is unscrewed  from the lamp, inverted, and the oil poured in at
the neck.   When these lamps overflow, it is commonly owing
to an increase in the heat  of the room, which causes the air in
the upper part of the reservoir to expand, and drive out  a por-
tion of oil.  As it is not easy to prevent this occurrence, lamps
are usually provided with receptacles at bottom to receive the
waste oil which runs over  at the wick.
   Argand Lamp.—This name is applied, after one of the in-
ventors, to all lamps with hollow or circular wicks;  and  of
course most of the  lamps already described, may be also Ar-
gand lamps, if furnished with a circular burner.  The intention
of the  Argand burner, is  to furnish  a more rapid  supply of air
to the flame, and to afford this air to the centre, as well as the
outside of the flame.  It  is  constructed by forming a hollow
cylindrical cavity, which  receives oil from  the main body  of
the lamp,  and at the same time  transmits air  through its axis,
or central hollow.   In this cavity is placed a circular wick, at-
tached at bottom to a moveable ring.  This ring is capable of
being elevated or depressed by means of a rack and pinion,  or
more commonly by a screw;  so  that the height of the wick 
182
ARTS  OF ILLUMINATION.
 may be varied to regulate the size of the flame.  On the out-
 side is placed a glass chimney, which is capable of transmitting
 a current of air, on the same principles as a common smoke
 flue.   When  this lamp is lighted, the  combustion is vivid, and
 the light  intense, owing to the  free and rapid  supply of air.
 The flame does not waver, and the smoke is wholly consumed.
 The brilliancy of the  light is still further increased,  if the air
 be made to impinge laterally against the flame.   This is done
 either by contracting the glass chimney near the blaze, so as to
 direct the air inwards, or by placing a metallic button over the
 blaze, so as to spread the internal current outward.
   Reflectors.—For obvious reasons, a lamp yields most availa-
 ble light, when it is placed in the centre of  a room, or space to
 be illuminated.  In this situation,  if  a reflecting surface be
 brought near to it, this surface by its reflection will increase the
 amount of light in one direction,  at the expense of intercepting
 it in another, so that the total advantage is not increased by
 the reflector.   But when a lamp is placed  near a wall, so that
 a part of its rays are wasted  by  falling immediately  upon the
 wall, in this case if a polished surface be  placed behind the
 flame, it reflects back most of the rays, which would  otherwise
 be lost upon the nonreflecting wall; and thus it increases the ef-
 fect of the light.   The  familiar  fact that rooms with light col-
 ored walls  are most easily lighted, is owing to the greater re-
 flective power  which such walls possess, when compared with
 darker surfaces.
   Hanging of Pictures.—As  the surface of varnished paint-
 ings has a considerable reflecting power, it happens that when
 the spectator stands in the way of the reflected light,  his eye is
 dazzled, and rendered  incapable of distinctly perceiving the
 picture.   Paintings, therefore, should  not be hung opposite to
 lights, nor in any situation in which a line drawn from  the place
 intended for spectators will make the same  angle with the sur-
 face of the picture, as a  line drawn from a window or other il-
luminating  point; the angle of reflection being  always equal
to the angle of incidence.  As a  general rule, a picture will be 
ARTS  OF ILLUMINATION.
183
in a bad  light  with regard to a spectator, whenever the image
of a window could be seen by him in a looking glass occupying
the same place as the picture.
   Transparency of  Flame.—If two  lamps  be  placed  by
the side  of each other, the flame of the one, when clear  of
smoke, does not intercept the light of the other, and casts little
or no shadow.  Count Rumford found that the  brilliancy of
flame is, in some high ratio, proportionate to its  elevation  of
temperature.  If several  concentric circular wicks, or several
parallel  flat wicks, be burnt near together, they produce more
light, in consequence  of  the accumulation of heat, than they
would do, if burnt separately.
   Glass Shades.—To relieve the eye from the glare of light,
produced by bright lamps, shades of roughened glass are fre-
quently used.   A rough surface  upon glass may be produced
by grinding it  with sand or emery, by corroding it with  fluoric
acid, or by covering it  with  powdered  glass and exposing it to
heat, till  the particles adhere.   Glass shades have the effect  to
disperse  the rays of light,  by the numerous reflections and re-
fractions which they occasion; till at length the light issues from
all parts of their surface, and it appears as  if the  glass itself
were the luminous body.
   Sinumbral  Lamp.—The reservoir of the sinumbral lamp, is
constructed on the same general principles with that of the As-
tral.  The ring, however, which holds the oil, is so formed as
to oppose the smallest diameter of its  section  to the rays of
light.  A large shade of ground glass is used, which nearly in-
closes the light, and by the  different refractions and reflections
given to the rays by the ground glass, they escape in all direc-
tions, so that there is no perceptible  shadow at a small distance
from the ring.   Reflectors are sometimes added, when it is de-
sired to throw the principal mass of light in one direction.
   Measurement of Light.—The following method of measur-
ing the  comparative illuminating power of different lights, is
founded on the law, that the amount of rays thrown on a given
surface,  is inversely as the square of the distance of the illumi- 
184
ARTS  OF ILLUMINATION.
 nating body.   Place two lights, which are to be compared with
 each other, at the distance of a few feet, or yards, from a screen
 of white paper, or  a  white wall.   On holding  a small  card
 near the wall, two shadows will be projected on it, the darker
 one by the interception of the  brighter  light, and  the  fainter
 shadow by the interception of the duller light.  Bring the faint-
 er light nearer to the card, or remove the brighter light farther
 from it, till both  shadows acquire the same intensity, which the
 eye can  judge of with great  precision, particularly from  the
 conterminous shadows  at the angles.   Measure now the distan-
 ces of  the  two lights from the  wall or screen, and the squares
 of these  distances will give the  ratio of  illumination.  Thus if
 an Argand flame and a candle stand at the distances of ten feet
 and four  feet respectively, when their shadows are equally deep
 we have  the square  of ten and the square of four, or 100  and
 16, as their relative quantities of light.    In this experiment the
 spectator should  be equidistant from each shadow.
   Gas Lights.—In  the  flame of a  common lamp or candle,
 the  combustible  matter is not burnt until it has first been  con-
 verted  into vapor, or inflammable gas.   This gaseous matter is
 burnt as fast as it is generated, in consequence of being brought
 immediately in contact  with the atmospheric air, and set on fire
 by the  same heat which produces it.   It is found, however, if
 certain combustibles be exposed to heat, and if the inflamma-
 ble gas, which they yield, be kept separate from the atmospher-
 ic air, that this gas may be  conveyed in pipes to any distance,
 and burnt for light in any place where a stream of it is discharg-
 ed into the  atmosphere.  In this way various combustibles may
 be used which are not capable of being burnt in lamps, and a
 brilliant and economical light obtained from them.  The ma-
 terials  chiefly employed for this purpose, are  pitcoal, and  ani-
 mal oil.   Various  other  substances  are capable of support-
 ing  gas lights,  such as  bitumen, rosin, oleaginous vegetable
 seeds,* other oily or resinous bodies, and even wood, and turf.

  * Professor Olmstead has found that cotton seed produces gas of a superior
 kind for purposes of illumination.  See his account of this article in Silliman's
Journal, vol. viii. p. 294, and x, 363. 
ARTS  OF ILLUMINATION.
185
 The inflammable gas, which is procured from all these substan-
 ces is  chiefly carburetted  hydrogen.  Of this two  kinds  are
 known, the first sometimes called defiant gas, and the other sub-
 carburetted  hydrogen.    Mr Brande, however, considers  the
 last species  as merely a mixture of the  first, with hydrogen.
 The fitness  of a mixed gas for purposes of illumination, is  de-
 pendant on the quantity of  carburetted hydrogen which it con-
 tains, other things being equal.
    Coal Gas.—The use of coal  gas for purposes of illumina-
 tion, appears to have been first  introduced by Mr Murdoch, in
 1792, although its  power of affording a luminous  flame  was
 known much  earlier.  It is found that the bituminous coals,
 and  particularly cannel coal, afford the most and the best illu-
 minating gas.   Some of  the Anthracites, according to Profes-
 sor Silliman, afford as much gas as Liverpool coal, but it burns
 with a feeble flame, and is unfit for  the purposes of illumina-
 tion.
   In the  manufacture of coal gas, the  coal is placed in iron
 retorts, which are subjected to a strong heat in  a furnace.   The
 gas is thus driven off mixed with the vapor of tar, oil, and am-
 moniacal  water, and in this  state is conducted by pipes first  in-
 to a horizontal trunk of cast  iron, called the hydraulic  main,
 and from thence into a condensing  apparatus, surrounded with
 cold  water,  where the vapors of the tar, oil, and water, are
 condensed  and fall down,  while the gaseous product is convey-
 ed along, containing several impure gases, such as sulphuretted
 hydrogen, and carbonic acid.
  In order to separate the carburetted hydrogen, from  these
 impurities, various contrivances have been adopted.  The usual
 method  of purifying coal gas, is to make it pass through a mix-
 ture of lime and water called  Cream of Lime, which absorbs  or
 combines with  the contaminating gases.  For this purpose a
 considerable number of purifiers are erected, and the lime and
 water are kept in a state of constant agitation, either by a steam
 engine, or by one or two men, till the  gas is rendered sufficient-
ly pure.  Sometimes the purification is effected by causing the
               24 
186
ARTS  OF ILLUMINATION.
gas to pass in contact with solid lime, newly slaked ; and some-
times by passing it through retorts  containing clippings of iron
made red  hot.  When thus purified the gas is conveyed by a
pipe to the gasometer.
   The  Gasometer, is a large  inverted vessel, made of mallea-
ble iron, or copper, either of a cylindrical or rectangular form,
and suspended  over a reservoir of water of a little larger size, by
means  of counter-weights.  The  gas is introduced  by pipes
ascending  from the bottom of the reservoir, and  rising a little
above the surface of the water.   While the gasometer is filling
with gas, it gradually rises out of the water, until it is filled, af-
ter which no more gas is admitted, and  its contents  are ready
to be distributed through the pipes  by which it is to be convey-
ed to the place intended to be illuminated by burning it.   As
the gas is forced out by  the weight of the  gasometer, and  is
burned, the gasometer descends gradually in the water, till the
whole of its contents  are expelled, when it is again  filled  by
the same process as before.
   The  gas being thus ready  for use, must be carried off by
pipes, the  diameter of which  is  proportional to the degree  of
light required.   It has been found that a pipe one inch in diam-
eter, will, under a  pressure of a  column of water from  five
eights to three  fourths of an inch, supply gas equal to 100 can-
dles ; and if there  was no friction, or mechanical  impediment,
the number of candles would  be found for  other  diameters of
pipe, by multiplying the square of the diameter of the pipe in
inches by  100.   The friction, however, or obstruction, dimin-
ishes so rapidly with the diameter of the pipe, that the number
of candles is always greater than this rule gives.  Thus a pipe
three inches in diameter will supply light equal to 1000 candles—
a pipe four inches, 2000—a pipe six inches, 5000—and a pipe
ten inches, about 14,000.*
   When the gas is to be burned in rooms,  shops, or streets, it
is allowed to escape through  small circular  apertures of from

      * Brewster's Edition of Ferguson's Mechanics, vol. ii. p. 273. 
ARTS  OF ILLUMINATION.
187
one  fortieth to one sixtieth of an  inch in diameter, which may
be arranged in various ornamented ways, or disposed in a cir-
cle, like  an argand burner,  with a current of air running be-
tween them.   The lights thus produced are equal, steady, and
of the most brilliant  kind.   When the supply of gas  is cut off,
they are  instantly extinguished.  When it is restored^ the invisi-
ble current flows out, and may be instantly lighted again by the
contact of  flame.
   Oil Gas.—It has been long  known to chemists,  that wax,
oil, tallow, he, when pa.ssed through ignited tubes, are resolved
into combustible gaseous matter, which burns with a bright light.
Of late years this gas has been much used for purposes of illu-
mination.   Oil gas is considered  in many respects  superior to
coal gas, and free from its inconveniences.  The material from
which it  is produced  containing no sulphur or other matter by
which coal gas is contaminated, it never produces a suffocating
smell in  rooms;  so  that  the costly operation of purifying the
gas  by lime,  and other means, is  avoided.   Nothing is con-
tained in oil gas which can injure the metal of which  the con-
veyance  pipes are made.
   The oil gas has a  further  advantage over coal gas, in con-
taining a greater  proportion  of Carburetted  hydrogen, so that
one cubic foot of oil gas is said to go as far as two or three of
coal gas.  This circumstance is of importance, as it reduces in
the same proportion,  the size of the gasometers, which are ne-
cessary to contain it.   Oil gas contains  about 75 per cent, of
carburetted hydrogen, while purified coal gas but seldom con-
tains more than 40 per  cent.
   In procuring this gas  a quantity of oil is placed in an air-tight
vessel, in such a manner, that it may pass slowly into  retorts or
iron tubes, which are  kept at  a moderate red heat.  Fragments
of  coke  or brick, are usually  inclosed  in  the tubes.  The
oil, in its  passage through the retorts, is principally decomposed,
and converted into gas proper for illumination, carrying with it,
however, some oil in the state of vapor.  To purify the  gas
from this oil, which is suspended in it,  and which occasions an 
188
ARTS  OF ILLUMINATION.
 empyreumatic smell, it is conveyed into wash vessels, whore,
 by bubbling through water, or through fresh oil, it is cooled and
 rendered fit for use.   It then passes  by a proper pipe into  a
 gasometer, from which it is suf.ered to pass off in pipes, in the
 usual manner, to its places of destination.
   The poorest kinds of oil, which are unfit for burning in lamps,
 produce excellent gas.   This is,  indeed, the chief  source of
 economy in the process.
   According  to  Mr Brande, a light  equal to ten wax candles
 for one hour,  requires  for its production, 2600  cubic  inches of
 pure carburetted hydrogen, or olefiant gas, 4875 cubic inches
 of oil gas, or  13120 cubic inches of coal gas.
    Gasmeter.—In dispensing  gas for the illumination of partic-
 ular rooms, it was found  necessary to possess some method of
 measuring the quantity expended  in each place.   An ingenious
 instrument called the gasmeter has been  introduced  for this
 purpose.   It consists of a horizontal cylinder partly filled with
 water, within  which another cylinder  revolves on  an axis, hav-
 ing  its  interior surface  divided  into several  compartments.
 These compartments, being successively filled with the gas, as
 it passes through, rise out of water  like  inverted buckets of an
 overshot wheel, and cause the inner cylinder  to revolve.  The
 number of revolutions  is registered  by machinery, and thus the
 quantity of gas which escapes in a given time is estimated.
   Portable Gas Lights.—The magnitude  and expense of gas
 works, prevents the use of them, except in  cases where a large
 number of lights are wanted,  within a convenient distance from
 the  gasometer.   The  gas, however, may be conveyed to any
 distance, by condensing it in strong  vessels of iron or  copper,
 made of a small or portable size.  The gas is forced into these
 vessels by a condensing pump, and when afterwards suffered to
 escape through a small orifice, is capable of supporting a flame
 for'many hours.  The economy, however, of this process has
 been doubted.
   Safety Lamp.—In coal mines an  inflammable gas is generat-
ed, called fire  damp by the miners, and composed chiefly of 
ARTS  OF ILLUMINATION.
189
  carburetted hydrogen.   This gas when mixed with atmospheric
  air is liable to take  fire from the flame of a lamp  or  candle,
  and to explode with great  violence.   Terrible accidents have
  happened, and many lives have been  destroyed, from these ex-
  plosions.   To prevent  such accidents, several troublesome and
  circuitous modes of obtaining light were resorted to  by  the mi-
  ners; such  as striking sparks from  a  wheel,  and  inclosing a
  lamp within a tight lantern, which was supplied with air from a
  bellows.   All these are now superseded by the safety lamp of
  Sir Humphrey Davy.  This important invention consists simply
  of a lamp, the flame of which is wholly enclosed in a cylinder
  of fine  wire gauze.   Its operation  depends on the principle
  discovered by Sir H. Davy, that explosive mixtures cannot be
  inflamed through minute apertures in metallic  surfaces, or tis-
  sues.   The wire gauze, being a  powerful conductor and radia-
t  tor of heat, cools a  flame which is in contact with it, so as to
  deprive it of the power of producing  an explosion on the other
  side.  If this lamp be immersed in  an explosive mixture, the
  gas will be inflamed, and burn on  the inside of the gauze cy-
  linder, but  not on the outside.  In these cases the flame of the
  lamp first enlarges,  and is then extinguished, the whole of the
  cage being  filled  with  a lambent blue light.   If the supply of
  gas be withdrawn,  this appearance  gradually ceases, and the
  wick becomes rekindled.
   Lamp without Flame.—This curious  instrument may  be
  made by  winding upon  the wick  of a lamp  containing alcohol,
  a fine wire  of platinum, not more than a hundredth  part of an
  inch in thickness.   There should be about sixteen spiral turns,
 one half of which should surround the wick, and the other half
 rise above it.   Having  lighted the lamp for an instant, on blow-
 ing it out, the wire will become  brightly ignited, and will  con-
 tinue to glow as long as any alcohol remains, without the blaze
 being any more renewed.   The principle  depends  upon the
 slow combustion which  is found to take place in inflammable or
 explosive mixtures, at a lower temperature than is necessary to
 produce inflammation.  This  combustion is not visible,  but the 
190              ARTS OF  ILLUMINATION.
heat is nevertheless sufficient to ignite minute solids exposed to
its influence.  In the lamp  which has been described, the ex-
plosive  mixture is the  vapor of alcohol  and  atmospheric air.
But the experiment may be varied, by using ether, camphor,
he, and by substituting platinum leaf for wire.
   Modes of procuring Light.—To obtain light and fire, when
wanted, in an expeditious manner, various instruments have been
introduced, constructed on  optical, mechanical,  and chemical
principles.   The methods by which  they operate  are  chiefly
the following.   1. By concentration of the solar rays, as in the
focus of a  common lens, or burning glass.   2. By  friction.
Dry wood takes fire, if rubbed violently  in the manner practis-
ed by savages, or if it be held against the surface of a wheel
which  revolves  rapidly.   Phosphorus takes fire by very slight
friction, and on this account is used in the phosphoric fire bot-
tles, the  matches of which,  after  being charged with a  minute
quantity of phosphorus, take fire by rubbing them on the cork.
3. By percussion.  When hard bodies, such as flint and steel,
are brought into collision, small  particles of ignited matter are
struck off in the form of  sparks, which  are sufficiently hot to
set fire to tinder, gunpowder, he  Common  firelocks,  tinder
boxes, he, operate on this principle.   4. By Compression.  If
a  piece of tinder  is confined in a small  cavity at the end of a
condensing syringe, it will take fire, if the piston  of the syringe
be driven down with a stroke, so as suddenly to condense the
air.   The  tinder  commonly used  for this purpose, is what is
called  German tinder, made of a fungus that grows on trees,
(Boletus igniarius) boiled in a solution of nitre and dried.  5.
By chemical action.  In the oxymuriatic fire boxes, the  match-
es are charged with chlorate of potash mixed with sulphur or
some other combustible.   When these are brought into  contact
with sulphuric acid, a violent chemical action  takes place, and
the match takes fire.   Homberg's pyrophorus takes fire on ex-
posure to the air.   It may be made by calcining alum with less
than an  equal  quantity of flour or sugar,  until  the  smoke and
flame disappear.  It  is then kept in close stopped bottles, and 
ARTS  OF ILLUMINATION.
191
if a little of it be shaken out upon any light combustible, as cot-
ton or tow, it causes it to inflame.   The platinum lights  de-
pend on a remarkable  property  discovered  by Dobereiner, in
platinum, by which a sponge made of that  metal, becomes ig-
nited when exposed to a stream of hydrogen gas.
  Accum, on Gas-light, 8vo.  1816;—Peckston, on Gas-lighting;—
Rumford's Works ;—Nicholson's Philosophical Journal, vol. i. 4to.
vol. xiv. 8vo. &c.;—Rees's Cyclopedia;—Ure's Chemical Dictionary. 
CHAPTER X.
                   ARTS OF LOCOMOTION.

   Animals of the more perfect kinds, possess the power of shift-
ing their place at will, which power they exercise both in trans-
porting their own bodies and in conveying other masses of mat-
ter.   The chief obstacles  which oppose locomotion, or change
of place, are  gravity and  friction, the  last of which is in most
cases a consequence of the  first.   Gravity confines all terres-
trial bodies against the  surface of the earth, with a force pro-
portionate  to  the  quantity of matter  which composes  them.
Before they can be removed from one spot of this surface to anoth-
er of equal height, they must either be lifted from the  ground
against the force  of gravity, or carried horizontally along the
surface, resisting with a degree of friction, which increases with
their weight.  Most kinds of mechanism, both  natural and ar-
tificial, which  assist locomotion, are arrangements for obviating
the effects of gravity and friction.
   Motion of  Animals.—Animals that walk, obviate friction by
substituting points of their  bodies instead of large surfaces, and
upon these points they turn, as upon centres, for the length of
each step,  raising  themselves wholly or partly from the ground
in successive arcs, instead of drawing themselves along the sur-
face.  The line of arcs which the centre of gravity describes,
is converted into an easy or undulating line, by the compound
action of the  different joints.  As the feet move in  separate
lines, the body has also a h.teral,  vibratory motion.   A  man,
in walking, puts down one foot before the other is raised, but
not in running.   Quadrupeds in walking  have  three feet upon
the ground for most of the  time; in trotting, only two.   Animals
which walk against gravity,  as the common fly, the tree toad, he, 
ARTS OF LOCOMOTION.
193
support themselves by suction, using cavities on the under side
of their feet, which they  enlarge  at pleasure, till the pressure
of the atmosphere causes them to adhere.   In other respects
their locomotion is effected like that of other  walking animals.
Birds perform the motion of flying by striking the air with  the
broad  surface of  their wings  in  a  downward  and  backward
direction, thus propelling the body upward and forward.   Af-
ter each stroke the wings are contracted, or slightly turned, to
lessen  their resistance  to  the atmosphere, then raised and
spread anew.   The  downward stroke also, being more sudden
than the upward,  is more resisted by  the atmosphere.  The
tail of birds serves as a rudder to direct the course upward or
downward.   When a bird sails in the air  without moving  the
wings, it is done in some  cases by the  velocity previously  ac-
quired, and  an  oblique  direction of the  wings  upward ;—in
others, by a gradual descent, with the wings slightly turned in
an oblique  direction  downward.   Fishes, in swimming  for-
ward, are propelled chiefly by  strokes of the tail, the extremity
of which being bent into an oblique  position, propels the body
forward and laterally  at the same time.   The lateral  motion is
corrected by the next stroke, in the opposite direction, while
the forward course continues.   The  fins serve partly to assist
in swimming, but  chiefly to balance the body, or keep it  up-
right ;  for the  centre of  gravity being  nearest the back, a  fish
turns over, when it is dead, or  disabled.*  Some other aquatic
animals, as  leeches, swim with a sinuous or  undulating  motion
of the body, in which several parts at once are made to act ob-
liquely  against the water.  Serpents in like manner advance
by means of the winding or  serpentine direction which they
give to their bodies, and by which a succession of oblique  for-
ces are brought to act against the ground.  Sir Everard Home
is of opinion that serpents use  their ribs in the manner of legs,

   The swimming bladder which exists in most fishes, though not in all, is
supposed to have an agency in adapting the specific gravity of the fish to the
particular depth in which it resides.   The power of the animal to rise or sink
by altering the dimensions of this organ, has been, with some reason, disputed.
               25 
194
ARTS OF LOCOMOTION.
 and propel the body forwards by bringing the plates on the un-
 der surface of the body to act successively like feet against the
 ground. *   Some  worms and larvae of slow motion,  extend a
 part of their body forwards, and draw up the rest to overtake it,
 some  performing this  motion in a direct line, others in curves.
   When   land  animals  swim  in  water,  they are supported,
 because their whole weight, with the lungs  expanded with air,
 is less than that of an equal bulk of water.   The head, howev-
 er, or a part of it, must be kept above water to enable the ani-
 mal to breathe, and to  effect this and  also to make progress in
 the water, the limbs are exerted in successive impulses against
 the fluid.  Quadrupeds  and birds swim  with less effort than
 man, because the weight of  the head, which is carried above
 water,  is,  in them,  a smaller  proportional part  of the whole,
 than it is in man.
   Inertia.—In consequence of the action of gravity upon bod-
 ies, their inertia becomes a greater obstacle to locomotion than
 it  would otherwise  be.  Every body tends by its inertia to
 preserve a state  of  rest, if it is still, and of uniform rectilinear
 motion, if it is not still.   Changes, therefore, not only from rest
 to motion,  but also changes of direction and changes of speed,
 are resisted by the force of inertia.  Bodies  moving  upon the
 earth's surface  are  obliged  by their  gravity to accommodate
 their  motions to the irregularities of this surface,  and conse-
 quently to  change often both their  direction and velocity.  The
 inertia thus becomes a continual source of expenditure of pow-
 er, although it  would not be  so, if bodies moved at a uniform
 rate and in a straight course.
   Aids to  Locomotion.—All  animals  are provided by nature
with organs of locomotion  best  adapted to their  structure and
 situation, and it is probable that no animal, man not being ex-

  * Lectures on Comparative Anatomy, vol. i. p. 116, &c.  Sir E. Home de-
duces  this fact from the anatomy of the animal, and from the movements
which he perceived, in suffering a large coluber to crawl over his hand. The
ribs appeared to be raised, spread,  carried forward, depressed and pushed
 backward, successively. 
ARTS OF  LOCOMOTION.
195
cepted, can exert his strength more advantageously by any oth-
er than the natural mode, in moving himself over the common
surface of the ground.*  Thus walking cars, velocipedes, &,c,
although  they  may enable a man to increase his velocity in  fa-
vorable situations for a short time, yet they actually require an
increased expenditure of power, for the purpose of transporting
the machine made use  of,  in addition  to the weight of the
body.  When, however, a great additional load is to be trans-
ported with the body, a man, or animal, may derive much assist-
ance from mechanical  arrangements.
   Wheel Carriages.—For  moving weights over the  common
ground with its ordinary asperities and inequalities of substance
and structure, no  piece of inert  mechanism is so  favorably
adapted as the wheel carriage. It was introduced into use in very
early ages, as affording a facility for the carrying of heavy loads,
and finally for transporting man  himself; not by his own pow-
ers, but by the strength of other animals which he had  subjugat-
ed to his use.   Chariots were  used in war, and  waggons in
agriculture, at a very remote period.
    Wheels.—The mechanical action of wheels applied to loco-
motive carriages is twofold.   They diminish friction, and also
surmount obstacles or inequalities of the road, with  more  ad-
vantage than bodies of any other form, in their place,  could  do.
The friction is diminished by transferring it from the surface of
the ground to the centre of the wheel, or rather to the place of
contact between the axletree and the box of the wheel.   So
that it is lessened by the mechanical advantage of the lever, in
the proportion which the diameter of the axletree bears to  the
diameter of the wheel.   The rubbing surfaces also, being kept
polished and smeared with some unctuous  substance,  are in the
best possible condition to resist friction.
   In like maimer the common obstacles that present themselves
in the public roads, are surmounted by a  wheel with peculiar

   * This remark of course does not apply to siluation« in which friction is ob-
viated, as upon water, ice, rail roads, &c. 
196
ARTS OF LOCOMOTION.
facility.   As soon as the wheel strikes  against a stone or simi-
lar hard body, it is converted into a lever for lifting the load
over the resisting object.   If an obstacle eight or ten inches in
height were presented to the body of a carriage  unprovided
with wheels, it would stop its progress, or subject it to such vio-
lence as would endanger its safety.   But by  the  action of a
wheel, the load is lifted, and its centre of gravity passes over in
the direction of an easy arc, the obstacle furnishing the fulcrum
on which the lever acts.
   Rollers.—Rollers placed under a heavy body diminish the
friction in a greater degree than wheels, provided they are true
spheres or cylinders, without any axis on which they are con-
strained to move.   If the rollers  be perfectly elastic and also
the plane upon which they move, there will be no sliding fric-
tion whatever; whereas the  wheel always rubs at its axis.  But
an offset for this advantage is found in the circumstance, that
the wheel maintains its relative place  in regard to the  load,
while the roller  constantly  falls  behind, and is obliged  to  be
taken up and replaced, at an expense of power.   A cylindrical
roller  likewise occasions  friction, whenever  its path  deviates
in the least  from a straight line.
   Size  of  Wheels.—The mechanical  advantages  of  a wheel
are  proportionate to  its size, and the larger it is, the  more
effectually does it diminish the ordinary resistances.   A  large
wheel will  surmount stones and similar obstacles better than a
small one, since the arm of the lever on which the force acts is
longer, and the curve described  by the  centre of the load is the
arc of a larger circle, and of course the ascent is more gradual
and easy. *
   A further advantage is derived from the circumstance, that in
passing over holes, ruts, or excavations, a  large wheel sinks less
than a small one, and consequently occasions less jolting and

  * If the plane on which a carriage moves, and the line of draught be both
horizontal, the advantage for surmounting an immoveable obstacle of a given
height, is as the square root of the radius  of the wheel.—See Playfair't
Outlines of J\Tatural Philosophy,  vol. i. p. 103. 
ARTS OF LOCOMOTION.                 197
expenditure of power.  The wear also  of small wheels ex-
ceeds that of larger ones, for if we suppose a wheel to be  three
feet in diameter, it will turn round twice, while a wheel  six feet
in diameter turns  round once.   Of course its tire will  come
twice as often in contact with the  ground, and  its  spokes will
twice as often have to support the weight of the load.   So that
by calculation, it should  last but half the length of time.
  On these accounts it would be advantageous to augment the
diameter of wheels to a great extent,  were it  not  for  certain
practical limits  which it is not found useful to  exceed.   One
of these is  found in the nature of the  materials which we are
obliged to use, and which, if employed to make wheels  of great
size, at the same time preserving the requisite  strength, would
render them cumbersome  and too heavy for use. *  Another
reason for  regulating the size of wheels by a limited standard
arises from the relative size of the animals commonly employed
for draught.  A wheel  should  seldom be of such  dimensions
that its centre would exceed in height the breast of the horse,
or other animal, by  which it is drawn ; because if this were
the case, the horse would draw obliquely downward, as well as
forward, and expend a part of his strength in acting against the
ground.
   Line of Traction.—In practice  it is  even found necessary to
place the  point of draught or centre of the wheels  lower than
the middle of the  horse's breast, for various reasons.   1. The
shape of the animal's shoulders require this direction.   2. The
horse exerts a greater force in proportion as the line of  draught
passes near the fulcrum, which is in his hind feet.   3. If a
horse draws obliquely upward,  a part of his force is employed
in lessening the pressure on the  ground,  and to  answer this
purpose most effectually, it has been remarked that  the  inclina-
tion of the  traces, or shafts, ought to be the same with that of a
road, upon which  the carriage  would just descend  by  its own
weight, f   According to Dr Gregory, a power which  moves a
* See the article Limit of Bulk, p. 48.
t Young's Natural Philosophy, vol. i. p  216. 
198
ARTS OF LOCOMOTION.
sliding body along a horizontal plane, acts with the greatest ad-
vantage as far as friction is concerned, when  the line of direc-
tion makes  an  angle of about 18j degrees  with  the plane. *
M. Deparcieux states from experiments with carriages, that the
angle made by the trace with a horizontal line, should be one of 14
or  15 degrees.  4.  Another reason  for  inclining the line of
draught, is, that a horse  depresses his body in proportion to the
force he is obliged to exert, in order that he may bring his own
weight to act more advantageously upon the load.  M. Deparcieux
has demonstrated that animals draw through the medium of
their weight, in all our common vehicles; and this fact becomes
obvious when  we  consider, that if a horse had no weight, he
would be  unable to draw,  but would simply be raised on his
hind feet, by any exertion to advance while in his  harness.
   In  the  foregoing  considerations, it is necessary to recollect
that the conditions  which  enable a horse to  exert his greatest
force, are not those which promote his greatest velocity, and
that the means of increasing his speed, are obtained, as in other
cases, by the sacrifice of power.
   When there are four wheels, the line of draught ought to be
directed to a point between the  two axletrees, or rather to a
point directly under the  centre of gravity of the load, and such
a line should always pass above the axle of the fore wheels.
   Broad Wheels.—Much controversy has existed in regard to
the comparative utility  of  wheels having a broad, or a narrow
circumference.   The disadvantages of broad wheels are, that
they are heavier than narrow ones, that they are more expensive,
and that they include in their path a greater number of stones or
projecting obstacles.  Their advantages are, that they pass more
easily over ruts and holes,  and that in soft and sandy roads they
sink to a smaller depth,  f   But the great benefit  which results

  * Treatise on Mechanics, vol. ii. p. 18.
  t The latter advantage, however, is of a more equivocal kind than appears
at first view ; for although they sink less deeply, they displace more earth in
sinking to the same  depth.  Still, however, the advantage, upon calculation,
remains on the side of the broad wheel. 
ARTS OF LOCOMOTION.
199
 from broad wheels is of an indirect kind, and  arises from the
 improvement of the roads which takes place under their use.
 They tend to prevent deep and narrow ruts, and act as rollers
 in levelling the surface.
   Form  of  Wheels.—If roads  were  in  all  cases  level and
 smooth, wheels should be made  exactly cylindrical,  or with all
 their spokes  parallel to the same plane.  But since the unequal
 surface of most roads exposes carriages to frequent and sudden
 changes of position, it is found advantageous to make the wheels
 a little conical, or as it is commonly termed, dishing, so that the
 spokes may  all diverge with their extremities from the carriage.
 In this  case, whenever the carriage is thrown  into an inclined
 position, and the centre of gravity shifted towards one wheel,
 the spokes on the under side of that wheel become more near-
 ly vertical, and  are in a more  advantageous position to sustain
 the pressure.  This will be  seen  in  Fjg.  1, at the bottom
 of the page.   In muddy roads there is a convenience attend-
 ing the  dished wheel, in having  its circumference further  from
 the body  of the carriage, than that of a straight wheel upon the
 same hubb * would be.  Some disadvantages at the same time
 attend upon  this form of the  wheel, the principal of which  is,
 the increase  of friction which it occasions.   A conical wheel, if
 left to itself, tends to travel in a circle round a point where the
 apex  of the cone would be situated.  If it is obliged to advance
in a straight line, it has a degree of lateral motion and  friction,
 which increases in proportion as it deviates from the cylindrical
form.   In common cases, a slight degree of the dishing form is
best, but  it should never  be carried to such an  extent as to
create much friction, or endanger the bending of the spokes.
   Fig.  l.
A           B
  In the opposite figure A represents the
cylindrical, and B the dished form of the
wheel.
  * This word, instead of nave, is so generally used in this country, that it
would be a useless refinement to avoid it.  The same is true of the word fac-
tory for manufactory, and also of many mechanical terms.
 
200
ARTS OF LOCOMOTION.
   Axletrees.—When wheels are perfectly upright, the ends of
the axles  should be cylindrical, but in dished wheels they  are
made conical and inclined downward so as to make their under
surface horizontal.   In this  case the wheels spread most at top,
and  the lower spokes are most nearly vertical.  The  ends of
the axletree are often inclined a little forward, which arrange-
ment causes the wheels to run  inward, and prevents them from
pressing on  the finch pin.  The friction, however, is increased.
In some locomotive carriages, the axle is fixed to both wheels,
and turns  with them.  This mode of connexion  causes great
strain  and friction, whenever the path is in any other than a
straight line, from the necessity, which is  produced, that  the
wheels should keep pace with each other in their revolutions.
   Springs.—The effect of suspending a carriage on springs, is
to equalize  the motion, by causing every change to be more
gradually  communicated to it, and  to obviate shocks by con-
verting percussion into pressure.   Springs are not only useful
for the convenience of passengers, but they also diminish the
labor of draught; for whenever a wheel strikes a stone, it rises
against the pressure of the spring, in many cases without mate-
rially disturbing the load, whereas, without the spring, the load,
or a part of it, must rise with every jolt of the wheel, and  will
resist this  change of place with a degree of inertia proportion-
ate to the weight and the suddenness of the percussion.  Hence
springs are highly useful in baggage waggons and other vehicles
used for heavy transportation. *
   Attaching of Horses.—Horses  draw  most advantageously
when they are either single, or harnessed abreast of each other.
When  two  horses draw side by side, they are equally near to
the load, and have the same line of traction.  If their traces
are attached,  as is frequently done, to  hooks on the  ends of a
crossbar, which in its turn  is  connected to the  carriage by a
staple  projecting behind, a compensation  will be thus made
for any difference in the strength or activity of  the animals.
v See a paper by Mr Gilbert, in Brande's Journal, vol. 19. 
ARTS OF LOCOMOTION.
201
In Fig. 2, the centre E upon which the bar moves is consider-
ably behind the points of attachment, A and B.   Hence when
one  end falls back, so that the arm A B assumes the  position
C D, the foremost horse will have          Fig. '2.
the  disadvantage of acting  by  a
lever  equal only to E F, while the
other horse acts by a lever  equal   jl\
to EC.  In the narrow streets of    c'            &
cities a custom has arisen of harnessing draught horses before
each  other in a single line, probably for the sake of room  and
the convenience of the driver.  But in this situation  only the
shaft  horse has an advantageous line of draught.   The remain-
ing horses draw nearly in a  horizontal line, and of course  at a
disadvantage.  Besides this, the foremost horses  being attached
to the ends of the shafts, do  not act directly upon the load, but
expend a part of their force  in vertical pressure upon the back
of the shaft  horse, which  is  increased in drays,  sleds, and  all
low carriages.  This will be seen by inspecting  Fig. 3, where
                          Fig. 3.
it is obvious that the line of draught of the first  horse cannot
become  direct, without crippling down the shaft horse.   The
best mode of remedying this difficulty, would apparently be, to
attach the traces of the forward horse to a strong  hook project-
ing downward from  the end of each shaft, so as to bring the
traces into the proper line of traction, by directing them more
nearly towards the centre of the wheels.   It is  true that the
shaft  horse derives a certain degree of mechanical  advantage
from  vertical  pressure, like  that which  would result from an
increase of his weight.  Yet this, although  useful in short ex-
ertions, is not so when continued through a  day's fatigue.
26 
202
ARTS OF LOCOMOTION.
                         HIGHWAYS.

   Roads.—Roads intended for the passage of wheel carriages
are made more level and of harder  materials, than the rest of
the ground.   In  roads, the travel on which  does not authorize
great expense, natural materials alone are employed, of which
the best are hard gravel, and very small stones.   The  surface
of roads should be nearly flat, with gutters at the sides to facil-
itate the running off of water.  If the surface is made too con-
vex, it throws the weight of the load unequally upon one wheel,
and also that of the horses on one side, whenever the carriage
takes the side of the road.   Hence drivers  prefer to take  the
middle or top of the road, and by pursuing the same track  oc-
casion deep ruts.   The  prevention of ruts  is  best effected by
flat and solid roads, and by the use of broad wheels.  It would
also be further effected if a greater variety could be introduced
in the width of carriages.   Embankments at the sides to keep
the earth from sliding down, are best made by piling sods upon
each other, like bricks, with the grassy surface at right angles
with the surface of the bank.  But stone walls are preferable
for this purpose, when the material can be readily obtained.
   Pavements.—Pavements are stone coverings of the ground,
chiefly employed in  populous cities and  the most frequented
roads.  Among us they are  made of pebbles of a roundish form
gathered from the  sea  beach.  They should consist  of the
hardest kinds of stone,  such as granite,  sienite, he   If  flat
stones are   used, they require to be artificially  roughened, to
give secure foothold to horses.   In Milan, and some other pla-
ces, tracks  for wheels  are made of smooth stones, while  the
rest of the  way is  paved  with small or rough stones. *
   The advantage of a good pavement  consists  not only in its
durability,  but in the facility with which  transportation on it is

  * The streets of many of the ancient cities were paved, as those of Rome,
Pompeii, &c.  But the streets of London were not paved in the eleventh cen-
tury, nor those of Paris in the twelfth. 
ARTS OF LOCOMOTION.
203
effected.  Horses draw more easily on a pavement, than on a
common road, because no part of their power is lost in chang-
ing the form of the surface.   The  disadvantages of pavements
consist in their noise, and in the wear  which they occasion of
the shoes of  horses, and tires of wheels.  They should never
be made of pebbles so large as to produce much jolting by the
breadth of the interstices. *
   McAdam Roads.—The system  of road-making which takes
its  name  from Mr McAdam, combines the advantages of the
pavement and gravel road.  The McAdam roads are made en-
tirely of hard stones, such as granite, flint, he, broken up  with
hammers into small pieces not exceeding an inch in diameter.
These fragments are spread  upon the ground to the depth of
from six to ten inches.  At first the roads thus made are heavy
and laborious to pass, but in time the stones become  consolidat-
ed and form  a mass of great hardness,  smoothness, and perma-
nency.   The stones become  partly pulverized by the action of
carriage wheels, and partly imbedded in the earth beneath them.
The consolidation seems to be owing  to the angular shape of
the fragments, which prevents them from rolling  in their beds,
after the insterstices  between them are  filled.  Mr McAdam
advises that no other  material should be added to the broken
stones,  apparently with a view to prevent the  use of  clay and
chalk which abound in England.  It appears, however, that a little
clean gravel spread upon the stones, causes them to  consolidate
more quickly, and has the good effect of excluding the  light
street dirt, which otherwise never fails to become  incorporated
in large quantities among the  stones.

  * Mr Telford  has constructed in  England, a kind of paved road, in which
the foundation consists of a pavement of rough stones and fragments, having
their points upward.  These are covered with very small stone fragments and
gravel, for the depth of four inches, the whole of which, when rammed  down
and consolidated, forms a hard, smooth, and durable road. 
204
ARTS OF LOCOMOTION.
                         BRIDGES.

   The construction of small bridges is a simple process, while
that of large ones, is, under certain  circumstances, extremely
difficult, owing to the fact that the strength of materials does
not increase in proportion to their weight,  and that there  are
limits beyond which no structure of the kind could be carried,
and withstand its own gravity.   Bridges differ in their construc-
tion and in the materials of which they are  composed.  The
principal varieties are the following.
   1.  Wooden Bridges.—These, when built over shallow and
sluggish  streams, are usually supported upon piles driven into
the mud, at short distances,  or upon  frames of timber.   But in
deep  and powerful currents it is necessary to support  them on
strong stone piers and abutments, built at as great  a distance as
practicable from each other.   The bridge  between these piers
consists of a stiff frame of carpentry,  so constructed with refer-
ence to its material, that it may act as one  piece,  and  may  not
bend, or break, with its own weight and any additional load to
which it may  be exposed.   When  this frame is straight,  the
upper part is compressed by the weight of the whole, while  the
lower part is  extended  like  the  tie beam of a roof.  But  the
strongest wooden bridges are made with curved ribs, which rise
above the abutments in the manner of an arch, and are not sub-
jected to a longitudinal strain by extension.   These  ribs  are
commonly connected and strengthened with diagonal braces,
keys, bolts, and straps of iron.  The flooring of the bridge may
be  either laid above them, or suspended by  trussing underneath
them.   Wooden bridges are common  in this country, and some
of them are of large  size.   One of the most remarkable is  the
upper Schuylkill bridge at Philadelphia, which consists of a
single arch, the span of which is 340 feet.
   2.  Stone Bridges.—These, for the most part, consist  of
regular arches built upon  stone piers  constructed  in the water,
or upon abutments at the banks.   Above the arches is made a 
ARTS OF LOCOMOTION.
205
 level or sloping road.   From the nature of the material these
 are the most durable kind of bridges, and many are now stand-
 ing which were built by the ancient Romans.   Several of the
 stone bridges across the Thames, at London, are distinguished
 for elegance and strength.   The stone piers on which  bridges
 are  supported, require to be of great solidity,  especially when
 exposed to rapid currents, or to floating ice.  Piers are usually
 built  with their  greatest length in the direction of the  stream,
 and with their extremities pointed or curved, so as to divide
 the  water and allow it to glide  easily past them.   In building
 piers it is often necessary to exclude the  water by means of a
 coffer dam.   This is a temporary inclosure formed by a double
 wall of piles and planks having their interval  filled with clay.
 The  interior space is made dry by pumping,  and kept so till
 the structure is finished.
   3. Cast  Iron Bridges.—These  have been constructed in
 England out of blocks or frames of cast iron, so shaped as to fit
 into each other, and  collectively  to  form ribs and  arches.
 These bridges possess great strength, but are  liable to be  dis-
 turbed by the expansion  and contraction of the  metal with heat
 and cold.
   4. Suspension Bridges.—In these the flooring, or main body
 of the bridge, is supported on strong iron chains, or rods, hang-
 ing in the form of an inverted  arch from one point of  support
 to another.   The points of support are the tops of strong pillars,
 or small  towers, erected for the purpose.  Over these pillars
 the chain passes, and is attached  at  each extremity of the
 bridge to rocks or massive  frames of iron firmly secured under
 ground.   The  great advantage of suspension  bridges consists
 in their  stability of equilibrium, in consequence  of which a
 smaller amount of materials  is necessary for their construction,
than for  that of any other bridge.   If a suspension bridge be
 shaken, or thrown out  of equilibrium, it returns by its weight to
its proper place, whereas the reverse happens in bridges which
are built  above  the level of their supporters.  One of the most
remarkable  suspension bridges, is that over the  Menai Strait on 
206
ARTS OF LOCOMOTION.
the coast of Wales, the span of which, or rather the water way,
is 5O0 feet,  and the distance between the points of support, or
centre of the pieces, 560 feet.   It is suspended by four wrought
iron cables which pass over rollers on the tops of the pillars, and
are fixed to iron frames under ground which are kept down by
masonry.
  5.  Floating Bridges.—Upon deep and sluggish water, sta-
tionary rafts of timber  are sometimes employed,  extending
from  one  shore to another, and  covered with  planks, so as to
form  a passable  bridge.   In  military  operations, temporary
bridges are often formed by planks laid upon  boats, pontoons,
and other buoyant supporters.

                        RAIL ROADS.

  In  the best constructed public roads, a great amount of pow-
er is expended in overcoming  the disadvantages which are  in-
separable from their construction, and the nature of their mate-
rials.   The chief loss of power depends on the continual change
of form which  carriages  occasion in roads, by the crushing  of
stones, cutting of ruts, and other displacements  of the material
of which the road is made ;  which processes serve to consume
power, without forwarding the  progress of the carriage.
  The object of a rail road is to furnish a hard,  smooth, and
unchanging  surface for wheels to run upon.  These  surfaces,
in most cases, consist of parallel rails of iron, raised  a little
above the general level of the  ground, and having a gravelled
road between the rails, so that the rail road combines the ad-
vantages of  good foothold for horses, and of smooth, hard sur-
faces  for  the wheels to roll upon.   The wheels  are made
smooth and  true, and guides, to prevent them from slipping off,
are affixed either to the wheels, or to the rails.
  Rail roads are a modern invention, and  their  greatest im-
provements  have been made  within the present century.   In
comparing the effect of a rail road with that of a common turn-
pike  road, a saving is made, according  to  Mr  Tredgold, *  of
* Treatise on Rail Roads and Carriages, p. 3. 
ARTS OF LOCOMOTION.
207
 seven eighths of the power, one horse on a rail road producing
 as much effect as eight horses on a turnpike road.   In the ef-
 fect produced by a given power, the rail road is about a mean
 between the turnpike road and a canal, when the rate is about
 three miles per hour ;  but when greater speed is desirable, the
 rail road may equal the canal in effect, and  even surpass it.
   The earliest rail roads appear to have been  constructed of
 wood  only.  But  at the present  day iron  is employed  in all
 rails from which durability is expected.   In some cities tracks
 of  hewn  stone are laid for wheels in the streets, but  these are
 seldom executed with sufficient accuracy to deserve the name
 of  railways.  Of the iron rail road, there  are three principal
 varieties.   1. The Edge rail.   2.  The  Tram road.   3. The
 Single rail.
   Edge Railway.—In this  species the  rails are laid with the
 edge  upward,  and the carriage is retained upon  them by a
flange, or projecting edge, attached to the wheels, instead of the
 rail.  These rails, when made of cast iron, are commonly about
 three feet long, and four or five inches deep in the  middle, the
 outline being curved on the under side, to produce equality of
 strength.   Fig. 4 represents a side view of a common cast iron
 railway.  The ends of the rails are received in a piece of cast
                           Fig. 4.
iron, called a chair, and these chairs are affixed to large blocks
of stone with a broad base,             Fig. 5.
called  sleepers, which  are
previously  placed  in   the
ground upon a proper level.
Fig. 5 is a section,  or end
view of the rail road, togeth-
er with the wheels of a car-
riage, and the flange which
serves to guide them. 
208                ARTS OF LOCOMOTION.
 Rails  are now frequently made of wrought iron with a form
 nearly  similar  to  that  which has  been  represented.    As
 this material is costly  when  employed  alone, it is  sometimes
 used in thin bars as a covering to wooden  rails, particularly in
 this country where timber is plenty, and iron expensive.*   An-
 other and a better  method has been adopted of laying straight
 bars  of  wrought  iron  upon  tracks  of  hammered granite.
 Wrought iron rails have the advantage of reducing the number
 of joints, a circumstance which greatly increases  the strength,
 as well as smoothness of the road.   The comparative durability
 of wrought, and of cast iron rails, is as yet not  fully settled.
    Tram Road.—Tram roads  are  flat  rails, made usually of
 cast iron, with an elevated edge or flange, on one side, to guide
 the wheels of carriages in their path.  Tram rails are weaker
 than edge rails, when made of the same  amount of material,
 and it is sometimes  necessary to strengthen them with ribs un-
 derneath.   They are capable of being used for ordinary wheel
 carriages, but the introduction of wheels which are not perfect-
 ly smooth, is  always injurious to the road.  Tram roads are
 more liable to be covered with dirt than rails of other kinds.
   Single Rail.—Carriages may be made to run upon a single
 rail, by elevating the rail from the ground,  and suspending the
 load beneath it.   In Mr Palmer's railway, the rail is  about
 three feet above the surface of the ground, and is supported by
 pillars placed at distances of  about nine  feet from each other.
 The carriage consists of two receptacles, or boxes,  suspended
 one on each side of the rail by an iron frame, and having  two
 wheels placed one before the other.   The  rims  of the wheels
 are concave, and fit the convex surface of the rail, and the cen-
 tre of gravity of the carriage, whether loaded or  empty, is so
 far below the upper edge of the rail, that the receptacles hang
 in equilibrium, and will bear  a considerable  inequality of load
 without inconvenience, owing to the change of fulcrum allowed
 by the breadth of  the rail, which is about four  inches.   The

  * The durability of this combination of wood and iron, remains  to be settled
by longer experience. 
ARTS OF LOCOMOTION.                209
 alleged advantages of the single rail  are, that it is more free
 from lateral friction  than the other kinds of railway, and that
 being  higher from the ground, it is less  liable to be  covered
 with dust and gravel, and lastly that it is  more  economical, the
 construction of one rail being less expensive than of two. *
   Passings.—When the amount of travel on a rail road is very
 great, it becomes necessary that the  road  should be double,
 one set of tracks being provided for carriages moving in each
 direction.   Where there is less travel, a single road is sufficient,
 if it be provided with double places, called sidelings, for carria-
 ges to pass each other at convenient  distances.   But in both
 cases the  travelling is  liable to be retarded  by the difficulty
 which exists, during a great part of the way, for carriages to
 pass each other  when  moving in the same  direction, those of
 slow motion obstructing the progress of those which are intend-
 ed for greater speed.   In order to obviate  this difficulty, and
 also to diminish the number of passing places, Mr Treadwell
 proposes f to regulate the times of starting  in both directions,
 and also the velocity  of  the faster and the slower carriages, by
 a uniform arrangement, so that  they shall always move in con-
 cert and meet at the passing places at stated  times, and  at no
 other times or places.  By an easy calculation the more rapid
 vehicles may be so regulated as  to overtake  the  slower  ones
 exactly at the passing places,  and a coach  moving at the  rate
 of  nine  miles an hour, may experience  no  hindrance from  a
 multitude of waggons moving with a third part of  the velocity.
   When  forks in a rail  road occur, at the  passing places, or
 elsewhere, a part of the rails is rendered moveable, so as to di-
rect the wheels upon  either track.   When the railway crosses
 a public road, it is made to pass at a lower level than the com-
 mon surface, and is protected from carriage wheels by an elevat-
 ed  edging of wood or stone; but when the single rail crosses a

  * A railway of this kind was invented more than  twenty years ago, by
 Henry Sargent, Esq. of Boston.
  t Franklin Journal, vol. iv. p. 278.
               27 
210
ARTS OF LOCOMOTION.
road, a part of it must be made to swing open  like a turnpike
gate.  Railways require to be kept as free as possible from dirt,
which greatly increases the resistance.   Mr Palmer found upon
a tram road, that it required 19 per cent, more power to draw
the  same  carriages when the rails were slightly covered with
dust, than when they were swept clean.
   Propelling Power.—Horses are commonly  employed for
drawing loads  upon railways, a horse being supposed capable
of drawing eight  times as  much,  as  upon a  common road.
Locomotive steam  engines  are much employed upon railways,
in England.   They were at first made  to propel carriages by
means of a toothed wheel, which acted  upon a rack attached
to one of the rails ; but at the present  day, they are made  to
act by the friction only of  the  carriage wheels upon the plain
rail.   These engines  are  always made  of  high pressure,
since those of low pressure  are  rendered too heavy by the
weight  of the  water   necessary   for  condensation.   It has
been proposed to place  stationary engines  at short  distances,
which should draw carriages forward from one to the other by
endless chains, thus saving the transportation  of the engines.
Where the declivity of the road is great, loaded carriages some-
times descend by their own gravity, and at the same time draw
up the empty ones by  means of pullies.   To prevent carriages
from acquiring  too great  a velocity in descending, a crooked
lever, called a brake or convoy, is  applied to the surface  of the
wheels, so as to retard them by its friction. *   When loaded
carriages  are transferred from one part of the road, to another
of greater elevation, they are either drawn up an inclined plane
with ropes, by horses, or  stationary engines; or they may be
lifted perpendicularly, by pullies.

  * A retarding friction is produced, when necessary, in mountainous countries,
upon common roads, by chaining one of the wheels, when the carriage goes
down hill, so as to prevent its turning. The same effect is produced in a safer
manner, by placing a wooden shoe like a runner, under one of the wheels. 
ARTS OF LOCOMOTION.                21 1
                         CANALS.

  Canals  are artificial channels for water, cut for the purpose
of admitting inland navigation.   The great utility of canals in
facilitating transportation, has caused them to be constructed in
all ages.  The canals of the ancients were chiefly made  on one
level, so as to form merely artificial rivers, or creeks.  Those
of the moderns, by means of locks, are carried indiscriminately
over ground which is depressed or elevated.  In level tracts of
country, if the earth is of suitable character, canals are easily
made.  But in loose and crumbling soils, in  undulating, rocky,
and mountainous tracts, and in those which  are intersected by
large streams; their construction becomes expensive and diffi-
cult.   To surmount these difficulties, loose  soils are defended
with  firmer materials, vallies are passed  by  enbankments, hills
are penetrated by deep cuttings or tunnels, rivers are  crossed
with aqueducts, and declivities  are ascended  and descended by
locks.  In order that water may not be wanting in any part of
the canal, a supply is insured at the highest level, and this grad-
ually passes off through the locks, to the lowest.   The  streams
which furnish the water at this,  and other  points, are called
feeders.
   Embankments.—Canals  are dug with sloping sides, to pre-
vent  the banks from caving in.  The boats being in almost all
cases drawn by horses, a firm, uninterupted towing path  is form-
ed on one of the banks.   The banks are liable in time, to be-
come indented and washed away, by the constant  agitation of
the water, occasioned by the  passage of boats.  To  prevent
this,  they are sometimes secured by driving close rows of stakes
 against the banks; but the only effectual protection is found in
 walling the banks with stone.   When the canal crosses a sec-
 tion of country, the surface of which is lower than the intended
 surface of the water, the canal is raised to the proper  level by
 means of embankments.   These  are artificial Banks, or dykes,
 made of such materials as will not be liable  to leak,  and of such 
212
ARTS OF LOCOMOTION.
 form and strength that they will not be broken by the pressure
 of the water.  The surface of these banks is of a sloping form,
 and is secured by sodding, and in some  instances, by piles, or
 stone walls.  Where the nature of the  earth renders leakage
 probable, it is common to  cover the bottom  and sides of the
 canal  with a lining of puddle, which  is formed  from loam, or
 clay and gravel, worked up with water.   For additional securi-
 ty a trench is dug in each bank to a greater  depth than  the
 bottom of the canal,  and  filled with puddle.
   It sometimes happens that the embankments act as a dam to
 prevent the land on one side of the canal, from being properly
 drained.   In this case, culverts, or subterranean passages  are
 constructed  underneath the canal, but not communicating with
 it; to effect  the  necessary draining.   Culverts  are made  of
 brick or stone, and require to be strong and tight.
   Aqueducts.—When a canal crosses a river, or a deep ravine,
 it is supported at the proper level by an aqueduct.  This struc-
 ture resembles a stone bridge, formed  of strong piers and arch-
 es, of regular masonry, rendered as tight as  possible  with hy-
 draulic cement.   Upon the top, a level  channel for the water
 is formed.   This  is  secured with strong and tight  walls  on
 the sides,  and lined within by a coating of  clay.  Room for
 the  towing path  must be preserved, on  one of the  sides.  In
 England, aqueducts have sometimes been made of cast iron.
   Tunnels.—Tunnels are subterranean  passages, most fre-
 quently cut  through the base of hills, to afford a level water
 course  for  canals.   Tunnels are also made  for the passage of
 railways, and, in some cases, of highway roads.   When they
 are obliged to be cut through  solid rock, which is done chiefly
 by blasting, their  formation is difficult, but they require no ar-
 tificial  security for their  subsequent protection.   But tunnels
 which  are made in soft  earth, require to be arched  over for
 their whole length with  stone or brick;  and in loose,  springy
 ground, the bottom likewise must be defended with an inverted
 arch.   That <^lnnels  may  be properly  ventilated, especially
while digging, shafts or vertical passages are sunk  at proper dis- 
ARTS OF LOCOMOTION.
213
tances, in which fires are kept burning to create a current for
discharging the foul air.  One of the most remarkable  tunnels
is that at Worsley, on the Duke of Bridgewater's canal, which
with all its branches is estimated at eighteen miles in length.
   Gates  and  Weirs.—As all canals are liable to have their
banks broken through during violent rains and freshets, it is im-
portant to lessen the injury which results  from such accidents,
by retaining as much of the water in the canal as possible. To
effect this  object, safety gates and stop gates, are placed  at
suitable distances  from each other, on the canal, so  that by
closing them at any time in case of accident, the escape of that
part of the water which is beyond them, may be prevented.
These gates are  sometimes attached to the  sides, and some-
times lie upon the bottom.
   Certain parts of the banks called weirs, are made lower than
the rest, to discharge the  superfluous water, and keep  the sur-
face at a proper level.   To prevent them from being gullied or
worn away by the attrition of the water, they are commonly
made of stone, or  sometimes of wood.
   Locks.—When a canal changes from one level to another of
different elevation, the place where the change of level takes place,
is commanded by a lock.  Locks  are tight  oblong inclosures
in the bed of the canal, furnished with gates at each end, which
separate the higher from the lower parts of the canal.   When
a boat passes up  the canal,  the lower gates  are opened, and
the boat glides into the lock, after which the lower gates  are
shut.  A sluice communicating with the upper part of the ca-
nal is then opened, and the lock rapidly fills with water, elevat-
ing the boat on its surface.  When the lock is filled to the
highest water level, the upper gates  are opened, and the boat,
being now on the  level  of the upper  part of  the canal, passes
on its way.  The reverse of this process is performed, when
the boat is descending the canal.
   Locks are  made of stone  or brick, sometimes of wood.
 The walls are sometimes  erected  upon an inverted arch, and
 also upon piles, if the soil is alluvial, or  loose.   They are laid 
214
ARTS OF LOCOMOTION.
with hydraulic cement,  and  rendered  impervious  to  water.
The gates are commonly double, resembling  folding  doors,
turning upon  coin posts which are next the walls.  They meet
each other in most  instances, at an obtuse angle, and the pres-
sure of the water serves to keep their contact more firm.   The
hydrostatic pressure in these cases, being in full force in a di-
rection perpendicular to the surface of the gates, has a different
action from that of  the pressure of gravity applied to a roof, or
similar structure; and gives to long gates a greater comparative
disadvantage, than to short ones.  Cast  iron gates are some-
times used in England, curved in the form of a horizontal arch,
with their convex side opposed to the water.   Valves are small
sliding shutters which admit a stream of water for the purpose
of gradually  filling  or emptying the lock, to prevent the shock
of suddenly opening the gates.
   In  situations where there is a scarcity of water, the waste
occasioned by frequently opening  the  gates for the passage of
boats, is  too  great  for the amount supplied to the canal.   In
these cases, to economize the water, reservoirs are provided at
different heights on each side  of the lock.   The water in the
upper parts of the lock, is discharged into these reservoirs, and
only that in the lower parts is suffered to escape into  the lower
canal.   Afterwards, the water in these reservoirs is used to fill
again the lower parts of  the lock, and thus  the same water is
made use of a second time.
   In  China, where inland navigation is much practised, it is
said there are no locks, but boats are transferred from one lev-
el to another, by means of inclined planes.   This method is
sometimes practised in Europe, and it had a zealous advocate
in the late Mr, Fulton.  To effect this transfer  most advanta-
geously, two boats  passing in opposite directions, are connected
together by a chain  passing over  a pully.   One boat in de-
scending the plane assists by its weight to draw the  other up-
ward.    Sometimes, instead of  inclined  planes, perpendicular
lifts have been proposed, by which the  boats are hoisted direct-
ly by pullies from  one level to another, or lowered in the op- 
ARTS OF LOCOMOTION.
215
posite direction by the same means.  The objection to all these
modes exists in the strain to which the boats are exposed, un-
supported by the  pressure of the water.   Various  expedients
have been proposed for altering the level of the water, and
transferring boats, by means  of large plungers, diving chests,
he, but none of them, as yet, appear to have been approved
in practice. *
  Boats.—Canal boats are  made narrow,  for passing each
other, and draw water  proportioned to the depth of the canal.
Their length is limited  only by that of the locks.  They are
drawn by horses on the tow path,           fio-, 6.
being kept by  the rudder from
coming in contact with the bank.
No  species  of oars, poles,  or
paddle wheels are allowed, on account of the  injury  done to the
bottoms  and banks,  by their use.  It is said, however, that
the  steam  engine has  in some cases been used without injury
to the canal, by causing the  paddle wheels to work in a water
passage, or casing, which passes through the boat above its bottom.
  Size,of Canals.—Canals differ greatly from each other, not
only in their  length,  but their  size, and  the  draught of water
which they  admit.  One of the  largest canals, as far as the
volume  of water is concerned, is the Great Dutch canal which
connects the city of  Amsterdam with the Helder, on the north
coast of Holland.  This  canal is  50 miles in length,  124 feet
in width, at the surface of the water, 36 feet wide at bottom,
and about 21 feet deep.   It is large enough to permit one frig-
ate to pass another.  The Caledonian canal, extends from the
Murray   Frith, on the eastern  coast of Scotland,  to  Loch
Eil,  on  the  western,  and  admits of the  passage  of large
ships.   It is 120  feet wide at the water surface, and 50 wide
at bottom.  The  depth of water  is 20 feet.  The  distance
from sea to sea, is about 59 miles, of which 37^ is lake naviga-
tion, and 21^ is cut. f   The Canal of Languedoc,  in France,

  * Repertory of Arts, vol. i, ii, and xxiii.
  I Supplement to the Encyclopedia Brittannica, and Edinburgh Encyclopedia
 
216
ARTS OF LOCOMOTION.
 is 64 leagues in length, and connects the Atlantic  ocean with
 the Mediterranean sea.  It is 64 feet wide at the surface  and
 navigable for vessels of 100 tons.  The great New York, or Erie
 Canal, is 360 miles long, and extends from the Hudson river, at
 Albany, to Lake Erie, at Buffalo.   It is 40 feet wide at the sur-
 face, 28 feet wide at bottom, and has four feet depth of water.

                          SAILING.

   Form of a Ship.—The movement of bodies through water,
 if performed within certain limits of velocity, is attended with
 less  resistance than that which takes place in most other modes
 of transportation.  A body, however, of given size will encoun-
 ter a greater or less resistance from the water, according to its
 proportions, and the sort of surface which it opposes to  the
 fluid.  In calculating the proper form for a ship, it is necessary
 to consider the kinds of pressure  to which bodies moving in
 fluids are  subject.   If we  suppose an  oblong square box, or
 parallelopiped,  as  A B C D,            p-    ^
 in Fig  7,  to  move  through              JL      jb,
 the  water in the direction of „    __--'"'            \.
 its length, the pressure will be       """'*•••...            ,.••'"
 increased before, and diminish-               C      jj
 ed behind it, the surface of the water being elevated at the an-
 terior extremity, and  depressed  at the posterior;  an  effect
 which increases in a high ratio as the velocity becomes greater.
 The  principal  part  of the  water  which  is before the moving
body, divides and passes off by the sides, but a certain quantity
of what is called dead water, is pushed along in  advance of the
moving body, nearly in the same manner as if it were a part of
the body itself.   The  shape of  this dead water at the surface,
is found to be that of an irregular triangle, and hence it becomes
 advantageous to add to the moving body  an extremity, or bow,
having nearly the same shape as the dead water, and occupy-
ing its place, as  in the dotted line BED.   On the other hand,
there occurs behind the moving body a depression of surfa^0, 
ARTS OF LOCOMOTION.
217
and a partially empty space, which is also  of a triangular, or
wedge form, consisting of the room which the moving body has
just left, and into which the  water upon each side has not yet
flowed.  The cavity which is thus formed,  resists the progress
of the body by its negative pressure.  Its  effect is readily un-
derstood, when we consider that if the water before the moving
body be raised one foot, while the water behind it is depressed
one foot, the difference of pressure upon the  two extremities
will be equal to that resulting from two feet.   On this account
it is advantageous to add to the moving body a tapering,  or
wedge-shaped extremity behind, capable of occupying this cavi-
ty and nearly answering to it in shape, as  represented by the
dotted line A G C.   The consequence will be, that the water,
which is advancing from  both  sides to fill up the vacuity, will
meet  the  tapering  sides of the  vessel soon enough to ob-
viate, or greatly diminish the  negative  pressure.   The  form
produced  by this  general outline, varied by a proper curvature
of  the sides  and  bottom,  corresponds nearly to that which
is   adopted  in the  construction of  ships,  and also  to  that
pursued by nature in the structure of fishes.   If a vessel be in-
tended for a fast  sailer, its proportionate length  and its sharp-
ness before and behind, must be increased, since  both the  posi-
tive and negative pressure, and the extent of the dead water
and vacant space, will increase with the velocity,
   Keel and Rudder.—The use of the keel,  which is a project-
ing timber, extending the whole length of the ship's bottom, is
to  assist in confining the motion of the ship to its proper direc-
tion, and by its lateral resistance, to diminish the disposition to
roll or vibrate from side to side.   The rudder, which is a per-
pendicular part attached by braces resembling hinges, to the
stern post of the  vessel, serves to govern the ship's course, by
altering the relative resistance of its two sides.   Thus, while
the ship is under way, if the rudder is turned to one side, it re-
ceives an impulse from the water on that side, causing the stern
to  turn towards the opposite side, where no such resistance ex-
               28 
218
ARTS OF LOCOMOTION.
ists,  thus altering the direction  of the keel, and the general
course of the vessel.
   Effect of the Wind.—When a ship sails in the same  direc-
tion as the wind, she is said to be scudding, or sailing before the
wind, and if she had but one sail, it would act with the greatest
advantage, when perpendicular, or nearly so, to the wind.
   When a ship advances  against the wind, and endeavours to
proceed in the nearest direction possible  to the point of com-
pass from which the wind  blows, she  is said to be close hauled.
A large ship will sail against the  wind  with her keel at  an an-
gle of six points, with the  direction of the wind, and sloops and
smaller vessels may sail much nearer.   When a ship is neither
sailing  before  the  wind, nor close hauled, she is said  to be
sailing  large.  In this case, her sails are set in an oblique posi-
tion, between the direction of the wind, and that of the intend-
ed course ; as represented in the  various plans of vessels in
Fig. 8, where  the  direction of the wind is represented by  the
                           Fig. 8.
 
ARTS OF LOCOMOTION.
219
arrow, and the position of the yards and sails, which is necessa-
ry for proceeding on the various points  of compass, is shown by
the transverse lines on each plan.   The relation of the wind  to
the course of the vessel is determined by the number of points
of the compass between the  course she is steering, and the
course which she would be  steering, if close hauled.  In Fig.
8, the  ships a and b are close hauled, and the ships c and  d,
the former steering east by north,  and the latter west by north,
have the wind one point large.  The ships e  and/, one steer-
ing east, and the other west, have  the- wind two  points large.
In  this case, the wind is at right  angles with  the keel, and is
said to be upon  the beam.    The  ships g and h, steering  south
east, and south west, have the wind six points large, or as it is
commonly termed, upon the quarter, and this is considered  as
a very favorable manner of sailing, because all the sails coope-
rate to increase  the  ships velocity, whereas when the wind is
directly aft, as in the vessel m, it  is partly  intercepted by the
after sails, and prevented from striking with its full force on those
which  are forward.   The force of a wind which strikes obliquely
upon the  sails, supposing them flat surfaces, is resolvable into
two forces, one of which  tends to push the vessel ahead, and the
other to push her sideways.   If the form of the vessel, instead
of being  oblong, were circular, like a tub, she  would move in
the direction of the diagonal of a  rectangle, representing  these
two forces, and  her course would be at right angles with the
position of the sail, or in the direction of the line  A B, in Fig.
9.  But owing to the oblong shape of the vessel, and the  influ-
ence of her keel, it requires  about twelve times as much  force
to push her  sideways, as to push  her head foremost.*  The
oblique impulse, therefore, will carry her a great  distance for-
ward, in the time that she is drifting a short distance to the lee-
ward, and it is this  relative  difference of progress which ena-
bles a vessel to advance even against the wind.   The angular
deviation  of  a ship's real course  from  her  apparent  course

         * Robison's Mechanical Philosophy, vol. iv. p. 620. 
220
ARTS OF LOCOMOTION.
upon  which her head is directed, is called the leeway.  In the
vessel, Fig 9, with the wind blowing in        Fig.  9.
the  direction  of the  arrows, and the       ^>   v^
sails set as represented,  if the vessel          45r\\  /
were  moving in a railway, or unchange-          \\\)\
able channel, her course would be B D,      ■►_»  V%A
but in the water she drifts  so much  to       «-*■ /\N^
the leeward, that her real course is B C,            '■&-  ^\
and the angle C B D, represents the amount of leeway.
   Stability of a Ship.—The masts of a ship, when acted  upon
by the pressure of the wind against the sails, are so many lev-
ers, the tendency of which, is, to overset her.   To counteract
this tendency, a sufficient weight of ballast,  or cargo,  is stowed
in the bottom of the hold, to carry the centre of gravity into the
lower part of the hull, so that this part will always preponderate,
while the relative buoyancy of the upper part causes the vessel
to right, as often as  her position is disturbed.  If the ballast is
too light, or is stowed too high in the hold,  the vessel is said to
be too crank, and rolls more, and cannot carry so much sail
without danger of oversetting.   On the other hand,  if the bal-
 last is too heavy,  and placed too  low, the vessel is  said to be
 too stiff, and  not  only draws so much  water as to impede her
 velocity, but is liable  to  have her masts  endangered by the
 shocks which result from the suddenness of her motions.   In
 regard to shape, an increase  of the  width of  a ship, increases
 her stability, but at the same time, detracts from her power, as
 a fast sailer.
    Steam Boats.—Experiments on the propulsion of vessels  by
 steam,  were made in Europe, and this country, at different
 times  during the  last century, but the first  successful  introduc-
 tion of steam navigation on a large scale, was made in America
 by the late Mr Fulton, about the year  1807.  The application
 of the steam  engine to navigation, has  given to vessels the ad-
 vantage of greater speed and regularity in the performance of
 their passages, without interruption  from  the changeable, and
  often adverse, operation of the elements.   In the  action of the 
ARTS OF LOCOMOTION.
221
steam engine, as in that of rowing, a vessel is propelled by a
succession of impulses, which act against  the inertia of  the
water.
  A power acting within a boat, whether of men, of horses, or
of steam, may be applied to the-water in various ways.  Some
of the  principal of these,  are  the  following.   1. A system of
oars, or paddles have been made to act with alternating strokes,
rising out of water at the end of each stroke.   2. An  alternat-
ing paddle has been contrived, which is continually immersed,
and  which folds up like  the  foot of a water  fowl, during  the
backward stroke.   3. It  has been proposed to drive a current
of air, or a current of water, out at the stern of the vessel.   4.
Spiral wheels and  water screws, or wheels with oblique vanes,
like those of a wind mill, have been made to turn under water,
with their axes parallel to the keel of the vessel.  5.  Oblique
planes  acting with an alternate, instead  of a revolving stroke,
were recommended by Bernoulli.  6.  Paddle wheels.   These,
from their simplicity and advantageous mode of action, have in
common use superseded all the rest.  They consist of paddles
or floatboards attached to the arms, or  spokes, of a wheel, the
axis of which is at right angles with the  keel.  Their  common
place is on the sides of the boat, as in the annexed figure.
                         Fig.  10.
  The outline of the floatboards, or paddles, is commonly rec-
tangular, though Mr Tredgold recommends that their outer ex-
tremity should be parabolic.  The best position for the paddles
is in a plane passing through the axis of the wheels, but with this
position, they  strike the water obliquely in entering, and lift a 
222
ARTS OF LOCOMOTION.
 considerable quantity on quitting it; both of which motions oc-
 casion loss of power.  Attempts have been made to correct this
 disadvantage by various mechanical arrangements, in which the
 paddles are made to enter and leave the water perpendicularly;
 but want of simplicity, and objections of various other kinds, have
 prevented them from coming into use.  It has  been proposed
 to fix a series  of paddles  upon longitudinal  chains, passing
 round wheels, and parallel to each side of the vessel.   By this
 mode a number of perpendicular paddles would act upon the
 water at once; but it will be  seen, that as no more of these pad-
 dles  can  operate  usefully, than  are  sufficient to put the water
 between them into motion, a part of the series will be less use-
 ful than if it acted upon water at rest.  In  wheels of the com-
 mon  form,'it is advantageous to have a double row of paddles,
 one outside the other, and so placed that the paddles of one se-
 ries shall be opposite the  intervals of the other, and thus  enter
 the water successively, and in  different places. *
   Steam boats are best adapted  to the navigation of rivers and
 straits, or sounds,  where  the water is comparatively smooth.
 They are also used in the open  sea, but the violence of the
 waves renders the action  of the paddle wheels irregular, and it
 is found  difficult for them to carry fuel sufficient to supply the
 engine during long voyages.   These obstacles, however, have
 been  in part  surmounted, and steam boats now ply along the
coasts both of America, and  Europe.  The steam ship Savan-
 nah, crossed the Atlantic, in  1819, and was 21  days from land
 to land, during 18 of which,  she was able to use her engine.

                       DIVING BELL.

   The diving bell is an inverted vessel, containing air, and used
 for the purpose  of enabling  persons to descend with safety to
great  depths under water.  It is made tight at the top and sides,

  * For examinations  of the different propelling powers, see the Edinburgh
 Encyclopedia, article  ' Navigation Inland,' ascribed to  Mr  Telford; also
Tredgold on the Steam Engine, p. 309. 
■>
ARTS OF LOCOMOTION.
223
but is entirely open at bottom.   Its principle is the same  with
that of a gasometer,  and  may  be familiarly illustrated by im-
mersing an  inverted  tumbler in a vessel  of water.   The air
cannot escape from the inside of the vessel, being necessitated
by the order of specific gravities, to occupy the upper part of
the cavity.
   Diving  bells appear to have been first introduced in the be-
ginning  of the sixteenth century.   They were first known as
objects of curiosity only, but have been since applied to the re-
covery of valuable articles from wrecks, the blasting and min-
ing of rocks at the bottom of the sea, and the  practice of  sub-
marine architecture.   They may be made of almost any shape,
but the  common form has been that of a bell, or hollow cone,
made of wooden staves, and strongly bound with hoops,  having
seats  for the  occupants on the inside.   It is suspended  with
ropes from a vessel above, and is ballasted with heavy weights
at bottom, which serve to  sink it, and to prevent it from turning
over.   More recently diving bells have been made of cast iron.
The kind  of bell used at  Howth,  near Dublin, * is an oblong
iron chest, six feet  long, four broad, and five high, thicker at
bottom  than at top, and weighing  four  tons.  It has  a  seat at
each  end, and is capable of holding four persons.   The upper
part is pierced with  eight or ten holes, in which  are fixed the
same number of strong convex glasses, which transmit  the light.
As the air in the bell  becomes  contaminated by breathing, it is
renewed by letting  down  barrels, or small bells, of fresh air,
which are transferred to the large bell;  or else by keeping  up
a constant supply through a pipe, by means of a forcing  pump,
which is worked by men at the surface.
   Persons who descend in diving bells, often experience a pain
in the ears, and a sense  of pressure, occasioned by the  con-
densation  of the air within the cavity of the bell.  These symp-
toms  gradually pass off, or habit renders the body indifferent
to them, so that workmen  remain under water, at the depth of

         * Edinburgh Philosophical  Journal, vol. v. p.  8. 
224                ARTS OF LOCOMOTION.

twenty feet or more, for seven or eight hours in a day, without
detriment to the health.
   Submarine Navigation.—A machine was invented  during
the American revolution, by Mr Bushnell of Connecticut, which
was capable of containing a person in safety under  water, and
of being governed and steered  in any direction at pleasure.   It
is described *  as being a hollow  vessel of a spheroidal form,
composed of curved pieces of oak, fitted  together and  bound
with iron hoops, the seams being caulked and covered with tar
to render them tight.  A top or head,  was closely fitted to the
vessel, and served the purpose of a door.   In this were insert-
ed several strong pieces of glass to admit  the light.   The ma-
chine contained air enough to render  it buoyant, and to support
respiration.  A quantity of lead was attached to the  bottom for
ballast.   The vessel was made to sink by admitting water, and
to rise, by detaching a part of the  leaden  ballast, or by  expel-
ling water with a  forcing pump.  It was propelled horizontally,
by means of revolving oars placed obliquely like the sails of a
windmill, on an axis which entered  the  boat through  a tight
collar, or water joint, and was turned  with a crank within.  A
rudder was also employed for steering the vessel.  When fresh
air was  required, the vessel rose to the surface and took in air
through apertures at the top.   The intention of this machine
was to convey a magazine of powder  under ships of war for the
purpose of blowing them up.   Several experiments were made
with it, which, though unsuccessful in their  object, nevertheless
proved the practicability of this species  of locomotion.
  The late Mr Fulton,  made  various experiments on subma-
rine navigation, in a boat large enough to  contain several per-
sons, furnished  with masts and sails so as to be capable of pro-
ceeding at the surface of the water, and also of plunging, when
required, below the surface, f   While under water, its  motions
were governed  by two machines, one  of which caused it to ad-
vance horizontally, while the other regulated its ascent and

           * Silliman's Journal, vol. ii. p. 94.
           t See Colden's Life of Fulton, 8vo. New York, 1810. 
ARTS OF LOCOMOTION.
225
descent, its depth below the surface  being  known by the pres-
sure on a barometer.  A supply of fresh air was carried down
in the boat, condensed into a strong copper globe, by which
the  air of the boat was replaced when it became unfit for res-
piration.   Mr  Fulton's object was the  destruction of ships of
war, by bringing underneath them an explosive engine called a
torpedo.

                       AEROSTATION.

  Balloon.—A balloon is a  sphere,  or bag, formed of some
light material, such  as silk, and rendered impervious to the air,
by  covering it  with elastic varnish.   It is filled with a gas-
eous fluid, lighter than the surrounding atmospheric air, and has
a car suspended at the bottom.   If the  specific gravity of the
whole mass is less than that of an equal bulk of the atmospheric
air which surrounds it, the balloon  will  ascend into the atmos-
phere, and  remain suspended, until by the  escape of its gas, or
other means, it  becomes heavier than the surrounding air, when
it will again descend.   Balloons were invented in  France, by
the Montgolfiere, about 1782.  Those which were first employ-
ed by them were filled with common air rarified by heat; but
these required that  a fire should be constantly kept burning be-
neath them, to keep  them afloat.   Hydrogen gas was after-
wards employed, and  this fluid, being permanently about four-
teen times less  dense than common air, is undoubtedly the best
material for aerostation.   Carburetted hydrogen, though heav-
ier than hydrogen,  has also been employed of late on account
of its cheapness, being furnished in large quantities at the man-
ufactories of illuminating gas.
   Balloons are made by sewing together pieces of silk, the
shape of which corresponds to that of the part included by two
meridians of the artificial  globe.  They  have also  been made
of linen and of  paper.  They  are  varnished with a solution of
elastic gum, to  render, them tight.   A net  work is thrown over
the top of the balloon, to which is attached by strings, a car of
               29 
226
ARTS OF LOCOMOTION.
wicker  work, underneath the  balloon.   The  whole  is kept
down by a sufficient quantity of ballast, and ascends  into the
atmosphere when a part  of  the ballast  is thrown  over.   It  is
made to descend again by suffering a part of the gas to escape
through a valve provided for the purpose.
   The  regulation of the ascent and descent of balloons, is the
extent of control, which has been hitherto obtained over them.
All attempts to guide or propel them, by means of wings, sails,
oars, &c, have hitherto  failed, and the machine can only pro-
ceed at the mercy of the winds.   The small degree of  buoy-
ancy which balloons possess, does not permit them to carry suf-
ficient weight of material, to furnish the medium of an adequate
propelling force.   By taking advantage, however,  of favorable
winds, voyages  have been  made in them  to  the distance  of
300 miles; and persons have ascended to the height of 20,000
feet and upwards.  The velocity of balloons varies with  that of
the wind, but has in some instances amounted to the rate of 70
miles an hour. *
   Parachute.—The danger which attends falling from great
heights, is in consequence of the continual acceleration of veloci-
ty which  falling  bodies experience.  When, however, the re-
sistance of the atmosphere becomes equal to the force of gravi-
ty, the motion is  no longer  accelerated, but becomes uniform.
A parachute  is an appendage to a balloon, formed somewhat
like an umbrella,  and  is  designed to break  the force of  a fall,
by means of  the large surface which  it  opposes in its progress,
to the atmosphere.  It is made of silk, or canvass, and is plac-
ed underneath the balloon, having the car suspended from it
by cords.  When the balloon is at any height in the air, the
parachute may be detached from it, and will immediately fall
with the car to the ground.   But the resistance of  so large a
surface to the atmosphere, causes the fall to be gradual and easy,

  * M. Gay-Lussac,  on the 6th of September,  1804, ascended 23,100 feet
above Paris.  M. Garnerin, September 21st, 1827, passed  in seven hours and
a half, from Paris to Mount Tonnere, a distance of 300 miles.  This  voyage
was performed in the night, and during a storm. 
ARTS OF LOCOMOTION.
227
so that a person may descend with a parachute in safety from
the greatest heights.  The  size of the parachute  employed by
M. Garnerin, and with which he  descended  from a height of
2000 feet, at  Paris, in 1797, was  25 feet in  diameter.  The
parachute was folded up at the beginning of the fall, but soon
expanded itself by the resistance of the atmosphere.  The on-
ly inconvenience which was experienced, arose from a violent
oscillating motion.
  Brewster's Edition of Ferguson's Lectures on Mechanics, &c. 2
vols, 8vo. 1823;—Anstice on Wheel Carriages;—Edgeworth  on
Roads and Carriages, 8vo.;—Deparcieux sur le tirage des chevaux,
in the Mem. de VAcad. Paris, 1760;—Young's Lectures on Natural
Philosophy;—McAdam, on Roads,  8vo. 1823;—Tredgold, on Rail
Roads, 8vo. 1825;—Wood, on Rail Roads, 8vo. 1825;—Strickland's
Reports on Canals, Railroads, &c, oblong fol. Philad. 1820 ;—Article
Canal, in Rees's Cyclopedia, written by Mr J. Farey ;—Articles Navi-
gation Inland, Railway, Bridges, Aeronautics, &c, in the Edinburgh
Encyclopedia;—Chapman on Canal Navigation,4to. 1797;—Fulton
on Canal Navigation, 4to. 1796;—Smeaton's Reports, 3 vols, 8vo.
1812;—Pront, Architecture Hydraulique, 2 torn. 4to. 1790;—Belidor,
Architecture Hydraulique, 4 torn. 4to. 1750;—De  Cessart, Travaux
Hydrauliques, 2 torn. 4to. 1808 ;—Reports to the House of Commons
on Roads, Steam Boats, &c, 1822,  &c.;—Article  Seamanship,  in
the  Encyclopedia Brittannica,  by Prof.  Robison;—Dupin, Voyage
dans la Grand Bretange, 6 vols, 8vo. with plates, fol. 1825. 
CHAPTER XI.
                ELEMENTS OF MACHINERY.

  Machines.—By a machine, may be understood a combina-
tion of mechanical powers, adapted to vary the direction, appli-
cation, and  intensity, of a  moving force,  so  as to  produce a
given  result.  The  advantage which machines possess over
common  manual  labor, is generally that of increasing  or im-
proving the product of an operation.  This end they accom-
plish, by  enabling us to apply a common force more advanta-
geously, or to employ the most powerful' force derived  from
natural agents,  with precision and  efficacy.   By the aid of
machinery any number of instruments, or operative parts, may
be made  to move in concert, in -every possible  direction, with
any degree of velocity ; and to reciprocate with each other in
perfect harmony, so that complex operations are performed by
them,  with a precision which often exceeds the skill of the
most expert artist.
  Motion.—The motion  which takes place in machines is for
the most part, either rotary or reciprocating.  A rotary motion
is that in which the  moving parts revolve round an axis, as in a
wheel, a  crank, or a fly.  A reciprocating or alternate motion, is
that in which a body  retraces its own path, or moves alter-
nately backward and forward in the same track, which may be
curved, as in the beam of a steam engine, or rectilinear, as in
the  piston.   Most  compound  machines  possess  both  these
kinds of  motion,  or varieties  derived  from them ; and the dif-
ferent ways of producing  and  communicating them in the re-
quisite times and places, constitute a principal subject of atten-
tion with machinists. 
ELEMENTS OF MACHINERY-              229
ROTARV, OR CIRCULAR MOTION.
Fig. 1.
  When it is intended that  one  wheel or  axle  shall propel
another, various contrivances are  adopted to connect  the pro-
pelling part with that which is to be moved.   The  mode of
connexion is varied according to the  distance, the relative ve-
locity required, and  the direction in which motion  is to be
communicated.
  Band Wheels.—If two wheels be  connected by a belt, or
band, passing round their circumferences, they will move simulta-
neously, provided the friction of the band is sufficient to prevent
it from  slipping.   When a round  cord is used,  any degree of
friction  may be produced by receiving  the cord in  a sharp
groove,  at the edge of the wheel.  But the stiffness  of cords
forms in many cases, an objection to their use.   When a strap,
or flat band,  is used, its friction may be increased
by increasing its width.   The surface at the cir-
cumference of a wheel, or drum, which  carries a
flat band, should not be exactly cylindrical, but a
little convex, in which case  if the band inclines to
slip off  at either side, it returns again by  the tight-
ening of its inner edge, as may be seen in  a turner's
lathe.   When wheels are connected in the shortest
manner by a band, as in Fig. 1, they move in the
same  direction.  If  the  band  be crossed, as in
Fig.  2,  they  will move  in opposite  directions.
Wheels,  whose axes are situated in different planes,
may turn each other if the band be sufficiently long.
If no slipping  were  to  take place in the  band,
wheels of equal size would move with equal velo-
city, and those of different sizes, with velocities  in-
versely  proportionate  to their respective circumfer-
ences.  But since the band is  liable to yield or slide
somewhat during the  revolution, the velocity of  the
driven wheel is commonly a little less in proportion,
than that of the wheel which  drives it.
Fig. %
 
230
ELEMENTS OF MACHINERY.
   Rag Wheels.—Where  it is  necessary that the  velocities
 should be exactly proportionate, also  where great resistance is
 to be overcome, chains of various kinds are substituted, bypass-
 ing them round wheels, in the place of belts and ropes.   These
 chains lay hold upon pins, or enter into notches on the circum-
 ference of the wheels, so as to              Fig. 3.
 cause them to turn simultane-
 ously.   Such wheels are de-
 nominated  rag  wheels,  and
 have a uniform relative velo-
 city.  Fig.3. They are  used
 in locomotive steam engines, chain water wheels, he
   Toothed  Wheels.—Toothed  wheels  afford  a more  regular
 and effectual mode of communicating rotary motion, than any
 other kind of connecting mechanism.   They move of necessity
 in opposite  directions, and  their relative  velocity is inversely
 proportionate to their  number of teeth.   Thus if a wheel hav-
 ing forty teeth drives another of ten teeth, the second will make
 four revolutions while the first makes  one.   The connexion of
 one  toothed wheel with another, is called gear or gearing, and
 when  both wheels with  their teeth are in the direction of the
 same plane, it is called spur gearing.  It is desirable in tooth-
 ed  wheels, as far as possible, to diminish  friction, and to pro-
 duce uniformity of force  and motion.  A uniform motion may
 be  produced, if the form of the acting face of the  teeth be a
 curve of the epicycloidal kind ;  the outline of the  teeth of one
 wheel being the curve which would be described  by the revo-
 lution of a curve upon a given  circle, while the outline  of the
 teeth of the other wheel, is  described by the same curve  rolling
 within the circle.   It may also be produced, if the teeth  of one
 wheel be straight, circular,  or of any  regular figure whatever;
 provided the teeth of the other wheel,  be of a figure compound-
 ed of that figure and of an epicycloid. *
  * For investigations relating to the teeth of wheels, see  Camus on the Teeth
of Wheels, translated, London, 8vo. 1806 ;—Buchanan on Mill Work, chap.
i. &c.;—Brewster's Ferguson's Lectures, vol. ii. p. 119;—Gregory's Mechan-
ics, vol. ii. p. 451 ;—also a Treatise by Mr Blake, in  Silliman'f Journal, vol.
vii. p. 86.
 
ELEMENTS OF MACHINERY.
231
   Of two wheels which are unequal in size, the larger is called
the wheel, and the smaller the pinion.   The acting portions of
the wheel are called teeth ;  and of the pinion, more commonly,
leaves.   The name of lanterns is given to pinions with two
heads connected by cylindrical teeth, or trundles.   In Fig.  4,
the  line  joining  the  centres            ^.^  .
B and F of the wheel and pin-
ion, is called the line of centres,
and when this line is  divided
into two parts, JF A and BA,
which are to each other as the
number of leaves in the pinion
is to the number of teeth in the
wheel; B A is called the primi-
tive radius *  of the wheel, and
F A, the primitive radius of the
pinion ; while' the lines or dis-
tances F fandBb, are called the
true radii. The circles X AX
and R A R are called the prim-
itive circumferences, and by workmen, the pitch lines.
   Friction, to a certain extent, cannot be avoided, in teeth of
the  common kind, whose  acting faces are at right  angles with
the plane of the  wheels to which they belong.  It may, howev-
er, be much  diminished, by making the teeth as small and  as
numerous, as is consistent with their strength;  for the quantity
of friction necessarily increases with the distance of the  point
of contact from the line of centres.
   Spiral  Gear.—In common cases, the teeth of wheels are
cut across the circumference, in a  direction parallel to the axis.
In the spiral gear, now much used in cotton mills, in this coun-
try, the teeth are cut obliquely, so that if continued they would
pass round the  axis like the threads of  a  screw.   In conse-
quence of this disposition, the teeth come in contact only in the
* Called the proportional radius by Buchanan. 
232
ELEMENTS  OF MACHINERY.
line of centres, and thus operate without friction.
Fig. 5.  The action of these wheels, it is true, is
compounded of two forces, one of which acts in
the direction of the plane of the wheel, and the
other in the direction of  its axis.  The  latter
force occasions a degree of friction, which  being
expended at the end of the axle, may be regard-
ed  as  inconsiderable.   The  remaining  force
goes to produce rotary motion.
   The spiral  gearing has been applied to clockwork, and  has
the peculiarity that it admits of a smaller pinion than any other
gearing.  Thus,  if a very  small  cylinder have  a spiral groove
so cut in it as to  extend  once  round its circumference, it  will
perform one  revolution  for every tooth of the wheel which
drives it.   The  groove  may be  cut indefinitely near to  the
centre of the pinion or cylinder, without weakening it so much
as would happen in other forms of the pinion. *
   Bevel Gear.—When wheels are not situated in the  same
plane, but form an angle with  each other, the spur  gearing al-
ready described,  is changed for teeth of a different description.
In this case,  the bevel gearing is commonly employed, consist-
ing of wheels which are frusta of cones, having their teeth cut
obliquely, and  converging toward the point where the apex of
the cone would be  situated.   According as the  relative magni-
tude of the wheels varies, the  angle  of the
bevel must be different,  so that the velocities
of the wheels may be in the same proportion
at both ends of their oblique  sides or  faces.
For this purpose the faces of all the  teeth
must be directed  to the point where the axes
of the two wheels  would  meet.  The bevel
gearing is shown  in Fig 6,  and Fig.  12.
  * The spiral gear has been used at Waltham, Mass. and elsewhere, for about
fifteen years, and is commonly considered here as  the invention of Mr
White.  Something analogous to it, under the name of Inclined Plane Wheels.
was published in London, by Mr T. Sheldrake, in 1811.
 
ELEMENTS OF MACHINERY.
233
   Crown  Wheel.—Circular motion  is also communicated  at
right  angles, by means  of teeth  or  cogs,  situated  parallel
to the axis  of the wheel.   Wheels  thus     pigM  7,
formed are  denominated crown, or contrate
wheels.   They act either  upon a common
pinion, or upon a lantern.   The crown wheel
is  represented in Fig. 7.   It is less in use
than the bevel gear before described, having
more friction.
   Universal Joint.—The contrivance called Hooke's universal
joint, is  sometimes used instead of wheels, to communicate
circular  motion in an oblique direction.   It consists of two
shafts, or axes, each terminating in a semicircle, and connected
together  by means of a  cross,  upon  which  each semicircle is
hinged.   Fig.  8.   It  is obvious
that when  one shaft is turned, the
other must revolve  likewise;  and
this will be the case whenever the
angle by which one shaft  deviates
from the direction of the other, does
not exceed 40 degrees.  By means
of a  double universal joint, circular
motion may be communicated at an
angle of from 50 to 90 degrees.
   Perpetual Screw.—The perpetual or endless screw, some-
times called worm by mechanics, is made use of to convey
circular  motion from  an axle  to a toothed wheel,  situated  in
the direction of the same plane with the  axle.   The relative
velocity of a wheel driven by a screw is        Fig.  9.
very  slow, for if the  screw have only a
single thread, the wheel will advance the
breadth of one tooth only for each revo-
lution of the screw.   This mechanism  is
of great use  in  producing an equable
slow motion in  machinery, and also  in
increasing  mechanical power.   Fig. 9.
               30
 
234
ELEMENTS OF MACHINERY.
The motion may be reversed, or conveyed  from the wheel to
the screw if the obliquity of the threads be sufficiently increas-
ed.  A spiral  wheel and a toothed wheel may    Fig. 10.
be  made to turn  with  equal  velocity, or any
desired proportion of velocity, by the construc-
tion represented  in  Fig. 10.   A  is a wheel
seen edgeways, its  axis being  B C.  Its cir-
cumference is furnished with  spiral  ridges,
which  as the wheel  turns, cause the pinion D
to revolve in the plane of the axis B C.
   Brush  Wheels.—In light machinery, wheels sometimes  turn
each other by means of bristles or brushes  fixed to their cir-
cumference.   They may also communicate circular motion by
friction only.  In this case the surface brought  in contact is
formed of the end grain of wood, or it is covered with leather
or some other  elastic substance, and the two wheels are pressed
together to increase the friction.
   Ratchet Wheel.—The ratchet or detent wheel, is intended
to prevent motion in one direction, while it permits it in another.
For this purpose the teeth are cut with their faces inclining in
one direction,  and a small lever or catch, is so
placed as to enter  the indentations and stop
the wheel if it turns backward,  but slides over
the teeth without  obstructing them, if it moves
forward.  Fig. 11.   Ratchet wheels are gen-
erally  employed to prevent a weight raised by
a machine from  descending, and to  obviate
other retrograde movements.
   Distant  Rotary Motion.—When it is  required to  transmit
circular motion to a distance, for example from one extremity
or story of a building to an-
Fig. 11.
other,  various  methods  are
employed.   The most com-
mon is by band wheels, or
drums connected  by leather
belts of the requisite length.
This mode is considered most
Fig. 12.
 
ELEMENTS OF MACHINERY.
235
economical.   When  a precise  velocity is  required, a rolling
shaft  geared at  both ends, as in Fig. 12, is to be preferred.
A double  crank having its             pig, 13.
two  parts at right  angles
with each other,  and con-
nected with a similar crank
by stiff rods or bars, answers
the same purpose.   Fig 13.
If triple  cranks are used, cords will  serve  instead of bars for
connexion, because  in  this case, some part of the first  crank
will always be in a  situation to draw the second, and a rigid
medium will not be necessary.
   Change of Velocity.—It is sometimes necessary that a ma-
chine should be propelled with a velocity which is not equable,
but wkich continually changes in a given ratio.  This happens
in cotton  mills where it is  necessary  that the speed of certain
parts of the machinery should continually  decrease from the
beginning to the end of an operation.  To effect this object
two cones, or conical drums, are used having their larger diam-
eters  in opposite  directions.  They  are connected by a belt,
which is so governed by proper  mechanism,      jVo-  14
that it is gradually moved from one extremity    fl       D
of the cones to the  other,  thus acting upon   f
circles of  different  diameter, causing  a con-  /
tinual change of velocity in the driven cone,  f~
with relation to that which  drives it. Fig. 14.     TJ
   A change of speed is also effected by a decreasing series of
toothed wheels placed in the order of their size upon a com-
mon axis,  and fixed.   A  corresponding series in an inverted
order are  placed upon another axis, and not fixed, but capable
of revolving about  the  axis, like  loose pullies*   The axis of
this second series, is  made  hollow  and contains a moveable
rod which has a tooth projecting through a longitudinal slit in
one side of the axis.  This tooth serves to lock any one of the
wheels by  entering a notch cut  for  its reception.   Only one 
236
ELEMENTS OF MACHINERY.
wheel, however, can be  locked at a time,  the    Fig. 15.
others remaining loose, so that the axis will re-
volve with a velocity which is due to the rela-
tive size of the particular wheel which is locked,
and of the wheel which drives it.  By succes-
sively  locking  the   different  wheels  an in-
crease or  decrease  of  speed  is  obtained. *
Fig. 15.
   Another  mode of changing speed is produced by  a  large
and  small  wheel  placed  at  right angles with    „   .„
each other, and  acting by friction only.  The
edge of the  smaller wheel  is  kept in close
contact with the disc  or flat  surface  of  the
larger wheel, so  that the smaller wheel  will
revolve faster or slower, according to the dis-
tance at which  it is kept from  the centre of
the larger wheel.  The distance may be varied
at pleasure.   Fig. 16.
   It is  sometimes requisite that a wheel or axis should  move
with different velocity in  different parts of a single  revolution,
as in orreries, he   This may  be          F'   11
effected  by an  eccentric   crown
wheel acting on a long  pinion as in
Fig.  17.   It may also be accom-
plished in a different way by a cone
furnished with a spiral line of teeth,
acting on another cone, the position
of which is reversed.
   Fusee.—In the preceding arrangements for changing velocity,
there is a corresponding change of force, which is in an inverse
ratio to the change  of  velocity.   They may therefore be em-
ployed  for varying  force, as well as  speed.   The fusee of a
common  watch is  a  contrivance  adapted  to  this  purpose.
When a watch is recently wound up, the spring which propels

   *A mechanism of this kind is used iu the Cotton Factory at Newton, Mass.
and there is one nearly similar in Bramah's planing machine.
 
ELEMENTS OF MACHINERY.
337
it is in the state of greatest tension.   As this spring relaxes or
uncoils itself, its power decreases, and in order to correct this
inequality, the chain through  which it  acts, is wound upon a
spiral fusee.   The  fusee  B is an axis  surrounded by a spiral
groove, the distance of the groove from the axis  being made
to increase gradually from the top to the bottom, so that in
proportion as the force of the  spring is diminished, it may act
on a longer lever.  The  general outline of the fusee must be
nearly such, that its thickness at any part  may diminish in the
same proportion  as it becomes more distant from the point at
which the force would                Fig. 18.
than that of habitual estimation.   Fig. 18.


          ALTERNATE  OR RECIPROCATING MOTION.

   This name is applied to movements which take  place con-
tinually backwards and forwards in the same path.   An alter-
nate motion may take  place about a centre, in which case the
moving parts will describe  arcs of circles, as in a tilt hammer,
or the beam of a  steam  engine; or  it  may  be confined by
guides so as to  pursue a rectilinear path, as in the saw of a saw-
mill.   In most  complex machines, both rotary and  reciprocat-
ing motions occur, and these motions  are converted into each
other by any of the following contrivances.
   Cams.—If tyhe  axis  of a wheel  be situated in any other
point than its centre, the wheel thus rendered eccentric,  may
produce by its revolution an alternate motion in any part  ex-
posed  to its action.   Circles,  hearts, ellipses, parts  of  cir-
cles,  and projecting parts of various forms, are made  to pro-
duce alternate  motion, by continually altering  the  distance of
some  moveable part  of  the machine,  from  the  axis about 
238
ELEMENTS OF MACHINERY.
which they revolve.   Such  projecting parts are called cams.*
In the various forms which  are shown in the figures, the part
removed by the cam is supposed to return  by its own gravity,
or by some other power, so as to keep up the alternate motion.
In the circular eccentric cam, or wheel, Fig. 19, the sliding or
reciprocating part A B, will ascend and descend with an easy
motion, being never at rest unless at the instant  of changing its
direction.  Eccentric  wheels if surrounded  by a hoop, as at
H,  in PL  IX, perform the same office  as cranks.   In  the
semicircular cam, Fig. 20, the reciprocating part will  remain
at rest on the periphery of the cam during  half the revolution,
but in the remaining half it will approach the axis and  return.
In the quadrant  cam, Fig. 21, the reciprocating part will re-
main  at rest on the  periphery during  the  first  quarter of the
revolution ; during the second it will descend to the axis; dur-
ing the third it will be at rest upon the axis, and  during  the
fourth it will return to its original situation.   The narrow cam,
Fig. 22, causes  the  reciprocating part to rise and fall in one
half the  revolution,  and to remain at rest on the axis  during
the other half.   In these  figures the  angles of the  cams  are
made sharp, for the sake of demonstration, but in practice they
are generally rounded,  to  produce  more  gradual changes
of motion.   The elliptical  cam  Fig.  23, causes  two alter-
nate movements  for each revolution; and the triple  cam in

Fig.  19.    Fig. 20.     Fig.  21.    Fig.  22.    Fig. 23.
    A          A            AAA
CP
CP
s
           r-B-B   JSL,B
O"     D      ~Q     ~7
  * This word is spelt cam, camm, and comb, by diSerent writers.  In French
came.  Borgnis. 
ELEMENTS OF MACHINERY.
239
Fig. 24, applied to a tilt, or trip ham-         Fig. 24.
mer,  causes three strokes for one rev-
olution.  In  this case  the  cams are
called wipers, and it is common to ac-
celerate the reciprocal motion, by add-
ing to the action  of  gravitation, the
elastic force of a spring, or by the recoil
of the handle from a fixed obstacle.   A cam in the form of a
heart, called a heart wheel, is  much used  in cotton  mills to
cause a regular ascent  and  descent of the rail on which the
spindles are situated.*
   When an easy motion is desired, as in most large machinery,
the acting outline of the cam should be curved ; but to produce
a sudden stroke it should be straight.   The number of cams
may be indefinitely  multiplied,  if a rapid,  or vibrating move-
ment is required.   This is in effect done, when  the teeth of a
wheel act  upon a spring or weight, as in a watchman's rattle,
or in the feeder of a grist mill.
   Crank.—The common crank affords one of the simplest and
most  useful  methods  for  changing  circular  into  alternate
motion, and  vice  versa.   The  single crank, Fig. 25,  can only
be used upon the end of an axis.  The bell crank, Fig. 26, may
be used in any  part of an axis.  The  double crank, Fig. 27,
   Fig.  25.              Fig. 26.                Fig. 27.
Hj=±
n
m

  * For an investigation of the curves proper for different cams and wipers,
see Brewster's edition of Ferguson's Mechanics,  vol. ii. p. 126, &c.  For
producing an easy and uniform motion, spiral, epicycloidal, and other curves
are requisite; but for abrupt, forcible motions, such as occur in tilt hammers,
curves of equal action are to be avoided. 
240
ELEMENTS OF MACHINERY.
produces two alternate motions, reciprocating with each other.
The alternating parts in all these  cases, are  attached to the
crank by connecting rods, or by some of the kinds of mechan-
ism hereafter  described.   The motion produced by  cranks is
easy and gradual, being most rapid  in the middle of the stroke,
and gradually retarded  toward  the extremes;  so that shocks
and jolts in the  moving machinery are  diminished, or wholly
prevented by their use.
   Parallel Motion.—The name of parallel motions is given to
those arrangements which convert circular motion, whether con-
tinued or alternate, into alternate rectilinear motion, and vice versa.
Thus the beam  of a steam engine moves in circular arcs, while
the piston moves in right lines.   They cannot, therefore, be rig-
idly connected together, without doing violence to the  machine,
and it becomes necessary to convert one movement into the oth-
er by the intervention of proper mechanism.   A moveable par-
allelogram is principally used for this  purpose, and will be de-
scribed under the head of Steam Engine.  A similar contrivance
of a more simple form is shown in Fig. 28. C D is a rod mov-
ing back and forwards in a right line.   Every point of junction
is  a hinge or joint.   G E  is a  rod moveable about E as a cen-
tre ; and F H a rod of the same
length, moveable about F as  a
centre; these centres being equal-
ly distant  from the path of C D.
G H is a bar connecting these two
rods and having  the rod C D at-
tached by a joint to its centre.
When the whole is set in motion
the joint G will describe the cir-
cular arc IK, and the joint  H will
describe the circular arc  G H,
while the joint C will pursue  an
intermediate, or rectilinear course.
   Various other methods  are practised to  insure a rectilinear
motion, though most of  them are attended with greater friction
 
ELEMENTS OF MACHINERY.
241
than that last described.  Thus  the  alternating part is often
confined to a rectilinear path by sliding in grooves,  guides, or
holes,   or   between  friction            Fig. 29.
wheels'; a   connecting  rod
uniting the straight and circular
motions, as in the last instance.
In Cartwright's steam engine,
the straight movement  of the
piston is secured by connecting
it  with two cranks  acting in
opposition to each other, and
having  their axles  geared to-
gether  by  wheels,  as  repre-
sented in Fig. 29.
   The connecting rod may be dispensed with,    Fig.  30.
if  a transverse groove, or slit, be cut in the al-
ternating part, of a length equal to the diameter
of the crank's revolution ; as in Fig. 30.   The
end of the  crank, seen at a, in its  revolution  A
traverses the whole length of this groove which
is  cut in the crossbar A B, while the main bar
C D, has an alternate  motion  in the straight
path to which it is confined.  As  the  space of
ascent  or descent of the  bar  C D is always
equal to the versed  sine of the  arc described
by the crank, the motion of the bar will be accelerated towards
the middle  of its oscillations,  and retarded towards the  ex-
tremes.  A more equal motion can be produced, if desired,
by  substituting for the straight groove, a curvilinear  groove
somewhat like the figure od ; but this  method is attended with
much friction and little use.
   Sun and Planet Wheel.—The mechanism which  bears  this
name,  was invented by Mr Watt, to convert reciprocating,  into
circular motion in the Steam Engine ;  the use of the crank for
this purpose being at one time  secured by  patent  to another
               31
 
242
ELEMENTS OF MACHINERY.
 individual.   In  Fig.  31, a view is given      Fig.  31.    A
 of the sun and  planet wheel.   A is the
 end of a beam having  a  reciprocating
 motion.   B is the fly wheel of the en-
 gine, to  which a rotary motion is to be
 communicated.   Upon the axis of this
 fly wheel a small toothed wheel is firmly
 fixed.  A second toothed  wheel is con-
 nected to the  first,  by a loose  crank, so
 as to be capable of revolving freely about
 it.   This second wheel is firmly fixed
 upon the  end of a connecting rod, which
 is attached by a joint to the beam of the engine.   The two
 wheels being in gear,  it is obvious that as the beam A rises and
 falls, the  second  wheel  with the assistance of the fly, will re-
 volve quite round  the first, and if the  number  of teeth be
 equal, the first, or sun wheel, must perform two rotations on its
 axis, while the second, or planet wheel revolves once round it.
   Inclined Wheel.—In Fig. 32, AB is a wheel
 placed obliquely on its axis C D.  The edge, or
 periphery, of this wheel is received in a notch at
 B, of a sliding bar E F. As the wheel revolves,
 the bar E F will move up and down, once dur-
 ing each revolution.   This reciprocal  motion
 may be indefinitely varied by bending the  edge
of the wheel  into  different  curves and an-
 gles.
  Epicycloidal Wheel.—A very
 beautiful method  of converting
 circular  into  alternate  motion
or  alternate   into  circular,  is
 shown in Fig.  33.   A B  is a
fixed ring, or wheel, toothed on
its  inner  side.  C is  a toothed
wheel of half the diameter of
the  ring,  revolving  about  the
 centre of  the  ring.   While
 
ELEMENTS OF MACHINERY.
243
C
X\S\J\S\S^fU\J\S\S)\
this revolution of the  wheel C is taking place, any point what-
ever on its circumference will describe a straight line, or will
pass and  repass  through a diameter of the circle once during
each revolution.  This is an elegant application of the law that
if a circle rolls on the inside of another of twice  its diameter,
the epicycloid described is a straight line.  In practice, a piston
rod, or other reciprocating part, may be attached to any point
on the circumference of the wheel C.
  Rack and Segment.—If an  alternating motion is required,
the velocity of which shall be always equal, a rack  is best
adapted   to  produce this            Fiv. 34.
effect.  In Fig. 34, A B is
a parallellogram having a
rack on two  opposite  sides.
C is a half wheel toothed on
its curved side, and having
its  centre  equally distant
from the two racks.  It is obvious from inspection, that as this
half wheel  revolves,  its  teeth  will act successively upon the
two racks,  and  cause  the parallelogram to move  back  and
forwards with a uniform  motion.   The change, however, from
one direction to the other will be nearly instantaneous, so that
this plan will only  answer in machinery which is very light, or
of slow  motion.   The teeth of the half wheel must cover
somewhat less than  half a circle, that  they may not  become
engaged in  one  rack, before  they are disengaged from the
other.
   Rack and Pinion.—Another contrivance which renders the
change more gradual, is re-
presented in Fig.  35.   AB
is a double rack, with  circular
ends fixed to a beam,  capable
of moving in the direction of
its length.   The rack is driv-
en  by a pinion P, which  is
capable of moving up and  down in a groove m n, cut in the
 
244             ELEMENTS OF MACHINERY.

cross-piece.   When the pinion has moved the rack and beam
until it comes to the end  B, the projecting piece a meets the
spring s, and the rack is pressed against the pinion.  The pin-
ion, then working in the circular end of the rack, will be forced
down the  groove m n until it works in the lower  side of the
rack, and moves the beam back in the opposite direction ; and
in this way the motion is continued.   The motion of the pin-
ion in the  groove will  be diminished, if instead of a double
rack, we use a single row of pins which are parallel to the axis
of the pinion, as in some of the machines called mangles.
   Belt and  Segment.—An  alternate  circular   Fig.  36.
motion is converted into an  alternate  rectilinear
motion, in  fire engines, dressing machines, he
by a belt or chain fastened to each end of a seg-
ment,  or other portion of a wheel.  The two
belts pass by each other and are attached to the
opposite ends of an alternating  part.   When the
segment turns in either direction, it draws after it
the alternating part in a straight line.   Fig. 36.
   Scapements.—In clocks and  watches an alternating motion
is produced in the pendulum and balance wheel, by means of
the mechanism called a scapement.  In the more simple scape-
ments two  teeth, called pallets, are made  to vibrate on a com-
mon axis.   They are connected with a toothed  wheel in such
a manner, that one pallet enters between the teeth of the wheel
whenever the other is thrown out of their reach.  As the wheel
revolves, its teeth successively impinge  against  one or the other
of these pallets, and by causing them successively to escape,
communicate  to their  axis a vibrating, or  alternate motion.
The crutch scapement, Fig. 37, is an arch situated in the  same
plane with  the scape wheel, and parallel to the plane in which
the pendulum vibrates.  Its pallets successively enter and escape
from the teeth of the wheels, and receive from it a vibrating
motion.   In the old or common  watch  scapement,  Fig.  38, a
contrite, or crown wheel is used as the scape wheel and the
pallets a and b are placed upon  the axis of the balance wheel,
.0) 
ELEMENTS OF MACHINERY.
245
so as to meet the  teeth successively on opposite sides of  the
circumference of the  scape wheel.  A variety of other more
complicated forms of the scapement are also in use.
    Fig. 37.                           Fig. 38.
^^/\/f\y\y\y\^^.
U
             CONTINUED RECTILINEAR MOTION.

   A long continued rectilinear motion is not to be produced in
the parts of a machine, except so far as it partakes of the na-
ture of a  rotary  or  a reciprocating motion.   Thus a band
passing round pullies is  a modification of rotary motion, and
a rack, which is obliged to return at intervals, has a reciprocating
motion.  But to a certain extent, the motions of both may be
regarded as continuously rectilinear.
   Band.—If it is required to produce  motion in a right line,
which shall be  always in one direction, as for example in the
feeding parts of machines, a band  passing  round pullies or
drums, is the method  most  commonly practised, as in Fig. 1.
If a precise velocity is required, the  band may be perforated
with  holes, and received  upon short pins at the circumference
of the wheels ;  or the rag wheel and chain represented in Fig.
3, may be substituted. 
246
ELEMENTS OF MACHINERY.
   Rack.—If a slow rectilinear motion is required only for lim-
ited times, such a mechanism  may be used as will permit the
moving part to retrace  its own path at intervals, and regain its
original situation.   Fig.  39.              Fig.  39.
A rack, which is a straight  (-----------------------------,
bar having teeth  on  one  VVVVWUj^J^^^
side, will move in this man-             <^       ^>
ner "if it be acted on by a            S   ©    ?
toothed wheel, or by a per-             £\      A>
petual screw.   If the thread                Vu^
of a perpetual screw be formed of different obliquity in different
parts of its circumference,  the progressive velocity of the rack
will be unequal, instead of being uniform.   And if a part of the
thread be  in a plane at right angles with the axis of the screw,
the rack will  be at rest while that part of the screw revolves in
contact with it.
    Universal  Lever.—A rack  is  also propelled by means of a
catch, or dog, connected with some part of the machine which
has an alternating motion.   The catch causes the rack to ad-
vance the  length of one tooth, at each stroke      Fig, 40.
of the alternating part.   The universal lever,
sometimes called the lever  of  La  Garousse,
consists of a bar  moving upon a centre, and
having  a moveable catch or hook attached to
each side and acting upon the oblique teeth of
a double rack, or of a ratchet wheel, so  that
the  alternating motion  of the  bar causes a
progressive  motion  of  the  rack or  wheel.
Fig. 40.
   Screw.—A  common  screw is often made use of to produce
rectilinear  movements, when the  motion is intended to be very
slow, or when  great power is required.
   Change  of Direction.—A change from one path or direction
to another, forming an angle  with it, may be produced by sev-
eral of the mechanical  powers.   Thus a cord passing over a
pulley, may change a perpendicular to a horizontal motion, as at
 
ELEMENTS OF MACHINERY.
247
P, PL VIII, or to one at any other angle required. A bent lever
like  that represented by y z in PL IX, produces the same ef-
fect, provided the moving parts are confined, by guides, to their
respective  paths.  An inclined  plane also, if it moves through
the length  of one side of a parallelogram, will cause another
body to move through the length of the contiguous side at right
angles.   This  method, however,  is attended  with  much
friction.
   Toggle  Joint.—The knee joint,  commonly called in this
country, toggle joint, affords a very  useful mode of converting
velocity into power, the motion  produced being nearly at right
angles with the direction of the  force.  Its operation is seen in
the iron joints which are used to uphold the  tops of chaises.
It is also introduced into various modifications     Fig 41.
of the  printing press, in  order  to obtain  the
greatest power at the moment of the impres-
sion.  It consists of two rods or bars connect-
ed by a joint, and increases rapidly in power
as the  two rods approach to the direction of
a straight line. *  In Fig. 41, a moving force
applied in  the  direction C D, acts with great
and constantly increasing power to  separate
the parts A and B.

         OF ENGAGING AND DISENGAGING MACHINERY.

   In many cases,  particularly  where numerous machines are
propelled  by a common power, it is important to  possess the
means of stopping any one of them at pleasure, and of restoring
its motion, without interfering with the rest.    To produce  this
 effect, a great variety of combinations have been invented un-
 der the name of couplings.  These, in most instances, are
 sliding  boxes which  move  longitudinally upon shafts or axles,

   * An investigation of the  power of this combination, is given by the late
 Professor Fisher, in Silliman's Journal, vol. iii. p. 320.
 
248
ELEMENTS OF MACHINERY.
and serve to engage or lock a shaft which is at rest, with one
which is in motion; so as practically to convert the  two into
one, until they are again unlocked.   Couplings are sometimes
provided with clutches, or glands, which are projecting teeth,
intended to catch on other teeth or levers, and  thus  lock the
shafts  together.   Sometimes they have  bayonets, or pins
adapted to enter holes.   Sometimes the connexion is produc-
ed by friction alone, by pressing  together surfaces, which are
either flat, or conical.   Sometimes, also, wheels are thrown in-
to, and out of gear, which is done by causing wheels to slide in
the direction of their axles, or in some cases by elevating and
depressing the axle itself.  These methods, however, are diffi-
cult and unsafe.  The live and dead pulley, afford perhaps the
simplest mode of engagement.   They consist of two parallel
band-wheels on the  same axle, one of which is fast, and the
other loose, or capable of turning without the axle.  The band
which communicates the power, is placed upon the loose pul-
ley, when it is desired to  stop the machine, and  upon the fast
pulley when it is intended to set the machine in motion.  A
common  band  may also be made to admit of motion or rest,
according  as  it is rendered  tense or loose,  by a tightening
wheel pressed against its side by a lever.

                  OF EQUALIZING MOTION.

   In most machines, both the moving force and the resistance
to be overcome, are liable to fluctuations of intensity  at differ-
ent times.  As  such  variations influence both the  safety and
efficiency  of machines, it is necessary to provide against them,
by some appendage, which  shall equalize either the supply, or
the distribution,  of the power.
   Governor.—The name of governor has been given to an
ingenious  piece  of mechanism, which has been  introduced to
regulate the supply of steam in steam engines, and of water in
water mills, so as to render the power  equable,  and propor-
tionate to the resistance to be surmounted.  It is represented 
ELEMENTS OF MACHINERY.
249
in Fig. 42.   A B and A C, are two lev-       Fig. 42.
ers or arms, loaded with  heavy balls at
their extremities B and C, and suspended
by a joint at A upon the upper extremity
of a revolving  shaft  AD.   At  a,  is a
collar,  or sliding  box, connected to the
levers by the rods a b, and a c, with joints
at their extremities.   It follows that when
the  weights B  and C diverge, the collar
a will  move upward  on the shaft A D
and vice versa.   The  governor thus con-
structed, is  attached  to  some revolving
part of the  machine.   In this state if it turns too  rapidly, the
balls B and C move  outwards by their centrifugal force and
draw upward the collar a.   If,  on  the other hand, the speed
diminishes,  the balls  are allowed to  subside,  and the collar
moves down upon the shaft.  In the steam  engine the collar
has a circular groove, which receives the end of a forked lever.
As  the  collar  rises and falls, this lever turns  upon its fulcrum,
and acts remotely to open or close a throttle valve which  is
placed in the  main steam  pipe. *  Whenever, therefore, the
machine moves  too rapidly, the  balls  recede from the centre,
the collar  rises,  the  lever  moves  the valve, and by partially
closing  the  pipe,  diminishes the  quantity of steam  admitted
from the boiler.   If the machine moves too slowly, the reverse
takes place, and a larger amount of steam is admitted.
   In water wheels, where a greater power is necessary to con-
trol the supply of water, the governor is usually connected to
the  sluice gate by the intervention of wheel work.  This may
be  done in several ways, one of which  is as  follows.   The
 lower part of the shaft A D, carries a wheel  at D acting  upon
 two others beneath it, M  and N.   While the  machinery moves
 with its  proper speed, the wheels M and N are  both unlocked
 and turn loosely round their axles, and the  gate is stationary.
But when the velocity increases  or diminishes, the collar a ris-

   * For a farther account of the governor, see the article Steam Engine.
                32
 
250
ELEMENTS OF MACHINERY.
es or falls, and by means of a cam, acts upon a lever above it,
or upon another  below it, so as to lock one of the wheels M or
N,  by moving a clutch  situated at d.  These wheels being
upon a common  axle, are capable of turning this axle different
ways.  When, therefore,  one  wheel is locked to the axle, it
acts by turning a  perpetual screw, to open the sluice gate.
When the other is locked, the  axle and  the screw turn in the
opposite direction, and partially close the  gate.
   The foregoing are some out of various modes in which  the
governor is applied.  In windmills it is so  adapted as to increase
the feeding,  or  supply of  corn, when the  mill goes too fast,
and also to vary the distance of the millstones from each other,
if necessary.  It has also  been applied to clothe and unclothe
the sails in proportion to the strength of the wind.
   Fly Wheel.—It is  an  object of great importance, in  ma-
chines, to have  the means of accumulating power when the
moving force is in excess, and of expending it when the mov-
ing force operates more feebly,  or  the resistance increases.
This  equalization of motion is  obtained by what is called a fly,
which is generally made in the form of a heavy wheel,  though
sometimes in the form of arms or crossbars with weights at their
extremities.  A fly being made to revolve about its axis keeps
up the force by  its own inertia, and  distributes it in all parts of
its  revolution.   If  the  moving power slackens  it impels  the
machine forward, and if the power lends  to move the machine
too fast, it keeps it back.
   Fly wheels are  capable of accumulating  power to a great
extent.   A  small force  continually applied to the surface of a
heavy revolving  wheel will accelerate its velocity till it shall be
equal to that of  a musket ball, and its  momentum almost irre-
sistible.  Fly wheels, to act with the greatest efficacy, should be
made with the least possible surface, that  their motion may not
be  impeded by the resistance  of the  air.   They should be
made of iron, and  if they  cannot be  cast in one piece  they
should be firmly hooped  or bolted  together, that the parts may
not separate by their centrifugal force.   Fatal accidents  have 
ELEMENTS OF MACHINERY.
251
 occurred from the bursting of large stones used as flies, or as
 grindstones in cutlery works,  their velocity and  centrifugal
 force being so great as to overcome their  cohesive attraction,
 and to project the parts to a distance with great violence.
   Besides the modes already described, other methods are
 employed  to  retard and  equalize the velocity  of machinery.
 A kind of fly is used in music boxes, and in the  striking part
 of clocks, in which  the broad  surface of vanes, upon the cir-
 cumference of a wheel, is made to act against the air, until the
 resistance becomes equal to the propelling  force, so that the
 velocity can increase no further, but becomes uniform.  Pen-
 dulums and balances,  acted on through  the different  kinds of
 scapements, are also means of  equalizing motion.

                         FRICTION.

   A part of the force by which machines are  moved, is ex-
 pended in overcoming  their friction.   Hence it is desirable to
 obviate as far  as possible  this kind of resistance.  Friction is
 supposed to arise chiefly  from the roughness and  inequality of
 the surfaces of bodies.    No polish  can  be  given to a surface
 mechanically, so fine as to render it perfectly smooth.   When
 surfaces move over each other, a certain force is necessary to
 disengage the  minute asperities of one surface  from those of
 the other, either by causing them to rise over each other, or by
 bending or breaking them down.
   Friction is increased  by the  roughness of bodies, and also
by the force with which they are pressed together.  But it is
very little affected by the  extent of the surfaces in contact.   It
is greatest  at  the moment when  motion  begins; it does not,
however, change  afterwards as  the  velocity changes, but con-
tinues to retard with a uniform  force, whether the motion per-
formed be slow or rapid.  There are  several points in regard
to friction upon which writers are not agreed.
  Friction in  machinery  is to be  diminished by making  the
surfaces which rub upon each other as smooth as possible, and 
252
ELEMENTS OF MACHINERY.
by covering them with some unctuous substance.  Black lead
in fine powder is sometimes interposed between surfaces  to
diminish friction, and soapstone applied in the same manner, is
still  more  useful.  It is supposed, by some, that different me-
tals moving upon each other, occasion less friction, than surfaces
of the  same metal.   But the most important mode of diminish-
ing friction, is to employ a rolling,  or turning motion,  instead
of a sliding motion, in all cases where it is practicable; and by
simplicity of construction to  avoid  all unnecessary contact of
moving surfaces.
   Remarks.—In the construction  of machines no  subject  is
more deserving of attention  than simplicity of parts and struc-
ture.   The more complex machines are, the more expensive
they are to erect, the more  liable to get out of  order, and the
more  difficult to repair.   An increased  expenditure  of power
is also occasioned by  their friction.   A complex machine may
evince  great ingenuity on the  part of the inventor, and  may
have cost much labor and science to complete it.   Yet it is sure
to be superseded, the moment that a more  simple, cheap, or
expeditious way of attaining the same object  is  discovered.
The improvement of the mechanist or engineer more frequently
consists  in the simplification of his means, than it does in the
construction of complex and difficult pieces of workmanship.
  Buchanan on Mill Work and other Machinery,2vols, 8vo. 1823;—
Robison's  Mechanical  Philosophy, vol. ii. p.  181;—Nicholson's
Operative  Mechanic,  8vo.  1825;—Gregory's  Mechanics, 1826;—
Brewster's edition  of  Ferguson's  Mechanics,  1823;—Borgnis,
Mechanique Appliquee aux Arts, 4to. Paris, 1818,  Tom. 3, Composition
des  Machines;—Lanz et Bettancourt, sur la Composition des Ma-
chines, Paris, 4to.  1819;—Hachette,  Traitt Elementaire des Ma-
chines ;—Lecpold, Theatrum Machinarum Universale, 7 vols, folio,
Leipsic, 1724, to 1774. 
CHAPTER  XII.
      OF THE MOVING FORCES USED IN THE ARTS.

  Sources of Power.—It is the office of machines to receive
and distribute motion derived from an external agent, since no
machine is  capable of generating motion, or moving power,
within itself.  The sources from which the moving power ap-
plied  to machinery is obtained,  are  various, according to the
nature of the object, and the amount of force which is required.
Men  and animals, water, wind, steam, and  gunpowder are the
principal agents employed as first movers in the arts.   Their
power may be ultimately resolved into those of muscular ener-
gy, gravity, heat, and  chemical affinity.  But although these
are the  sources of all  the important force which is artificially
employed in moving large masses of matter, yet certain other
agents are also capable of producing motion upon a more limit-
ed scale, such as magnetism, electricity, capillary attraction, he
   Vehicles of Power.—Besides the original forces which have
been  mentioned, there are certain intermediate  agents which
serve to accumulate  and transmit power, after the first mover
has ceased to operate.   These agents commonly act either by
their  elasticity, their  gravity, or their  inertia.   Springs and
compressed air are examples of vehicles acting by their elasti-
city, and- their usefulness  continues only till they have recover-
ed  the  situation from  which they were disturbed by another
force.  In like manner a weight  acting  by its gravity on an
axle or wheel, prolongs for a season the influence  of the power
by which it was wound  up.   Fly wheels are also vehicles which
serve by their inertia to continue the action of a force while it in-
termits.   Vehicles of power are highly useful in equalizing the
irregularities which are incident to prime movers, in prolonging 
 254     OF THE MOVING FORCES USED IN THE ARTS.

 their action through convenient periods of time, and in multiply-
 ing the modes of their application.
   A  fundamental distinction among  mechanical  agents, both
 original and secondary, consists in this; that in some the inten-
 sity of their action, or the acceleration they produce in a given
 time, is the same, whether  the body acted upon be at rest or
 in motion; in others it is greatest when the body acted on is at
 rest, and becomes less as its velocity increases.  Gravity is the
 only force  which is certainly known to act with equal  intensity
 on bodies in motion, and at rest; though magnetism probably
 possesses the same property.   Every  other  important power
 acts more forcibly on a body  at rest, than on one which  has
 already acquired  motion in the direction in which it acts. *
 This happens with the strength of animals, the  impulse of fluids,
 and the elasticity of springs.

                      animal  power.

  Muscular energy is exerted  through the contraction of the
 fibres which constitute animal muscles.   The bones act as levers
 to facilitate and direct the application of this force, the  muscles
 operating on them through the medium of tendons, or otherwise.
 Muscular  power is much greater in some animals, than it is in
 man, owing to their size, or more  active  mode of life.   It is
 greatest in beasts of prey.
  Men.—The power of a man to produce motion in  weights
or obstacles, varies according to the  mode in which he applies
 his force, and the number of muscles  which  are  brought into
 action.  In the  operation of turning  a  crank, a man's power
 changes in every part  of the  circle which  the  handle de-
 scribes.  It is greatest when he pulls the handle upward from
the height of his knees, next greatest when he pushes it down on
 the opposite  side, though here  the power  cannot exceed the
 weight of his body, and is therefore less than can be exerted in

     * See Playfair's Outlines of Natural Philosophy, vol. i.  p. 107. 
         OF THE MOVING FORCES USED IN THE ARTS.     255

pulling upward.   The weakest points are at the top and bottom
of the circle, where the handle is pushed or drawn horizontally.
   If a windlass be provided with two cranks placed at right
angles with each other, two men will perform much more work,
than they could if the cranks were disconnected, because at the
moment  one puts forth his strength to the least advantage, the
other is exerting his with the greatest effect.
   The  mode in which a man can exert the greatest active
strength, is in  pulling upward  from  his feet,  because the strong
muscles of the back as well as those of the upper  and lower
extremities, are then brought advantageously into action, and
the bones are  favorably situated by the fulcra of the levers be-
ing near to the resistance.  Hence the action of rowing is one
of the most  advantageous  modes of muscular exertion,  and no
method which has been devised for propelling boats by the la-
bor of men, lias hitherto superseded it.
   According to Mr Buchanan, the comparative effect produced
by different modes of applying the force of a man, is nearly as
follows.  In the action of turning a crank, his  force may be re-
presented by the  number  17.   In  working at a pump, by 29.
In pulling downward, as in the action of ringing a bell, by 39.
And in pulling upward from the feet, as in rowing, by 41. *
   In estimating the  different  applications of  animal force, we
must take into  consideration not only the resistance  they can
overcome, but the velocity with which they move, and the length
of time  for which  they can be continued.   Violent efforts  are
not true specimens of a man's labor, since they can be exerted
for a short time only.  A moderate computation of an ordinary
man's uniform strength, is that he can raise a weight of10 pounds
to the height of 10 feet once in a second, and continue this labor
for 10 hours in the day. f  This is supposing him  to use  his
force under common mechanical advantages, and v/ithout any
deduction for  friction.

  * See Brewster's Edition of Ferguson's Mechanics, vol. ii. p. 9.  The whole
numbers are 1742, 2856, 3883, and 4095.
  t Young's Lectures on Natural Philosophy, vol. i. p. 131. 
256
OF THE MOVING FORCES USED IN
   Hones—Horses are often employed as movers of machm-
ery by their  draught.   A horse draws with greatest advantage
when the line of draught is not horizontal, but inclines upward,
making  a small angle with  the  horizontal plane, as already
stated, page  197.   The force of  a horse diminishes as his
speed'increases.  The following proportions are given by Pro-
fessor Leslie for the force of the horse employed under differ-
ent  velocities.  If  his force  when moving at the rate of two
miles  per hour, is represented by the number 100, his force at
three miles per hour will be  81,—at four miles per hour 64,—
 at five miles 49,—and at six miles 36.  These results are con-
 firmed very nearly by the  observations of Mr  Wood. * In this
 way the force of a horse  continues to diminish, till he attains
 his  greatest speed, when  he can barely carry his own weight.
   Various  estimates have been made of a horse's power, by
 Desaguliers, Smeaton, and others,  but the estimate now gener-
. ally adopted as a standard for measuring the power of steam
 engines,  is that  of  Mr  Watt,  whose  computation is  about
 the  average of those given by the other writers.  The measure
 of a horse's power, according to  Mr Watt, is,  that he can  raise
 a weight of 33000 pounds to the  height of one foot in a minute.
   In  comparing the strength of horses with that of men,  Desa-
 guliers and  Smeaton consider the force of one horse to be  equal
 to that of five men ; but writers differ on this subject.
   When a horse  draws in a mill or engine of any kind,  he is
commonly made to move in a circle, drawing after him the end
of a lever which  projects  like a radius  from a vertical shaft.
Care  should be taken that the horse-walk, or circle, in which
he moves, be large enough in diameter, for since the horse is
continually obliged to move in an oblique direction, and to ad-
vance  sideways as well as forward, his labor becomes  more
fatiguing, in proportion as the  circle in which he moves becomes
smaller.
   In some ferry boats  and  machines, horses are placed on  a
revolving platform,  which  passes  backward under the feet
* Treatise on Rail Roads, p. 239. 
OF THE MOVING FORCES USED IN THE ARTS.
257
 whenever the horse exerts his  strength in drawing against  a
 fixed resistance, so that the horse propels the machinery with-
 out  moving from his place.   A horse may act within still nar-
 rower  limits, if he is made to stand on the circumference of a
 large vertical wheel, or upon a bridge  supported by endless
 chains which pass round two drums, and are otherwise support-
 ed by friction wheels.  Various other methods have been prac-
 tised for applying the force of animals, but most of them  are
 attended with great loss of power, either from friction, or from
 the unfavorable position of the animal.

                      WATER  POWER.

   Water  and wind, considered as prime  movers, are applica-
 tions of the force of gravity, since  without gravity there would
 be neither wind, nor currents of  water.  The force of water is
 generally  applied to the  circumference  of wheels, which it
 causes to revolve, either by its weight, by its lateral impulse, or
 by both  conjointly.  Water wheels are generally  used in
 one  of three forms.  These are the overshot wheel, in which
 the  water descends from the  top of the wheel to  the  bot-
 tom ; the breast wheel, in which  it is received at about half the
 height of the wheel, and the undershot wheel, where it acts by
 the impulse of a current  flowing under the wheel.   The over-
 shot wheel is the most powerful kind, and is always to be em-
 ployed where a sufficient fall of  water can be obtained.
   Overshot Wheel.—This is a wheel, or drum, the circumfer-
 ence of which is occupied by  a series
of cavities,  commonly  called buckets,
 into  which the water is delivered  from
 one or more spouts  at  the  top of the
 wheel.  By inspecting Fig. 1, it will be
 seen that the buckets on  one side of the
 wheel  are  erect, and will consequently
become loaded with water ;  while those
on the other side  are  inverted, and of
              33
 
258     OF THE MOVING FORCES USED IN THE
course empty.   It follows that the loaded side will always pre-
ponderate, and by descending will  cause the wheel to revolve.
  If it were  possible,  says Dr Robison, * to  construct  the
buckets in such a manner, as to remain  completely filled  with
water till they came to the bottom of the wheel, the  pressure
with which the water urges the wheel round its axis, would be
the same as if the  extremity of the horizontal radius were con-
tinually loaded with a quantity of water sufficient to fill a square
pipe, whose section is equal to that of the  bucket, and whose
length is the diameter of the wheel.   But such a state of things
is impossible,  and if a bucket be full while at top, it will begin
to lose water as soon as it turns into  an oblique position, and
must continue  to do so, till it  reaches the bottom.
   The attention of engineers has been directed to giving the
buckets  such a form as will enable  them to retain the water
for the longest time on the circumference of the  Fig. 2.
wheel.  The  form  represented in,Fig. 2, answers
this purpose tolerably  well, and from its simplicity
is the  one most commonly used, but it may be im-
proved still farther by giving an additional inclination
inward to the outer edge of the bucket, as seen in
Fig. 3.   As  the  best  economy of the  water power
requires  that  the buckets should not be completely
filled, the form here represented will retain the water
until it has descended  low on the  wheel.   To pro-
mote this object still further, Mr Burns has divided
the bucket by a partition which is parallel  to  the  rim of the
wheel, constituting  one bucket within  another.  In this mode
of construction the  water does not enter with the same  facility,
but is longer in escaping. *
   In order to prevent  the inertia of the water, when it is first
laid upon the buckets,  from impeding the motion of the wheel,
   * Mechanical Philosophy, vol. ii. p. 592.
 intfroTuVrKnfurmed by Dr  Brewster>that Burns's improvement has not been
 buckets  i£ rint° PraCtiCe' °wing to thediffi^Hy of filling the inner
 uuciteis.  Mechanics, vol. ii. p. 49.                       5
 
OF THE MOVING FORCES USED IN THE ARTS.
259
it is desirable that the water when it enters, should have a velo-
city corresponding as nearly as possible to that with which the
wheel is revolving.   And as we cannot  give to the water the
direction of a tangent to the wheel, the velocity with which it is
delivered on the wheel, must be so much greater than the in-
tended velocity of the rim,  that it shall be equal to it when it
is  estimated  in  the  direction  of a tangent.  To  facilitate as
much as possible  the entrance of  the water, it is common to
deliver the water through an aperture, which is  divided by thin
plates of board or metal, placed in  an oblique position so as to
direct the stream of water into the  buckets in the most perfect
manner, as represented  in  Fig. 6.  In order to detain  the
water as long as possible, the  lower part of the wheel is often
made to revolve in a concave cavity just large enough to receive
it, and called in this country, the apron, as seen in Fig. 9.
   A difficulty often  occurs in the  entrance of water into  the
buckets,  by the resistance of the air already  in  the  bucket,
which causes the water to regurgitate and spill.   This evil may
be entirely prevented by making the spout considerably narrow-
er than the wheel, so as to leave room for the escape of the air
at the two ends of the bucket.
   The pressure of the atmosphere  occasions sometimes a seri-
ous  obstruction to the motion  of overshot wheels, by causing a
quantity of  back water to be  lifted, or sucked up, by the as-
cending  inverted bucket, when it first leaves the water.  This
difficulty  is remedied by making a few small  holes near  the
base of the bucket, and communicating  with the next  bucket.
Through  these  the air will  enter and prevent the suction.  It
is true that,  when on the descending side, these  holes will allow
the escape of some  water, but as this water only  flows  from
one  bucket to the next, its effect is inconsiderable when com-
pared with the advantage  gained.   Air,  as Professor Robison
observes, will escape through a hole about 30 times faster than
water, under the same pressure.
   With respect to variations in the fall, the same writer remarks
that since the active pressure is measured by the pillar of water 
 260     OF THE MOVING FORCES USED IN THE ARTS.

 reaching from the horizontal plane where it is delivered on the
 wheel, to the horizontal plane where it is spilled by the wheel,
 it is evident that it must  be proportionate to this  pillar, and
 therefore we  must deliver it as high  and  retain it as long  as
 possible.  This maxim obliges us to use a wheel whose diam-
 eter is equal to the whole fall.  We shall not gain anything by
 employing a larger wheel, for although we should gain by using
 only that part  of the  circumference, where the weight will act
 more perpendicularly to the radius, we shall lose more by the
 necessity of discharging the water  at a greater height from the
 bottom. *
    Chain Wheel.—When there is a very small supply of water
 falling from a  very great head, the double overshot wheel, with
 a  chain of buckets, is a valuable  machine.   This wheel is re-
 presented'in Fig. 4, where two rag wheels      Fig. 4.
 are placed,  one  at top,  and the other at
 bottom, and a  series of buckets are  fixed to
 an endless chain, the links of which fall into
 notches  in  the  circumference of the  rag
 wheels.   The water  issuing from  the mill
 course is introduced into the buckets on one
 side at top.   The  descent of the loaded
 buckets on this side puts the rag wheels in
 motion,  and the  power is conveyed  from
 the shaft of the upper wheel, to turn any
 kind of machinery.    When the  buckets
 reach the bottom  they allow the water to escape, and ascend-
 ing empty on the opposite side, they again  return to the spout
 to be filled as  before.   In this machine, the  buckets have in
 every part of their path the same mechanical effect to turn the

  * Mechanical Philosophy, vol. ii. p. 600.
  On this subject Dr Brewster remarks, that if we employ a wheel the
 diameter of which is higher than the fall, we may take advantage of any cas-
ual rise of the water above  its usual level, and by a particular form of the de-
livering sluice, introduce the water higher upon the wheel and thus actually
increase the height of the fall.
 
        OF THE MOVING FORCES USED IN THE ARTS.     261

wheels, and they do not allow the water to escape till they have
reached almost the lowest part of the fall.
  This species of wheel possesses another advantage, namely,
that by raising the lower  wheel and taking out two or three of
the buckets it maybe made to work when there is such a quan-
tity of back water as would otherwise prevent it from moving.
  Dr Robison, has described a machine of this kind, in which
plugs, or horizontal floatboards, are fixed to a chain.   On the
descending side these plugs pass through a tube, a little greater
in diameter than that of  the  floats, and the water acting upon
these floats as it does in the case  of a breast wheel, gives mo-
tion to the two rag wheels.
  In  regard to the most  advantageous velocity to be produced
with a given  quantity of water in  an overshot  wheel, various
mathematicians have concluded, that the slower a wheel moves,
the greater is its power of performance.  But the experiments
of Mr Smeaton lead to the conclusion, that in practice there is
a limit of velocity, and  that  overshot wheels  do most work
when their circumferences move at the rate of about three feet
in a second.
   Undershot  Wheel.—An  undershot        Fig.  5.
water wheel,  is a wheel  furnished with
a series of plane  surfaces, called  floats
or floatboards, projecting from its circum-
ference for the purpose of receiving the
impulse of the water, which is deliver-
ed by a proper canal, with great velocity,
upon  the under part of  the wheel.   A
wheel of this kind is represented in Fig. 5.
  When  an undershot  wheel is put in motion by a stream  of
water striking against one of its  floatboards, in a direction  at
right  angles with the radius, the action of the water will dimin-
ish, as the velocity of the wheel increases, till at last  the mo-
mentum of the water, or  of the accelerating force, is just equal
to the momentum of the resistance, or of the retarding force.
The motion of the wheel will then become uniform.
 
262
OF THE MOVING FORCES USED IN THE ARTS.
   By calculation it appears that a machine  thus driven by the
impulse of a stream produces the greatest effect, or does most
work in a given time, when the wheel  moves with one third of
the velocity with which the  water moves. *   But in practice
this rule is liable to some  variation, for the water  does  not es-
cape as soon as it has  given its impulse, but is  confined by the
channel for some time, and acts  with a variety of influences.
In Mr  Smeaton's experiments, which are cited as authorities
by most writers since his time, it was  found that an undershot
wheel  when  working to the greatest advantage, had a velocity
which  varied from one third to  one  half the velocity of the
stream ; and that in great machines it was nearer to the latter
of these limits, than the former.
  It is advantageous that the size of undershot wheels should be
as great as circumstances will permit,  and it ought never, says
Dr Brewster, to be less than seVen times the natural depth of
the stream at the bottom of the  course, f   In regard to  the
best number of floatboards a difference of opinion has prevail-
ed, but it is now generally admitted  that  the more floatboards
a wheel has, the greater and more uniform will be its effect. J
According to  the experiments of Bossut, it  appeared that a
wheel with 48 floatboards  produced a  greater effect  than one
with 24,  and the latter  a greater effect than one  with  12.
Smeaton's experiments justify the same conclusion, though he
found that on adapting to the wheel a circular sweep of such
length, that one  floatboard entered into the curve, before  an-
other left  it, the  effect came so near to the former, as not to
give any  hopes of advancing it by increasing  the number of
floats beyond 24 in the wheel experimented on. §
  In regard to the position of the floatboards,  they should  not
be in the  direction of  the  radius, but inclined from  it slightly
backwards.   From the experiments of  Deparcieux and Bossut,

  * Playfair's Outlines of  Natural Philosophy, vol. i. p. 214:—and Robison,
622.
  t Ferguson's Mechanics, vol. ii. p. 17.
  f Gregory's Mechanics, vol. i. p. 462.                § Ibid. p. 476. 
        OF THE MOVING FORCES USED IN THE ARTS.     263

it appears  that there is a very sensible advantage gained by in-
clining the floatboards to the radius of the wheel  about 20 de-
grees, so that the lowest floatboard shall not be perpendicular,
but have  its point turned up  the stream about 20 degrees.
This inclination causes the water to heap up along the  float-
board, and act by its  weight. *   The  floats should for this
purpose be made much broader in the direction  of the radius
than the vein of water which they intersect, is deep.  Another
advantage attending this obliquity of the floats is, that they are
less resisted,  when they rise out of the water.
   The best way of delivering the water on an undershot wheel
in a close mill course, according to Dr Robison, is to let it slide
down a very  smooth channel without touching the wheel, till it
arrives near  the  bottom, at which place the  wheel should be
exactly fitted to  the  course.   The floats should  be broader
than the depth of the water, so  as never to be wholly immersed,
but allowing the intercepted  water to heap up against them.
If the bottom of the course be an arc of a circle having a great-
er radius than that of the  wheel, the water  which slides down
will be gradually  intercepted by the floats, or strike upon more
than one at a time.  In this  country it is often the practice to
admit the water directly from  the bottom of a pond, or reser-
voir,  instead of  causing it to glide  down  a separate channel
from near the top ; and this method is found  very effectual.
   Back Water.—The back water, or tail water, is that portion
which has past by the wheel.   This portion is not only useless,
but in most cases injurious, since by its inertia and weight,  it
resists the escape of the floats  and empty buckets in their pas-
sage upward.   Its effect is increased in times of floods or fresh-
ets, so that it is often  necessary to place wheels  higher  than
they otherwise would be,  to provide against it.   A method of
getting rid of back water in times of flood, has been invented
by Mr Perkins in this country,  and Mr Burns in Scotland.  It
consists in a separate passage  by which a current  of water is

           * Robison's Mechanical Philosophy, vol. ii. p. 625. 
264    OF THE MOVING FORCES USED IN THE ARTS.

taken from the mill-lead, or flume, as at A in Fig. 6, and pass-
                         Fig-. 6.
 es with great rapidity under the wheel, and  thenqe  under the
 flooring  at  B.  This  rapid  current has the effect to take off
 arid carry away the back water from beneath the wheel, while
 it is prevented from returning by the force of the same current,
 and the barrier at C.   The water which is expended to main-
 tain this current is no more than would run over the waste gate
 in a time of freshet.
   Besant's  Wheel.—To  diminish the retardation occasioned
 by back  water,  Mr Besant has invented a wheel in which the
 floats are placed obliquely in  a double row,      pi„  7
 as in Fig. 7, where the wheel is represent-
 ed  as seen edgeways.   Each pair of floats
 forms  an  acute  angle  open  at its vertex.
 By this construction the floats escape more
 gradually and  with less resistance from the
 back water, and likewise  the resistance of
 the atmosphere is prevented, by the admis-
 sion of air at the open angle of the  floats.
  Lambert's Wheel.—As water acts most advantageously upon
undershot wheels, when the floats are perpendicular to the sur-
faces of the  stream, it has been attempted in  different ways to
keep them  always in a vertical position.  In the method pro-
posed by Mr Lambert, the floats are hung upon hinges or piv-
ots at the extremities of the spokes, and are kept in a vertical
position by a large iron  ring which is suspended from the lower
 
         OF THE MOVING FORCES USED IN THE  ARTS.     265

extremities of the whole, and is  allowed to pass during the
revolution through a slit in the middle of each float.  In Fig.
8, is a view of one side of the wheel
with the ring  attached.   A is the          **£• 8-
centre of the wheel, B B are spokes
or arms of the water wheel, C D,
C D are the floatboards which are
here  seen edgeways.   EE  is a
large iron ring  connected by joints
to the lower  extremity  of all the
floatboards,  and  serving by  its
weight  to keep them  in a vertical
position.  This wheel is  probably
too complicated  for common use.
The iron ring is kept from moving
sideways  by  guides,  or  friction
wheels, placed at each side.
   Breast Wheel.—The breast wheel is intermediate between
the overshot and undershot wheels, having the water  delivered
upon it at about half its height, or at the
level of its axis.  In breast wheels in
England, buckets are not commonly
employed, but the floatboards  are
fitted accurately, with as little play as
possible, to the mill  course, so  that
the water, after acting upon the float-
boards by its impulse, is detained be-
tween them in the mill course, and
acts by its weight till it reaches the lowest part of the wheel.
A breast wheel is represented  in Fig. 9, as it is often construct-
ed in this country with buckets,  instead of floats, and with a
part of its circumference fitted to the mill course, or apron.
   Horizontal  Wheel—A horizontal wheel with oblique floats,
sometimes called in this  country a tub wheel, is turned  by  a
current  of water discharged against the floats in the manner re-
34 
266      OF THE MOVING FORCES USED IN THE ARTS.
presented  in  Fig.  10.              Fig.  10.
This method is said to be
in  common  use on  the
continent of Europe,  and
but  seldom employed in
England.  It is a disad-
vantageous mode  of ap-
plying power, and  is only
recommended in   corn-
mills by its simplicity, the
millstones being turned  directly by the axis of the water wheel,
without  the  intervention of other wheels, or gearing.   In the
same manner another kind of tub wheel, which is a sort of in-
verted cone furnished with spiral floats on its inside, is made to
revolve  horizontally, by discharging into it a current  of water
from above.
   Barker's  Mill.—This machine,  which is also sometimes
called  Parent's mill, is driven by an application of the force of
water  different from any of those which have been already de-
scribed.   This application  con-
sists, not in the direct use of the
weight, or impulse, of water, but
in that of its  reaction, or counter
pressure.   The principle of this
simple machine may be seen by
inspecting Fig. 11, where C D is
a revolving vertical tube, carrying
a  millstone m on the  upper part
of its axis.  At the bottom of this
tube is a horizontal  tube A B, at
the extremities of  which are two
apertures A  and B, opening in
opposite  directions.  A stream of water is introduced from the
mill course above,  and flows out at the apertures at A and B,
and in this way keeps up a continued  horizontal rotary motion
around the axis D m.
 
         OF THE MOVING FORCES USED IN THE ARTS.     2D /

   In order to understand how this rotary motion is produced,
we may suppose the apertures  to be shut, and the tube C D
filled with water.  The area of the apertures A and  B will then
be pressed outward  by a force equal to a column of water
whose  height is C D, and whose base is equal to the area of
the apertures.   Every part of the tube AB sustains a similar
pressure; but as these pressures are balanced by  equal  and
opposite pressures, the machine remains at rest.   But when
the aperture at B  is  opened, the pressure  at that place is re-
moved, and therefore the area will be carried round in a direc-
tion opposite to that of the aperture, by a pressure which  is
due to the height of the column and  area of the aperture.
The same thing happens with the other area, and the two pres-
sures carry round the vertical axis in the  same direction.
   An  improvement  has  been made  in  Barker's mill  by dis-
pensing with the tube C D, retaining only its axis ; and intro-
ducing  the water on the under side of the transverse tube at D.
For  this purpose the water is brought down from the reservoir
at E, by a separate passage, and introduced at D through a water
joint, which suffers the arms of the tube to revolve without much
loss of water.   Such a passage is represented by the  shaded
part E F D.   The upward pressure of the water may be made
to support a great part of the weight of the machine.

                      WIND  POWER.

   Currents of water, being  limited in magnitude, can be con-
fined in their action to one side of a wheel.   But it is not easy
to do the same with  currents of wind, on account of their in-
definite magnitude, and the difficulty of screening one half of
the wheel advantageously from their action.  It is therefore
common to employ vertical windmills, having a number of sails
placed  obliquely to the wind, and turning on a horizontal axis
which  is parallel to the wind, or nearly so.   The  action of the
wind in this case is resolved into two  forces, and since the sails
cannot obey the first by moving in the direction  of the wind,
they obey the second and move at right angles with  it. 
268     OF THE MOVING FORCES USED IN THE ARTS.

   Vertical Windmill.—The  common  windmill has  usually
four sails, and  sometimes six or eight.   The power of these
sails to turn their axis  depends, when other things are equal,
upon their degree of obliquity in regard to the wind.   The an-
gle which is most effectual for giving motion to the sails from a
state of rest, is an angle of 35-1 degrees with the weather, or with
the plane in which the sails revolve. *  But the angle which pro-
duces the greatest action upon a sail at rest,  is not the most ef-
fectual when a sail is in motion.  As the motion increases, the
action of the wind diminishes, and in order to preserve this ac-
tion, the sails require to be brought nearer to the wind.   And
since each part of the sail, in  revolving, has a different velocity,
those parts which are nearest the circumference, being swiftest,
are not acted  upon so powerfully by  the wind, as those which
are nearer  the  centre ; on  which account  it is useful to give
the sails a slight spiral curvature, so as to make the angle with
the weather at the  extremity of  the  sail, less than it is at the
centre.   When, however, the sails are perfectly plane, it is ad-
vantageous, according to Mr  Smeaton, that  the angle of the
sails with the weather, should be 18 degrees, or less ; in other
words, that their  angle  with the axis should  be 72 degrees, or
more.   The velocity of the sails in this case at their outer  ex-
tremity, is often found to be more than twice that of the wind.
   Adjustment of Sails.—On  account of the inconstant nature
of the  motion of the wind, it is necessary to  have some provi-
sion for accommodating the resistance'of the sails, to the degree
of violence with which the  wind  blows.   This is commonly
done by clothing and unclothing the sails; that is, by covering
with canvass or thin boards, a greater or smaller portion of the
frame of the sails, according to the force of  the wind at differ-
ent times.   A method has been devised for producing the same
effect,  by  altering  the  obliquity of the sails; and windmills
have been so made, as to regulate their own adjustment, by the
force of the wind.  If we suppose a windmill, or windwheel, to

* Determined by Parent—see Brewster's Ferguson's Mechanics, vol. ii. p. 61). 
        OF THE MOVING FORCES USED IN THE ARTS.     269

consist of four arms, and that the sails were connected to these
arms at one edge, by means of springs; the yielding of these
springs would allow the sails to turn back, when the wind should
blow with violence ; and their elasticity would bring them up to
the wind whenever its force abated.   This effect has been pro-
duced by a weight acting on the sails through a series of levers.
A loose iron rod, passing through the centre of the axle of the
windwheel, receives the action of the weight at one end, and
communicates it to the sails at the other.
   Sometimes a governor like that  described on page 249, is
used to regulate the velocity of windmills which are built for
grinding, by  increasing the supply of corn to be ground, or of
work to be done, whenever the force of the  wind  increases.
The governor is also applied in a  very ingenious  manner to
furl or unfurl a portion of the sails, thus accommodating them
to variations of the win/f.
   As it is necessary that a  windmill should face the wind from
whatever point it blows, the whole  machine, or a  part of it,
must be capable of turning horizontally.   Sometimes the whole
mill is  made to turn  upon a strong vertical post, and is there-
fore  called a post mill; but more commonly the roof, or head
only, revolves, carrying with it the windwheel and its shaft, the
weight being  supported on  friction rollers.   In order that the
wind itself may regulate the position of the mill, a large vane,
or weathercock, is placed  on  the side  which is opposite  the
sails, thus turning them always to the wind.   But in large mills
the motion is regulated by a small supplementary windwheel,
or pair of sails, occupying  the place of  the vane, and  situated
at right angles with the principal windwheel.  When the wind-
mill is in its proper position, with its shaft parallel to the wind,
the supplementary  sails  do not  turn.  But when  the wind
changes, they are immediately brought into action,  and  by
turning a series of wheelwork, they gradually bring round the
head to its proper position.
   As  the  resistance occasioned  by the side of the building
makes a difference in the  force  of  the  wind upon  the upper 
270     OF THE MOVING FORCES USED IN THE ARTS.

and under sails, it is common to incline the sails, and  their ax-
is, in such a manner that  the lower sails  shall be farther from
the building, than they would be if in a vertical position.
   Horizontal Windmill.—This name is given to those wind-
mills which turn on a vertical axis.  Various methods are em-
ployed in their construction, in most of which the wind acts by
its  direct impulse, as  in an  undershot  water wheel.   In  the
most common  forms,  the  sails, like floatboards, present their
broadside to the wind on the acting side of the wheel, but are
folded  up, or turned edgewise on the returning side.   These
wheels, however, are found to be greatly inferior to the vertical
windmill, in the amount of work  which they  are capable of
performing, and at the present day they are little  used.
   As wind is the most uncertain of all the moving agents, and
fails totally in times of  calm,  it is not common to depend upon
this power in large works, provided otjier moving forces can
be obtained.   The steam engine has in many cases superseded
it, but it  is still used in certain places for grinding corn,  pump-
ing water, and driving inferior machinery.   Upon the ocean it
is a locomotive agent of incalculable importance.

                       STEAM POWER.

   Steam.—The power of steam depends on the tendency which
water possesses to expand into vapor,  when  heated to a cer-
tain temperature.   Many other substances, and  perhaps all,
have the same  tendency, and those which  are volatile at low
temperatures might doubtless be made the sources of moving
power in the arts.   But since water, which is the most  cheap
and abundant of these substances,  fortunately possesses also
the greatest number of requisites for an expansive  agent, it is
not likely to be superseded by any other material.
   When  water is conrerted into  steam,  it expands to about
1700 times its original volume, * so that a cubic inch  of water

  * 1633 times, according to Gay-Lussac.  See Ure's Dictionary, article Calo-
ric.—1711 times according to Tredgold. 
OF THE MOVING FORCES USED IN THE ARTS.
271
furnishes about a cubic foot of steam, at 212 degrees of Fahr-
enheit, under the common pressure of the atmosphere.   Water
cannot, however, be converted  immediately into steam by the
application of a boiling temperature, but requires a certain pe-
riod to effect its volatilization.  This period is about six  times
as great, as that which is necessary to raise it from the freezing
to the boiling point, supposing the supply of heat to be uniform.
The amount of heat which is absorbed, or rendered  latent, by
the conversion of water into steam, is about 950 degrees. *
   The power of steam to produce motion in other bodies, de-
pends upon the increase of its own volume, and whatever body
resists this increase will be acted upon by a force proportionate
to the elastic power of the steam, and the circumstances un-
der which the  resistance is made.   In a vessel boiling in the
open air we are not sensible of the magnitude of this force, be-
cause the steam, and the resisting medium against which  it
acts, are both invisible.   But when we consider that the steam
when first generated, has to lift off from the water, before it can
assume  its elastic  form, the weight of  the  superincumbent
atmosphere, and that  this weight in the  atmospheric column
which presses on a vessel  only two feet in diameter, is equal to
several  tons, we may easily conceive of the force which attends
this expansion.
   Furthermore, since  steam has the property of immediately
condensing into water, as soon  as  its temperature is  reduced
below 212 degrees, it follows that the   atmospheric  weight
which has been lifted by  the formation of the steam, will
immediately fall, when the steam condenses;  and with a force
equal to that by which it was  raised.  This furnishes an indi-
rect or secondary application of the power of steam.
   But the powers of steam are not limited by the effects which
it produces at the common boiling temperature.   If steam be
separated from the contact of water, and  exposed to a farther
increase of temperature, it will continue to expand by the law
"950 according to Watt.—967, Ure. 
272     OF THE MOVING FORCES USED  IN THE ARTS'.

which governs the increase of all  gaseous bodies, and  will
double its volume  once for every 480 degrees of Fahrenheit's
thermometer. *   And furthermore,  if water  itself be inclosed
in strong vessels and  thus  heated, its expansive force will be
prodigiously greater than that of steam  alone, since  every par-
ticle of the water tends to generate steam of high temperature,
and to occupy the  space  which is due  to such steam.  In a
common boiler  containing water  and steam, each  addition of
caloric causes a fresh  portion of steam to rise,  and to add its
elastic force to that of the steam previously existing, so that an
excessive pressure is soon  exerted  against  the inside of the
vessel, if the augmentation of heat has been considerable.   At
212 degrees Fahrenheit, steam has an elastic force equal to the
pressure of the atmosphere.   If it be farther heated in contact
with water, it will have a force equal to that of two atmospheres
at about 250 degrees,  of four atmospheres at 293 degrees,  and
of eight atmospheres at 344  degrees.  These are the results in
round numbers  of Mr Southern's experiments, and they  are
nearly confirmed by those of Drs Robison and Ure.
   At temperatures below 212 degrees,  steam has still a certain
elastic force which discovers itself  whenever the  pressure of
the atmosphere is taken off.  Thus its elastic force  at 180 de-
grees is equal to about half  an  atmosphere,  and it has some
force at all temperatures above the freezing point.    ,
   Steam expands in all directions alike, and is useful as a mov-
ing agent, only by its pressure.   It cannot, like water and wind,
be made to act advantageously by its impulse in the open  air,
for the momentum of so light a fluid, unless generated in vast
quantities, would be inconsiderable.   Some of ihe  earliest  at-
tempts, however, at forming a steam engine,  consisted in direct-
ing the current of steam from the mouth of an eolipile, against
the vanes or floats of  a revolving  wheel, f   In order that the
pressure of steam may be rendered available in machinery, the
steam must be confined  within a cavity which is air-tight, and
  * Ure's Dictionary of Chemistry, Art. Caloric and Gas.
  t Such was the engine of Branca in the beginning of the 17th century. 
OF THE MOVING FORCES USED IN THE ARTS.
273
 so constructed that its dimensions, or capacity, may be altered
 without altering its tightness.  When the steam enters such a
 vessel, it enlarges the actual cavity, by causing some moveable
 pan to recede before it, and from this moveable part, motion is
 communicated to  machinery.   A hollow  cylinder having  a
 moveable piston accurately fitted to its bore, constitutes a ves-
 sel of this kind.  It was used more than a century ago by
 Newcomen,  and as  it is found to combine more advantages
 than  any other kind of  arrangement for motion,  its  use  has
 never been  superseded.   The piston thus employed has a re-
 ciprocating motion, which is converted, when necessary, into a
 rotary  one, by the appropriate mechanism.
   Applications of Steam.—The pressure  of steam is capable
 of being applied to use in three different ways, and these modes
 have  given rise to some of the  most  important  varieties of the
 steam engine.  The three methods which are used for obtaining
 power from  steam are,  1. By condensation, as in the atmos-
 pheric engine.   2.  By generation, as in the simple high pres-
 sure  engines.  3.  By expansion, as  in
 WoolPs engine, Watt's expansion engine,
 and some others.  These methods have
 been  illustrated by Mr Tredgold by a
 figure like that in the margin.   Suppose
 a cylindric vessel A B C D to be placed
 in a vertical position, with a given depth
 of water in the bottom* and an air-tight
 piston above the water  balanced  by a
 weight D equal to its own weight and
 friction.  In this state let heat be applied
 to the base A C ; then as the water be-
 comes converted into steam of slightly
 greater force than the atmospheric pres-
 sure,  the piston  will  rise  till  the whole
 water is in a state of steam.  It must  be
observed, however, that the generation
of this  steam, which  is of atmospheric
               35
 
274     OF THE MOVING FORCES USED IN THE ARTS.

elastic force, affords no available power, but is simply sufficient
to balance the column of atmospheric  air, and  exclude it from
a given height of the cylinder.
   By Condensation.—In the state of things just described, if
the steam be suddenly condensed into  water by the application
of cold, it is obvious that the  piston will be driven  downward
with a force equal to the weight of the atmosphere which pres-
ses on the piston,  and through a distance  equal to that  which
the piston had been raised by the generation of steam.   It fol-
lows that  the power of steam which is of atmospheric elastic
force,  is,  when  speedily condensed,   directly  proportionate
to the  space which  it  occupies.   If the temperature of this
steam be raised above 212  degrees,  it will occupy a larger
space, the increase  being  equal to the expansion of steam by
the given  change  of temperature.   But  a quantity  of heat
nearly  equivalent to the  increase of volume will be absorbed,
and hence, says Mr Tredgold, the effect of a given quantity of
fuel would not be increased  by the expedient. *
   By  Generation.—Suppose the same cylinder and apparatus
to have  heat  applied to its base, with only the difference of the
piston being  loaded with a given pressure per inch of its area.
The generation of the steam will raise the loaded piston, but
the height through which it will be raised will be less than if it
were not loaded.  The steam having to act in opposition both
to the pressure  of  the atmosphere and the load on the piston,
the space it will occupy will be in the inverse ratio of the pres-
sures which  oppose it, supposing  the steam  of atmospheric
elastic force to have been of the same  temperature.   Thus, if
the load on the piston be equal to twice the atmospheric pres-
sure, the piston will be raised  only one third of the height,  but
on rapid condensation it descends with three times the pressure,
and, therefore, whether the steam be generated of atmospheric
elastic jbrce, or of a greater  force, the power it affords  by gen-
eration  and condensation is the same at the same temperature,
and this power is directly as  the elastic  force of the steam, mul-
* Tredgold on the Steam Engine, p. 157__159, 
OF THE MOVING FORCES USED IN THE ARTS.
275
 tiplied by the space it occupies, supposing  that  the  motion of
 the piston is rectilinear.
   But if, as in the last case, a loaded piston be raised, and then
 a valve be opened which allows the steam to escape, the whole
 power gained will be equal only to the weight raised, descend-
 ing from the  height to which it  was  raised; and the  power
 which would have resulted from  condensation will be lost, and
 the loss is equal to the pressure of the atmosphere  acting through
 the height to which the piston was raised by the steam.   This
 is the nature of the common high pressure steam engine.   It is
 obvious, that the greater the elastic force of the steam, the less
 is  the proportionate loss by neglecting to condense it under
 these circumstances; but, it may be remarked, that  unless the
 valve aperture be equal to the diameter of the  cylinder,  the
 steam cannot escape at the  necessary rate without part of the
 load  acting to expel  it;  and so  much  more of the  effective
 force  will of course  be  lost.   The effective  power is as the
 space the steam  occupies, multiplied by the excess  of elastic
 force above the atmospheric pressure.
   By Expansion.—Retaining the same loaded piston, let it be
 raised by the conversion of a given quantity of water into steam,
 to the height which corresponds to the load and temperature.
 Then if the load on the piston be wholly removed at that height,
 the steam will raise  the piston by expanding till  it becomes
 nearly of the same elastic force as the atmosphere, and its con-
 densation will produce the same effect  as if the steam  had been
 generated of atmospheric elastic force at first.  Consequently,
 the effect in raising the load on the piston is wholly additional,
 and the joint effect of a high pressure and condensing engine is
 produced by the same  steam.   Hence by this combination of
 effect, the power  of steam of high elastic force will  be nearly
 doubled.
   This is not, however, the mode by which steam can be ap-
 plied  with the greatest advantage ; for instead of removing the
load on the piston wholly at the  heightto which it was raised
by the generation of the high pressure steam, a part of it may 
276     OF THE MOVING FORCES USED IN THE ARTS.

be removed, and then the steam would expand to a height  de-
pending on the portion of the load removed ; at that height re-
move a second portion, and so on, successively, till the steam
becomes of atmospheric elastic force.   In  this case, as far as
the load was raised in parts by the expansion of the steam, the
effect is greater than in the preceding combination.  This  il-
lustrates the principle of the high pressure expansion engines of
Evans, Woolf,  and some others.
   Again, let the piston be raised unloaded,  as in the first case,
by the conversion of a certain quantity of. water into  steam of
atmospheric elastic force.  When the piston is at that height,
add  a weight  equal  to  half  the   atmospheric  pressure  to
the line passing over the pulley.  Then the  elastic force of the
steam  being  unbalanced, the  piston would  rise till that elastic
force would be half the atmospheric  pressure, or till the piston
would be at double its former height.   Now suppose the steam
to be condensed, and the weight removed from the  pulley at the
same instant.   Then the power of the descent, after deducting
the power added to produce the ascent, will be one half more
than it would have been by simply condensing steam of atmos-
pheric elastic  force.   This illustrates the principle of the  ex-
pansion engines of Hornblower and Watt;  and it  differs from
the principle of Woolf in using steam only of low pressure.
The weight  added to the line  passing over  the pulley is intro-
duced  here merely to exemplify the mode of applying a portion
of the excess of power which is accumulated in the fly wheel,
in one part of the  operation, to assist the machine  through the
rest.
   It has been assumed that steam at least of atmospheric elas-
tic force was  generated, but this is not a necessary  condition,
for it frequently occurs that engines work with steam of less
elastic force.   The same mode of illustration will show whence
this happens.   Let half the pressure of the  atmosphere on the
piston  be  balanced  by a weight over a pulley.  Then on the
application of heat, steam of half the atmospheric  elastic force
would  be generated, and  raise the piston to double the height 
OF THE MOVING FORCES USED IN THE ARTS.
277
that it would be raised, in common cases, by steam capable of
supporting the atmospheric pressure.   Consequently on its being
condensed, the descending  force will be half the atmospheric
pressure  acting through double  the height;  and the  steam
produces the same effect as before.
  The  foregoing methods of the application of steam will be
found apparent in the different forms of the  steam engine, in
which they have been called into use.
   The  Steam Engine.—The steam engine  is a  machine by
which  the power derived from steam is converted to practical
use.  It has  occupied the attention of philosophers and artists
for more than a century, and is now brought to so great a de-
gree of perfection as, in the opinion of many scientific men, to
leave little probability of its  further improvement.  Whether
viewed  with reference to the great skill which has been  em-
ployed in perfecting it, or the  importance and extent of its ap-
plication, it may justly be viewed as the  noblest production of
the arts  in modern times.  For acquiring a clear conception of
the steam engine as it is now  commonly constructed, it will be
useful to consider, first, the  boiler in which the power is gener-
ated, and  secondly  the engine  in which it is directed and
applied to use.
   Boiler.—On  account of the gradual rate at which water
boils away, it is necessary in most engines to keep a large quan-
tity constantly heated, to afford steam with  sufficient rapidity
for its consumption by the engine.  This water is inclosed in a
strong tight vessel, called the boiler, which is made of iron or
copper, and rests in contact  with a furnace.  It is  requisite,
that a boiler should be of sufficient  strength to resist the great-
est pressure which is ever liable to occur from the expansion of
the steam.   It must also offer a sufficient extent of surface to
the fire, to insure the requisite amount of vaporization.   In
common low pressure  boilers, it requires about  eight  feet of
surface of the boiler to be exposed to the action of the fire and
flame, to boil offa cubic foot  of water in an hour,  and a cubic 
278     OF THE MOVING FORCES USED IN THE ARTS.

foot of water thus converted into steam is equal to a one-horse
power. *
   The strongest form for a boiler, and one of the earliest which
was used, is that of a sphere, but this form is the one which of-
fers least surface to the fire.  The figure  of a cylinder is on
many accounts the  best, and it is now  extensively used, espe-
cially for engines  of high pressure.  It  has the  advantage of
being easily constructed from  sheets of metal, and the form is
of  equal strength except at the  ends.    In such a boiler,  the
ends should be made thicker than the other parts.   The fur-
nace is so constructed that the flame and hot smoke  may pass
under the whole  length of the boiler,  and  afterwards around
both its sides, before escaping to  the chimney.
   In what are called flue boilers, a cylindrical furnace is placed
within a  cylindrical  boiler, so that  the  fuel  is  surrounded by
water on all sides, and communicates to  it nearly all its heat,
except the portion which passes up the chimney.
   In large engines, which are of low pressure, the form of the
boiler, which  was used by Mr Watt, still continues to be em-
ployed, particularly  in England.   In this boiler the upper half
is a semicylinder, while the lower half is nearly rectangular,
with the under side concave, so that a cross section  would
nearly resemble a horse-shoe.  This boiler is less strong than
those of a cylindrical form, but it offers a larger surface to  the
fire, without occupying much  more  space.   A boiler of this
kind, as it is fitted up in large engines, with appendages for reg-
ulating its own fire, water, and steam, is represented in PI. VIII.
Fig. 5.  A part of the furnace is supposed to be taken away,
to  bring the boiler into view,  and  also a portion of the boiler is
removed to show its  inside.
   Appendages.—In  the figure above referred to, B B B B is
the boiler, made of thick sheets or plates of rolled iron strongly
rivetted  together, a part of which are  removed to show  the
interior.  It is supposed to be half full of water at the boiling

 * See Tredgold on the Steam Engine, with the following correction, p. 124,
line 2 from the bottom.  For steam read  water. 
OF THE MOVING FORCES USED IN THE ARTS.
279
 temperature.   C is the steam gauge the object of which is to
 determine the degree of pressure  acting within the boiler.  It
 is a bent iron tube, or inverted syphon, one end of which com-
 municates with the boiler, and the other end with the atmos-
 phere.  The tube  is partly filled with  mercury, and as the
 pressure of the  steam  increases,  the mercury  will  be driven
 outward and will rise in the external  leg of the syphon.  As
 the height of the column of mercury cannot be seen, the tube
 being opaque, a small wooden stem is made to float in the tube,
 with its end projecting by the side of a graduated scale.  Every
 inch in height which the stem rises,  shows a difference of two
 inches in  the two surfaces of the mercury in the tube, and in-
 dicates a pressure of about a pound upon  every square inch of
 the inner  surface of the boiler.   And as low pressure engines
 are seldom worked  with more than three or four pounds to the
 square inch, the mercury seldom rises higher than three or four
 inches in such engines.   In high pressure  engines, the mercu-
 rial guage is not so easily applied, for these engines  are  fre-
 quently worked at a pressure of several atmospheres, and each
 additional atmosphere requires an addition of nearly 15 inches
 to the column of mercury.
   W is a large opening called the. man hole, of sufficient size
 to permit  a man to  enter the boiler to clean or examine it.   It
 is closed by a strong iron plate.   D is the steam pipe which
 conveys the steam  to the engine.   It is provided with a throttle
 valve, which is a circular disc, or partition, turning on an axis,
 and connected with the governor  described on page 249    Its
 use is to regulate the supply of steam by closing the pipe/if the
engine goes too fast, or by opening it, if it is too  slow.   F F
 are the guage cocks which  indicate the  height of water in the
 boiler.  Their extremities stand at different depths in  the boil-
 er, one being below the surface  of  the water, and the other
 above it.  When the water is at the proper height, one of these
 wiH emit steam, on being opened, and the other will emit watT

lell,   ^^ ^ °n ^ ^ inS-d 0f *>  top of 
280     OF THE MOVING FORCES USED IN THE
   For  keeping up a regular supply of water to the boiler, a
vertical tube G called the feed pipe is used.   Upon its top is a
small cistern H H H H, which  is kept full of water by a pump
worked by the engine.   At the bottom of this cistern is a valve
E, connected to one end of the  lever a b.   At the other end
of this  lever is a wire a c, which passes through a steam-tight
opening at d, and supports a stone float c upon the surface of
the  water, the stone being counterbalanced by  a weight at the
valve e.  When  the water lowers in the boiler, the stone float
descends  and by acting upon the lever a b, opens  the valve e.
Water  immediately flows in from the cistern  and  continues to
do so, till the float rises and shuts the valve.   It will be observ-
ed that the column of water in the feed pipe  must  be  suffi-
ciently  high to counterbalance the pressure  of steam in the
boiler.   On this  account it cannot be applied in high pressure
engines, without  making it of a very inconvenient  height.  In
these  engines, therefore,  water is supplied to the  boiler  by ?
small forcing pump, worked by one of the reciprocating parts
of the engine ; and it is frequently heated before being pumped
in, that it may not check the production of steam.
   For  the purpose of regulating the fire, the feed pipe is fur-
nished  with an iron bucket O, hung by a chain which passes
over two pullies P P, and is attached by its other extremity to
an iron damper A, which commands the chimney.   When the
steam in the boiler is urged to  too great an extent, it forces the
water upward in the feed pipe  and causes the iron bucket to
ascend.   This lowers the damper into the smoke flue, and by
thus intercepting  the current of air, checks the force of the fire.
In some boilers the passage, which brings air to the fire, is in-
tercepted, instead of the smoke flue.
   To prevent the boiler from bursting, if by accident the pres-
sure of the steam  should  become too great for  the strength of
the boiler, a safety'valve is provided  at S, opening outward.  It
is  kept down by a weight, so that it cannot be  raised except by
a greater force than that which is required to work the engine.
It  is highly important,  however,  that it should not be liable to 
MOVING FORCES USED IN THE
281
any other weight or incumbrance, than that which the engine
requires,  and to prevent this danger it is inclosed m a case
which is kept locked.  When the engine stops working, or the
steam is generated too rapidly for its  expenditure, the safety
valve rises, and the superfluous steam rushes out with a hissing
noise.
  Another safety valve is also provided, which differs from the
preceding in opening inwards.  It is  kept up by  a counter
weight on a  lever,  and its use is to prevent the weight of the
atmosphere  from crushing in the sides of  the boiler, when the
engine stops working, and the steam cools.
   As  boilers are  usually proved  before being  submitted to
use, the  accident of bursting does not happen from a general
want of strength, unless the safety valve be overloaded.   It is
most likely to happen either from neglect, in suffering the water
to get too low, so  that the metal is softened by heat, or  else
from the corrosion of the metal in places, by oxidation,  after
long exposure to the fire.  If a sediment is suffered to accu-
mulate to a considerable  depth on the bottom of the boiler, it
has  the effect to exclude the water from contact with the metal,
so that the metal becomes hotter, and is more rapidly oxidated,
and even softened, by the heat.
   Besides  the  forms of the boiler  already mentioned, various
others have  been employed, such as combinations of tubes, and
other figures, intended to multiply  surface, for the  purpose of
raising more steam from the same amount of water, in a  given
time.  They have been applied in some high pressure engines,
but in most cases,  the simpler forms are preferred.  In Per-
kins's engine, a strong vessel called a generator, is kept  full of
water heated to a  high temperature.   Portions  of the  water
are  successively forced out, and reliance is placed on the heat
already in this water, to produce from it the requisite amount
of steam.
   Engtnc—The  steam being generated in sufficient quantities
in the boiler, it is next applied to use in the working or moving
part, which we have called the engine.   Of this engine a great 
282     OF THE MOVING FORCES USED IN THE ARTS.

variety of forms and  modifications have been  proposed  and
adopted, at different times.  A few of those which are effectual
m their principle, and  most extensively employed, will now be
considered.
   Noncondensing  Engine.—The  simplest form of the  steam
engine, is that of the noncondensing, commonly called the high
pressure  engine.   In  this engine, the apparatus for condensa-
tion is dispensed with, and the steam is worked at a high tem-
perature,  and afterwards discharged into  the open air.   Of
course a part of the  force of the steam is expended in over-
coming  the pressure  of the atmosphere, and the surplus only
can be applied to drive  machinery.  That this surplus may be
sufficient to produce  the requisite power,  a pressure of 30 or
40 pounds on a circular inch, above the atmospheric pressure,
is commonly kept up  in these engines. *
   The  manner  in which the engine is  made  to operate, is
briefly as follows.   The steam in  escaping from  the boiler to
the open air, is obliged to pass through the  cylinder, the  cavity
of  which is  closed,  except where it communicates with the
valves.   By the  opening  and  shutting of these valves, the
steam is made to enter the cylinder alternately at each end, and
escape by the opposite  end.   But in doing this, its passage is
always  intercepted by the piston, so that before  it can escape,
it must  move the piston from one end to the other of the cy-
linder.  The  repetition of this movement gives  motion to a
beam, or other alternating part, from which it is communicated
by a connecting  rod  and  crank, to a fly wheel, in the same
manner as is seen in the condensing engine, PI. IX. hereafter
to be described.   The  figure  there represented may be con-
sidered  as a noncondensing  engine, if we  remove from it the
condenser and its appendages,  occupying the lower part  of the
plate.   B represents  the boiler, C the pipe which conveys  the
steam, D the cylinder, E the piston, F the beam, h the  crank,
G the fly wheel.
* See Tredgold on the Steam Engine, p. 181. 
OF THE MOVING FORCES USED IN THE ARTS.
283
   The  different  apparatus  of valves, by which the entrance
and escape of steam is regulated, also the other appendages of
the engine, will be considered in another place.   In arranging
the time of their  opening and shutting, it is usual to allow not
quite all the steam to escape at the end of the stroke.  A small
portion  is retained to receive the shock of the piston, and by
its elasticity to destroy its  momentum,  and cause it to recoil
back without loss of force.
   Noncondensing engines sometimes work by the generative
force of steam, and sometimes by the generative and expansive
force.   They are used in cases where simplicity and lightness
is required, as in locomotive engines;  also in situations  where
a sufficient supply of water for  condensation cannot easily be
obtained.   They  are  inferior in safety to condensing engines,
yet as they cost  much less at the outset for the  expense of
building, they  are often preferred for  small,  or  temporary
works.   In proportion to the high temperature at which the
steam is worked,  great caution is necessary  in regard  to the
strength and management of the boiler in these engines.
   Condensing Engines.—Engines of  this  class are fitted up
with an apparatus for condensing the  steam into water,  so that
a vacuum, nearly complete, is formed in one part of the cylin-
der, just before  the stroke of the piston into that part takes
place.  By this  construction the resistance of the atmosphere
is avoided, and thus the  power of the engine to perform work,
is much increased.   The steam also  is sufficiently powerful
for use, at compatively low temperatures, and hence arises the
increase of safety which is found in low pressure engines, a name
given  to  those condensing engines,  which  are worked  with
steam of moderate elastic force.
   In the atmospheric  engine, invented by Newcomen, the pis-
 ton  was raised by the steam, aided by a counter weight, till it
 arrived at  the  top of  the  cylinder, which  was left perfectly
 open.  A jet of water was then admitted  into the bottom of
 the cylinder, which  suddenly condensed the steam, so that, a
 vacuum being formed, the piston was driven down by  a  force 
OF THE MOVING FORCES USED IN THE ARTS.
 equal to the weight of the column of superincumbent air.  The
 water was now excluded by a stop cock, and the  steam read-
 mitted.   The piston was thus again raised, and the process re-
 peated as before.
   A great  inconvenience attended this method, arising from
 the  circumstance, that the cylinder itself required to be heated
 and cooled at each stroke of the piston, thus occasioning great
 delay,  and an unnecessary  expense  both of fuel  and of cold
 water.   To remedy this evil, Mr Watt  invented the separate
 condenser, which is a strong vessel situated at a distance from
 the  cylinder, but communicating with it by a pipe, so  as to
 form with it a common cavity, without reducing materially, its
 temperature.  Into  this vessel the jet of cold water is thrown,
 and as all the communicating pipes are governed by valves, or
 cocks, the cylinder  below the piston  is alternately filled with
 steam from the boiler, and emptied of steam by  the condenser.
   In the double acting engine, invented by Mr Watt, the top of
 the cylinder was closed,  and rendered air-tight, the rod of the
 piston only passing through it.  Thus  the  cylinder is divided
 by the piston into  two cavities, both communicating  with the
 boiler, and both with the condenser.   By the aid of valves, an
 alternate communication is kept up, so that the steam being al-
 ternately admitted at both ends, impels the piston  successively
 in both directions, while the  condenser, at the same, time de-
 stroys the resistance.   In this engine, compared  with the  single
 engine of Mr Watt, which  was previously in  use, a double
 quantity of steam is used, and a double power  exerted in the
 same space and time.
   Description.—In PI. IX,  is a view of a double acting steam
 engine, nearly as constructed by Murray,  and  upon the same
 general principles as those of Mr  Watt, varying,  however, in
 the valves, and some other particulars.
   A represents the furnace, which is here shown in section, as
 is  also the boiler  above it, and all the principal  cavities of the
 engine.  The  flame and hot smoke, after passing  underneath
the boiler for its whole length, return through the side passages
d d, before they are discharged into the chimney. 
        OF THE MOVING FORCES USED IN THE ARTS.     285

  B is the boiler, which, in  this example, is of a  cylindrical
form, a shape better adapted for strength than that represented
in PI. VIII.   The appendages represented in PI. VIII. are not
here repeated.   Some of them, indeed,  are not used in steam
boats, and in small engines.  The boiler  is commonly made  of
sheets of iron, strongly rivetted together and tightened by ham-
mering.  If intended to contain  salt  water, the boiler is made
of copper, to prevent corrosion.
  C C C is the steam pipe, which carries the steam from the
boiler to the cylinder through the valve I.   It is made of cast
iron, and its joints screwed together by flanges.
   D is the cylinder, communicating by passages at  the top and
bottom  with the valve I.   The cylinder is made of cast iron,
and accurately bored to make its inner surface smooth and true.
  E the piston, which, by its rod e, gives an alternating  motion
to the beam//, about its centre F, the other end of which, by
another connecting rod g,  gives motion to the heavy fly-wheel
G G, by means of a crank h.  Thus, after the engine has be-
gun to work, its power  is  accumulated in the fly wheel, and a
circular motion may be communicated from it to any  machinery.
  H is an eccentric  circle on the axle of the fly wheel G.
It gives motion through  the medium  of its  levers wx and
yz, and the connecting  rods  Hw,xy  and zl, in a manner
easily understood, by inspection, to the valve I.
   I is a coffer valve, capable of sliding up and down, and hav-
ing a cavity on the side next the cylinder.   By moving up and
down it opens and  shuts  the  passages,  and admits the steam
alternately to each end of the cylinder ; and at the same time
forms a communication between the opposite end and the con-
denser.
   W is the  governor, which regulates the speed of the  engine.
It  resembles the governor  described in Chap. XI, but has its
moveable collar on the top  at s.   It may be turned by a band
from the axle of the fly wheel, or placed directly over the axle,
and geared to it by bevel wheels.  When the fly wheel moves
too fast, the balls of the governor recede from their centre, and 
286
OF THE MOVING FORCES USED IN THE ARTS.
by acting on the lever r s, cause it to turn  upon its fulcrum t,
and  partially to close the  steam pipe by a throttle valve at K.
When the velocity  abates, the balls  subside, and  the  valve
opens so as to admit more steam.
   L is the air pump, the use of which is to discharge the air
and water which collect in the condenser, M.
   M is the  condenser, which is an  empty cylindrical vessel
immersed in a cistern of cold water, S S, and  communicating
with the cylinder by the pipe  O.  It has a valve or cock com-
municating with the cistern, and moved by the rod gg, through
which a jet of cold water enters it for the purpose of condensing
the steam.
   N a small cistern, filled with water.   Into this cistern enters
a pipe from the  condenser M, the top of which pipe, is covered
by a valve,  which is called the blow-valve, or sometimes the
snifting valve.   Through this valve, the  air contained in the
cylinder D, and passages from it, is discharged, on the engine
being first set in motion.
   O the eduction-pipe, which conducts the steam from the
valve I, to the condenser M.
   P the pump  which  supplies with water the  cistern, or cold
well S S, in which the condenser and discharging pump stand.
   Q Q iron columns which support the beam.   Of these the
engine has four, although only two are shown.   They stand
upon  one entire plate, seen edgewise, on which the principal
parts of the engine are  fixed.
   R R the recess below the floor, for  containing the cistern of
the discharging pump, condenser, he'
   The  condenser M, and the  air pump  L, communicate  by
means of a horizontal pipe  containing a valve  m, opening to-
wards the pump; the piston n  of this  pump, also contains two
valves, and the cistern T, at the top of the pump cylinder, con-
tains  other two valves, which,  like those of the piston  n, open
upwards.   When the piston E of the cylinder is depressed, the
piston n of the  discharging pump, it will be obvious to inspec-
tion, will be depressed  likewise, and its valves open, while the 
        OF THE MOVING FORCES USED IN THE ARTS.     287

valve m closes; hence the water of the  condensed steam, as
well as the injection  water, and any vapor or air which may
be present, having passed  through the valve m, passes  through
the piston  n; and when that piston is drawn up, its valves close
and prevent  their return, as in common pump work.   The
water and air that have thus got above the piston, as the latter
rises, open the valves at the bottom of the cistern T, in  which
the water remains  till it is full, but the air passes into the  at-
mosphere.  As the  water in the cistern  T is in a hot state, a
part of  it, for the  purpose of economizing fuel, is pumped  up
and returned to the boiler, the pump rod  being attached to the
great beam.
   The  steam constantly  rushing into  the condenser M, has a
perpetual  tendency to heat that vessel, as well as the water of the
cistern S S, in which it stands; the whole of the steam, if this
were unchecked, would not be condensed, or the condensation
would  not be sufficiently  rapid, because  the  injection  water
itself flows out of this cistern.   A part of the water is therefore
allowed to flow from this cistern by a waste pipe, and an equal
quantity of cold water is  constantly supplied by the pump  P.
   The cylinder D,  is in many cases surrounded by a case, to
keep it from being cooled too much by contact with the exter-
nal atmosphere.
   Expansion Engines.—The steam which  impels an  engine
is always  diminished in volume, by the resistance which it has
to overcome, and tends naturally to occupy a larger space than
that to which it is confined while the engine is at work. If it
be dismissed into the air, or  into the condenser, while  under
its greatest working  pressure, it will not have produced  all  the
useful  effect  which it is capable of affording.   If, on the con-
trary, it be separated and placed under  circumstances  where
it can still expand further, before it is dismissed, this expansion
will be  so much additional gain to  the power of the engine.
Its general principles have already been discussed.
   The expansive power  of steam may be converted  to use in
various ways, and  most of the common forms of the steam 
288
OF THE MOVING FORCES USED IN THE ARTS.
engine may be made to act expansively by a proper arrange-
ment of their valves.  In Watt's engine, this effect is produced
by cutting off the steam from the cylinder before the stroke of
the piston is completed, leaving it to the steam already in the
cylinder to  assist by its expansion  in  completing the stroke.
The steam in the boiler being thus intercepted, acts only at in-
tervals.  Nevertheless, its whole disposable  force is accumulat-
ed in the fly wheel, while, at the same time, the force arising
from the expansion of steam in the cylinder, serves to increase
the total amount.   A great  augmentation is thus produced in
the useful effect of an engine, with  the same amount of  fuel,
and water.
   Mr Hornblower, who was one  of the first inventors of the
application of expansive steam, employed two cylinders having
their  pistons connected to the same beam.   In the smaller  of
these, the steam  was used at full pressure,  after which it was
discharged into the  larger cylinder, where it again  acted by its
expansive force.   This method affords a more  equable mode
of applying the expansive force of  steam,  than that used by
Mr Watt, but the engine is more complex and expensive.
   Mr Woolf afterwards adopted the plan of two cylinders  with
the addition of using his steam at a high pressure, together with
a condenser.  He appears to have exaggerated the expansive
force of steam, at high  temperatures, as various other projec-
tors  have done.  His engines,  however, continue to be  used
and approved, in  some parts of England and Wales.
   Valves.—The valves of steam  engines are shutters, which
guard the avenues to the boiler and condenser, so that by open-
ing and shutting them, at the required time, the  steam may be
made to enter, or escape, at either end of the  cylinder.   Valves
of a great  variety of forms,  have  been  used  in different en-
gines,  some of which  have a reciprocating,  others  a rotary
motion.  The puppet valve is a cone, or frustrum of a cone,
which  is fitted, like a cover,  to a conical  aperture,  which it
opens by rising, and closes by falling.   A valve  of this kind is
seen at V. in PI.  IX.  Sliding valves are those which do not 
        OF THE MOVING FORCES USED IN THE ARTS.     289

rise, but slide  on and off of their apertures.   Some of these
have a cavity on their under side, capable of connecting two
apertures together,  or of forming a  communication between
them, while a third aperture is  shut.  This is the  case  with
the valve I, in PI. IX.  Rotary valves are usually constructed
like common stopcocks, excepting that they  command more
passages than one at the same time.   If the handle  be placed
in one position, it opens one passage while it closes another; if
in a different position, it closes the first, and opens the second.
A throttle valve is a partition turning on  an axis, and  placed
across the interior of a pipe.   If turned edgewise, it permits
the steam  to  pass, but if turned transversely it obstructs  its
passage.  This valve is commonly placed in the main steam
pipe,  and connected with  the governor to  regulate the quantity
of steam supplied by the  boiler.   See K, in PI. IX.
   On account of the heat which is kept up in steam engines,
the principal valves require to be of  metal, and  are  fitted  by
grinding closely to their seats.   Valves made with leather, like
the common clack  valve  of a pump,  can  only be used  about
the condenser, where the temperature is low, as the valve m
PI. IX.
   Pistons.—As  the  piston is  liable  to continual wear by its
friction against the  inside of the cylinder, it can only be kept
sufficiently tight by rendering its circumference elastic.   This
is commonly  done by  winding it with hemp loosely twisted.
The  hemp  packing,  however,  gets out of order in  time, and
requires to be renewed.  To remedy this evil,  various plans
have  been introduced, for making elastic pistons of metal only.
The pistons invented by Cartwright and Barton, consist of sev-
eral parallel circular plates in close  contact with each other.
These  are cut into segments, and the segments pressed out-
ward by steel springs, care being taken that the  fissures in the
different plates do  not coincide.  In the piston of Jessop, a
spiral coil of steel is wound on the circumference of the piston,
which expands by its own elasticity, so as to keep in  tight con-
                37 
290
OF THE MOVING FORCES USED IN THE ARTS.
tact with the cylinder.   To increase the tightness and elasticity
of the piston, a hempen packing is placed within the coil. •
   Parallel Motion.—A simple form of a parallel  motion, for
converting the rectilinear motion of the piston into the curvili-
near one of the beam, has already been described on page 240.
Another form is shown in PI. IX, where the rod a b turns upon
the joint a as a fixed centre, while the rod c b turns upon b as
as a centre.   While the point c would  describe a curve  about
its centre b, the point b describes an opposite curve about its
centre o.  These  two  curvatures compensate each other, so
that the point c to which the piston is attached, describes nearly
a straight line.
   The parallel motion  was introduced by Mr Watt,  and is
probably attended with less friction than any other arrangement
for effecting the same object.   It requires, however, to be con-
structed with great accuracy.   Various other methods have
been applied to convert the rectilinear, into a curvilinear move-
ment.  Sometimes the piston is confined to its path by guides,
or friction wheels, and  connected  to the beam by a double
joint.  In Newcomen's  engine, where the principal force was
in the downward stroke, the  piston was connected by a chain
to an arched head at the end of the beam.   In Cartwright's
engine, the  piston  was attached to two  opposite cranks which
were geared together,  as  shown on page 241.   In some of
Murray's engines,  the epicycloidal  movement was employed.
See page 242. *  In Maudslay's engine, and  some others, in-
stead of a beam, a cross  head is used,  the  whole of which
moves up and down in  guides, instead of turning on a centre.
In  the vibrating  engines of Lester and others, the cylinder is
hung upon a moveable axis, and in Morey's engine, the cylin-
der revolves like a fly wheel, the piston being made to act on a
fixed crank.
   Historical Remarks.—The following are some of the most
interesting facts in the history of the Steam Engine.

  * For an  account and figure of an engine of this kind, see Farey on the
Steam Engine, p. 686, and PI. XVII. 
        OF THE MOVING FORCES USED IN THE ARTS.     291

  The ancient  Greeks  and  Romans appear to have been ac-
quainted with the power of steam to produce motion, and in-
vented the eolipile, which was a close vessel containing water,
and which gave out a forcible current of steam whenever the
water was heated.   The  force of this  current was  used by
Hero to produce a revolving motion.
  The power of confined steam,  acting by its pressure,  was
discovered by the Marquis of Worcester, and an account of its
effect published by him in 1663.  He produced a steam pow-
er sufficient to burst a cannon, and  constructed a machine ca-
pable of raising water to the height of forty feet.   He has not,
however, left  any drawings or particular  description  of his
machine.
  In  1698,  a patent was  granted  to Thomas Savery, for a
method of raising water by steam.   This apparatus consisted
of a boiler, a separate steam vessel, and pipes commanded by
valves.  The steam from the boiler was first admitted so as to
fill the steam vessel.   It was  then  condensed, and the steam
vessel filled with water which rose by the atmospheric pressure
from  the well or mine.   The steam was then readmitted, and
the water in the vessel  was  driven  upward to the top of the
pipes, and discharged.
  About the year 1705,  Thomas  Newcomen, constructed a
working steam engine, which has since been called the atmos-
pheric engine.   It contained a cylinder and piston, and an al-
ternating beam, which was applied to raise water by working a
pump.  The water was condensed in the cylinder itself, and
the  valves were moved by  hand, until an attendant contrived to
make the machine move its own valves, by attaching strings to
the  working beam.
  After this the steam engine continued without any important
alteration, for more than  half a century, when about "1769, the
discoveries and inventions of James  Watt, gave a new spring to
the energies of this machine,  and have more than doubled the
power which it formerly  possessed.   Mr Watt's improvements
were  numerous and important, but those of greatest value were 
OF THE MOVING FORCES LSED IN THE ARTS.
the following.   1.  He introduced the separate condenser.   2.
He applied the  double action of steam by clpsing the top of the
cylinder, and admitting the steam alternately at each end.   3.
He converted to use the  expansive power of steam, by cutting
off the current before the end of the stroke.   Mr Watt also in-
vented the  principle of the  parallel motion,  and applied  the
governor to regulate the supply of steam.
   In  1802, the first high pressure or noncondensing  engines
were constructed by Oliver Evans, in Philadelphia, and in the
same  year by Trevithick and Vivian,  in England.  The idea
of such an engine  had  before  occurred to Leupold, Watt,  and
others.  The first steam carriage was put in motion on a rail-
way, by Trevithick and Vivian, in 1805.
   Steam  navigation was suggested in England  by Jonathan
Hulls, in  1736.  It was first  tried in practice by the Marquis
de  Jouffroy in  France, in 1782, and nearly at the same time
in America, by James Rumsey of Virginia, and John Fitch of
Philadelphia.   It was first made practically successful by Rob-
ert Fulton, at New York, in  1807.   The first  steam vessel
which crossed  the Atlantic, was  the American ship Savannah,
in 1819.
   Projected  Improvements.—Besides the improvements which
have  been actually effected in the construction and application
of the steam engine, a variety of projects for increasing  the
power and usefulness of this agent, have from time to time occu-
pied the  attention  of ingenious  men.  Of the improvements
which have  been  attempted,  some are  opposed by obstacles
which have not yet been satisfactorily surmounted, and others
by difficulties in themselves  insurmountable.  The following
have been among the  most prominent  subjects of speculation.
   1.  Rotative  Engines.—These  are  engines in whicli the
steam  is so applied as to produce a direct  rotary motion with-
out the  intervention of a rectilinear movement.   Engines on
this principle have been constructed in many different ways.
An idea of one of the most obvious forms may be obtained from
the excentric, pumps described in the following Chapter, whicli 
        OF THE MOVING FORCES USED IN THE ARTS.     293

have been converted into steam  engines, by reversing the mo-
tions, and changing the resistance for the power.   Some rota-
tive engines have been constructed on the principle of Barker's
mill; others have been made by immersing an overshot wheel
in a  cistern of heated fluid, either water, oil, or melted metal,
and delivering the steam under the ascending or inverted buck-
ets, so  that when these were filled with  steam, the full buckets
on the  opposite side might preponderate and cause the wheel
to revolve.   But in general the rotary  engines hitherto con-
structed, have either been feeble in power, or encumbered with
excessive friction, on account of the extensive  packing which
is necessary to keep them tight;  so  that none of them have
found  their way into  use.  It is probable  that no method of
constructing a variable cavity for steam, which  is in other  re-
spects  suitable, affords so advantageous a mode  of applying
the  power,  as the  cylinder and piston producing rectilinear
motion.
   Use of Steam at high  Temperatures.—In noncondensing or
high pressure  engines, the power which is convertible to use,
consists  of the surplus which remains,  after  overcoming  the
pressure of the atmosphere.   Of course the higher is the tem-
perature at which  the steam is worked, the  greater is the total
gain, supposing the  absorption of heat  and the production of
power to  continue  to take place in  equal proportions.  This
consideration, with other expected advantages, has given rise to
many attempts to improve  the steam engine, by devising modes
of applying steam  at much higher  temperatures than  those
which  it has been ordinarily found practicable to employ.   At-
tempts of this kind have also frequently been founded upon an
undue estimate of the elastic force of steam at high tempera-
tures,  and of the absorption of heat during its production.   In
practice, it is  found difficult  to obtain a material capable of
confining water and steam  in safety, when raised to such a tem-
perature as to produce a pressure often or more atmospheres;
since,  independently of the strain upon the joinings, the cohesive
 strength of metals is diminished, and their oxidation  promoted,
by exposure to great heat. 
294     OF THE MOVING FORCES USED IN THE ARTS.

   Use of Vapors of low  Temperature.—Certain  liquids  such
as alcohol, ether, sulphuret of carbon, and a liquid obtained by
condensing oil gas, have been proposed as substitutes for water,
in producing  steam, on  account of the low  temperature  at
which they are  converted into  vapor.   Thus alcohol boils at
about 173 degrees of Fahrenheit, sulphuric ether at 98 degrees,
muriatic ether at 51  degrees, * sulphuret of carbon at 116 de-
grees, and oil gas, liquid,  at 186 ; all of which are lower  than
the boiling  point of water.  Some  of  these, when raised  to
the boiling point of  water, have a much greater elastic  force
than that fluid.  Thus the sulphuret of  carbon at 212 degrees,
has an elastic force  equal to about four atmospheres, f and
sulphuric ether of nearly six atmospheres.   But these advan-
tages are nearly counterbalanced by the small spaces through
which these vapors act, their volume at their boiling point, be-
ing only from about  an eighth to a third part of that of steam,
at the boiling point  of water.   To this  disadvantage may be
added the expensive character of these substances, and the
difficulty of condensing them without loss, in any working en-
gine.   Some of them  likewise,  as the ethers,  act chemically
upon  metals, and could not on this account be employed in en-
gines made of the common materials.
   Gas Engines.—It has  been  attempted to obtain  power for
propelling  machinery,  from  the combustion, or explosion,  of
inflammable elastic  fluids, such  as coal  gas, and the vapor  of
combustible liquids, mixed with  atmospheric  air.  In combus-
tions  of this kind, rarefaction  and  subsequent condensation
take place, which if conducted within  suitable cavities,  may
be made to afford a  moving power,  applicable to  machinery.
The principal engines which have been  constructed for using
this power, are those of Messrs  Morey, in this country,  and
Brown, in England.   If a power of this kind  could be made
to afford an adequate propelling  force- for locomotive engines
upon  public roads,  it  would possess  an   advantage  in the

           * Ure's Dictionary.
           \ See Tredgold's tables, Steam Engine, p. 78—81. 
        OF THE MOVING FORCES USED IN THE ARTS.     295

lightness of the machinery, compared*with the weight of steam
engines with their water and  fuel.  But it remains for experi-
ence to determine, whether the space  through which the force
will act, taken in connexion with the cost of the materials, can
render this an economical source of power.
  In addition to the  foregoing  method of procuring  power by
the  combustion  of gases, Sir  H. Davy has proposed the  em-
ployment of certain  fluids which are volatile  at common  tem-
peratures, but which have  been  condensed into liquids  under
great pressure,  such as carbonic acid,  ammonia,  he   His
views  are  founded upon the immense difference which  exists
between the increase of elastic force in gases under high, and
low temperatures, by similar increments of temperature. ,  But
doubts have  been raised upon this subject, with regard to the
space through which the force of these gases  will act, and also
in regard to the  quantity pf heat required to produce the change
of temperature  required.*
  Steam  Carriages.—It has long been a favorite object with
projectors to construct a form of the steam engine in connexion
with a carriage, which should be  capable of propelling  itself
upon the public roads.   Locomotive engines are capable of
moving themselves upon rail roads, and of drawing with them
additional loaded carriages; because in this case the motion is
uniform, and  very little of the power is expended in surmounting
obstacles, or changing the form of the road.   But upon a public
highway it requires,  by a common estimate, about  eight times
as much power to propel a carriage, as it does upon a rail road.
Of  course the weight and inertia of an engine capable of  pro-
ducing this power, must increase somewhat  in the  same  pro-
portion, and a great part of the power will  become  necessary
to transport the machine itself.   The inertia,  also, will be  con-
tinually brought  into unfavorable  action by the jolts and  con-
cussions inseparable from highway travelling, and thus endanger
the  destruction of a machine  requiring such nice  adaptation

  * Philosophical Transactions, 1826, Tredgold on the Steam Engine, p. 84. 
296     OF THE MOVING FORCES USED IN THE ARTS.

of parts  as the steam engine.  It appears that steam carriages
have been made to run upon good  roads, during short experi-
ments, while the engine was new.   But we have no account, as
yet, of any one having long performed this kind of  service.
   Steam Gun.—Mr J. Perkins,* whose experiments on the
steam  engine are well known, has attempted  the employment
of the expansive  force of steam, as a substitute for gunpow-
der, in throwing projectiles.  The steam gun  invented by him,
is somewhat  similar in its construction to the  air gun, but the
power is derived  from a magazine of water  heated to a very
high temperature, so that when  portions of it are  discharged
from the vessel containing it, they  produce steam  enough  to
project a cannon ball with great force.  The balls are admitted
into the  gun, in succession, from a hopper,  and can be  dis-
charged  at the rate of 24 in a minute.   It appears from some
experiments made with these guns in France, that  the projec-
tile force of steam  is greatly  inferior to that of gunpowder,
a consequence, no doubt, of the vast difference which is known
to exist in the initial force of the two agents;  nevertheless, the
rapidity  with which the discharges may be made, seems capa-
ble of advantageous  employment  in some situations.

                        GUNPOWDER.

   Manufacture.—Gunpowder  is a solid  explosive mixture
composed of nitre, sulphur, and  charcoal, reduced  to powder,
and mixed intimately with each other.   The proportion of the
ingredients varies very considerably; but good  gunpowder may
be composed of the following proportions;—76  parts of nitre,
15 charcoal, and 9 sulphur, equal to 100.  These ingredients
are first  reduced to a fine powder separately, then  mixed in-
timately,  and formed into a thick paste.  This is done by
pounding them for a long time in  wooden mortars, at the same
time moistening them with water,  to  prevent the  danger of
  ' The public are indebted to  Mr Perkins for the art of steel engraving, the
nail machine, and many other useful inventions. 
        OF THE MOVING FORCES USED IN THE ARTS.     297

explosion.  The more intimate is the mixture, the better is the
powder, for since nitre does not detonate, except when in con-
tact with inflammable  matter, the whole detonation will be more
speedy, the more numerous the surfaces in contact.   After the
paste  has dried a little, it is placed upon a kind of seive  full
of small holes, through  which it is forced.  By that process it
is divided into grains,  the size of which depends upon the size
of the holes through which they have passed.
   The  powder when  dry, is put into barrels, which  are  made
to turn round on their axis.  By this motion the grains of gun-
powder rub against each other, their  asperities are worn off,
and their surfaces are made  smooth, the powder is then said to
be glazed.  The granulation and glazing of the powder causes
it to explode  more  quickly,  perhaps by facilitating the passage
of the flame among the  particles.
   Detonation.—When gunpowder comes in contact with any
ignited  substance, it explodes, as  is  well known, with  great
violence.  This effect may take place even in a vacuum.   A
vast quantity of gas or elastic fluid  is emitted,  the sudden pro-
duction of which, at a high  temperature, is the  cause of the
violent  effects which  this substance produces.  The combus-
tion is evidently owing to the decomposition of the nitre by the
charcoal and sulphur.    The products are carbonic oxide, car-
bonic acid, nitrogen,  sulphurous acid, and probably sulphuret-
ed hydrogen.   Mr  Cruikshanks has ascertained  that no per-
ceptible quantity of water is  formed.   What remains after  the
combustion, is potash combined with a small portion of carbon-
ic  acid, sulphate of potash, a very small proportion of sulphuret
of potash, and unconsumed charcoal.
   Force.—The elastic fluid which is generated, when gunpow-
der is fired, being very dense, and  much heated, begins to ex-
pand with a force at least 1000 times greater than that of  air
under the ordinary  pressure of the atmosphere.  And  allowing
the pressure of the atmosphere to be 14^ pounds upon  every
square inch, the initial force, or pressure, of  fired gunpowder
will be equal to at least 14,750 pounds upon every square inch
               38 
OF THE MOVING  FORCES USED IN THE ARTS.
of the surface  which  confines it.   But this estimate, which is
that of Mr Robins,  is one  of the  smallest which have  been
made.  According to Bernoulli, the initial elasticity with which
a cannon ball is impelled, is at least equal to 10,000 times the
pressure of the  atmosphere,  and from Count Rumford's exper-
iments it appears more than three times greater than this.
   Gunpowder  on account of its expensiveness, and the  sud-
denness and violence  of its action, is not employed as a reg-
ular  moving  force for machinery.  It is chiefly applied to the
throwing of shot and other projectiles, and the blasting of rocks.
   When a ball is  thrown from a gun, the greatest force is ap-
plied to  it by  each  particle  at the  moment of its  explosion.
But  since the  ball  cannot at once acquire the same  velocity
with  which the elastic fluid if at liberty would expand, it con-
tinues to be acted upon  by  the fluid,  and its motion is acceler-
ated in common cases, until it has  escaped from the mouth of
the piece.  The  accelerating force,  however, is not uniform,
and  hence the  following  circumstances deserve attention.  1.
The  elasticity is inversely as the space which the fluid occu-
pies,  and, therefore,  as it forces the ball out of the gun, it con-
tinually diminishes.   2.  The elasticity would diminish in this
ratio, even if the temperature  remained the same; but it must
diminish in a much  greater ratio, because a reduction of  tem-
perature takes  place, both from the dispersion of the heat, and
the absorption of it by the fluid itself, during its rarefaction. 3.
The fluid propels  the ball by following it, and acts with a force
that  is, cetazrus  paribus,  proportionate to the excess of its ve-
locity above the velocity of the ball.  The greater the velocity
that the ball has acquired, the less, therefore, is its momentary
acceleration.   4.  From this change of relative velocity, there
must be a period, when  the velocity of the ball will  exceed
that of the elastic fluid, and  therefore the proper length  for a
gun  must be that, in which the ball would leave the mouth, at
the time when  the velocities are equal; and all additional length
of the piece beyond  this,  can only serve to retard the   ball,
both  by friction and  atmospheric pressure. 
        OF THE MOVING FORCES USED IN THE ARTS.     299

  The force of fired gunpowder is  found to be  very nearly
proportionate to the quantity employed ; so that if we neglect
to consider the resistance of the atmosphere, then the height
to which  the ball will rise, and its greatest horizontal range,
must  be  directly as the  quantity of powder, and inversely  as
the weight of the ball.   Count Rumford, however, found that
the same quantity of powder exerted somewhat  more force
upon  a large ball, than on a smaller one.
  Properties of a  Gun.—The essential properties of a  gun,
are  to  confine  the elastic fluid  as  completely as  possible,
and to  direct the  course of the  ball to  a rectilinear path ;
and hence  arises the necessity of an  accurate  bore.   The
windage, or space produced  by the difference of  diameter
between  the ball and the bore, greatly diminishes the effect of
the powder, by allowing a part  of the elastic fluid  to  escape
before the ball.   The advantage of a rifle barrel is chiefly de-
rived from the more accurate contact of the  ball with its cavity.
When the bore is twisted, it is  also supposed to produce a ro-
tation of the ball round  an axis, in the direction of its motion,
which renders it less liable to deviate from  its path on account
of  irregularities in the resistance of the air.   The usual charge
of  powder is one fifth, or one sixth of the weight of the ball;
and for battering, one  third.  When  a twenty four pounder is
fired  with two thirds of its weight of powder, it may be thrown
about four miles, the  distance being reduced by the resistance
of  the air, to about one  fifth of that, which it would describe if
thrown in a vacuum. *
   It is certain that  the grains of gunpowder do not inflame at
once, but that the inflammation ojccupies  time in  being commu-
nicated from one particle to another, so that they act success-
ively, rather than simultaneously, in  impelling the  ball.   This
circumstance contributes greatly to the safety of fire  arms,  for
if the whole charge  of  powder exploded  at once, the piece
would be in danger of bursting before the inertia of the  ball
* Young's Natural Philosophy, vol. i. p. 350, 
300     OF THE MOVING FORCES USED IN THE ARTS.

would  be overcome.  It is on  account of the suddenness of
their detonation, that the various  fulminating powders are inap-
plicable to use in fire arms.  The  bursting of a gun  may be
occasioned by the defective condition of  the metal, the dispro-
portionate amount of the charge, the adhesion and inertia of
the shot, or the inertia of some other body opposing the escape
of the  charge.  It is from this  last circumstance that a gun is
liable to burst, if fired with its muzzle under water.
   To enable gunpowder to exert its full  effect, the proportions
of the  cavity of the  piece, to the charge, should be such, as to
allow all the  grains to explode before they leave  the  cavity ;
and also to permit  the  elastic fluid to expend as much of  its
pressure as is capable of accelerating the ball.   The superiori-
ty of a musket over a pistol, arises from its prolonging the ac-
tion of the powder in this way.   But for reasons already  stat-
ed, there  are limits to the length of the barrel, which cannot
be usefully exceeded, and  these  have been nearly settled by
common practice.
  Blasting.—The splitting of rocks by gunpowder is perform-
ed by drilling holes  to a certain  depth, and inserting a charge
of powder at the  bottom.  The hole is then filled up by ram-
ming in fragments of stone, bricks, or other hard substances,
keeping in a steel wire, which is afterwards withdrawn to fur-
nish a  passage for the  priming by which fire is communicated
to the charge.  To prevent the danger of a  spark, copper wire
is often used instead of steel.  And to prevent the small  frag-
ments  from flying  about, it is found useful  to cover the rocks
with brush wood, or some other elastic substance.
   Rocks may be blasted at a# considerable  depth under water,
by  means of the  diving  bell, which enables workmen to  drill
and charge them in safety.  In the method practised at Howth,
in Ireland, after the charge is inserted, a tin tube is carried up
from the rock to the surface of the water.   It is kept empty
and made water tight by screwing the  joints to each other as
the bell ascends.   The powder is ignited by  dropping  pieces
of red hot iron through  the  tube, from a boat at the surface. 
OF THE MOVING FORCES USED IN THE ARTS.     301
When  the depth  exceeds twelve  feet, no danger or inconve-
nience is experienced by the boats, beyond a violent eruptive
ebullition of the water.
  Smeaton's Miscellaneous papers, 4to. 1814;—Robison's Mechani-
cal  Philosophy,  vol. ii.  and iii.;—Gregory's  Mechanics;—Brew-
ster's Ferguson's Mechanics;—Nicholson's  Operative Mechanic,
8vo.;—Parey's Treatise on the Steam Engine, 4to. 1827; this is the
most extensive work on its subject;—Tredgold on the  Steam En-
gine, 4to.  1828; this is the  most  philosophic work on the subject;—
Stuart on the Steam Engine, 8vo. 1824;—Partingdon on the Steam
Engine,  8vo. 1825;—Bossut Traits  Theoretique et Experimental df
Hydrodynamique, 1771;—Du Buat Traits d' Hydraulique, &c. 1786,
&c.;—Playfair's Outlines of Natural Philosophy, 8vo. 1819;—Ure's
Dictionary of Chemistry;—Works of Coulomb, Desaguliers, De
La Hire, Deparcieux, Hutton, Robins, Rumford, &c. 
CHAPTER  XIII.
               ARTS OF CONVEYING WATER.

   The employment of water as an agent for producing motion,
has  already been considered.  It remains to attend to the va-
rious modes by which this  fluid  may be  conveyed from one
place to another, either for, use in the arts, or for application to
the necessary  purposes of life.  The principal circumstances
which require  attention under this head are the following.  1.
The conducting of water from one place to another having the
same, or a lower, level.   2.  The raising of water to  a higher
level.   3. The projection of water through the atmosphere.

                  OF CONDUCTING WATER.

   Aqueducts.—When water flows in a current or stream, as in
rivers  or  canals, it does  so in  obedience to  gravitation, and in
consequence of the surface  being lower  at the  end  towards
which it is flowing, than  in that from which it proceeds.  Its
motions are governed by laws somewhat different from those of
solid  bodies descending upon  inclined  planes, and this differ-
ence  is owing to the  want of cohesion among the particles.
Instead of moving simultaneously,  the particles continually
change their relative position, so that while one portion of the
fluid  may be moving  rapidly,  another  may be stationary, or
even moving by an eddy  in a contrary direction.    The motion,
however, will continue both  in open  channels, and in properly
constructed pipes, until an equilibrium is produced, by  the sur-
face at both ends of  the channel, arriving at the same level.
Aqueducts are  artificial channels or conduits for the  convey-
ance  of water in a horizontal  or  descending direction.   The 
ARTS OF CONVENING WATER.
303
aqueducts constructed by the ancient Romans, were among
the most costly monuments  of their  arts.   Several  of these
were from thirty to a hundred miles in length, and consisted of
vast covered canals built of stone.   They were carried over
valleys and  level tracts of country upon arcades, which were
sometimes of stupendous height and solidity.  A similar meth-
od has been practised in some modern cities of warm or tem-
perate climates.
   In  colder latitudes, if the  course of the aqueduct is above
the ground, the water is liable to be interrupted by freezing in
winter.  It  has therefore  become  common to resort to subter-
ranean  passages for water, which  are  placed so deep as to be
below the reach of frost, and  are,  also, favorably situated both
for convenience and economy.  Culverts and drains which are
intended merely to remove and expend water, are usually made
of brick or stone ; but for conveying  water with the  smallest
expenditure by loss, water pipes are most frequently resorted
to.
   Water Pipes.—The pipes by which water is conveyed be-
neath the ground, are generally of small or moderate size, and
are intended  to be water tight.  In  consequence  of a well
known law  of fluids, a water pipe may possess any degree of
flexure, and any number of curvatures below the level of the
fountain head ; yet if it be not obstructed by air, or any other
internal obstacle,  it will rise at the discharging end,  and may
be delivered at the height of the original level. *   Pipes  for
transmitting water have been made  from  a great  variety of
materials.   It  is  desirable that they  should possess  strength,
tightness, and  durability, and that the material of which they
are composed, should  not be capable of contaminating the
water.   Wooden  pipes are commonly hollow logs, perforated
by boring through  their axis, and connected together by making
the end of one log conical, and inserting it into a conical cavi-

   * It appears that the use of water pipes was not unknown to the ancients.
Some  rules respecting the use of leaden and earthen pipes are given by
Vitruvius, de Architecture, Lib. viii. 
304
ARTS OF CONVEYING WATER.
 ty in the next.  When large trunks are required, they are com-
 posed of thick staves, and hoops, like a cask.  They  should,
 where practicable, be imbedded in clay, and buried at a greater
 depth  than the frost is  ever known to penetrate.  Wooden
 pipes,  are  in  common use  in this  country,  but  are liable to
 decay, especially  at the joints, where their thickness is smallest.
 In salt marshes they are more durable, though still liable to de-
 cay  from  the  attrition and decomposing effect  of the water
 within them.
   Iron pipes are at  the present day, considered  preferable to
 those of wood, being stronger and in most situations more dur-
 able.  They are  made of cast iron, with a socket, or enlarged
 cavity at one end, into which the end of the next pipe is re-
 ceived.  The joints thus formed are rendered tight, either by
 filling the interstices  with lead, or by driving in a small quantity
 of hemp, and filling  the remainder of the socket with iron ce-
 ment, made of  sulphur, muriate of ammonia,  and  chippings of
 iron.   Copper pipes are extremely durable, and  are made of
 sheet copper, with the edge turned up and soldered.   They
 require to be tinned  inside, on account of the poisonous char-
 acter of some of the  compounds, which are liable to be  formed
 in them.   Lead pipes' are much employed for small aqueducts,
 owing to the facility with which they can be soldered, and bent
 in any direction.   They  are commonly cast in short  pieces,
 and  afterwards elongated by drawing  them  through  holes, in
 the same manner  as wire.   Leaden pipes, in  general, are sup-
 posed not to contaminate the water contained  in them, because
 the carbonate of  lead, which is sometimes formed in them, is
 insoluble in water.  They are not safe, however, for  pumps
 and  pipes  intended to convey acid liquors.   Stone pipes pre-
 serve the water contained by them in a very pure  state. They
 are,  however, expensive, on  account of the  labor of working
them, with   the exception of soap stone, which,  being easily
shaped  and bored, may be usefully applied to the purpose of
conveying  water,  in those  places where it is  easily procured.
Earthen pipes  made of common pottery ware and glazed on 
ARTS OF CONVEYING WATER.
305
the inside, are sometimes used, but are more liable to be brok-
en than most of the other kinds.
  Friction of Pipes.—In a river, or open channel, it is observ-
able that the  water flows most rapidly in the  middle of the
upper surface, while it is most retarded at the  edges, and at
the bottom.   In like manner in a cylindrical pipe, the fluid has
the greatest velocity at the centre, or axis, and the smallest ve-
locity at the  surface,  or where it is in contact with  the pipe.
The force by which this retardation is occasioned, is common-
ly called friction.   It differs in many respects from the friction
of solids, and more resistance  is  occasioned by  the  internal
action of the  fluid particles upon each other, than by the con-
tact of the solid surface in which they  are contained.   The
investigation of the  laws which govern the movements of fluids
is  intricate, and the  results  of experiment have not  agreed
with the  previous conclusions of theory.   Various writers on
the science of hydraulics have treated this subject with an ex-
tensiveness of research, which can only be understood from
their  own works.   Among the more simple practical facts, to
which it is useful to attend, the following may be briefly stated.
1. The velocity of water  is  greater in a large pipe than in a
small one  having  the same  position, and hence a large pipe
will discharge more  water in a given time, than a number of
small ones having jointly the same capacity.   A pipe of two
inches diameter will give more water  than five pipes of one
inch diameter; it being ascertained that the squares of the dis-
charges are very nearly as the fifth powers of the diameters. *
2. Irregularities and  inequalities in the diameter of the pipe,
diminish the amount of water which they transmit, by altering
the direction of the particles, and by changing their velocity, so
as to renew the  resistance of inertia.   3.  In like manner  all
curves and angles, which occur in the pipe, have a similar retard-
ing effect, by creating new motions or counter currents.  4. The
form of the end of the pipe which communicates with the foun-
tain head, or reservoir, greatly affects the quantity of water re-
           "Robison's Mechanical Philosophy, vol. ii. p. 57S
               39 
30G
ARTS OP CONVEYING WATER.
ceived by it.  If it be gradually enlarged like a trumpet mouth,
a larger quantity of water will be received  than by any of the
modes which follow, because the direction given to the particles
by this form, is most favorable to their admission.  If the en-
trance to the pipe be abrupt, in consequence of the cavity  be-
ing wholly cylindrical,  the particles will have a tendency to
cross each other, and less  water will enter  the pipe in a given
time.  And if the end of the pipe projects  into the reservoir,
a variety of opposing forces will be produced among the parti-
cles moving toward the entrance, so that a smaller quantity
will be received by the pipe, than  in either of the preceding
cases.
   The form of the discharging orifice also influences the quan-
tity of water delivered by a pipe in a given  time.   If the end
of the pipe be enlarged,  by adding to it a frustum of a hollow
cone, the  amount of water discharged in some cases, may be
prodigiously increased. *   This fact, described by Venturi, ap-
pears to be the result of the pressure of  the  atmosphere, aided
by the inertia and cohesiveness of the water.
   Obstruction  of Pipes.—Water  pipes are liable  to  be ob-
structed,  chiefly by the  following  circumstances.   1.  By the
freezing of the water in winter, if the pipe has not been laid suffi-
ciently  deep.  2.  By the  deposition of sand and mud in the
lower parts of the pipe.   To obviate this, the water should
pass through a strainer before it enters the pipe.   And if plugs
are placed at the lower parts of the  bendings, then whenever
these are opened, the water rushes out with  sufficient  rapidity
and  carries the deposition with it.  3. By the  penetration of
roots, or the growth of aquatic  vegetables in the cavity of the
pipe.  This principally happens  in  wooden  pipes,  after they
begin to decay.   4. By the collection of air in the upper parts
of the bendings.  - This is a serious evil  and may take place
in all pipes which have an undulating course, or more vertical
curvatures than one.  When air is thus confined in the pipes,
the water will not rise to the same height at the discharging end,

    * See Edinburgh Encyclopedia, Art. Hydrodynamics, p. 194, 495. 
ARTS OF CONVEYING WATER.
307
as at the fountain head.   The air being the lighter fluid, tends
to occupy the highest part of the bendings.  Any pressure
applied at the fountain head  tends to push this air a little be-
yond the highest part, so as to make it occupy a portion of the
descending side of the  curve.   Of  course  the  sum of the
weights in the descending sides, will be less than the sum of the
weights in the ascending sides,  and  the  fluids will  not be in
equilibrium, except  when  the  water at  the  fountain head is
higher than that at the discharging end.   The conditions  upon
which this equilibrium is produced are the same as those which
sustain the fluid at different levels in Hero's fountain, the spiral
pump, and the  hydrostatic  lamp.
   The  prevention of this  evil consists  in  avoiding vertical
curves, and in laying the pipe, if possible, with an uninterrupt-
ed slope,  or at least with  only  one  slope in  each  direction.
When this is done, the air will escape, at one, or  both, ends of
the pipe.  But when vertical curves are  unavoidable, an  open
tube, the height of which is equal to that of the fountain head,
should be attached to the highest  part of  the curve.   By this
arrangment  the air  will readily escape.   In like manner if a
tight air box be fastened upon the  upper part of the curve, and
filled with water, the air will escape into this box and displace
the water, without interrupting the current in the pipe.   The
air box may be made to regulate  itself,  and to discharge the
air when it is full, by means of a  valve in the top connected
with  a floating,  hollow  copper ball.   As the  air increases, the
copper ball  will subside with the water, till it opens the valve
for the air to escape.   In Fig. 1, A B represents  an undulating
                        D  Fig.  1.     c           A
B 
308
ARTS OF CONVEYING WATER.
pipe, of which A is the  fountain head  and B the  discharging
end.  The water and air will arrange themselves as represent-
ed by the darker and lighter parts of  the  tube, and being in
equilibrium, no water will be discharged.   If an upright tube,
C, be attached to either of the upper flexures, it will discharge
the air from that flexure.   Or if a tight box, or vessel, D, be
substituted, with a copper float and valve, it will have a similar
effect.  Simple punctures  made in the upper part of the pipe
also answer a temporary purpose.
   Syphon.—The  syphon may be regarded  as  an instrument
for the lateral  conveyance,  rather than the  raising of water,
since the fluid must always be delivered at a lower level, than
that at which it is received.  Thfe syphon is a bent tube, of
which one extremity, or leg, is longer than the other.  If the
shorter leg  be inserted  in a fluid,  and the air  be exhausted
from  the  longer leg, by suction or otherwise, till the syphon is
full of water,  then the  column of fluid in the longer leg will
preponderate,  and a current will take  place.  This will  con-
tinue either till the water in the feeding vessel sinks below the
end of the syphon, or that in the  receiving vessel rises to the
same height with the other.   As the movement  depends upon
the pressure of the atmosphere,  water cannot be raised in a
syphon to a greater height than 34 feet.
   For practical use the longer leg of the syphon is often  clos-
ed with a stop cock, and the air  exhausted from it by a small
pump, till the leg is full.  The stop cock is  then opened, and
the fluid immediately flows through the syphon.

                    OF RAISING WATER.

   The lateral conveyance  of water is effected in the modes
already described, by the aid of its own gravity.   The raising
of water is effected against gravity, by the employment of some
moving force.  Hydraulic machines for raising water, may be
impelled by a current, or  fall,  of the  water itself, or by any
other moving agent.  Among a great variety of machines which 
ARTS OF CONVEYING WATER.
309
have been constructed for this use,  the  following are some of
the most noticeable.
   Scoop  Wheel.—If a water wheel is provided with a hollow
axle, and if in the place of spokes, or radii, it is-furnished with
crooked tubes, or cavities, of a suitable curvature, it will raise
water to the height  of  its own axis, whenever it revolves in the
direction of the mouths of the tubes.  Each spoke, or  curved
tube, as it dips its extremity in the water, lifts a certain  portion
of the  fluid, and as the  revolution continues, this water  will
flow through the tube approaching   .      Fig. 2.
nearer  to the axis, until it is dis-
charged into the central hollow.  To
prevent the water from regurgitating,
the inner ends of the tubes must be
guarded by valves,  or else  made to
project for a  short distance into the
central cavity, as seen at A in Fig. 2.
In the  latter case it is necessary «that
they should enter at # different dis-
tances  from  the end of  the  axle.   The  axle may also be di-
vided  into as many longitudinal compartments, as  there are
tubes in the wheel.   This was done in the ancient tympanum,
a machine described by Vitruvius, which was somewhat similar
in its principle to the scoop wheel.
   Persian  Wheel.—The  Persian wheel, in certain respects,
resembles the scoop wheel, and is sometimes combined with it
in the same machine.  It differs from it in its effect, by raising
the water through the whole diameter of the wheel.  Its form
is easily understood,  by supposing a number of buckets to be
hung round the circumference of a  water wheel, upon pivots,
at equal  distances.   As the wheel turns, the buckets are suc-
cessively immersed in the  water  at the bottom, and filled.
They  then pass upwards till they arrive at the top of the wheel,
where they strike a fixed obstacle and are overset, discharging
their water into a trough placed at the top to receive it.  This
machine is said to be in  common use in several of the Oriental
countries.
 
310
ARTS OF CONVEYING WATER.
  Noria.—The machine used  in Spain  under the name of
noria,  consists  of  revolving buckets like  the Persian wheel.
But instead of a single wheel, two drums,  or trundles, are em-
ployed, and the buckets are attached to ropes or chains passing
round  them.   In  Spain, earthen pitchers are said to be used,
but in other countries wooden buckets are employed, like those
of an overshot wheel.   A  sufficient idea of the form of the
noria may be obtained by inspecting the figure of the  chain
wheel on page 260, and supposing the motion reversed.
  Rope Pump.—Instead of a series of buckets connected by
ropes or  chains, a similar effect is sometimes  produced by a
simple rope, or a bundle of ropes, passing over a wheel above,
and a pulley  below, moving with a velocity  of about 8 or 10
feet in a second, and drawing up a certain  quantity of water by
its friction. It is probable that the water commonly ascends with
about half the velocity of the rope.  While the water is prin-
cipally supported by the friction of the rope,  its own cohesion
is sufficient to prevent it from wholly falling, or being scattered,
by any accidental inequality of the motion.  The portion raised
is collected in a trough at  the top.
  Hydreole.—This name is given by M. Mannoury  Dectot, to
an invention for raising water by the admixture of atmospheric
air.  If a  column of water be  intimately mixed with air in
small bubbles,  the air will occupy some time in ascending to
the surface, and the mean while the collective specific gravity
of the  whole  column will be much less, than if it consisted of
water  alone.   If a vertical tube be placed in a reservoir of
water,  and if  a quantity of air be injected into the bottom of
the tube, by a bellows, or  forcing pump, the  water in the  tube
will immediately rise to a higher level, and remain until the air
has escaped at the top.  And if the tube be  of proper height,
the water will overflow in the same manner as it does during the
ebullition of boiling liquids.  This appears, however, not to be
a very economical mode of applying force.
  Archimedes' Screw.—This name is given to a machine form-
ed by one  or more  pipes wound spirally round a cylinder which 
                ARTS OF CONVEYING WATER.            311

revolves on an axis in an oblique situation.   It is used in some
places under the name of water snail.   Its mode of operation,
may be easily  conceived, by supposing a tube,  formed into a
hoop, to be rolled up an inclined plane, in which case the fluid
would be forced, by the elevation of the tube behind it, to run
as it were up  hill.   The  screw  is         Fig, 3,
usually turned by a water wheel. Dur-
ing each revolution the lower end of
each spiral tube is immersed in the
water and dips  up  a certain quantity.
This water, by its gravity,  keeps to
the lower side of the screw, as seen
in Fig. 3, but  at the  same  time,  in
consequence  of the  revolutions  of   =—-^=~=------
the screw, it passes  continually upward until it is delivered  at
the highest end.
   This instrument is sometimes made-by fixing a spiral parti-
tion round a cylinder, and covering it with an external coating,
either of wood or of  metal.  It  should be so placed with  re-
spect to- the surface of the water, as to fill in  each turn one
half of a convolution ; for when the orifice  remains always im-
mersed, its effect is much diminished.  It is  generally inclined
to the  horizon in an  angle  of between 45 and 60 degrees;
hence  it is obvious that its  utility is limited  to  those cases in
which  the water  is only to be raised to  a  moderate  height.
The spiral is seldom single, but  usually consists of three  or
four separate coils, forming  a screw which rises more  rapidly
round  the cylinder.
   A water screw which  operates in a similar manner, may be
made by a spiral partition  wound upon a central axis, and re-
volving by itself within a smooth hollow cylinder, to the cavity
of which it is nearly  fitted.   In this form, however, there is
some loss by the leakage  between the screw and the cylinder
which contains it.
   Spiral Pump.—This machine  is  formed by a spiral pipe
consisting of many  convolutions,  arranged  either in a single
 
312
ARTS OF CONVEYING WATER.
plane, as in Fig. 4, or in a cylindrical or       Fig. 4.
conical surface,  and revolving round  a
horizontal  axis.  The pipe is connected
at  one  end, by a  central water  tight
joint, to an ascending pipe, while the oth-
er end receives,  during each revolution,
nearly equal quantities of air and water. It
was invented about 1746, by AndrewWirtz, =
a pewterer at Zurich, whence it is often called the Zurich ma-
chine.   It is  said to have been used  with great success at Flo-
rence, and in Russia.  Dr Young states that he has made use
of  it for raising water to a  height of forty  feet.   The end of
the pipe is furnished with a spoon, containing as much water as
will fill half of one of its  coils.  The water  enters the pipe a
little before the spoon has arrived at its  highest situation, the
other half remaining  full of air.   The air communicates the
pressure of the column of water to the preceding  portion, and
in this manner the effect of nearly all the water in  the wheel is
united, and becomes capable of supporting the column of water,
or of water  mixed with air, in the  ascending pipe.  The air
nearest the joint is compressed into a space much  smaller than
that which it occupied at its entrance, so that where the height
is considerable, it becomes  advisable to admit a larger portion
of  air than would naturally fill half the coil.   This lessens the
quantity of water raised, but it lessens also the force required to
turn the machine.   The joint should be conical, in order that
it may be tightened when it becomes loose, and  the pressure
ought to be removed from it as much as possible.  The loss of
power,  supposing the machine well constructed, arises  only
from the friction of the water  on the pipes, and the friction of
the  wheel on its axis; and where a large quantity of water is
to be raised to a moderate height, both of these resistances may
be rendered inconsiderable.  But when the height is very great,
the  length of the spiral must be much  increased, so that the
weight of the pipe becomes extremely cumbersome, and causes
a great friction on the axis, as well as  a strain on the machinery.
 
ARTS OF CONVEYING WATER.
313
   Centrifugal Pump.—The centrifugal force, has sometimes
been employed, in conjunction with the pressure of the atmos-
phere, as an immediate  agent in  raising water, by means of a
rotary  pump.   The machine called a centrifugal  pump, con-
sists of a vertical pipe, capable of revolving round  its axis, and
connected  above with a horizontal  pipe, which is open at one,
or at both ends,  the whole being  furnished with proper valves
to prevent the escape of the water, when  the machine  is at
rest.   As soon as the rotation becomes sufficiently rapid, the
centrifugal force of the water in the horizontal pipe causes it
to be discharged  at the ends, its place being supplied by means
of the pressure  of the  atmosphere on  the  reservoir below,
which forces the water to ascend through the vertical pipe.  This
machine may be so arranged, that, according to theory, very lit-
tle of the force applied is lost; but it         Fig. 5.
has failed of producing  in  practice a
very advantageous effect.   In Fig. 5,
a  centrifugal  pump is represented.
The machine is first filled with water
through the funnel A, while the valve
at D prevents the water from descend-
ing.  The whole is then made to turn
rapidly, and  the water is discharged
from the ends of the horizontal part,
into a circular  trough, a  section of
which  is seen at  B and C.
   Common Pumps.—A pump is a machine so well  known,
and so generally  used, that the  denomination has sometimes
been extended to hydraulic  machines of all kinds.   The term,
however, in its strictest sense, is to be understood of those ma-
chines, in which  the water is raised by the motion  of one solid
within  another, and this motion is usually alternate, but some-
times continued,  so as to constitute a rotation.  In the pumps
most commonly used, a cavity is  enlarged and contracted by
turns, the water  being  admitted into it through one valve, and
discharged  through another.
              40
363480 
314
ARTS OF CONVEYING WATER.
   The common household pump has otherwise been called the
sucking pump, from the circumstance that the water is raised
in it, by  the  pressure  of the atmosphere.   In this country,
pumps are made for common use,  both in wells, and in ships,
by boring logs so as to  produce a large hollow, and inserting
two hollow wooden plugs called boxes, at different heights, both
of which  are  furnished with valves, or clappers, opening  up-
wards.  The  lower box is made stationary,  and   Fig. 6.
serves merely to prevent the water which is rais-
ed, from running back.   The upper box is a hol-
low  moveable  piston, attached by  its rod to the
handle or brake, of the pump.  When the pump
is full of water, every stroke of the  handle raises
this box, together with the column of water above
it.   When the handle is lifted, the box is pushed
further down into the water, while its valve opens
to allow the water  to pass through.  In Fig. 6,
this pump is represented with the box just begin-
ning to descend.  The  valve then shuts, and the
second stroke of the pump raises another column
of water to the  spout.  As  the  action of this pump depends
upon the pressure  of the atmosphere, water cannot be raised
by it from a depth of more than 34 feet below the upper valve,
and in practice a much shorter limit is commonly assigned.
  Forcing Pump.—The  forcing pump  differs    Fig. 7. b
from the common sucking pump just described,
in having a solid piston without a valve, and the
spout, or discharging orifice,  placed below the
piston.  When the  piston is  raised, the lower
valve of the pump  rises and  admits the water
from  below, as in the common pump.  But
when the piston is depressed, the water is thrown
out through a spout in the side, which has a
valve opening  outward, at a, in Fig  7.  In a
forcing pump  the water  cannot be brought from
a depth of more than 34 feet below the piston,
but it can  afterwards be sent up to any height
 
ARTS OF CONVEYING WATER.
J5IO
desired, in a pipe a b, because the pressure communicated by
the downward  stroke of the piston, is not dependent on the
pressure of the atmosphere, but upon the direct force applied
to the piston.
   Plunger  Pump.—A  very effectual  pump for raising a
large  quantity of water to a small height, is shown in Fig. 8.
                          Fig.  8.
It is made by fitting two upright beams or plungers, A and B,
of equal thickness throughout, into cavities nearly of the same
size, allowing them only room to move without friction, and
connecting the plungers together by a horizontal beam moving
on a pivot.  The water being  admitted, during the ascent of
each plunger, by a large valve  in the bottom of the cavity, at
C and D ; it is forced,  when the plunger descends, to escape
through a second valve at E or F, in the side  of the  cavity,
and to ascend by a  wide pipe to the top of the machine.   The
plungers ought not to be in any  degree tapered, because in this
case a  great force would  be unnecessarily consumed, when
they descend,  in throwing out the  water,  with  great velo-
city, from the  interstice  formed  by their  elevation.    This
pump  may be  worked by a laborer  walking  backwards and
forwards,  either on  the beam, or on a board suspended below
it.  By means  of  an apparatus  of  this kind, described by
Professor Robison,  an active man, loaded with a weight of 30
pounds, has been  able to raise 580 pounds  of water every
minute, to a height  of 11£ feet, for  ten  hours a day,  without
�...�:.:..C 
316
ARTS OF CONVEYING WATER.
fatigue.  This, says Dr Young, is the greatest effect produced
by a laborer that has ever been correctly stated by any author;
it is equivalent to somewhat more than 11 pounds raised through
10 feet in a second, instead  of  10 pounds, which is a fair esti-
mate of the usual force of  a man, without any deduction for
friction.
   Delahire's Pump.—A pump, partaking of the nature of a
forcing and  a sucking pump, is  sometimes called amzedpump.
In Delahire's pump, which  is of this kind, and    Fig. 9.
shown in Fig. 9, the same  piston  is made to
serve a double  purpose, the rod working  in a
collar of leathers, and the water being admitted
and  expelled in  a similar  manner, above  and
below the piston, by means  of a double appar-
atus of valves and pipes.  When the piston is
depressed,  the  water enters the  barrel at the
valve   A, tind  goes out at B.    When  the
piston is elevated, it enters  at C, and  escapes
atD.
   For forcing pumps of all kinds, the common piston, with a
collar of loose  and  elastic  leather, is preferable to  those of a
more  complicated structure.  The pressure of the water on the
inside of the leather makes  it sufficiently tight, and the friction
is inconsiderable.  In some  pumps the leather is omitted, for
the sake  of  simplicity, the loss of water being compensated by
the greater  durability of the pumps ;  and this loss will be the
smaller in proportion as the motion of the piston is more rapid.
   Hydrostatic Press.—This powerful  machine is essentially a
forcing pump, aided in its action by the well known  properties
of hydrostatic pressure.  It appears to have been invented by
Pascal, previously to 1664, and recommended by him as a new
mechanical  power.  It was, however, practically lost sight of,
till it was reinvented by Mr Bramah, more than a century af-
terwards.  In this press the water is forced, by a small pump,
into a strong iron cylinder,  in which it acts on a much  larger
piston; consequently this piston is urged by a force as much
 
ARTS OF CONVEYING WATER.
317
greater than that which acts on the first        Fig. 10.
pump rod, as its surface is greater than         nTiil—
that of the small one.  In Fig. 10, the
water is forced by the pump A through
the pipe B, into the cylinder C, in
which it acts very powerfully upon the
large  piston D, and raises the bottom
of the press E.  The upward force,
by which the material above E is com-
pressed, exceeds the force which is applied  to the pump, as
much as the surface of the piston D, exceeds  that of the piston
of the pump.   In practice, the cylinder C requires to be made
much thicker than here  represented.
   Lifting Pump.—Where the height through which the water
is to be raised is considerable, some inconvenience might arise
from the length of the barrel through which the piston rod of a
sucking pump  would have to  descend, in order that the piston
might remain within the limits of atmospheric pressure.   This
may be avoided by placing the moveable valve below the fixed
valve, and introducing  the piston at the bottom of the bar-
rel.   It is then worked by means of a frame on  the  outside.
Such a machine  is called a lifting  pump.   In common with
other forcing  pumps, it has the disadvantage of thrusting the
piston before  the rod,  and thus tending to bend the rod, and
produce an unequal friction on the piston, while, in the sucking
pump, the principal force always tends to straighten the rod.
   Bag Pump.—A bag of leather has  sometimes  Fig.  11.
been employed for connecting the piston  of a
pump with the barrel, and in this manner nearly all
friction is avoided.  It is probable, however,  that
the want of durability would be a great objection to
such a machine.  In  Fig.  11, A  represents a
leathern bag   attached  to a  number  of hoops.
This bag is alternately extended and contracted,
like a bellows, by every stroke of the piston,  and   ]HJ
raises the water without  friction  against  the    ||
pump.
 
318
ARTS OF CONVEYING WATER.
  Double acting Pump.—The rod of a  sucking  pump may
also be made to work in a collar of leather at the top, as at A
in Fig. 12, and the  water may be forced  through   Fig.  12. B
a valve  into an ascending pipe B.   By  applying
an air vessel to this, or to any other forcing pump,
as is done in fire engines, its motion may be equal-
ized, and its performance improved ; for if the ori-
fice be large enough, the water may be forced into
the air vessel, during the stroke of the pump, with
any velocity that may be required, and  with  little
resistance from friction ; whereas the loss of force,
from the frequent accelerations and retardations of
the whole body of water, in a long pipe, must always be consider-
able.  The condensed air, reacting  on the water, expels it
more gradually, and in a continual stream, so that the air ves-
sel has an effect analogous to that of a fly  wheel in mechanics.
  Rolling Pump.—A  pump of this
kind is formed by a barrel, or hollow
cylinder, shown in section in Fig. 13,
having two partitions.  One of these,
A B is fixed,  and  the other  C D, is
composed  of two  wings,  or  valves,
capable of an alternate  motion about
the axis of the cylinder.    When the partition C D turns in one
direction, the water  in  the cavity C is driven out at the ori-
fice a, and will rise in a pipe attached to that orifice.  At the
same time the  water in the cavity D is forced out at the ori-
fice d.   While this is taking place, fresh portions of water en-
ter the  remaining cavities at w and z. When  the partition CD
has moved as far as possible, it then returns in the opposite di-
rection and drives out the water through y and x, and receives
fresh water through b and c.   The orifices which receive  the
water have valves opening  inward, and those which discharge
it have  valves opening outward.   The  machine is worked by
arms attached to the axis of the cylinder, which for this pur-
pose projects through a collar in the ends  of the vessel.
 
ARTS OF CONVEYING WATER.
319
  For the sake of simplicity, a sector of a cylinder, is some-
times used, in which case a single partition, or valve, like a door
on hinges, traverses the whole cavity, and only half the  number
of orifices  are  necessary, to admit and discharge the water.
Fire engines, for projecting  water, have been constructed  in
both these methods by different inventors.
  Eccentric Pump.—The  eccentric pump,
a section of which is shown at Fig. 14,
consists of a hollow cylinder a d, in the in-
terior of which a solid  cylinder  b, of the
same length, but of about half the diameter,
is made to revolve, by its axle passing through
water tight collars in the ends of the exterior
cylinder.  The internal cylinder is so plac-
ed,  that its surface  comes in contact with
some part of  the  internal surface of the
larger cylinder.  The surface of  the  small
cylinder, is  also furnished  with  four large valves> or flaps,
turning on hinges, and partaking of its own curvature, so that
when they are shut down,  they form no projections, but appear
as  parts of the  same  cylinder.   These  valves are made to
open by springs or otherwise, so that when  one of  them  is
brought by the revolution of the internal cylinder into  the nar-
rowest  part of the internal space, it is pressed down and shut;
but as the inner cylinder moves on, the valve  being gradually
carried  forward, will  continue to open until  it arrives at the
widest  part of the cavity.   It is  then pressed down again by a
 continuation of the revolution.   In this way the water behind
 the valve is drawn up from the feeding pipe by the atmospheric
 pressure, while that before the valve is forced  upward into the
 delivering pipe.  As  each  of the  valves performs the same
 operation  in  its turn, this pump affords a constant supply of
 water.
    Rotative  steam engines have  been constructed by different
 projectors, on the principle  of this pump,  as  well as  the
 following. 
320
ARTS OF CONVEYING WATER.
   Another form of an eccentric pump, is seen     Fig.  15.
in Fig.  15.   The roller, or solid cylinder, A,
revolving within the reservoir, or hollow cy-
linder, B F, carries  with it the slider, D E,
which is made to sweep the internal surface
of this cylinder by revolving in the direction
from  C to F,  so that the water is drawn up
by the pipe C, and discharged by the pipe F.
   An objection to all pumps of this  sort, is, that if they  are
made tight enough to hold water, they occasion a great degree
of friction on  account of the extensive contact of the  moving
surfaces.   The continual change,  also, which takes place, both
in the  direction  and velocity  of  the  water,  is productive of
great resistance from inertia.  The  stream at the  delivering
orifice, although never  wholly intermitted, is by no means uni-
form  in its velocity.
   Arrangement of  Pipes.—The  pipes, through which wa-
ter is raised, by  pumps of  any  kind, ought  to be as short
and as straight as possible.  Thus, if we have  to raise water to
a height of 20 feet, and to carry it to a horizontal  distance of
100,  by means of a forcing pump, it will be more advanta-
geous to raise it first vertically into a cistern 20 feet above the
reservoir, and then  to let it run along  horizontally, or find its
level  in a bent pipe,  than to  connect  the pump immediately
with a single pipe, carried to the place of its destination.   And
for the same reason a sucking pump should be placed as nearly
over  the well as possible, in order to  avoid a loss of force in
working it.  If very small pipes are used,  they will much in-
crease the resistance, by the friction which they occasion.
   Chain Pump.—Water has sometimes been  raised by stuffed
cushions, or by oval blocks of wood, connected  with an endless
rope,  or chain, and caused, by means of two wheels, or  drums,
to rise in succession in the same barrel, carrying the water in a
continual  stream before them.  The  magnitude, however, of
the friction, appears  to be an objection to this method.   From
the resemblance of  the  apparatus to a string  of beads, it has
 
ARTS OF CONVEYING WATER.
321
been  called a bead pump,  or paternoster work.   When flat
boards are  united by chains,  and employed instead of these
cushions, the machine has been denominated a cellular pump ;
and in this case the barrel is usually square, and placed in an
inclined position.   There is, however a considerable loss from
the facility  with  which the  water  runs back.   The chain
pump, used in  the navy, is a pump of this kind, with an upright
barrel, through which leathers, strung on a chain, are drawn in
constant succession.  These pumps are only employed when a
large  quantity  of water is to be raised, and they must be work-
ed with considerable velocity in order to produce any effect at all.
   The Chinese work their cellular pumps, or bead  pumps, by
walking on bars which  project from the axis of the wheel, or
drum that drives them, and whatever objection may be made
to the choice of the machine, the mode of communicating mo-
tion to it must  be allowed to be advantageous.
   Schemnitz Vessels, or Hungarian Machine.—The mediation
of a portion of air,  is employed  for raising water, not only in
the spiral pump, but also in the air vessels of Schemnitz, in the
manner shown in Fig. 16.  A column of water,    Fig. 16.
descending  through a pipe C, into a closed re-
servoir, B, containing air, obliges the air to act,
by means of a pipe D, leading from the upper
part of the reservoir or air vessel, on the water
in a second  reservoir, A, at  any distance either
below or above it, and forces  this water to as-
cend  through  a third  pipe, E,  to any height
less  than  that of the first  column.   The air
vessel is then emptied, the second   reservoir
filled, and the whole operation repeated.  The
air must,  however, acquire a density, equivalent
to the pressure, before it can  begin to act;  so
that if the height of the columns were 34 feet, it must be re-
duced to  half its dimensions before any water would  be raised;
and thus  half of the  force would  be  lost.   But  where  the
height is small, the force lost in this manner is not greater than.
              41
 
322
ARTS OF CONVEYING WATER.

that which is usually spent in overcoming friction, and other
imperfections of the machinery employed ;  for the quantity of
water, actually raised by any machine, is not often greater than
half the power which is consumed.  The force of the tide, or
of a river rising  and falling  with  the tide, might easily be ap-
plied by a machine pf this kind, to the purpose of raising water.
Thus if at low  tide the vessel  A was filled with air, then at
high tide the water flowing down the tube E, would cause  the
water in the vessel B to  ascend in the pipe C.
   Hero's Fountain.—The  fountain of Hero, precisely  resem-
bles in its operation, the  hydraulic vessels of Schemnitz, which
were probably suggested to their  inventor by the  construction
of this fountain.  It may be used  simply to raise water, or to
project it upwards in the form of a jet, as in Fig.    Fig.  17.
17.   The  first  reservoir C of the fountain  is
lower than the orifice of the jet.   A pipe de-        i^i
scends from it to the air vessel, B, which is at        k
some distance below, and the  pressure of the       '\\
air is communicated, by an ascending tube, D,  \ E\
to a third cavity, A, containing the  water which A.
supplies the jet.  In this form of the machine, the
water will continue to spout from  the  pipe E, J>
until all the water in the reservoir C, has de-
scended  into the  vessel B.   The principle of
Hero's fountain  has been  applied  to raise  oil
in lamps, and one of its  most simple forms  has already been
described under the head of hydrostatic, lamp, page 179.
   Atmospheric  Machines.—The  spontaneous  vicissitudes of
the  pressure of  the air,  occasioned by changes in the  weight
and temperature of the  atmosphere,  have  been  applied by
means of a series of reservoirs, furnished  with proper  valves,
to the purpose of raising water by degrees to a moderate height.
But it seldom happens that such changes are capable of pro-
ducing an elevation in the water of each reservoir of more than
a few inches, or at most  a foot or two, in a day; and the whole
quantity raised, must therefore be inconsiderable. 
ARTS OF CONVEYING WATER.
323
  Hydraulic Ram.—The  momentum of a stream  of water,
flowing through a long pipe, has also been employed for raising
a small quantity of water to a considerable  height.  The pas-
sage of the  pipe being  stopped by a valve, which is raised by
the stream, as  soon as its motion  becomes  sufficiently rapid,
the whole column of fluid must necessarily concentrate its ac-
tion  almost instantaneously  on the  valve.  In  this  manner
it loses the  characteristic property of hydraulic pressure, and
acts as if it were a single solid; so that, supposing the pipe to
be perfectly elastic, and inextensible, the impulse may  over-
come any pressure however great,- that might be opposed to it.
If the valve opens into a pipe leading  to an  air  vessel, a
certain quantity of the  water will be forced in, so as to con-
dense the air,  more or less rapidly, to the  degree that may be
required  for raising a portion of the water contained in it, to a
given height.   Mr Whitehurst  appears to have been the first
that employed this method ; it was afterwards improved by Mr
Boulton  ; and the  same machine has attracted much  attention
in France under the denomination of  the hydraulic ram of M.
Montgolfier.
   Fig. 18 represents this machine.   When the  water in  the
                         Fig. 18.
                                             E 1
pipe A B has acquired sufficient velocity, it raises the valve B,
which immediately stops its further passage.  The momentum
which the  water has acquired will then force a portion of it
through the valve C into the air vessel D.  The condensed
air at D, causes the water to rise into  the pipe E, as long as
the effect of the horizontal column continues.  When the water
becomes quiescent, the valve B will open again by  its own 
324
ARTS OF CONVEYING WATER.
weight, and the current will be renewed, until it acquires force
enough to shut the valve, and repeat the operation.

                   OF PROJECTING WATER.

   If a degree of force, or pressure, be applied to water suffi-
cient to raise  it through a tube to a given height, the same
force would also cause it to spout through an orifice, in a con-
tinued  stream, or jet, to nearly  the  same  height, in common
cases.  The  height, however, can never be fully as great, for
various reasons.   One of these is found in the friction of the
ajutage, or  discharging orifice, which acts as a retarding force.
Another  obstacle is the resistance  of the  atmosphere, which
increases in a rapid ratio, as the velocity of the water becomes
greater, and which is also greatly augmented as the water di-
vides, and  spreads out a greater surface to the resistance of
the air.   A third obstacle consists in the resistance which the
water offers to itself.   The parts first projected, being constant-
ly retarded  in their ascent by gravity and  atmospheric resist-
ance, oppose the progress of the  parts which are last projected,
and which  have the  greatest  velocity.   And as fluids  move in
all directions, this impulse of different parts of the water against
each other, tends to widen, and  consequently to shorten the
column.  In a vertical jet, moreover, the weight of the falling
water opposes the ascending column,  and hence a fluid will
spout higher,  if the jet be turned a little to one side, than if it
be perpendicular.
   Fountains.—Artificial fountains which throw a perpetual jet
of water, usually act by the  pressure of a reservoir of water,
situated at a greater height than that of the jet produced.  The
water is conveyed from the reservoir to'the place of the foun-
tain, in pipes, and if the orifice from which it issues be  directed
upward, it will spout to a height approaching that of the reser-
voir.   It will always, however, fall  short of this height, for the
reasons already stated ;  and the difference will be greater in
jets  of great  height, than it is in lower  ones; since it  is found 
ARTS OF CONVEYING WATER.
325
by experiment, that the differences between the heights of the
jets and of the reservoirs, are as the squares of the heights of
the jets themselves. *   Fountains are chiefly used for purposes
of ornament, and  when of large size require to be fed  from
the elevated parts of rivers, or bodies of water having a high
level.   At Peterhoff, in Russia, there are two  fountains which
spout a column of water 9 inches in diameter, to the height of
sixty feet, and the fall of the returning water produces a concus-
sion sufficient to shake  the ground.
   Fire Engines.—The engines used for extinguishing fires in
buildings,  are in effect a  species of forcing pumps, in which
the water is subjected to pressure sufficiently strong to  raise it,
by a jet or otherwise, to the required height.  But if the forc-
ing pump were used  alone, the water would  issue only in in-
termitting jets, in consequence of the reciprocating motion of
the pump,  and thus a great part of it would become ineffectual.
In order to make the  discharge uniform,  and thus keep up a
continual stream, a strong vessel filled with air, is attached to
the engine.  Into this vessel the water is forced by the  pumps,
and as the air cannot  escape, it is  condensed  in proportion as
the  water accumulates, until it reacts upon the surface of the
water  with great power.   If the air be condensed into  half the
space  which it originally  occupied, it will  act upon the water
with a pressure  equal to that of two atmospheres, and will be
adequate to raise water through a tube  to the height of 33 feet,
or to project  it  through  the atmosphere  to nearly the  same
height.  When the air is condensed to one third of its former
volume, in consequence of the air vessel being two thirds filled
with water, its elasticity will be three times greater than that of
the  atmosphere.  It will therefore  raise water in a tube to the
height of 66  feet, and would throw it to nearly the same height
were it not for the  resistances,  which have already been ex-
plained.
   The foregoing principle of the fire engine has been variously
modified, by adapting different kinds of pumps to the  air ves-
* Ascertained by Mariotte.  Bossut, Tom. ii. § 615. 
326
ARTS OF CONVEYING WATER.
sel, and by altering various details.   In the  engines of New-
sham and others, two cylinders, constructed like forcing pumps,
are worked by the  reciprocating  motions of  transverse levers,
to which  the  handles  are  attached.   In this way the water is
f6rced into  the air vessel, from which  it afterwards spouts
through a moveable pipe.  In some  other engines a single cy-
linder is used, the piston rod passing through a tight collar, as
it  does in  Watt's  steam  engine,  thus alternately receiving
and expelling the water at each end of the cylinder.  In Rown-
tree's engine, and some others, a mechanism is used like that of
the rolling pump, a part of the inside of a cylinder being trav-
ersed by a partition like a door hinged upon the  axis of the
cylinder, which  drives the water  successively from each  side
of the cylinder, into the air vessel.
   A long, flexible  tube, made of leather, and known among
firemen by the name of hose, is of great use in carrying the
spouting orifice near to the flames, and thus preventing the wa-
ter from being scattered too soon.   It also serves an important
purpose in bringing water from  distant reservoirs, by suction
created in the pumps of the engine.
   Throwing  Wheel.—A throwing wheel, otherwise  called a
flash  wheel, or fen wheel, is used  for  raising water, both by
lifting and projecting it.  Its structure resembles that of an un-
dershot water wheel, or more properly of a breast  wheel.   Its
under surface is received in a trough or channel, which curves
upward.   When the wheel is  made to revolve, it drives the
water before it,  and throws it out from the trough at a consid-
erable elevation.   These wheels are used for draining ponds,
marshes, he, and are turned by windmills, or  any other power.
If their movement is slow, they simply lift the water, and cause
it to overflow at the end of the trough.   But if they revolve
with much velocity, they are capable of throwing the water to
a still higher level. 
ARTS OF CONVEYING WATER.
327
  Robison's  Mechanical Philosophy, Articles Theory  of Rivers,
Water Works, &c.;—Gregory's Mechanics, vol. i.;—Young's Nat-
ural Philosophy, vol. i.;—Bossut  Traits Theoretique et Experimental
oV Hydrodynamique, 1771, &c;—Du Buat  Traits d' Hydraulique, et
Pyrodynamique, 1786, &c;—Venturi, RScherches Experimentales sur
les Fluides, 1797;—Rees's  Cyclopedia, article  Water;—Edinburgh
Encyclopedia, article Hydrodynamics;—And the Hydraulic Works of
Mariotte, Guglielmini,  Michelotti, D. and J. Bernoulli, D'
Alembert, Fontana,  M. Young, Prony, Vince, Juan,  Eytel-
wein, &c. 
CHAPTER  XP7.
      ARTS OF DIVIDING AND UNITING SOLID BODIES.

   Cohesion.—The  attraction of  cohesion,  which retains to-
gether the particles of solid bodies, is the foundation of  their
strength.   It exists in all solids, though  in different  degrees ;
and requires, before it can be overcome, the application of force
or of art, adapted to the strength and character of the particu-
lar body.  In some substances, cohesion, when once overcome,
cannot be reproduced in its original  state.   In others it  may
be restored by the intervention of fluidity, and in all, its effects
may be imitated by  mechanical arrangements.  The various
modes by which bodies may be divided, or united,  have an im-
portant agency in mechanical constructions, and other processes
of art.

                    MODES OF DIVISION.

   Fracture.—The simplest and least artificial mode by which
mechanical  division  is effected, is by breaking.  The  circum-
stances whieh influence the production of fracture by extension,
compression, lateral strain, and  torsion, have  been  considered
in the second chapter of this work.   In general, a  force acting
suddenly is more liable to occasion fracture, than one which
acts more gradually ; for in  this  case the parts  which  are first
strained may give way, before the  stress is proportionally dis-
tributed  among  the  remaining parts.   A mass of  plastic clay,
or of warm sealing  wax, will  bear to be gradually bent,  but
will break if the motion is sudden.   In like manner percussion
occasions fracture more readily  than pressure.   A crack, or
partial fracture, in a body, greatly promotes  the separation of 
       ARTS OF DIVIDING AND UNITING SOLID BODIES.    329

the remainder,  whenever a lateral force is  applied ; because
the strength of the sound parts tends to throw the strain more
immediately upon*the weakened points, as explained on page 47.
   Cutting.—Cutting instruments act, in dividing bodies, upon
the same principle as the wedge.   The blade of the instrument
is in general a thin wedge, but the edge itself is usually much
more obtuse.   Mr Nicholson has estimated the angle whicli is
formed  ultimately by the finest cutting edge, at about  56 de-
grees.   If  the edge  of an  instrument were not  angular,
but rounded or square, it would  still act as a wedge, by push-
ing before it a wedge-shaped portion of the opposing particles,
as is done by obtuse bodies moving in  fluids.   In general an
oblique motion is more favorable to cutting than a direct, and
this is because  the  edges of steel instruments are rough  with
minute asperities, like sawteeth.  This circumstance, however,
is of less importance when the material operated upon  is very
firm and the cutting is deep; for in this case the  friction and
compression consume  more  force, than  the actual  division.
This takes place with axes and chisels, which are necessarily
made thick to secure the requisite strength.
   The  quality in  tools which is  called  temper,  is opposed to
brittleness on the one hand and to flexibility on the other.  In-
dependently of the quality of the metal, it appears to be some-
what  influenced by temperature,  since  axes and  other  tools,
are liable  to break, or gap, in frosty weather, and razors  cut
best after being immersed in hot water.
  The kind of cutting which is performed by scissors, depends
upon the process called detrusion, in which the coherent parti-
cles are pushed by each other in opposite directions.  In this
case the cutting edges  require to be angular, but the angle not
very acute.   The  shearing of woollen  cloths, the slitting and
punching of metals, the cutting of nails, and various other me-
chanical processes,  are performed on this principle.
   Cutting Machines.—A variety of fibrous  and  woody sub-
stances, used by druggists and dyers, require to be reduced  to
a coarse powder like saw dust, to facilitate  the extraction  of
               42 
OJU   ARTS OF DIVIDING AND UNITING SOLID BODIES.

their  soluble matter.  This is not  easily done in  any of the
common mills, owing to the toughness of the  material.  It is
sometimes  effected by machinery with circular rasps or saws,
but a more economical application  of  a dividing force in these
cases, is obtained by the rapid  revolutions  of  a sharp cutting
instrument.   In a machine for cutting straw, a number of blades
revolve  upon an axis, with a fly.  In Bramah's surface planing
machinery,  and in Blanchard's ingenious engine for cutting de-
finite forms by a pattern, sharp instruments of different forms,
are made to revolve upon axles, or slide in  grooves, while the
material operated on is put in motion, so as to place  itself in
the proper  position  to receive the cut.
   Penetration.—Bodies are  penetrated   either  by  pushing
aside a portion of their substance, as  in driving a nail; or by
removing a portion, as in boring  and drilling.   In  addition to
the force  of cohesion, the resistance  opposed by a solid,  or
even  by a soft  substance, to the motion of  a body tending to
penetrate it, appears to resemble in some measure, the force of
friction, which  is nearly uniform, whether  the  motion be slow
or rapid, destroying a certain  quantity of momentum in a cer-
tain time, whatever the whole velocity may  be, or  whatever
may be the space   described.  Hence  arises an advantage in
giving a great velocity to a body which is to penetrate another,
since the distance to which a body  penetrates will be  nearly as
the square of its velocity. *   The same remark applies equally
to the action of cutting instruments.  The effect of a  hammer
in driving a nail, depends partly on the influence of velocity in
modifying friction, and partly upon the  momentum accumulated
in the hammer, the effect of which  resembles that  of a  fly
wheel.
   Boring and Drilling.—The processes of boring and drill-
ing, performed by  gimlets, augers,  centrebits,  drills,  he, is a
species of circular cutting,  in  which a cylindrical portion of
the  substance is gradually removed.   Drills are made to turn
    •
  * See Young's Natural Philosophy, vol. i. p. 225, and Playfair's vol. i. p. 97- 
       ARTS OF DIVIDING AND UNITING SOLID BODIES.    331

rapidly, either in one direction by means of a lathe wheel and
pulley,  or  alternately  in opposite directions, by a spiral cord
which coils and uncoils itself successively upon the drill, and is
aided by a weight or fly.   In  boring cannon the tool is  at rest,
while the cannon revolves,  and by this arrangement the  bore of
the cannon is formed with  more accuracy than according to the
old method of putting the borer  in motion, perhaps because
the inertia  of so large a mass of matter, assists in defining the
axis of the revolution with  more accuracy.   The borer is kept
pressed against the cannon by a regular  force.   Cylinders of,
steam engines are cast hollow and afterwards bored, but in this
case the borer  revolves, and the cylinder remains at rest.   In
either case it is important that the axis of the borer, and that of
the cylindrical material, should  coincide ; for when it is other-
wise, if the borer revolves, it will perforate obliquely, and if  the
material revolves, the perforation will be conical.
   Turning.—Turning is an elegant operation, used to produce
regular figures, the section of which is circular.   Like  boring,
it is a species of  circular  cutting, and is performed in  a well
known machine  called a lathe, in which the material to be  cut
revolves about its axis, while the  tool is kept stationary and
supported  by a rest.  Besides circular  forms, it  may  also  be
used to produce regular curvilinear figures, which may be mul-
tiplied  indefinitely.   The  effect of most lathes of complicated
construction, depends on a certain degree of motion, of which
the  axis is capable.  If this  motion be governed by a frame
producing  an elliptic curve,  any number of ovals, having  the
same  centre may be described  at once ;  and if a moveable
point  connected  with the  work, be  pressed  by a  strong spring
 against a pattern of any kind, placed at one end of the axis, a
 copy of the same form may  be made at  the other end of  the
axis.   Geometrical  lathes, governed by eccentric  wheels, and
capable of describing an indefinite variety of complex  figures,
upon a metallic plate, are  used for bank notes and ornamental
 designs. 
332   ARTS OF DIVIDING AND UNITING SOLID BODIES.

   Attrition.—The action of files, rasps, grindstones, and hones,
consists in successively  cutting or breaking away minute parti-
cles from  the surface of bodies.  They  are  used chiefly for
wearing off portions of hard  substances, particularly metals.
The surface of grindstones and whetstones, is kept moist with
water or oil, the use of which  is not so much  to obviate the
production of  heat by friction, as to prevent  the  adhesion
of foreign particles  from filling up the interstices of the grit.
In the finer kinds of grinding  and polishing, certain hard sub-
stances are used in the form of powder, such as emery, tripoli,
sand, putty, oxide of iron, he
   Sawing.—Saw Mill.—A saw, in many respects, resembles
a rasp, and acts by cutting or  breaking away large particles in
the direction of its own plane.  The  thinner the  saw is, the
easier is the  operation, since a smaller amount of substance is
removed by the teeth.   For  the  sake of this advantage, and
for economy of the material, the blades of saws  are made thin,
and often stretched upon  frames, to compensate the  want of
rigidity.   Saw mills erected for cutting logs into boards, con-
sist usually of saws attached to frames which have a reciprocat-
ing motion communicated to them by a crank connected with
a water wheel or steam engine.  A ratchet wheel is connected
with the saw by means of a bar and click; so that at every stroke
of the saw, the wheel is turned the length of  one tooth.   The
ratchet wheel acts by means of a rack, upon a carriage, which
supports  the  log, causing it slowly to advance, until the whole
length of the  log has past the saw.
   Circular Saw.—Circular saws, revolving upon an axis, have
the advantage that they act continually in the same  direction,
and no force is lost by a backward stroke.   They also are sus-
ceptible of much greater  velocity  than the reciprocating saws,
an advantage which enables them to cut more smoothly.   The
size of circular saws, however, is limited; for, if made too large,
and of the usual thinness, they are liable to waver, and bend
out of their  proper plane; and on the other  hand if  made
thick enough to secure  an adequate degree  of strength, they 
       ARTS OF DIVIDING AND UNITING SOLID BODIES.    333

waste both the power  and the  material, by  cutting  away too
much.  Hence they are not commonly applied to the slitting of
large timber, but are nevertheless very useful in smaller works,
for cutting off bodies, which can be included within a certain
distance of the axis, and thus  allow the  saw to be of small
size.   Circular saws, however,  of large size, are used in cut-
ting  thin# layers of mahogany for veneering; for in  this  case
the saw can be strengthened by thickening it on one side to-
wards the centre, the flexibility of the layer  of wood allowing
it to turn  aside, as fast as it is sawn  off.  Circular saws  may
be rendered  more  steady by giving  them a  great velocity, so
that the centrifugal force shall assist in confining the saw to its
proper plane.
   The sawing of marble is performed by saws made of soft
iron, and without teeth.  A quantity of sand  and water is kept
interposed between  them, and  the sand, becoming partly im-
bedded in the iron,  serves to grind away the marble.  These
saws are  worked horizontally for the convenience of retaining
the sand,  and are moved either by  hand, or by reciprocating
machinery.   The cylindrical blocks which form the  tambours,
or frusta, of columns,  are  sometimes  cut  out of marble, by
perforating the block at the  centre, and inserting an iron  axis,
to the ends of which are attached frames, upon which a narrow,
or a concave saw is stretched parallel to the axis.  An alternat-
ing motion is then given  to the frame, until the saw has cut its
way round the axis.
   Crushing.—When materials require to be broken into minute
parts, or when the texture of vascular substances is to be destroy-
ed, that they may yield their fluid  contents, the operation  of
crushing is resorted  to.  It is performed either by percussion
with hammers, stampers,  and pestles, or by simple  pressure
with weights, rollers, and runner stones.
   Stamping Mill.—For reducing  the ores of metals to pow-
der, a number of heavy vertical bars, called  stampers, are al-
ternately raised,  and suffered to fall, by the action of cams,
or  wipers,  projecting from the  arbor of  the mill wheel. 
ARTS OF DIVIDING AND UNITING SOLID BODIES.
The ore is placed in a trough  or  mortar beneath, where it is
acted upon by the stampers until  it is sufficiently comminuted.
A stream  of water  continually  runs  through the  stamping
trough,  carrying with it the  particles, which have become fine
enough to pass through a screen provided for the purpose.
   Bark Mill.—The bark used  by tanners is reduced to a
coarse  powder in various ways.  One  of  the  most #common
methods, is to crush  the  bark by the revolutions of a circular
stone, called a runner stone, which  resembles the wheel of a
carriage, travelling  round in a  continued  circuit.  The axis of
the stone is connected with a vertical shaft, so that the stone has
two  motions, one  round its own axis, which is horizontal, and
the other round the vertical shaft.   The bark is raked up into
a ridge  before  the  stone, and is crushed or ground up, by the
edge of the stone rolling  over it.   In some more  complicated
mills, the bark is successively cut  with knives,  beaten  with
hammers, and ground with stones, or cylinders".
   Oil Mill.—The oleaginous seeds from which oil is express-
ed, require to have their  substance  previously broken up  by
the operations of a mill.   In  one of  the best forms of the oil
mill, the seeds are first bruised to the consistence  of paste, by
the action of runner  stones.   The paste  is received in troughs
perforated with holes, through  which a portion of the oil drips,
and this part is considered the most pure.   The paste is then
put  into strong  bags and Subjected  to  pressure, as long as it
yields oil.   The remaining paste, or oil cake,  is next taken out
of the bags, broken to pieces, and  put into mortars.  It is here
beaten by the action of heavy stampers until reduced to a very
minute  state of subdivision.  The oil which is next pressed out
from it  is inferior in  quality to the first, in consequence of its
containing  more mucilage  and  farinaceous  particles.   The
seeds are  nevertheless subjected  to  another pressure,  after
having  been exposed to heat,  which  enables them to yield a
quantity more of oil, but of a still poorer quality.
   Sugar  Mill.—The  machine  by  which  sugar canes  are
crushed, usually consists of three -vertical  rollers, the middle 
      ARTS OF DIVIDING AND UNITING SOLID BODIES.    335

one of which is turned by a horse, or other power, and  turns
the remaining two by friction, or by toothed wheels; the latter
method being most  advantageous.   The  canes are supplied by
attendants, and are  drawn in and crushed between the first and
second rollers, after which they return and pass between the
second and third.  The juice which is pressed out by the same
operation, flows into a trough beneath.
   Cider  Mill.—When the  substances to be  crushed are  so
large that they  cannot readily be drawn  in between smooth
cylinders, it is necessary that the rollers should be indented at
their  circumference.  The  common cider mill is formed with
two indented cylinders, the teeth of one of which enter the in-
dentations of the other.   By this  arrangement the fruit to  be
ground is caught by the projecting parts of the rollers and reg-
ularly carried forward and ^crushed.   Formerly it was  the
custom to grind  apples by runner stones, similar to those used
in  bark  mills.   And at the  present day cylindrical, rasps  are
sometimes  employed, being  supposed capable  of  destroying
the texture of the fruit more  effectually.
    Grinding.—Grinding, in its most limited sense, may be con-
 sidered as a species of crushing, or breaking, in which the force
 acts  partly in a  lateral direction, so as to lacerate, rather than
 compress the material  acted upon.  It  is frequently produced
 in small  mills, by  a cylinder  or  cone, turning within another
 which is  hollow, the surfaces of both being cut  obliquely into
 teeth.  In larger mills it is commonly performed by one stone
 moving upon another.
    Grist  Mill.—The common mill for grinding grain, is con-
 structed  with two circular stones placed horizontally.   Buhr-
 stone is the  best material of which mill stones  are made,  but
 sienite and granite are frequently used, for indian corn and rye.
 The lower  stone is fixed, while the upper one  revolves with
 considerable velocity, and  is  supported by  an axis  passing
 through  the lower stone, the distance  between the two being
 capable  of  adjustment according to the fineness which it is in-
 tended to produce in the meal, or flour.  When the  diameter 
336   ARTS OF DIVIDING AND UNITING SOLID BODIES.

is five feet, the stone may make about 90 revolutions in a min-
ute without the flour becoming too much  heated.   The corn
or grain is  shaken out of a hopper by means of projections
from the revolving axis, which  give to its lower part or feeder,
a vibrating motion.  The lower  stone is slightly convex, and
the upper one somewhat more concave, so that the corn which
enters at the middle of the stone,  passes  outward for a short
distance  before it begins to be  ground.   After being reduced
to  powder, it is discharged at the  circumference, its escape be-
ing favored by the centrifugal  force, and by the convexity of
the lower stone.  The surface of  the stones is cut into grooves,
in  order to make them  act more  readily and  effectually on the
corn; and these grooves are cut obliquely, that they may assist
the escape  of the meal by throwing it outward.   The opera-
tion of bolting, by which the flour is separated  from  the bran, or
coarser  particles, is performed by a cylindrical sieve placed in
an  inclined  position  and turned by machinery.   The fineness
of  flour is said to be  greatest  when  the bran has not been too
much subdivided, so that it may be more readily separated by
bolting.    This takes place when the grinding has been per-
formed more by the  action of the particles upon  each  other,
than by the grit of the stone.  For this  sort of grinding, the
buhrstone is peculiarly suited.
   Color Mill.—The various coloring substances used by pain-
ters, when they are not  soluble in oil or water, require to be redu-
ced to an impalpable powder by grinding.  This is commonly
performed upon a smooth stone  slab, by trituration with another
stone  called a muller.   When the grinding  is performed by
machinery,  a large  muller of the shape of a pear, having a
groove cut in it for the  admission of the paint, is made to re-
volve in a mortar, the  bottom of  which is of a corresponding
shape.    In some color mills a horizontal stone cylinder revolves
in  contact with another stone, which is concave, and covers a
part of its convex surface.   In most cases the substance to be
ground is mixed with oil or water.  As some of the substances
used for pigments are of a poisonous character, they should be
ground in close cavities, or under water. 
ARTS OF DIVIDING AND UNITING SOLID BODIES.    337
                     MODES OF UMON.

  Insertion.—The mechanical modes of attaching bodies to
each other, usually consist in the insertion of their parts among
each other, or in the  application of other substances specially
adapted for the purpose of connexion.   Insertion is" performed
by various modes, the principal of which  are,  1.  Mortising,
in which the  projecting  extremity of  one  timber  is received
into a perforation in another. 2. Scarfing and interlocking, in
which the ends of pieces overlay each other, and are indented
together So as to resist longitudinal strain  by extension, as in tie
beams,  and ends  of hoops. 3. Tongueing  and rabating, in
which the edges of boards  are wholly, or partly, received by
channels in each  other.  4. Dovetailing, when  the parts are
connected by wedge-shaped indentations, which permit them to
be separated  only in one  direction. 5. Linking,  where the
ends of flexible  rods are  bent over each  other. 6.  Folding,
when the edges of flexible plates  are connected  in a similar
manner. 7. To these may be added the  combinations of flexi-
ble fibres, by tying,  twisting, weaving, he, in which the per-
manency  of the union depends upon friction.
   Interposition.—When two substances are mechanically unit-
ed by the intervention of  a third,  the  latter, from  its smaller
size,  should  be made of the strongest material.   Nails are a
common  connecting  medium in wooden  structures.  The sta-
bility of a nail depends  upon its  friction, or adhesion, and  is
increased by its roughness, the smallness of the angle made by
its  sides,  and the elasticity of the material into  which  it  is
driven.
   When the force tending to produce  separation is great, nails
do not afford  an adequate  security.   In such cases, it is com-
mon to  employ screws, which are  inserted by the force of tor-
sion and  cannot be  withdrawn by that of extension, while the
material is sound.  Where great  strength is required, bolts of
metal are used, which pass through the substances to be con-
               43 
338   ARTS OF DIVIDING AND UNITING SOLID BODIES.

nected, and are secured at their smaller extremity by a nut and
screw, or by a transverse key.  Rivets are short bolts, the two
ends of which are headed, or spread by hammering, after they
are inserted.
  Binding.—In some cases the materials to be connected are
not perforated,  but  surrounded by the connecting  substance.
Hoops and bands of metal, wood, and flexible fibres, are used
for this purpose.   In cases where it is applicable, binding ordi-
narily affords the strongest mode of connexion, but is attended
with the greatest expenditure of the connecting material.
   Locking.—For the temporary connexion of parts,  which
requires to be often repeated, latches, bolts, hooks, buttons, and
locks are employed.   Of these the lock is the only  one whose
structure is  at all complicated.   The principle upon  which
locks depend, is the  application of a lever to an interior bolt,
by means of a communication from without.   The lever is the
key, and the bolt receives from it a progressive motion in  either
direction.    The security of  a lock depends upon the number
of obstacles which can be interposed between the movement of
the bolt, and the action of any instrument, except  the proper
key.  The wards of locks are impediments of this kind,  and to
enable the  key to pass them, certain  portions of its  substance
are cut away.   Various  complicated  and difficult locks have
been constructed by Messrs Bramah, Taylor, Spears,  and
others.   In a very  ingenious lock invented  by Mr  Perkins,
twentyfour small blocks of metal of different sizes are introduc-
ed, corresponding to the  letters of the alphabet.  Out of  these
an indefinite number of combinations may  be made.   The
person locking the door, selects, and places, the blocks neces-
sary to spell a particular  word known only to himself, and no
other person, even if in possession of the key, can open the
door, without a knowledge of the same word.
    Cementing.—Cements are, for the  most part, soft or semi-
fluid substances, which have the property of becoming hard in
time, and  cohering with  other bodies to which they have been
applied.   A variety of these substances  are used  for uniting 
       ARTS OF DIVIDING AND UNITING SOLID BODIES.    339

different materials.   The compounds of lime and sand, which
constitute the ordinary building cements, have been considered
in Chapter First.   For uniting pieces of marble, plaster of Par-
is dried by heat, and mixed with water, or with rosin and wax,
is employed.  A cement for  iron is made by mixing  sulphur
and muriate of ammonia with a large quantity of iron chippings.
This is used for the joints of iron  pipes, and the  flanges of
steam  engines.  Turners, and some other  mechanics, confine
the material on which they are working, by a cement composed
of brickdust and rosin, or pitch.  The cement used by glaziers,
under  the  name of putty, is a mixture of linseed oil and pow-
dered  chalk.   China ware is cemented  by common paint,
made of white lead and oil, or by resinous  substances, such as
mastic and shell lac, or by isinglass dissolved in proof spirit or
water.   Bookbinders, and paper hangers, employ paste, made
by boiling flour, and a similar  but more elegant article under
the name of rice glue, is prepared  by boiling  ground  rice in
soft water to the consistence of a thin jelly.   Wafers are made
of flour, isinglass, yeast,  and white of eggs, dried in thin strata
upon tin plates, and  cut by a circular instrument.  The color
is given  by red lead, and  other pigments.   Sealing wax is
composed of shell lac and rosin, and is commonly colored with
vermillion.
   Glueing.—For uniting wood and similar porous substances,
common glue takes precedence  of all other cements.  It is
dissolved by heating it with  water, and is applied with a brush
to both the surfaces to be united.   Glue does not  adhere so
readily, if the surfaces be in the least oily, or if a coating of old
glue is previously upon them, or indeed if the pores are filled
with any  foreign substance.  The cementing  power  of glue
depends  upon the  strength which it possesses  when dry, and
the hold which it obtains upon the, wood,  by penetrating its
pores.   It  does not furnish a sufficient bond of union for surfa-
ces which are not porous, as those of metals; and it is not du-
rable when exposed to the action of water. 
340
ARTS OF DIVIDING AND UNITING SOLID BODIES.
   Welding.—Certain metals, such as iron and platinum, which
are exceedingly difficult of fusion, are capable of being united
by the process of welding.   This consists in hammering  them
together while they are at a very high temperature.   Bar iron
cannot be welded  without  raising it to a heat of nearly 60 de-
grees of Wedgewood's pyrometer.  Cast steel would be melted
at this temperature, and  therefore in  welding iron to steel, the
steel is raised only to a common white heat.   Care is taken to
prevent the  surfaces which are to be welded from being oxi-
dized too much, or else to detach  the scales when the metal is
brought to a welding heat.  The union of welded pieces probably
depends  on an incipient fusion of their surfaces.   When prop-
erly conducted,  the  metal is supposed to be as strong  in the
welded part, as in any other.
   Soldering.—The process of soldering consists in uniting to-
gether parts of the same, or of different metals, by the intervention
of a metallic substance  employed in  a state  of  fusion.    It  is
necessary that the uniting  substance should melt sooner than
the substance to be soldered, that it should adhere firmly to its
surface, and as far as practicable,  approach to the metal sol-
dered, in hardness and  color.  Iron is usually  soldered  with
brass, and hence the process is commonly called brazing.   An
alloy of tin and iron is sometimes  used instead of brass  for the
same purpose.   Copper may be united either by a hard solder
made of brass and zinc, or a soft solder composed of zinc and
lead.  Tin is soldered with pewter made of tin  and lead, with
sometimes a portion of bismuth.   Gold  and silver are  united
with  solders made of gold or silver, alloyed with copper or
brass.   Platinum is soldered with gold.  The  adhesion  of
solders depends upon an alloy being  formed between the sur-
faces in contact.
   As the oxidation of the surface of metals tends  to prevent
the adhesion of the solder, it is common to unite  with the sol-
der some additional substance, which may obviate this difficul-
ty.  In soldering  copper, brass, iron, he it is common  to em-
ploy borax, a salt which fuses  at the time when the  metals 
       ARTS OF DIVIDING AND UNITING SOLID BOD IES.   341

would be most liable to oxidate, and by enveloping the metallic
surface, prevents the farther action of the oxygen of the atmos-
phere.  Potash, soda, tartar, and various salts are used for the
same purpose.   Muriate  of ammonia has a remarkable  effect
in freeing the  surfaces of metals from  oxygen, which it does,
apparently, by combining with the metallic oxide, and carrying
it off as it sublimes.  In soldering the more fusible  metals, as
tin and lead, a carbonaceous substance is employed, such  as
rosin, or oil, which tends to cover the surface, and  also  to re-
duce the oxide to its metallic state, as fast as it is formed.
   Casting.—The process  of  fusion,  or melting,  affords  in
many substances, the most effectual method both of destroying
the  cohesion of  their particles, and of afterwards  restoring it
under new arrangements.  Many substances, both simple and
compound, such as  metals,  glass,  wax,  he, may  become
liquid and again solid, without essentially changing their physi-
cal qualities.  On the other hand, many  natural bodies, crys-
tallized minerals, and organic combinations,  cannot be fused
without changing their characteristic properties.   Some sub-
 stances are  with  difficulty fusible  when alone,  but become
 more  fusible when combined with another substance, as is the
 case of sand with an alkali, or iron with carbon.  Others again
 have their fusibility lessened by combination, as happens  in
 metals when they become oxidized.
   Fluxes.—The name of j/k,res"hasbeen given to certain sub-
 stances which assist fusion, either by expediting the process, or
 by protecting the substance melted from alteration.  In separa-
 ting metals from their ores, fluxes are  employed to render  the
 substances with which the metal is combined, capable of fusion.
 Thus if the ore abound with siliceous  earth or stone, an alka-
 line flux, such as potash, soda,  or tartar, has the effect of com-
 bining with the siliceous substances, and forming with them a
 vitreous  compound, which floats upon the top of  the  melted
 metal.   Tartar  also contains a portion of vegetable matter, the
 carbon and hydrogen  of which serve to deoxidize the  metal.
 Borax, common salt, and many other saline bodies, when melt- 
342    ARTS OF DIVIDING AND UNITING SOLID BODIES.

ed, prevent the oxidation of metals by protecting their surface
from the atmosphere.   Muriate of  ammonia, rosin, fatty sub-
stances, powdered charcoal, he, prevent or remove oxidation,
by combining  either with the oxygen, or with the oxide when
formed.
  Moulds.—The  moulds used for casting melted bodies must
be suited to the  temperature at which  the body  melts.  For
metals which  melt at a high heat, as copper,  brass, cast iron,
he, the moulds  are made of some  refractory substance, such
as loam, sand, pounded brick with plaster, or clay, he  Glass
is cast in moulds  made of copper, but  these require to be fre-
quently cooled.   Those bodies which melt at temperatures be-
low  that of ignition,  as tin, lead,  wax, he, may be cast in
moulds of any convenient metal, or of wood, and other inflam-
mable materials.
   The forms of some bodies may be changed, and their sepa-
ration or union effected, without the  agency of fusion, in vari-
ous ways.  It may be done  by  mixture with  water, as in clay
and plaster; by solution in water, as in glue, rice, and gum; and
by sublimation, as in camphor, and muriate of ammonia.
  Young's Lectures on Natural Philosophy;—Gregory's Mechan-
ics;—Nicholson's Operative Mechanic, 8vo.;—Gray's Operative
Chemist, 8vo. 1828;—Rees's Cyclopedia, and Brewster's Edinburgh
Encyclopedia, under various heads. 
CHAPTER XV.
          ARTS OF COMBINING FLEXIBLE FIBRES.

   Theory of  Twisting.—The strength of cordage, which is
employed in uniting bodies, and the utility of flexible textures,
which  serve for furniture or for  clothing, depend principally
upon the friction or lateral adhesion, produced by the twisting
and intermixture of their constituent fibres.
   A twisted cord is not so strong as the fibres which compose
it, supposing the fibres and cord to be of the same length.   The
object  of twisting  is to connect  successive numbers of short
fibres in such a manner, that, besides the mutual pressure which
their own elasticity causes them  to exert, any additional force
applied in the direction of the  length of the  aggregate, may
tend to bring their parts into closer contact, and augment their
adhesion to each  other.  The simple art of tying a knot, and
the more complicated processes of spinning, rope making, weav-
ing, and felting, derive most of their utility from this principle.
   By considering the  effect of  a force which is counteracted
by other forces acting obliquely,  it  will be seen that the opera-
 tion of twisting has a useful effect in  binding  the parts of a
 rope or thread together, and  also  that it has an  inconvenience
 in causing the strength of the fibres to act  with a mechanical
 disadvantage.  The greater is the obliquity of the fibres, the
 greater will be their adhesion to each other, but the greater also
 will be their immediate strain or tension, when a force acts upon
 them  in the direction of the whole cord.  From this it follows
 that after employing as much  obliquity and as much tension as
 is sufficient to connect the fibres firmly together, all that is su-
 perfluously added tends to weaken the cord, by overpowering the
 primitive cohesion of the fibres in  the direction of their length. 
 344        ARTS OF COMBINING FLEXIBLE FIBRES.

   The  mechanism of simple spinning is  easily understood.
 Care is taken,  where  the  hand is employed, to intermix the
 fibres  sufficiently, and to engage their  extremities as much as
 possible  in the  centre; for it is obvious, that if any fibre  were
 wholly external to the rest, it could not be retained in the yarn.
 In general, however, the materials are previously in such a state
 of intermixture as to render this precaution unnecessary.
   Rope  Making.—A single thread of yarn, consisting of fibres
 twisted together, has a tendency to untwist itself, the external
 parts being strained by extension,  and the internal parts by
 compression; so that the elasticity of all the parts resists, and
 tends  to restore  the thread  to its natural  state.   But if two
 such threads similarly twisted, are retained in contact at a given
 point of  the  circumference of each, this point is rendered sta-
 tionary by the opposition of the equal forces acting in contrary
 directions, and  becomes the centre, round which both threads
 are carried by the forces which  remain, so that they continue
 to twist  round  each other, till the new combination causes a
 tension, capable of  counterbalancing the remaining tension of
the original threads.   Three,  four, or  more  threads, may be
 united nearly in the same manner.  A strand, as it is called by
 rope makers, consists of a considerable  number of yarns thus
 twisted together, generally from sixteen to twentyfive;  a  haw-
 ser consists of  three  strands, a shroud  of four,  and  a cable of
 three hawsers or shrouds.   Shroud laid cordage has the dis-
 advantage of being hollow in the centre, or else of requiring a
 great change of form  in the  strands to fill up the  vacuity, so
 that in undergoing this  change, the  cordage stretches, and is
 unequally strained.   The relative position and the comparative
 tension of all the fibres in these  complicated combinations are
 not very easily determined by  calculation;  but it is found by
 experience to be most  advantageous for the strength  of ropes,
to twist the strands, when they are to be compounded, in such
 a direction as to untwist the yarns of which they are formed ;
 that  is, to increase the  twist of the strands themselves ;  and
 probably the greatest  strength is obtained when the ultimate 
ARTS OF COMBINING FLEXIBLE FIBRES.
345
obliquity of  the constituent  fibres  is  least,  and  the most
equable. *
   A very strong rope may also be made by twisting five or six
strands round a seventii as an axis.   In  this case the  central
strand, or heart, is found after much use to be chafed to oakum.
Such ropes are, however, considered unfit  for rigging, or for
any use in which they are liable to be frequently bent.
   Ropes are most commonly made of hemp, but various other
vegetables are occasionally employed.   The Chinese even use
woody fibres, and the barks of trees  furnish cordage to other
nations.   In spinning the yarn, in the process of rope making,
the hemp is fastened round the waist of the workman ; one end
of it  is  attached to a wheel turned by  an  assistant, and the
spinner, walking backwards, draws out the fibres with his hands.
When one length of the walk has been spun, it is immediately
reeled, to prevent its untwisting.  The  machines employed  in
continuing  the  process of rope  making, are mostly of  simple
construction, but both skill and attention are  required in  apply-
ing them so as to produce an equable  texture in every  part  of
the rope.   The tendency of two strands to twist, in consequence
of the tension arising from the original twist of the yarns, is not
sufficient to procure an  equilibrium,  because of ihe friction
and rigidity to be overcome.  Hence  it is necessary to employ
force to assist this tendency, and the strands or ropes will after-
wards retain  spontaneously the form which  has thus been giv-
en them.  The largest ropes even require external force in or-
der to make them twist at all.
   The  constituent ropes of a common  cable, when separate,
are stronger than the cable, in the proportion of about four  to
three ; and a rope worked up from  yarns 180 yards in length,
to 135 yards, has been found to be stronger than when reduced
to 120  yards, "in the  ratio of six to five.   The  difference  is
owing partly to the  obliquity of the fibres,  and  pa illy  to the
unequal tension produced by twisting, f

  * Young's Natural Philosophy, vol. i. Lect. xvi.       I Ibid,
               44 
346
ARTS OF COMBINING FLEXIBLE FIBRES.
                  COTTON MANUFACTURE.

  When the  fibres of cotton, wool, or flax, are intended to be
woven,  they  are  reduced, to fine threads of  uniform  size
by  the  well  known process of spinning.  Previously to the
middle of the last century, this process was performed by hand,
with the aid of the common spinning wheel.   Locks of cotton
or wool, previously  carded, were  attached to a rapidly revolv-
ing spindle  driven by a large wheel, and were stretched, or
drawn out by the hand, at the same time that they were twist-
ed by the spindle, upon which they were afterwards wound.
Flax, the fibres of which  are longer and more parallel, was
loosely  wound  upon a distaff, from which the fibres were  se-
lected and drawn out by the thumb and finger, and at the same
time were twisted by flyers  and wound upon a bobbin, which
revolved with a velocity  somewhat less than that of the flyers.
  The  manufacture of flexible stuffs by means of  machinery,
operating on a large  scale, is an invention of the  last century.
Although of recent  date, it has given birth to some of the most
elaborate  and wonderful combinations of mechanism, and al-
ready constitutes, especially in England and in this country, an
important source of national wealth and prosperity.
  Elementary Inventions.—The  character of the machinery
which has been applied to the manufacture of  cotton at differ-
ent times, has been various.  There are,  however, several
leading  inventions, upon which most of the essential processes
are founded, and which have given to their authors a greater
share of celebrity than the rest.  These are, 1. The spinning
jenny.   This machine was invented by Richard Hargreaves, *
in 1767, and in its simplest form resembled a number  of spin-
dles turned by a common wheel, or cylinder, which was work-
ed by hand.   It stretched out the threads as in common spinning
of carded cotton.   2. The water spinning frame, invented by
Richard Arkwright,  in 1769.  The essential and most impor-
  * Mr Guest in a late work attributes the invention both of the jenny and
water spinning frame, to Thomas Highs, of Leigh, England. 
           ARTS OF COMBINING FLEXIBLE FIBRES.        347

tant feature in this  invention,  consists  in the drawing out, or
elongating of the cotton, by causing it to pass between succes-
sive pairs of rollers,  which revolve with different velocities,
and which act as substitutes for the  finger and thumb, as ap-
plied in common  spinning.  These rollers are combined with
the spindle  and flyers  of the common flax  wheel.  3. The
mule.   This was invented by  Samuel Crompton, in 1779.   It
combines the principles of the two preceding inventions, and
produces finer yarn than that which is spun in either of the
other machines.   It has now  nearly superseded the jenny. 4.
The power  loom for weaving by water or steam power, which
was introduced about the end of the eighteenth century, and
has received various modifications.
   The  foregoing fundamental machines are used in the  same
or different  establishments,  and for  different purposes.   But
besides  these,  various  auxiliary  machines are necessary to
perform intermediate operations, and to prepare the material as
it passes from one stage of the manufacture to another.  The
number of these machines, and the changes and improvements
which have been made  in their construction from time to time,
render  it impossible to convey, in a work like the present, any
accurate idea of their formation in detail.  A brief view, how-
ever, of the offices which they severally perform, may be tak-
en  by following the raw material through the principal changes
which it undergoes in a modern  cotton factory, founded and
improved upon the general principles of Arkwright.
   Batting.—The  cotton, after having been  cleared  from its
seeds, at the plantation,  by the operation of ginning, described
on  page 33, is compressed  into bags for  exportation, and ar-
rives at the  factory in a dense and  matted  mass.   The first
operation to which it is submitted has for its object to disentan-
gle the fibres, and restore the cotton to a light, open, and uniform
state.   For this purpose, after being weighed out, it is submit-
ted to the operation of a machine called a picker, or of another
denominated a batter.   In  some of these  machines it is sub-
jected  to the action of a series of pins, in others to a sort of 
348       ARTS OF COMBINING FLEXIBLE FIBRES.

blunt knives, revolving with great rapidity;  the effect of which
is to beat up and separate the fibres, to disengage their unequal
adhesions,  and to reduce the  whole to a very light, uniform,
flocculent mass.
   Carding.—The  cotton next passes to the carding machines,
of which, when there are two, the first is called the breaker,
and the second the finisher.  In  this operation  the cotton is
carried  over  the surface of a revolving cylinder which  is cov-
ered with card teeth of wire, and which passes in contact with
an arch, or part of a concave cylinder, similarly covered with
teeth.   From this cylinder it is taken off by another, called the
doffing cylinder, which revolves in an opposite direction ; and
from this it is again removed by the rapid vibrating movement
of a transverse comb, otherwise  called the doffing plate,  moved
by cranks.  It then exists in the state of a flat, uniform, fleece,
or lap, which, after passing the breaker, undergoes the process
of plying, or doubling, by causing it to perform a certain num-
ber of revolutions upon a cylinder, or a perpetual cloth.  It is
then carded a second time, by the finisher, and the fleece, after
being taken off from this machine, is  drawn by rollers through
a hollow cone, or trumpet mouth, which contracts it to a narrow
band or sliver, and leaves it coiled up in a tin can, ready  for
the next operation.  The process of carding serves to equal-
ize the substance of the cotton, and to lay  its fibres somewhat
in a more parallel direction.
   Drawing.—The slivers of cotton are  next elongated  by  the
process of drawing.  This  operation is  the ground  work  or
principle of Arkwright's invention, and is used in  the  roving
and spinning as well as in the drawing frame.   It is an imita-
tion of  what  is  done by the  finger and  thumb in spinning by
hand, and is performed by means of two  pairs of rollers.  The
upper roller of the first pair, is covered with leather,  which,
being an elastic substance, is pressed by means of  a  spring or
weight.   The lower roller, made of metal,  is fluted in order to
keep a firm hold of the fibres of cotton.   Another similar pair
of rollers  are placed near those  which  have been  described. 
ARTS OF COMBINING FLEXIBLE FIBRES.       349
The second  pair, moving with a greater  velocity, pull out the
fibres of cotton  from the first pair of rollers.   If the surface
of the last pair move at twice or thrice the velocity of the first
pair, the cotton will be drawn twice or* thrice finer than  it was
before.  This relative velocity is called the draught of the ma-
chine.  This mechanism  being  understood, it will be«asy to
conceive  the nature of  the  operation of the drawing frame.
Several  of  the  narrow  ribbands or slivers from  the  cards,
(sometimes  termed  card ends) by being passed through  a sys-
tem of rollers, are thereby reduced  in size.  By means of a
detached single  pair of  rollers, the several  reduced ribbands
are plied or united into one sliver.
   The operations of drawing and plying serve to equalize still
farther the  body of cotton, and to bring its  fibres more into a
longitudinal direction.   These slivers are again combined and
drawn out, so that one sliver of the  finished drawing  contains
many plies of card  ends.   Hitherto the cotton has acquired
no twist, but is  received into  moveable tin  cans or  canisters,
similar to those  used for receiving the cotton  from the  cards.
   Roving.—The operation of roving communicates the first
twist to the  cotton.   It  is performed by a machine  called the
roving frame, or double  speeder.   The tin cans containing the
slivers of cotton, are placed upon this machine, and are made
to revolve slowly about their axes so as to produce a slight de-
gree  of twisting.  The  slivers then pass again through several
pairs of rollers  moving  with different speeds, and are thus still
further attenuated by drawing.   They are  then slightly spun
by the revolution of flyers, and are wound upon the bobbins of
the spindles, in  the form of a loose, soft, imperfect thread, de-
nominated the roving.
   The mechanism  of the double  speeder is complicated and
interesting, and  great ingenuity has been displayed in overcom-
ing the difficulties of its construction.  In order that the yarn,
or roving, may  be wound upon the bobbins in  even cylindrical
layers, it is necessary that the spindle rail, or horizontal bar
which supports the spindles, should continually rise and fall 
 350       ARTS OF COMBINING FLEXIBLE FIBRES.

 with a slow, alternate motion.  This is effected by heart wheels,
 or cams, in the interior of the machine.   Again, since the col-
 lective size of the bpbbin is augmented by the addition of each
 layer of roving, it is obvious that if the axis of the  bobbin re-
 volved always  with the same velocity,  the thread of roving
 would  fce broken in consequence of being  wound up too fast.
 To prevent this accident, the velocity of the spindles, and like-
 wise the motion of  the spindle rail, is obliged  gradually to di-
 minish from  the beginning to the end of an operation.   This
 diminution of speed is effected by transmitting the motion both
 to the spindle rail,  and to the bobbins, through two  opposite
 cones,  one of which drives the  other with a band, the  band
 being  made to pass slowly from one  end to the  other of the
 cones,  and thus  continually to alter  their relative speed, and
 cause a uniform retardation of the velocity of the moving parts.*
 As the roving is not strong  enough to bear  any violence, the
 spindles which  support the bobbins are geared to each other,
 so as to prevent any deviation from the proper velocity.
   A more simple form of the roving frame, has been invented,!
 in which  the gearing is dispensed with, as  well as the pair of
 cones which regulates the motion of the bobbins.  In this ma-
 chine the bobbins are not turned by the rotation of  their axis,
 but by  friction applied to their surface by small  wooden  cylin-
 ders which revolve in contact with them.   In this way the ve-
 locity of the  surface of  the bobbin will  always be the same,
 whatever may be its growth from the accumulation  of roving,
 so that the winding goes on at an equable rate.   To  prevent
 the  roving from  being  stretched, or  broken,  in its  passage
 from the  drawing rollers to the bobbins, it is  made to  pass
 through a tube  which has a rapid rotation, and which twists it
 in the  middle into a cord of some firmness.   It is again  un-
 twisted, as fast as it escapes  from the tube, and is wound upon
the bobbins in the form of a dense even cord, but without any
twist.
  * Instead of band cones, an ingenious mode of using  geared cones, now in-
troduced in several American factories, has already been described, page 236.
  t By Mr Danforth, of Massachusetts. 
ARTS OF COMBINING FLEXIBLE FIBRES.
351
   Spinning.—The bobbins which contain the cotton in a state
of roving, are next transfered to the spinning frame.  It it here
once more drawn out by rollers and twisted by flyers, so that
the spinning is little more than a repetition of the process gone
through in making the  roving, except that the cotton is  now
twisted into a strong thread, and cannot any longer be extend-
ed by  drawing.   The flyers of the  spinning frame are driven
by bands, which receive  their motion in some cases from a
horizontal fly wheel, and in others from a longitudinal cylinder. *
As the thread is sufficiently strong not to break with a slight
force,  the  resistance of the  bobbins by friction is relied oi^to
wind it up, instead of having the spindles  geared together and
turned with an  exact  velocity,  as  they are in the common
double speeder.   In the spinning frame the heart motion is re-
tained to regulate the  rise and  fall of the  rail, and in those
frames which  spin the woof,  or filling, it is applied by a  pro-
gressive  sort of cone,  the  section of which is  heart shaped,
and which acts  remotely to distribute the thread in conical lay-
ers upon the bobbins, that it may unwind the more easily when
placed afterwards in the shuttle.
   Mule Spinning.—The processes of water spinning already
described, are adequate to produce yarns of sufficient fineness
for ordinary fabrics.   But  for producing threads  of the finest
kind,  another process is necessary,  which is called stretching,
and which is analogous to that which is performed with carded
cotton upon a common  spinning wheel.  In this operation, por-
tions of  yarn, several yards long, are  forcibly stretched in the
 direction of their length.   It differs, therefore, from the opera-
 tion of drawing, in which a few  inches only are extended at a
 time.   The stretching is performed  with a view to elongate
 and reduce  those places  in the yarn,  which have  a greater di-
 ameter and are  less  twisted than the other parts, so that the
 size and twist of the thread may become pniform throughout.
 To effect  the   process of stretching, the spindles  are mounted

   * The latter method which had gone into disuse, is beginning to be revived
 and to  be considered most advantageous. 
 352        ARTS OF COMBINING FLEXIBLE FIBRE9.  '

 upon a carriage, which is moved back and forwards across the
 floor,  receding when  the threads are to be stretched, and re-
 turning when they are to be wound  up.  The yarn produced
 by mule spinning  is  more  perfect than any other, and is em-
 ployed in  the fabrication of the finest articles.   The sewing
 thread spun by mules is a combination of two, four, or six con-
 stituent threads, or  plies.   Threads have  been  produced  of
 such  fineness, that a pound  of  cotton has  been  calculated to
 reach 167 miles.
   Warping.—The  first step preparatory to weaving is to form
 sutfarp, which consists of parallel threads  continued  through
 the whole  length of the intended piece, and sufficient in number
 to constitute its breadth.   It was formerly the practice  to attach
 the threads to as many pins, and to draw them out to the re-
 quired length.   But as this method required too much room, a
 warping machine was subsequently used, in which the mass of
 threads intended  to constitute a warp,  was  wound in a  spiral
 course  upon a large revolving frame, which rose and fell so
 as to  produce the  spiral distribution.
   These methods are now superseded in this country by Moody's
 warping machine,  *  an ingenious piece of mechanism, in which
 a number of bobbins, equal to one eight part of the number of
 threads in the intended warp, are  arranged  upon  the surface of a
 concave frame.   The  threads pass through a reed  which  sepa-
 rates the alternate  threads as they are to be kept in the loom; af-
 ter which they are wound upon a beam, with  rods interposed at
 the end to preserve  the  separation.   But the most interesting
 part of the mechanism  is  a contrivance for stopping  the machine
 if  a single  thread of the warp breaks.   To effect this object, a
 small  steel weight,  or flattened wire, is suspended by a hook
 from  each thread,  so that it falls if the thread is broken.   Be-
 neath the  row of weights, a cylinder revolves,  furnished with

  * Mr Paul Moody, formerly of Waltham, and now of Lowell, is the inventor
of this machine;  likewise of the spinning frame, which winds the woof in
conical layers, and of  great improvements in the roving frame, the dressing
frame,  &c. 
ARTS OF COMBINING FLEXIBLE FIBRES.        353
 several projecting ledges extending its whole length parallel to
 the  axis.  When one of the weights  falls by the breaking of
 its thread, it  intercepts one of the ledges and causes the cylin-
 der to exert  its force upon an elbow, or toggle joint, which dis-
 engages a clutch, and stops the machine.   After the thread is
 tied, and the weight raised, the machine proceeds.
   Dressing.—As the threads which constitute  the warp are
 liable  to much  friction  in  the  process of weaving, they are
 subjected to  an operation called dressing, the object of which is
 to increase their strength and smoothness, by agglutinating their
 fibres  together.   To this end they are pressed between rollers
 impregnated  with mucilage made of starch, or some gelatinous
 material, and immediately afterwards brought in contact with
 brushes which pass repeatedly over them so as to lay down the
 fibres in one  direction, and remove  the  superfluous  mucilage
 from them.   They are then dried  by a series of revolving fans,
 or by steam cylinders, and  are ready for the loom.
   Weaving.— Woven textures  derive their strength from the
 same force of lateral adhesion which retains the twisted fibres
 of each thread in their situations.  The manner  in which these
 textures are  formed, is readily  understood.  On inspecting a
 piece of plain cloth, it is found  to consist  of two distinct sets
 of threads running perpendicularly to each other.   Of these,
 the longitudinal threads constitute the warp, while the transverse
 threads are  called the woof, weft, or filling, and consist of a
 single  thread passing  backwards  and forwards.  In weaving
 with the common loom, the warp  is wound upon a cylindrical
 beam, or roller.   From this, the threads pass through a harness,
 composed of  moveable parts called the heddles, of which there
 are two or more, consisting of a series of vertical strings con-
 nected to frames, and  having  loops  through which the warp
passes.   When the  heddles  consist of more  than  one set  of
strings, the sets are called leaves.  Each of these heddles re-
ceives its portion  of  the alternate  threads of the warp, so that
when they are moved reciprocally up and down, the  relative
position  of the  alternate  threads of the  warp is reversed.
               15 
354
ARTS OF COMBINING FLEXIBLE FIBRES.
Each time that the warp is opened by the  separating of its al-
ternate threads, a shuttle containing the woof, is thrown across
it, and the thread of woof is immediately  driven into its place
by a frame  called a lay, furnished with  thin  reeds,  or wires,
placed among the warp like the teeth of a comb.  The woven
piece, as fast as it is completed, is wound up on a second beam
opposite to the first.
   Power  looms, driven by water or steam, although a late in-
vention, are now  universally introduced into  manufactories of
cotton and woollens.   As the motions of the loom are chiefly
of a reciprocating kind, they are  produced in some  looms by
the agency of cranks, and in others by cams or wipers, acting
upon weights or springs.
   Twilling.—In the mode of plain  weaving last described,  it
will be observed that every thread of the warp crosses at every
thread of the  woof,  and  vice versa.  In articles  which  are
twilled or  tweeled, this is not the case; for in this manufacture
only the third, fourth, fifth, sixth, he threads cross each other
to form the texture.   In the coarsest kinds every third thread
is crossed, but in finer fabrics  the  intervals are less  frequent,
and in some very fine twilled silks, the crossing does not take
place till the sixteenth interval.  In Fig. 1 is shown a magnified
                          Fig. 1.
section of a piece of plain cloth, in which the woof passes al-
ternately over and under every thread of the warp.   In Fig. 2,
                          Fig.  2.
is a piece of twilled  cloth, in  which the thread of the woof
passes alternately over  four, and under one, of the threads of
the warp, and performs the reverse in its return.  To produce
this effect, a number of leaves of heddles are  required, equal
to  the number of threads contained in the interval between
each  intersection,  inclusive.   By the  separate movements of 
           ARTS OF COMBINING FLEXIBLE FIBRES.       355

these,  the  warp is placed  in the  requisite position  before
each stroke of the  shuttle.   A  loom invented in this  coun-
try by Mr Batchelder, of Lowell, has  been applied  to the
weaving of twilled goods by  water power.
   Twilled  fabrics are thicker  than plain ones, when of the
same fineness, and more flexible when of the same thickness.
They  are  also more  susceptible  of ornamental variations.
Jeans,  dimoties, serges, &,c, are  specimens of  this kind of
texture.
   Double  Weaving.—In  this species of  weaving, the fabric is
composed of two webs, each of which  consists of a separate
warp and a separate woof.  The two, however,  are interwoven
at intervals, so  as to produce various figures.  The junction of
the two  webs is formed by passing them at intervals through
each other, so  that  each  particular  part of  both is sometimes
above, and sometimes below.  It follows that  when different
colors  are employed, as in carpeting, the  figure  is the same on
both sides, but the color is reversed.   A section  of double
cloth is shown in Fig. 3.
                         Fig.  3.
  The weaving of double cloths is commonly performed by a
complicated machine called a draw loom, in which the weaver,
aided by an assistant, or by machinery, has the command of each
particular thread by its number. He works by a pattern, in which
the figure before him is traced in squares, agreeably to which the
threads to be moved  are selected  and raised, before each in-
sertion of the woof.   Kidderminster  carpets,  and Marseilles
quilts, are specimens of this mode of weaving.
   Cross Weaving.—This method is used to produce the light-
est fabrics, such as gauze, netting, catgut, he  In the kinds of
weaving which have been previously described, the threads of
the warp  always remain parallel  to  each other, or  without 
356       ARTS OF COMBINING FLEXIBLE FIBRES.

crossing.  But in gauze weaving,  the  two threads of  Warp
which pass between the same splits of the reed, are. crossed
over each  other,  and partially twisted like a cord, at every
stroke of the loom.   They are, however,  twisted to the right
and left, alternately, and each shot, or insertion of the  woof
preserves the twist which the warp has received.  A great va-
riety of fanciful textures are produced by variations of the same
general  plan.   Fig.  4,  represents the  cross weaving  used in
common gauze.
                          Fig.  4.


   Lace.—Lace is a complicated, ornamental fabric,  formed of
fine threads of linen, cotton, or silk.  It consists of a net work
of small meshes, the most common form of which is hexagonal.
In  perfect thread lace,  four sides  of the  hexagon  consist of
threads  which are twisted, while in the remaining two, they are
simply crossed.  Lace has been commonly made upon a cush-
ion or  pillow, by the slow  labor of artists.   A piece of  stiff
parchment is stretched upon the cushion, having holes pricked
through it, in which pins  are inserted.  The threads previously
wound  upon  small  bobbins, are woven round the pins  and
twisted  in various ways, by the hands, so as to form the required
pattern.  The expensiveness of the different kinds of lace is
proportionate  to the tediousness of the operation.   Some of
the more simple fabrics  are executed with rapidity, while oth-
ers, in  which  the sides of the meshes are plaited,  as in  the
Brussels lace, and that made at Valenciennes, are difficult,  and
bear a much greater price.
   The cheaper kinds of lace, have long  been made by ma-
chinery.   And recently the invention of Mr Heathcoats' lace
machine, has effected the fabrication of the more  difficult or
twisted lace, with precision and despatch.   This  machine  is
exceedingly complicated and ingenious, and is now in operation
in this country and in France, as well as in England. 
           ARTS OF COMBINING FLEXIBLE FIBRES.        357

   Carpeting.—Carpets are thick textures composed wholly or
partly of wool, and wrought  by several dissimilar methods.
The simplest mode is that used in weaving the Venetian car-
pets, which is a plain  texture, composed of a striped  woollen
warp, on a thick woof of linen thread.   Kidderminster carpet-
ing is composed by two  woollen webs, which  intersect  each
other in such a manner as to produce definite figures.  Brussels
carpeting has a basis composed of a warp and woof of strong
linen thread.   But to every two  threads of linen in the warp,
there is added a parcel of  about ten threads of woollen of dif-
ferent colors.  The linen  thread never  appears on the upper
surface, but parts of the woollen threads  are from time to time
drawn up in loops, so as to constitute  ornamental figures, the
proper color being each time selected from the parcel to which
it  belongs.  A sufficient  number" of these  loops is raised to
produce a uniform  surface, as seen  in Fig. 5, and to render
them equal, each row passes over a wire, which is subsequently
withdrawn.   In some cases the loops are cut through with the
end of the wire, which is sharpened for the purpose so as to
cut off the threads as it passes out.  In forming the figure, the
weaver is guided by a pattern, which is drawn in squares upon
a paper.   Turkey  carpets appear to be fabricated upon the
same general principles as the Brussels, except that the texture
is all woollen, and  the loops larger and always cut.
   Tapestry.—The name of tapestry is given to certain delicate
and complicated fabrics, in which the forms and colors of natu-
ral objects are produced  with such accuracy, as to resemble
fine paintings.  The mode of texture used to produce this ef-
fect, is in many respects analogous to that by which the finer
carpetings are made.   The minuteness, however, of the con-
stituent parts, causes the  sight of  the texture to be lost in the 
358        ARTS OF COMBINING FLEXIBLE FIBRES.
 general • effect  of the  piece.   The fabrication  of tapestry is
 slow,  intricate,  and very expensive.  The  most celebrated
 manufactory is that established by the family of Gobelins, and
 kept up by their successors, at Paris.
   Velvets.—The fine, soft knap, by which  velvet is covered,
 is produced by a method not unlike that which is used in car-
 peting, and tapestry.  It is formed of a part of the threads of
 the warp, which the workman puts in loops on a long channel-
 led wire.   Before the  wire is withdrawn, the row of loops is
 cut open by a sharp steel instrument, which is drawn along the
 channel of the wire.   Various other fabrics of silk, cotton, and
 wool, such as thicksets, plushes, corduroys, velveteens, he, are
 cut in  a similar manner.
   Cotton  counterpanes are woven with two shuttles, one con-
 taining a much coarser woof than the other.  The  coarser
 of the  threads is picked up at intervals, with an iron pin, which
 is hooked at the point,  thus  forming knobs which are made to
 constitute regular figures.
   In  cotton  fabrics, the web, when taken from the loom, is
 covered with an irregular knap, or down,  formed  by the pro-
jecting ends of the  fibres.  This is removed in  the finest arti-
 cles, by burning it off,  the heat being so managed  as not to in-
jure the texture of the cloth.   The operation is performed by
 drawing the  web very rapidly over an iron cylinder, whicli is
 kept constantly red hot, by a fire  within it.   The  velocity of
 the cloth prevents it from  burning, while   the loose filaments
 which  constitute the knap, are singed off.   The flame of coal
 gas has of late been applied to the same purpose.
   Linens.—This name belongs to fabrics which are manufac-
 tured  from flax, but those  made of hemp are similar in their
 properties, except in fineness.  The length and comparative
 rigidity of the fibres of flax, present  difficulties in the way of
 spinning it by the machinery which is used for  cotton and wool.
It cannot be prepared by carding, as these other substances
 are, and the rollers  are capable of  drawing it but  very imper-
fectly.   The subject of spinning flax by machinery, has attracted 
           ARTS OF COMBINING FLEXIBLE FIBRES.       359

much attention, and the emperor Napoleon at one time offered
a reward of a million of francs to the inventor of the best ma-
chine for this purpose.    Various individuals, both in this country
and in Europe, have succeeded in constructing machines which
spin  coarse threads of linen very well, and with great rapidity.
But  the manufacture of fine  threads, such as those used for
cambrics  and lace, continues to be performed by hand upon
the ancient spinning wheel.

                        WOOLLENS.

   The  fibres of wool,  being  contorted and elastic, are drawn
out  and spun by machinery in some  respects similar to that
used for cotton, but differing in various particulars.   Indepen-
dently of the quality of fineness, there  are  two sorts of wool
which afford the  basis of different fabrics,  the long wool and
the short.  Long wool is that  in which the fibres are rendered
parallel by the process qf  combing.  It  is also  known by the
name of worsted, and is the material of which camlets, bomba-
zines, he, are made.   Short  wool is prepared by carding, like
cotton,  and is used, in  different degrees of fineness, for broad-
cloths, flannels, and a multitude of other  fabrics.  This wool,
when carded, is formed into small  cylindrical rolls, which are
joined together, and stretched and spun, by a stubbing or rov-
ing  machine, and a jenny  or  mule, in both of which the spin-
dles are mounted  on a carriage, which  passes backwards and
forwards, so as to stretch the  material, at the same time that it
is twisted.   On account  of the  roughness  of the fibres, it is
necessary to cover them with oil or grease, to enable them to
 move freely  upon  each other  during the  spinning and weaving.
 After the cloth is woven, the  oily matter is  removed by scour-
ing, in order to restore the roughness to the fibres preparatory
to the subsequent  operation of fulling.
   In articles which are made of long wool,  the texture is com-
plete when the stuff issues from the loom.   The pieces  are
 subsequently dyed, and a gloss is communicated  to them by 
 360        ARTS OF COMBINING FLEXIBLE FIBRES.

 pressing them between heated metallic surfaces.   But in cloths
 made of short wool, the weaving cannot be said to have com-
 pleted the texture.   When the web is taken from the loom, it
 is too loose and open, and consequently requires to be submit-
 ted to another operation called fulling.   This is performed by
 a fulling mill, in which the cloth is  immersed in water,  and
 subjected  to repeated compressions  by the  action of  large
 beaters, formed of wood, which repeatedly change the position
 of the cloth,  and cause the fibres to felt and  combine  more
 closely together.   By this  process the cloth is reduced in its
 dimensions,  and the  beauty and  stability of the .texture are
 greatly improved.   The tendency to become thickened  by
 fulling, is peculiar to wool and hair, and does  not  exist in the
 fibres of cotton or flax.  It depends on a certain roughness of
 these  animal  fibres, which  permits motion  in  one direction,
 while it retards it in another.   It thus promotes entanglements
 of the  fibres, which serve  to shorten and thicken  the woven
 fabric.  Before the  cloth is sent to the fulling mill, it is neces-
 sary to cleanse it from all the unctuous matter, which was ap-
 plied to prepare the fibres for spinning.
   The knap, or downy surface of broadcloths, is raised by a
 process, which, while it improves  the beauty, tends  somewhat
 to diminish the strength of the texture.   It is produced by
 carding the cloth with a species of burrs,  the fruit of the com-
 mon teazle, (Dipsacus fullonum)  which  is  cultivated for the
 purpose.   This operation  extricates a part of the  fibres, and
lays  them  in a  parallel  direction.  The knap, composed  of
these fibres, is then cut off to an even  surface, by the process
of shearing.  This is performed in various ways, but in one of
the most common methods a large spiral blade revolves rapidly
in contact with another blade while the cloth is  stretched over
a bed, or support, just near enough for the projecting filaments
to be  cut off at a uniform length,  while the main  texture re-
mains uninjured. 
ARTS OF COMBINING FLEXIBLE FIBRES.        361
                         FELTING.

  The  texture of modern hats, which are made of fur and
wool, depends upon the process of felting, which is similar to
that  of  fulling already  described.   The  fibres  of these  sub-
stances  are rough in one direction only, a circumstance which
may be perceived by passing a hair through the fingers in op-
posite directions.   This roughness  allows the fibres to glide
among  each other,  so that when the mass is agitated, the ante-
rior extremities slide forward in advance of the body or poste-
rior half of the  hair, and serve to entangle and contract the
whole  mass  together.  The materials commonly used for hat
making, are the furs of  the beaver, seal, rabbit,  and  other ani-
mals, and the wool of  sheep.  The furs of most animals are
mixed  with a longer  kind of thin hair, which is obliged to be
first  pulled out, after which  the fur is cut off with a knife.
The materials to be felted are intimately mixed together by the
operation of bowing,  which depends  on  the  vibrations of an
elastic string; the  rapid alternations of its motion being pecu-
liarly well  adapted to remove all irregular knots and adhesions
among  the fibres, and to dispose them in a very  light and  uni-
form arrangement.   This texture, when pressed under cloths
and leather, readily unites into  a mass of some firmness.  This
mass is  dipped into a liquor  containing a little sulphuric  acid,
and when intended  to form a hat, it is first moulded into a large
conical  figure, and this  is afterwards reduced  in  its dimensions
by working  it for  several  hours with the  hands.  It is then
formed  into a flat surface, with several concentric folds, which
are still further compacted in order to make the brim, and the
circular part of the crown, and  forced on a block, which serves
as a mould for the cylindrical  part.   The  knap, or outer por-
tion  of  the fur, is raised with a fine wire brush, and the hat is
subsequently dyed,  and  stiffened on the inside  with glue.
  An attempt has been  made, and at one time excited  consid-
erable  expectation  in England, to form woollen cloths by the
              46 
362
ARTS OF COMBINING FLEXIBLE FIBRES.
 process of felting, without spinning or weaving.   Perfect imita-
 tions of various cloths were produced, but they were found defi-
 cient in the firmness and durability whic Ii belongs to woven fabrics.

                      PAPER MAKING.

   The combination  of  flexible  fibres by which paper js pro-
 duced, depends on the minute  subdivision of  the  fibres, and
 their subsequent  cohesion.   Linen  and  cotton rags,  are  the
 common material of which paper is made, but hemp and some
 other fibrous substances,  are used for the coarser kinds.   These
 materials, after being washed, are subjected to the action of a
 revolving cylinder, the surface of which is furnished with a
 number  of sharp  teeth,  or cutters,  which are so placed as to
 act against other cutters  fixed underneath the cylinder.   The
 rags are kept  immersed  in water, and continually exposed to
 the  action of  the  cutters for a number of hours, till they are
 minutely  divided, and reduced  to a thin pulp.  During this
 process a quantity of  chloride of  lime is mixed with the rags,
 the effect of which is to bleach them, by discharging the color-
 ing matter, with which any part, of them may be dyed, or oth-
 erwise impregnated.   Before the discovery of this mode of
 bleaching, it was  necessary to assort the rags,  and select only
 those which were white,  to constitute white paper.   If, howev-
 er, the bleaching  process be carried too far, it injures the tex-
ture of the paper  by corroding and weakening the fibres.
  The pulp composed of the fibrous particles mixed with wa-
ter is transferred to a large vat,  and is ready to be made  into
 paper.    The  workman is provided with a mould, which is a
 square frame  with a fine  wire  bottom,  resembling a sieve, of
the size of the intended sheet.   With this mould he dips up a
portion of the thin pulp,  and holds it in  a horizontal direction.
 The water runs out through the  interstices of the m/es, and
 leaves  a  coating of fibrous particles, in  the  form  of a sheet,
 upon the bottom of the mould.   The sheets thus formed are
 subjected to pressure, first between felts or woollen cloths, and 
           ARTS  OF COMBINING FLEXIBLE FIBRES.       363

afterwards alone.  They are then sized, by dipping them in a
thin  solution of gelatin, or glue, obtained from the shreds and
parings of animal skins.  The  use of the  size is to  increase
the strength of the paper, and by filling its interstices, to pre-
vent the ink from spreading  among the  fibres, by capillary at-
traction.   In blotting paper the usual sizing is omitted.
   The paper, after being dried, is pressed,  examined, selected,
and made into quires and  reams.   Hot pressed paper is ren-
dered  glossy by pressing it between hot plates of polished metal.
   Paper is also   manufactured by machinery, and  one of the
most ingenious  methods is that invented by the Messrs  Four-
drinier.  In this  arrangement, instead of moulds,  the pulp is
received in a continual  stream, upon the surface of an endless
web, or brass wire, which extends round two revolving cylin-
ders, and is kept  in continual motion forwards, at the same time
that it has a tremulous or vibrating  motion.   The  pulp is thus
made to form a long, continual  sheet, which is wiped  off from
the wire web, by a revolving cylinder covered with flannel, and
after being compressed between other cylinders is finally wound
into a  coil, upon  a reel prepared for the  purpose.
   Another  machine for making  paper consists of a horizontal
revolving cylinder of wire  web, which  is immersed in the vat
to the depth of more than half its diameter.   The  water pene-
trates  into this cylinder, being strained through the wire web, at
the same time depositing a coat of fibrous particles on the out-
side of the cylinder,  which  constitute  paper.   The strained
water  flows off through the  hollow axis of the cylinder, and
the paper is wound off from  the part of the cylinder  which is
above water, in the form of a continued sheet.
  Gray's Treatise on Spinning Machinery, 8vo. 1819;—Duncan's
Essay on the Art of Weaving,  8vo. 1808;—Guest's  History of the
Cotton Manufacture, 4to. 1823:—Borgnis Mechanique Appliquee aux
Arts, 1818; torn. 7, Machines  a  Confectionner les Etoffes;—Rees's
Cyclopedia, articles  Cotton Manufacture, Woollen Manufacture,
&c.;—Edinburgh Encyclopedia, articles Cotton Spinning, Cloth Manu-
facture, &c.  Much of the machinery invented in this  country, is not
described in European Works. 
CHAPTER  XVI.
                   ARTS OF HOROLOGY.

   Horology, or the  art of measuring time, has received the
attention,  and exercised the ingenuity of mankind from  the
earliest periods.   The lapse of thought and the routine of or-
dinary occupation, afford but imperfect indications of the real
passage  of time,  and the only exact standard by which periods
of duration can  be estimated, is that of governed and regular
motion.
   Sun Dial.—The diurnal movement of the earth with relation
to the heavenly bodies, is the most perfect standard of admeas-
urement for large periods of time.   It  is the only one by which
the brute creation and the uncivilized part of mankind, govern
their habits of life.  This motion has  been  converted to prac-
tical use,  for measuring small periods, by the employment of
the sun dial,  an invention  apparently of great antiquity, in
which the falling of a  shadow on a surface opposite to the sun,
indicates the hour of the day.  The  sun  dial  was known to
the ancient Egyptians, Chinese,  and  Bramins, and was used
by  the  latter  for  astronomical purposes.   It appears also to
have been known to the Jews in the time of Ahaz, about 740
years before Christ.   The  first sun dial at Rome, was set up
by Papirius Cursor, about 300  years before Christ, previously
to which time, Pliny tells us, there is no mention of any account
of time, but by the suns rising and setting.
   At Athens, there is now standing an  octagonal  building  erect-
ed by Andronicus Cyrrhestes, and commonly called the Tower
of the winds.   It is shown in PI. IV. Fig. 13.  Upon  each
of the eight sides of this building, is a flying figure carved in
relief, representing the particular wind which blew against that 
ARTS  OF HOROLOGY.
365
side.   Upon each side was also placed a vertical sun dial; the
gnomon or index, which cast the shadow, projecting from the
side, while the  lines indicating the  hour, were cut upon the
wall.   On the top, according to Vitruvius, was the figure  of a
Triton, which turned with the wind in the same manner as a
modern weathercock.  The lines of the dial upon the wall are
distinctly extant at the present day; and although the gnomons
have disappeared, the places where they were inserted are still
visible.
   Clepsydra.—Since the  sun dial could be used only in the
day time, and in clear weather, a different instrument was in-
vented by the  ancients, to be  used  within  doors, at all times;
and to this was  given the name of clepsydra.   The  clepsydra
was formed by a vessel of water, having a minute perforation
in the bottom, through  which  the  water issued drop by drop.
It fell  into another vessel, in which a light body floated, having
attached to it an index or  graduated scale.   As the water in-
creased in the receiving vessel, the floating  body rose, and by
its regularly increasing height furnished an approximation to the
correct indication of time. *
   The original  clepsydra  was but a rude instrument, and  must
have given imperfect indications of the true divisions of time.
When the vessel was first filled, the drops  must  have  fallen
faster, owing to the greater height  and pressure of the fluid ;
and in proportion as it became empty, the  dropping would be
slower,  in consequence  of the diminution of  this  pressure.
The  disadvantage, however, was  remedied in various ways by
the employment of two vessels, one of which was kept constant-
ly full by a supply from the other, and thus the water being al-
ways  at the same height,  furnished its drops under an equable
pressure.

   * This instrument was invented in  Egypt, but was brought into Rome from
Athens. Pompey, while consul, introduced it into the Roman Senate House,
and the orators were obliged to limit the length of their speeches by its divis-
ions of time, so that Pompey is designated by one of the historians, as the first
Roman who put bridles upon eloquence. 
366
ARTS  OF HOROLOGY.
   Water Clock.—An  instrument called a water clock, was in
use at a much later date, and was a subject of extensive man-
ufacture in some parts of Europe, a few centuries ago.  Sev-
eral modes of constructing  this instrument were devised, but
the following is one of the most ingenious.  A tight hollow cy-
linder, PI. X. Fig. 4, is suspended by cords wound  round its
axis, which will unwind as it runs down.  It has its interior
divided into several compartments, situated like the buckets of
a water wheel.  These compartments communicate with each
other by a minute aperture, through which water can pass slow-
ly from one compartment to another.   Before the machine is
put in motion, a small  quantity of water is introduced into the
lower compartments.   As the cylinder descends by the unwind-
ing of the cords,  it is obliged to revolve on its axis,  until  the
lower compartments which  contain the water, have risen so far
on the ascending  side as to produce an equilibrium.   It can
then unwind no faster than  the water escapes from one com-
partment to another,  through the minute  apertures.   As this
requires a considerable  time, the cylinder may occupy a day,
if  required, in descending from the top to the bottom of the
frame to which it is attached.   And if the sides of the frame
be marked with the hours of  the day, the axis of the cylinder
as it passes by them, will indicate the time of the day with as
much accuracy, as so imperfect a machine permits.
   Clock Work.—In modern  days, all other methods of meas-
uring time have given place to the  equable  motion produced
by the  action of  machinery  on the pendulum  and  balance.
Timekeepers constructed on this principle, began to be  known in
Europe about the 14th century, but were formed in a  rude and
imperfect manner, until the middle of the 17 th. Since that period,
the learning of philosophers and the ingenuity of artists have
been extensively applied to their improvement, and few subjects
connected with  the  mechanic arts, have called forth more in-
ventive acuteness,  elaborate experiment, and exact calculation.
   Before proceeding to a description of the entire mechanism
of a clock or watch, it will be useful to attend to some of the 
ARTS  OF HOROLOGY.
367
 general principles and essential parts of a timekeeper.   These
 will be most easily made intelligible by directing  the  attention
 to the following  subjects.  1.  The maintaining power.  2.  The
 regulating movement. 3. The method of connexion.
   Maintaining Power.—The force which is employed to sustain
 the  motions of  timekeepers, does not require to  be of a pow-
 erful kind.  It must, however, be  steady  and uniform in  its
 action.   Gravity and elasticity,  applied through the  medium
 of weights  and  springs, are  the only means  now employed to
 communicate  motion to these machines.  In clocks, the main-
 taining force is usually derived from a weight.   A  weight acts
 with perfect  uniformity from  the  beginning to the end of its
 descent, provided the line which  suspends it is of equal size
 throughout, and  that this line is wound upon a true  and perfect
 cylinder.   In portable  timekeepers, the weight,  for obvious
 reasons, cannot  be employed, and  the  spring, although a less
 perfect and equable power, is obliged to be substituted.   From
 the oldest clocks which remain, it appears  that the  spring was
 in use before the weight, and one of the first ever made is still
 preserved at Brussels, in which the spring is an  old sword
 blade, from which a piece of catgut is wound upon the  cylinder
. of the  first- wheel.   The principal  difficulty in the use of the
 spring, is, that its action is unequal, and that the more it is bent,
 the  greater force it exerts to  return  to its  natural situation.
 The spring of .a watch, as it is now used,  is a  long  plate of
 steel coiled up into a spiral form.   From  the outside of this
 proceeds a chain, which  is  attached, not  to  a  cylinder, as is
 done with the weight, but to  a spiral roller called a fusee, which
 by its conical form, gives to the spring an increased  mechanical
 advantage, in  proportion as its power  diminishes.  The fusee
 has  already been described, page 337.
    In some of the watches which are now made,  the fusee and
 the  chain are dispensed with.   The barrel which incloses the
 spring, has a toothed circle on  its outside, which turns round as
 the  spring unwinds, and gives  motion to the machinery.  But
 in this  case the spring is made larger than common, and only 
368
ARTS  OF HOROLOGY.
the middle part of its action is used, it being never wound up
so far as to call  forth its greatest  strength, nor  suffered to run
down so far as to be materially weakened.
   Regulating Movement.—In  the mechanism of clocks  and
watches, it is necessary so  far to retard the movement of the
maintaining force, i. e. of the weight or spring, that it  may be
hours and days  in expending itself,  and  that the timekeeper
may require  to  be  wound up only at  distant and  convenient
periods.   This is in part effected by, the successive combination
of wheels  and pinions, the last of which turns  round many
hundred times, while the first turns round  once.   But if a time
keeper  possessed only wheels and pinions, it would run down
with a rapidly accelerated  motion in the  course of a few sec-
onds.  It becomes, therefore, necessary to connect with it an-
other motion  which  cannot be  accelerated  beyond a certain
degree, by any given force.  This motion is obtained in clocks
from the pendulum, and in watches from the balance ; and it is
the one  which it  was proposed to consider as the second head
under the name of the regulating movement.
   Pendulum.—A  pendulum is a weight  capable of vibrating
about a  point from which  it is suspended.   If the  curve in
which the  pendulum moves  be a  circular arc, it is necessary •
that the length of the vibrations should be exactly equal; other-
wise the pendulum  will not keep true time.   But if the curve
be a cycloidal one, the pendulum will move back and forward
in equal  times, whatever be the  length of its vibrations.   In
practice, it is  found difficult to make a pendulum move  in a
cycloidal path without too much friction.   It is therefore cus-
tomary in clocks to use pendulums moving in circular arcs,
these arcs being  made to approximate to cycloids, by being as
short as possible.
   Pendulums, when set in motion, would continue to vibrate
forever, were it not for the  retarding effect of friction and the
resistance of the atmosphere.   The former of these is partly
obviated by hanging the pendulum upon a thin spring, the latter
by forming it with  a sharp  edge.   Still a  considerable  force is 
ARTS  OF HOROLOGY.                369
requisite to sustain the motion, and this force in clocks is deriv-
ed from the weight.
  That pendulums may vibrate in equal periods, and thus fur-
nish a correct measure of time,  it is  necessary that they should
always be of  uniform length, for pendulums of different lengths
differ in  their vibrations as the  square roots  of their  lengths.
Now  such is the  effect of heat in  expanding all known  sub-
stances, particularly  metals, that the same pendulum is always
longer in summer than it is in winter, and sufficiently so, to af-
fect  the  correctness of the  timepiece to which it is attached.
To remedy this difficulty, various ingenious contrivances have
been resorted to, the most common  of which  are combinations
of metals, so connected  as to expand in  opposite  directions,
counterbalancing each other, so as to keep the centre of oscil-
lation in one  place.  This is sometimes effected in the gridiron
pendulum, by combining bars, or rods, of steel and brass; and
in the  mercurial  pendulum, by inclosing a quantity of quick-
silver in a tube, near the bottom of the pendulum.
  Balance.—As the pendulum depends upon the force of grav-
ity for its motions, it obviously cannot be employed for watches,
or portable timekeepers, which are  liable to change their posi-
tion.   A substitute is found in the balance,  which is commonly
a wheel moving on an  axis, and which, when thrown backward
and forward, by opposite applications of the moving  force, per-
forms  its vibrations in equal times.   The  balance is liable to
the same irregularities from expansion and contraction, as the
pendulum, and is corrected  in a similar  manner,  and  watches
go best, when they are  kept in the uniform heat of the body.
  The quantity of matter  accumulated in  the  balance wheel
of a common watch, is so extremely  small, that it  seems  im-
possible that  it should exert a perfect regulating  power.   The
want of weight, however, is in some measure made up by
causing it to  perform  large vibrations, and  to move  with great
velocity.   The rim  of the  balance  wheel in a  good watch,
frequently  moves  through ten  inches in every second.  This
velocity  is produced by the  hair  spring,  which  throws  the
               47 
370
ARTS  OF HOROLOGY.
balance back to the point of equilibrium as fast as it is thrown
out in either direction by the moving force, thus performing for
the balance, what gravity does for the pendulum.   If the  hair
spring be taken away, a watch will lose more than 12 hours in
24, and  go much  more  irregularly.   The  operation of the
common  regulator of a watch, is to tighten or  relax  this  hair
spring by making its effective  part  longer or shorter, thus ac-
celerating or retarding the speed of the balance.
   Scapement.—It remains to consider the  third part or scape-
ment, by which  the  rotary  motion of the  wheels is converted
into the  reciprocating  one of the pendulum and  balance.  In
the scapement, a certain  part  connected  with the  pendulum
or balance, is put in the way of the last or most  rapid wheel,
so that only one tooth of this  wheel  can  escape by it during
each vibration.   Thus the pendulum  or balance, while it re-
ceives its motion from this wheel, becomes in its turn the regu-
lator of its velocity.
   The  crutch or anchor scapement,  used in clocks, and  the
common pallet  scapement with a contrate  wheel,  which is
the kind  most extensively used in  watches, have  been already
explained  under the head of  machinery, page  245.   The
horizontal   scapement,               Fig.  1.
Fig. 1, consists of a wheel
A, with elevated teeth,
the outer surface of which
is   curved   obliquely.
These  teeth  act upon
the edges  of  a hollow
half cylinder, C, the axis of which is  parallel to that of  the
wheel, and carries  the  balance  upon  one of its extremities.
When a tooth of the scape wheel strikes the first edge of the
cylinder, it causes it to recede,  moving the balance in one di-
rection.   The tooth then enters the hollow part of the cylinder
and strikes upon the opposite  side.   Before  it can escape, the
cylinder is obliged to turn in the opposite  direction,  and thus a
vibrating movement is kept up in the  cylinder and balance.
 
ARTS  OF  HOROLOGY.
371
   A multitude of other scapements, have also been introduced
by different artists, varying from each other in the complication
of their structure, and  accuracy of  their  movements.  But
these must necessarily be omitted.  The operation of the sim-
pler forms already described, will be more intelligible taken in
connexion with the wheel work next to be  noticed.
   Description of a Clock.—In PI. X, several views are given
of the mechanism of a clock,  consisting  of  the going part,
which moves constantly and carries the hands; and the striking
part, which  announces the hour.   Fig.  1, PI. X, is  an eleva-
tion of the clock with the wheels seen edgewise, shewing the go-
ing part;  the striking movements being omitted in this figure, to
avoid confusion.    Fig. 2, is a front view of  the wheel work of
both going and striking parts ;  and  Fig. 3, is the dial work or
mechanism immediately under  the  dial, or face of the clock,
and is that part which  puts the  striking train in motion every
hour.  A clock of this kind contains two independent trains of
wheel work, each with its separate first mover.  One is constant-
ly going, to indicate time by the hands on  ihe dial plate ; the
other is put in motion once in an hour, and strikes a bell to tell the
hour at a  distance.   The part marked a, in Figures 1 and 2, is
the  barrel of the going part;  it has a catgut  band, b, wound
round it, suspending the weight which keeps the clock in motion.
The part  marked 96, is a wheel, called the first or great wheel,
of ninetysix  teeth  upon the end of a barrel, turning a pinion
8, of eight leaves, on an arbor,* which carries the minute hand ;
also 64,  is a wheel of 64  teeth, on the  same  arbor, called
the centre wheel, turning the  wheel 60 by a pinion of eight
leaves on  its  arbor.   This last wheel gives motion to the pinion
of eight, on the arbor of the swing wheel 30, which has 30 teeth.

  * The terms arbor, shaft, axle, and axis, are synonymously used by mechan-
ics, to express the bar, or rod, which passes through the centre of a wheel.
The terminations of a horizontal arbor are called gudgeons, and of an upright
one, frequently, pivots.  The term axis in a more  exact sense  may  mean
merely the longest central diameter, or a diameter about which motion takes
place. 
.372
ARTS  OF HOROLOGY.
The parts d h, are the pallets of the scapement  fixed on an
arbor e, Fig 1st, going through the back  plate of the clock's
frame,  and  carrying a long lever /.   This lever  has a small
pin projecting from its lower  end,  going  into an oblong hole
made in the rod B of the pendulum.
   The pendulum  consists  of  an inflexible metallic rod, sus-
pended by a very slender piece of steel spring D, from a brass
bar E, screwed to the frame of the clock, having a weight at its
lower end not seen in the figure; in the present case 39| inches
from the suspension D.  When this pendulum is moved from the
perpendicular line, in either direction, and suffered to fall back
again, it swings  nearly as much  beyond the  perpendicular on
the contrary side,  and then returns.   This it will continue to
do for  some time,  and each of these vibrations will be perform-
ed in one second of time,  when the pendulum is of the above
length.   This is the measurer of the time, and  the office  of
the clock  is only to indicate  the  number of vibrations it has
made,  and to give  it a  small impulse  each time to keep it go-
ing, as the resistance of the air and elasticity of the spring D,
would  otherwise in a  short time cause it to stop.   By the ac-
tion of the weight applied to the cord b, which is called the
maintaining power, the wheels  are all turned round ; and if
the pallets d and h, were removed, the swing  wheel 30 would
revolve with great velocity in the direction from 30 to d, until
the weight reached the ground.   The teeth of these pallets are
so placed, that one of them always engages the wheel and pre-
vents it from turning more  than half a tooth at a time.  In  the
figure, the pallet d, has the nearest tooth of the wheel resting
on it, and the pendulum is  on the side h of the perpendicular.
When it returns, it moves the  pallet d, so  as to allow  the tooth
of the wheel to  slip off;  but in the mean time the  pallet h,  has
interposed its point in  the  way of the tooth next  it, and stops
the wheel till the next vibration or second.   The distance  be-
tween the two  pallets d and h, is so  adjusted, that only half a
tooth of the wheel escapes at each vibration ; and  as the wheel
has 30 teeth, it will revolve once in 60 vibrations, of one second 
ARTS  OF HOROLOGY.                373
each, or in one minute; consequently a hand on the arbor of this
wheel, will indicate seconds on the dial plate F, which is a cir-
cle divided into 60.   The pinion of eight on its arbor is turned
by  a wheel of 60, which consequently will turn once in seven
turns and a half of the other, or in seven  minutes 30 seconds,
or in one  eighth of an hour.  Its pinion of eight is moved by
a wheel of 64, or eight times itself,  which  will turn  in  one
eighth part of the time.   This will be an hour, and therefore
the arbor of this wheel, carries the minute hand of the clock. The
great wheel of 96, being 12 times the  number of the pinion
eight, will turn once in 12 hours,  and the barrel a with it.  The
cord of catgut goes  round 16 times, so that the clock  will go
eight days.
   The  hour  hand of the clock is turned by the wheel work,
shown in Fig. 1, and 3.  On the end of the arbor of the centre
wheel 64, a tube is fitted so as to  go round with it by friction.
This carries the minute hand, and if the  clock should  require
correction, the hand may be slipped round without moving the
wheels.   This tube  has a pinion of 40 teeth  on its lower end,
indicated by a dotted circle.   This turns another wheel 40, of
40 teeth, which has a pinion of  six teeth on its arbor,  turning
a wheel 72, of 72 teeth.   The two wheels 40, will both  turn
in an hour;  and 72, in 12  hours.  The  arbor of this wheel
has the hour  hand, and is a tube going over the arbor of the
minute hand,  so that the two hands are concentric.   The bar-
rel a, is fitted  to an arbor coming through the  plate of the clock,
 and  filed square to put  on a  key to wind up the  weight.
The  great wheel 96, is not fixed fast to the arbor, but  has a
click on it, which takes the teeth of a ratchet wheel cut on the
barrel; so that the  barrel  may be turned in one direction to
wind up the weight, without the wheel; but by the descent of
the weight, the wheels will be turned with the barrel by the click.
    Striking Part.—Having  now  considered the going part of
the clock, it remains to describe the  mechanism by which the
hour is struck.  In Fig. 2, 78 is a great wheel of 78 teeth,
provided with a barrel and click  as in 96 ; it turns a pinion of 
374
ARTS  OF HOROLOGY.
eight.   On  the  same arbor is a wheel 64, turning a pinion of
eight, on the arbor of the wheel o, of 48.   This turns  another
pinion of eight,  and wheel p, of 48,  which turns a pinion of
six, on the same arbor with a thin vane of metal, seen edgewise,
which is called the fly, and which, by the  resistance of the air
to its motion, regulates the velocity of the wheels.
   The wheel 64 has eight pins projecting from it, which raise
the tail n of the hammer, as they revolve.   The hammer is re-
turned violently when the  pins leave  its tail, by  a spring m,
pressing on the end of a pin put through its arbor ; and strikes
the  bell.  The  hammer  and bell  are behind the plate, and
therefore  unseen.  There is a short spring I, which the  other
end  of the pin through the arbor touches, just before the ham-
mer strikes the bell.  Its use is to lift the hammer off the bell,
the instant it has  struck, that it may not stop the sound.  The
pins  in the  wheel 64, must  pass by the  hammer  tail  78
times in striking the twelve hours, l-f-2+3-|-4-|-5-|-6-r.7-T-8-f-
9_|_10-f.ll-|-12 —78, and as its pinion has eight leaves, each
leaf of the  pinion answers to a pin in the  wheel 64.   Now as
the great wheel has 78 teeth, it will turn once in 12 hours, the
same as the other great wheel 96.  In the wheel 64,  eight of
its teeth  correspond to one of the pins of the hammer, and as
the pinion of the wheel o, has eight teeth, it (wheel o) will turn
once for each stroke  of the hammer.   By the remaining
wheels, one, o, multiplying  six  times, and the other,  p, eight
times, the fly will turn 6 x 8 =z 48  times for one turn of o,
which answers to one stroke of the hammer.
   Fig. 3, is also mechanism relating to the striking part.   Behind
r there is a small pinion of one tooth, called the gathering pal-
let, on the arbor of the wheel o, which consequently turns once for
each stroke of the hammer.  The part marked S r x is a por-
tion of a large  wheel, and is called the rack.   The  part t
is an arm attached to the rack, whose end rests against a spiral
plate, V, called  the snail, which is fixed on the tubular arbor
before described, of the hour  hand and wheel  72, and turns
round with  it once  in 12 hours.  The snail is divided  into  12 
ARTS  OF HOROLOGY.
375
equal angles, of 30 degrees eacb, and as it turns, each of these
answers to an hour.   The circular arcs, forming the circum-
ference of the snail, are struck from the centre of the  arbor
between each division, with a different radius, decreasing a cer-
tain quantity each time in the order of the hours.  The circu-
lar part of the rack, 14, is cut into teeth, each of which is of such
a length, that every step upon the snail shall answer to one of
them.  At w, is  a spring pressing against the tail of the rack,
and acting to throw the arm of the rack against the snail.  The
part g, is a click called the hawk's bill, taking into the teeth of
the rack, and holding it up in opposition to the spring w.  The
part i k is a three-armed detent, called the ivarning piece.  The
arm k is bent at  its end, and passes through a hole in the front
plate  of the  clock, so as to catch a pin  placed in  one of the
arms  of the  wheel p, Fig. 2, and which describes the  dotted
circle in Fig. 3.   The  other arm i, stands so as to fall in  the
way of a pin in the wheel 40.   In the present position of the
figure, the wheels of the  striking train  are in motion, and
would continue turning until the gathering pallet at r, which turns
once at each stroke of  the  hammer, by its tooth lifts the rack
s, in  opposition to the spring w, one tooth each  turn ; and the
hawk's bill g retains the rack, until a pin in the end of the rack
is brought in the way of the lever of the gathering pallet r, and
stops the wheels from turning any farther.  It is in this position
with  the  rack wound up, till its pin arrests  the tail r, that we
shall begin  to describe the  operation  of the striking of the
 clock.
   The wheel 40, as has been  said before, turns once in an
 hour, and consequently at the  expiration of every  hour, the
 pin in it takes the end i, and moves it towards the spring near
 it.   This depresses the end k, until it falls in the circle of the
 motion of the pin in  the wheel p, Fig. 2.  At  the same time
 the short tail depresses one end of the hawk's  bill, and raises
 the other g, so as to clear  the  teeth of the  rack s.   Immedi-
 ately the spring w, throws  the  rack back, until the end of its
 tail t, touches that part of the snail which is nearett it.   When 
376                ARTS OF HOROLOGY.

the rack falls back, the pin in it is moved clear of the gather-
ing pallet r, and  the wheels set at liberty.   The maintaining
power puts them in motion; but  in a very short time before
the hammer has struck, the pin  in the wheel p  falls against the
end of k, and stops the whole.   This operation happens a few
minutes  before the clock strikes, and this noise of the  wheels
turning, is called  the warning.   When the hour is expired, the
wheel 40 has  turned so far, as to allow the  end of * to slip
over  its  pin, as  in  the figure.   The  small   spring pressing
against it raises the  end k, so as to be within the circle of the
pin in the wheel  p, Fig. 2.   Every obstacle is now removed,
and the  wheels  run  on the pinion ; the wheel 64  raises the
hammer r, and it strikes on the bell;  the  gathering pallet r,
takes up the  rack,  one tooth at each turn, the hawk's  bill g,
retaining it until the pin x in the rack comes under the gathering
pallet r,  and stops the motion of the whole machine, till the pin
in the wheel 40 at the next hour  takes the  warning piece ik,
and repeats the  operation  we  have now described.   As the
gathering pallet turns once for each  blow of the hammer, and
its tooth  gathers up one tooth of the rack at each turn, it is evi-
dent, that the number of teeth which the rack is allowed to fall
back, limits the  number of strokes the hammer will  make.
This is done by  the rack's tail t, resting on the snail.  Each
step of the snail answers to one  tooth of the  rack, and  one
stroke of the  hammer.  At each hour, a  fresh  step  of the
snail is turned to the tail of the rack, and by  this  means the
number of strokes is made to increase one at each time from
1 to 12.
   Description of a Watch.—In PI. XI. several views are  giv-
en of the construction of a common portable  watch.   Fig. 1
represents the wheel work  immediately beneath the  dial plate,
and also its  hands, the circles of hours  and minutes being
marked,  though  the  dial on which these are  engraved is re-
moved-.  Fig. 2 is a plan of the wheel work all exhibited  at
one view, for which purpose the  upper  plate of the watch is
removed.  Fig.  3  is a plan of the balance,  and  the work 
ARTS  OF HOROLOGY.               377
situated upon the upper  plate.   Fig. 4 shows the great wheel
and the pottance  wheel  detached.   Fig. 5 the  spring barrel,
chain,  and fusee detached;  and Fig. 6 is an elevation  of all
the movements together, the works being supposed to be  open-
ed out into a straight line, to  exhibit them all at  once.  Fig. 7
is a detached view of the balance, together with the scapement,
in action.
   The principal frame for supporting the acting parts of the
watch, consists of two circular plates, marked C and D  in the
figures.  Of these the former is called the upper plate, and the
latter  the  pillar plate, from the circumstance that the four pil-
lars, E  E, which unite the two plates and  keep them a prop-
er distance asunder, are fastened firmly into the lower  plate;
while  the other ends pass through holes in the upper plate, C,
and have small pins put through the ends of the  pillars, to keep
the  whole together.  By drawing out these pins,  the  watch
may be taken to pieces.   The pivots of the several wheels being
received in small holes made in these plates,  they of course
fall to pieces as soon as the  plates are separated.
   The maintaining power is a spiral steel spring,.which is coil-
 ed up close  by a tool used for the purpose, and put into a brass
 box called the barrel.   It is marked A in all the figures, and is
 shown separate in Fig. 5, with the spring in it.   The spring has
 a hook at the outer end of its spiral, which is put through a
 hole,  a, Fig.  5, in the side  of the  barrel, and rivetted  fast
 to it.   The inner  end of the spiral has an oblong opening  cut
 through it, to receive a hook upon the barrel arbor, B, Fig. 5.
 The pivots of this arbor pass through the top and bottom of the
 barrel, and one of them is filed square to hold a ratchet wheel,
 b, Figs 1  and 6,,which has  a click and  keeps  the  arbor from
 turning round, except in one direction.   The two pivots of the
 arbor are received in pivot  holes  in the  plates C D of the
 watch, and  the pivot which  has the ratchet  wheel upon  it, pas-
 ses through the plate.  The  wheel marked b, Figs. 1 and 6,
 with  its click, is therefore on the outside of the  pillar plate D
 of  the  watch.  The top of the barrel has a cover or lid fitted
                 48 
378
ARTS  OF HOROLOGY.
into it, through which the upper pivot of the arbor projects;
thus the arbor of the barrel is to be  considered as a fixture,
the click of the ratchet wheel preventing it from turning round,
while the interior end of the spiral spring being hooked, assists
in rendering it stationary.  The  barrel  thus  mounted  has a
small steel chain, d, Figs. 2 and 6, coiled round its circumfer-
ence, and  attached to it by a small hook of the chain which
enters a little hole, made in the circumference of the barrel at its
upper end.   The  other  extremity of this chain is hooked to
the lower part of the fusee, marked F, Figs. 2, 5, and 6, and
the chain is disposed either upon the circumference of the bar-
rel, or in the  spiral groove cut round the fusee for its reception,
the arbor of which  has pivots at the ends, which are received
into pivot holes made in the plates of  the  watch.   One pivot
is formed  square  and  projects  through the plate, to fit the
key by which the watch is wound up.
  It is evident that when the fusee is turned by the watch-key,
it will wind the chain off the circumference of the  barrel on
itself; and as the outer end of the spring  is fastened  to  the
barrel,  and the other is hooked to the  barrel arbor,  which as
before mentioned, is prevented  from  turning by the click of
the  ratchet  wheel,  a b; the  spring will  be coiled  up  into a
smaller compass  than  before.  Its reaction, therefore, when
the key is taken off, will  turn  the barrel, and by the chain,
turn the fusee and  give motion  to the wheels of the  watch.
The fusee has a spiral groove cut round it, in which the chain
lies;  this groove is  cut by an engine,  in such a form  that the
chain shall pull from the smallest part, or radius, of the fusee,
when the spring is quite wound up, and therefore acts with its
greatest force on the chain.  From this point the groove grad-
ually increases in diameter, so that as the spring unwinds and acts
with  less power, the chain operates on a larger  radius of the
fusee; and the effect upon  the arbor of the fusee, or the toothed
wheel attached to it, will always be equal, and cause the watch
to go with  regularity. 
ARTS  OF HOROLOGY.
379
  To prevent too much chain being wound upon  the  fusee,
and  by that  means  breaking the chain or overstraining the
spring, a contrivance called a guard-gut is added.  It is a small
lever, e, Fig. 2, moving on a stud fixed to the upper plate C
of the watch, and pressed downwards by a small spring,/.  As
the chain is wound upon the fusee, it rises in the spiral groove,
and  lifts up the lever until it touches the upper plate.   It is
then in a position to intercept  the edge or tooth, g, of the  spi-
ral piece of metal seen on the top of the fusee, and thus stops
it from being wound up  any further.
  The  power of  the  spring is transmitted to the balance by
means of several toothed wheels, which multiply the number of
revolutions which the chain makes on the fusee, to such a number,
that though  the  last or balance wheel  turns 91 times  every
minute, the fusee  will at the same time turn so slowly, that the
chain will  not be drawn  off from it in less than 28 or 30  hours,
and it will  make only one turn in four hours.  This assemblage
of wheels is called the train of the watch.   The first toothed
wheel, G, is attached to  the fusee, and is called the great wheel.
It is shown separated from the fusee, in Fig. 4, having  a hole
through the  centre to receive  the  arbor of the fusee, and a
projecting  ring upon  its surface.  The  under surface  of the
base of the fusee is shown in Fig. 5, at F, having a circular
cavity cut in it to  receive  the corresponding  ring  upon  the
great wheel G, Fig. 4.  A ratchet wheel, i, is fixed ^ast upon
the fusee  arbor, and  sunk within the cavity excavated  in the
lower surface of the fusee.  When the wheel  and fusee  are
put together, a small click, h, Fig. 4, takes into the teeth  of the
rachet i.   As the fusee  is turned  by the watch-key  to wind up
the watch, this click slips over the  sloping slides of the teeth
without turning the great wheel;  but  when the fusee is turned
the other way by  drawing the chain from the spring barrel, the
click catches the teeth of the ratchet wheel, and causes the
toothed wheel to turn with the fusee.
   The  great wheel,  G, has 48  teeth  on  its circumference,
whicli take into  and turn a pinion of 12 teeth, fixed on  the
same arbor with the 
380
ARTS  OF HOROLOGY.
   Centre wheel, H, so called from its situation in the centre of
the watch; it  has 54 teeth to turn a pinion of six  leaves,  on
the arbor of the-
   Third wheel, I, which has 48  teeth.  It is sunk in a cavity
formed in the  pillar plate, and turns a pinion of  six, on the  ar-
bor of the
   Contrate wheel, K, which has 48 teeth cut parallel  with its
axis, by which it turns a pinion of six leaves, fixed  to
   The balance wheel, L.   One of the pivots of the arbor of this
wheel turns in a frame, M, called thepottance,orpotence, fixed to
the upper plate, and shown separately in Fig. 4. The other pivot
runs in a small piece fixed to the upper part, called the  counter
pottance, not  shown in any  of the  figures; so that when  the
two plates are put together, the balance wheel pinion may work
into the teeth of the contrate wheel, as shown in  Fig. 6.  The
balance wheel, L, has 15 teeth, by which it  impels the balance
op.  The arbor of the balance,  which is called  the verge,
has two small  leaves or pallets  projecting from it,  nearly at right
angles to each other.  These are acted upon by the teeth of the
balance wheel, L, in such a  manner, that at every vibration the
balance  receives a  slight impulse to continue its  motion, and
every vibration so made, suffers a tooth of the wheel to escape
or  pass  by, whence this part is  called the scapement of  the
watch, and constitutes its most essential part.   The wheel L,
is sometimes  called the  scape wheel, or crown wheel.   Its  ac-
tion is explained by Fig. 7,  which  shows the wheel and bal-
ance  detached.  Suppose in this  view, the pinion h, on  the
arbor of the balance wheel or crown wheel, i k,  to be actuated
by the main  spring which  forms the maintaining  power, by
means of the train of wheel-work, in the direction of the arrow,
while the pallets m  and n, attached to the axis of the balance,
and standing  at right  angles to each other,  or very nearly so,
are long enough to fall  in the  way of the  ends of the sloped
teeth of the  wheel  when turned round at an angle of 45  de-
grees, so as to point to opposite  directions, as in  the figure.
Then a tooth in the wheel below for  instance,  meets with the 
ARTS  OF HOROLOGY.
381
pallet n, supposed to be at rest,  and drives  it before it a cer-
tain space, till the end of the tooth escapes.  In the mean time
the balance, ospr, attached to the axis of the  pallets, contin-
ues to move in the direction r o sp, and winds up the small
spiral, or hair spring,  q, one  end of which  is fast to the
axis, and the other to a stud on the upper  plate of the frame.
In this operation, the spring opposes the momentum given to
the balance by this push of the tooth upon the pallet, and pre-
vents the balance  going quite round ; but the instant the tooth
escapes, the  upper pallet, m, meets with another tooth at the
opposite side of the wheel's  diameter, moving  in an opposite
direction to that below.  Here this pallet receives a push which
carries the balance  back again,  its momentum as yet be-
ing  small in  the   direction  ospr,  and  aids  the spring,
which now unbends itself till it comes to its  quiescent position,
then swings beyond that point, partly by the impulse from the
maintaining power on the pallet m, and partly by the acquired
momentum of the moving balance, particularly when this pallet
m, has escaped.   At length the pallet n again meets with the
succeeding tooth, and is carried backward by it in the direction
in which the balance is now moving,  till the maintaining power
 and force of the unwound spring together overcome the  mo-
 mentum of the balance, during which  time the recoil of the
 balance wheel is apparent, and  also of the seconds hand, if the
 watch has one, its place being on the arbor of the contrate wheel.
 Then the wheel brings the pallet n back again till it escapes,
 and the same process takes place with the pallet m as has  been
 described with respect to pallet n.  Thus two contrary excur-
 sions or oscillations of the balance take place before one tooth
 has  completely escaped, and for this reason there must always
 be an odd number of teeth in this wheel, that a space on one
 side of the  wheel  may always be  opposite to a tooth on the
 other, in order that one pallet may be out of action  while the
 other is in action.
    The upper pivot of the verge is supported in a cover screwed
 to the upper plate, as shown at N, in Fig. 6, which extends over 
382
ARTS  OF HOROLOGY.
the balance and protects  it from  violence.  The lower pivot
works  in the bottom of the  pottance, M.  at t, Fig. 4.  The
socket for  the  pivot of the balance wheel, is made in a small
piece of brass, v, which slides in a groove made in the pottance,
as shown Fig. 4, so that by drawing the slide  in  or  out, the
teeth of the balance wheel shall  just clear one pallet before it
takes the other; and upon the perfection  of this adjustment,
which is called  the scaping of the watch, the performance of it
very greatly depends.
   It now remains to show the communication of this motion to the
hands of the watch, which indicate the time on the dial plate.
The hands are moved by  the  central arbor,  which  comes
through the pillar plate and projects a considerable length.   It
has a pinion of 12 leaves, called
   The common pinion, w, Fig. 6, fitted upon it, the  axis of
which is a tube formed square at the end, to fix on the minute
hand, W.  It fits tight upon the projecting  arbor of the centre
wheel,  and therefore turns with it, but will slip round to set the
hands  when the watch is  wrong and requires to be rectified.
The common pinion is situated close to the pillar plate, and its
leaves  engage the teeth of
   The minute  wheel, X, Figs. 1  and 6, of 48 teeth,  which is
fitted on a pin fixed in the  plate, and its pinion, a:, of 16 leaves,
which is  fixed to it, turns
   The hour wheel,  Y, of 48 teeth.   The  arbor  of this is a
tube, which is put over the tube of the cannon pinion carrying
the minute hand, and has the  hour hand, Z, fixed on it, to indi-
cate the time upon the dial plate.   Thus, by the cannon pinion,
w, which is to the minute  wheel, X, as one is to four, and the
pinion  x of this, which is to the  hour wheel, Y, as one is  to
three,  the  hour wheel Y, and its hand z, though  concentric
with the cannon pinion and minute hand, make but one revolu-
tion during 12  revolutions  of the  other; therefore one turns
round in an hour, and the  other turns round once in 12 hours,
as the  figures on the dial show. 
ARTS  OF HOROLOGY.
383
  It is necessary to have some regulation by which the rate of
the watch's movement  may be adjusted, for hitherto we have
only spoken of making the watch keep always to a uniform, or
certain rate of motion, but it is necessary to make it keep true
time.   This can be done by two means, either by increasing
or diminishing the force of the main spring,  which increases or
diminishes the arc which the balance describes ; or it may be
done  by  strengthening or weakening the  hair spring, which
will cause the balance to move quicker or slower.
   The hair  spring,  otherwise called the pendulum spring, q,
Fig. 3, is fixed to a stud, upon the plate c, by one end, and is
attached to the verge of the balance by the  other.
   The regulation  is effected by means of what is called the
curb.   This is a small lever, z, Fig. 3, projecting from a circu-
lar ring, r r, which may  be considered as its centre of motion,
but perforated  with a hole through  the centre, large enough to
contain  the hair  spring within it.    A  circular  groove is
turned out in the upper plate, nearly concentric with the bal-
ance,  and the ring, rr, fits into this.  Both are turned rather
largest at the bottom, in the manner of a  dove-tail; but the
ring being divided at the side opposite to the  lever, z, can be
sprung up and rendered so much smaller as to get it into the
groove, and, being oace in, the elasticity of the  ring expands
it, so  as to fill the  groove completely.   In  this state it may be
considered as a lever which describes a circuit  round the verge
 as a centre, and the  end of it points to a divided arc engraved
 on the  upper  plate, one  end of which  is marked F,  and
 the other S, denoting that the index or lever, z, is to be moved
 towards one or the other, to make  the  watch  move faster or
 slower as its regulation requires.
    The manner of its operation is thus ; the end of the lever,
 or index, z, continues within the circle a small distance towards
its centre, and  passing beneath  the outer turn of the  spiral
 spring q, has two  very small pins rising up from it, which in-
 clude the spring between them.  The actual length of the hair
 spring is therefore to  be estimated from these pins to the place of 
384
ARTS  OF HOROLOGY.
its connexion with the verge.  Now by altering the position
of the index, this acting length can be regulated at pleasure, to
produce such vibration of the balance as will make the watch
keep true time.   By shortening the length, the spring becomes
more  powerful,  and returns the'balance  quicker, so  that it will
vibrate in less time.   This is  effected by moving the index to-
wards F.   On the other hand, turning  the index  toward  S,
lengthens the spring by which it becomes more delicate, and
less powerful, returning the balance slower than before.
  Many watches, instead of the arc and  index, have a circular
curb, or regulator, which is turned by a central arbor, to which
the watch-key is applied, when it is necessary to move it.
  Delicate  watches have  jewelled pivot holes for the top and
bottom of the verge, to diminish  the  friction.   These jewels
are diamonds, rubies,  and other  stones, which unite great hard-
ness with durability.   Each consists of two pieces, one of whicli
has a cylindrical hole  drilled through it to receive the pivot, the
other is a flat piece, making  the rest or  stop which forms the bot-
tom of the hole.   Both stones are ground circular on the edge,
and are fitted and burnished into small  brass rings,  which are
fastened into the bearings above and below by two small screws
applied to each.   The addition  of jewels to a watch is a  great
advantage, as they do not tend to thicken the oil, which  brass
is apt to  do,  in consequence of the oxidation of the  metal.
  Cumming's Elements of Clock and Watch Work, 4to. 1766;—Ber-
thoud Histoire de la Mesure du  Temps par les Horloges, 2 torn. 4to.
1802;—Harrison on Clock  Work and Music, 8vo. 1775;—Robison's
Mechanical Philosophy, article Watch Work, vol.  iv.;—Martin's
Circle of Mechanical  Arts, 4to.  1818;—And the Encyclopedias of
Brewster, Rees, and Nicholson, under various heads. 
CHAPTER  XVII.
                  ARTS OF METALLURGY.

   The term metallurgy, in its most comprehensive sense, sig-
nifies the art of working metals in every different way.   In a
more precise and limited sense,  it is confined to the separating
of metals from their ores,  and assaying them to  ascertain their
value.  In  the present chapter, it is proposed to make use of
the  term in its more general  meaning, so far, at least,  as  to
comprehend certain processes in the management and manu-
facture of metals, which  are  sufficiently interesting  to  merit
the attention of the general student.
   Extraction of Metals.—Metals are found in nature in various
states.  When uncombined, or when combined only with each
other, they  are said to be  in a native state.   When combined
with other substances, so that the metallic properties are in some
measure disguised,  they are  said to be mineralized, or in the
state of ore.   The substance with which the metal is combined,
is termed its mineralizer.   The most common  states of com-
bination in which the metallic ores are found, are oxides, com-
binations  of oxides with  carbonic,  sulphuric,  muriatic, and
phosphoric  acids; and  sulphurets.   These ores occur under
various forms, sometimes  crystallized, and  often  destitute of
any regular figure.  They are  met with, generally, in veins,
penetrating the strata;  and in this case, are usually blended or
intermixed  with  various  earthy fossils, as calcareous spar,
fluor spar,  quartz,  he   The  accompanying  fossil is termed
the gangue or matrix of the metal.   Some metallic ores occur
■ in beds, or in large  insulated masses.
   To separate the  metal, after it  is dug from  the mine, the
mass is broken up  and subjected to the operations of sorting,
               49 
386
ARTS  OF METALLURGY.
stamping, washing, roasting,  smelting, and refining.   Sorting
consists merely in the separation of the different pieces of ore
into lots, according  to the products they are expected to afford,
and the treatment  they are likely to require.    After the ore is
sorted, it is carried  to the stamper, or stamping mill, which has
been  described in a former chapter.  The process of stamp-
ing, breaks and pounds up the ore, together with its gangue, in-
to a coarse powder.   From the stamping mill, the  pounded
ore is conveyed  to the washing, a process in which advan-
tage is taken  of the difference of specific gravity.   The oper-
ation  of washing, is sometimes performed by hand, in wooden
vessels, or in troughs  which cross a  current  of  water;  and
sometimes, if the ore is rich and valuable, upon inclined tables
covered  with cloth.   In  this process the heavier parts  con-
sisting of the metallic ore, sink  first to the bottom, while the
stony  matter, which is lighter  than the  ore, being longer in
sinking, is carried farther down the current, and thus separated
from the rest.
   The next  operation, which is that of roasting, is employed
to drive off the sulphur, arsenic, and other volatile parts which
the mineral may contain.   It is performed in a variety of ways,
and by different processes, according to the nature of the  ore,
and the degree of heat required.   The roasting is sometimes
performed  in the  air, and sometimes in  furnaces,  among the
fuel.  Smelting  consists,  in general, in fusing the roasted ore,
with a view to extract the metal, though the term is sometimes
applied to the melting of  metal in any state,  especially iron.
The immediate object  of this process is to reduce the metal, or
to separate the oxygen  with  which  the  metal has either been
naturally combined, or has united during the operation of roast-
ing.   This is done, by placing in a furnace alternate  layers of
charcoal, or coke, and of the metallic  matter ;  a strong heat is
then excited  by bellows;  the carbonaceous matter attracts the
oxygen, while the metal is reduced, melted, and run out at the
bottom of the furnace.   The  volatile metals are obtained by
sublimation  or  distillation.  Even  after  these operations, the 
ARTS  OK METALLURGY.
387
metal is seldom  pure, but is combined with some other metal,
or metals, which have been present in the ore.   If these are
in small quantity, and do not injure the metal, they are in gen-
eral disregarded.  If it is necessary, however, to separate  them,
or if, from their value, the  separation is an object of importance,
different processes are followed, adapted to  each particular
metal.  All the operations subsequent to smelting, are compre-
hended under the general name of refining, because their ef-
fect is always to obtain a purer  metal.   The  different metals
are refined by different processes.
   Assaying.—The art of assaying metallic ores, is that of an-
alysing them in  small quantities, so as to discover their compo-
nent parts.   It  requires a knowledge of the  relations of the
metals to the other chemical agents, and is varied in its different
stages as applied to each.  The general process consists in se-
lecting proper specimens of the  ore, which is  done by taking
equal  portions of that which appears to be  the  richest, the
poorest,  and of medium  value, and  reducing these to coarse
powder, which is washed  to carry off any earthy or stony mat-
ter.  It is then roasted in  a shallow earthen vessel under a muf-
fle, to expel  the volatile principles.  It  is lastly reduced, by
mixing it with fluxes, and applying a more or less intense heat,
as the metal is more or less  refractory.   The  metallic matter
existing in the ore is thus  obtained.   This, it is obvious, may
consist of various metals, and if there  is reason to believe this,
and it be of importance to ascertain it, it is submitted to opera-
tions  adapted to the  metals  which  may be supposed  present.
Sometimes, an accurate analysis is made at once of the metal-
lic ore in the  humid way; the metal being  dissolved by the
different acids, and precipitated by the alkalis,  earths, and oth-
er re-agents.   The  assaying of the precious metals is usually
CDnfined to  ascertaining the  quantity  of gold  or silver in any
alloy  or compound, without regard to the  other constituents.
   Alloys.—The metals  are capable of combining with  each
other by fusion, and to these combinations, the name  of alloy
is given.  They all  retain the general metallic properties,— 
388
AR'I*  OF METALLURGY.
lustre, opacity, and density, and even, in the greater number of
cases, the properties of the constituent metals  remain in the
combination, only somewhat  modified.   In general, alloys are
more hard and  brittle than the individual metals of which they
consist, though  this, as well,as the other changes of properties,
is considerably  influenced by the proportions in which the in-
gredients  are combined.   They  have also in general a greater
fusibility than the  mean fusibility of the  respective metals.
The alloys of quicksilver, called amalgams, are usually soft, or
liquid, according to the proportions.  The metals combined in
alloys are generally more susceptible of oxidizement than in
their  separate  state, owing  probably to the diminution in the
power of  cohesion, by the combination, or perhaps to an elec-
trical action. From their peculiar properties, some of the alloys
are extensively used, as brass, which is an alloy of copper and
zinc ; and pewter,  which is an alloy of tin and  zinc, or lead.
   A degree of condensation usually attends these  combinations,
so that the specific gravity of the  alloy is greater than the mean
specific gravity of its constituent  metals.   In brass, for exam-
ple, it is one tenth  greater, and in some cases, the condensa-
tion is such, that the  density is even greater than that of the
heavier metals combined, as in the alloy of silver and  quick-
silver.  Sometimes, however, the particles assume such an ar-
rangement, that the density is less than  the mean, as in the ex-
amples  of the  alloy of copper with silver, and of gold with
tin, and gold with iron.
   In these combinations, there exists a certain order of attrac-
tions, by which  one metal is more disposed to unite with  anoth-
er, than a  third is.   The  difference, however, is  not very
considerable; hence, three, four, or more  metals can be com-
bined together.  Some, however, are difficult to unite, as iron and
lead, and  iron and quicksilver.   The combination seems to be
in some measure  regulated by the relations of fusibility and
specific gravity ; so that the affinities being equal, the  metals
are less disposed to combine, as  they differ more in their fusi-
bility and  specific  gravity;  and  where the affinity is weak,  a 
ARTS  OF  METALLURGY.
389
considerable difference of this kind may prevent any combina-
tion whatever.


                           GOLD.

   Gold exists in various  minerals, but the greatest part of the
gold in the possession of  mankind, has been found in the form
of grains and  small  masses,  among the alluvial sands which
constitute certain plains, and margins of rivers.  In this state
it is usually alloyed with small portions of other metals, partic-
ularly silver and copper.
   Extraction.—When native gold is found in a state of mixture
with  foreign  matters, its extraction is commonly performed
by amalgamation with quicksilver.   After having been freed,
by pounding and  washing,  from most  of  the  stony  matter
mixed with it, it is triturated with ten times its weight of quick-
silver, until  an  amalgam  is  formed.  This is separated  from
any superfluous earthy  matter,  and subjected to pressure, in-
closed in leather, by which the more fluid part is separated and
forced through the leather, while the more consistent amalgam,
containing the  greater part  of the  gold, remains.   It is then
subjected to distillation in retorts of earthen ware, to separate
the quicksilver, and the remaining  gold is  afterwards fused.
When the gold is contained in other ores, the ore is roasted to
 drive off the more volatile principles, and to oxidize the other
metals.   The  gold is then  extracted by amalgamation, by li-
 quefaction  with lead, by  the  action of nitric acid, or other
methods adapted to each ore, according to its constituent parts.
    Cupellation.—Gold obtained in any of these ways, is always
 more or less alloyed, particularly with silver or copper.  The
 first  step in its purification, is the process of  cupellation.   To
 explain the nature of this, it is necessary to observe, that  lead
 is a metal very fusible,  and extremely  easy of oxidizement,
 forming an oxide which easily  vitrifies, and which favors  the
 oxidizement and  vitrification of other metals.  A portion of
 lead, therefore, is added to the  impure gold, more or less,,ac- 
390
ARTS  OF METALLURGY.
cording to the quantity of alloy which it contains, of which the
workman judges by the color, hardness, elasticity, and specific
gravity of the gold.   They are melted together, and exposed
to heat on a cupel, which is a vessel  made of bone  ashes, or
sometimes of wood ashes, under a muffle, or, in the large way,
on the hearth of a refining furnace.  The lead passes to the
state of oxide, is vitrified, and at the same time promotes the
oxidizement  and vitrification of the foreign metals.   The vitri-
fied  oxide is absorbed  by the porous  cupel, or,  in  the large
way, the greater part is driven off by the blast of bellows, and
removed.   When the greater part  of the foreign metals is ab-
stracted, the  remaining  fused metal exhibits  various  prismatic
colors, which succeed each other quickly.  It at length sudden-
ly brightens and its surface becomes highly luminous.   This is
regarded as the  completion of the process.   The  metal  is al-
lowed to become solid,  and while yet hot is detached.
   Parting.—The gold, even after having  been submitted to
this process,  may still be alloyed  with silver, which  being near-
ly as difficult of oxidizement, is  not  removed by the action of
the lead.   It is therefore  lastly  subjected to  the operation of
parting.  The metal is rolled out thin, and cut into small pie-
ces.   These are digested with a moderate heat in diluted nitric
acid, which dissolves  the silver, leaving the gold undissolved in
a porous mass.   It has been found, however, that when the
proportion of silver is small to that of gold, the  latter protects
the former from the  action of the acid.   The previous  step of
quartation, as it is named, is  therefore employed,  which con-
sists in fusing three parts of silver with one  of the gold, and
then  subjecting this  alloyed  metal, rolled out, to the  operation
of the acid.   These are the operations employed in commerce.
To obtain gold perfectly  pure, still  another process is perhaps
necessary,—dissolving.it in nitro-muriatic acid, and adding  to
the solution  a solution  of sulphate  of iron,  which,  attracting
the oxygen,  precipitates the gold in the metallic state.
   Cementation.—The  process of cementation, is performed by
beating  the alloy into thin plates, and placing  these in alternate 
ARTS OF  METALLURGY.
391
layers, with a cement containing nitrate of potass,  and sulphate
of iron.   The whole is then exposed to heat, until a great part
of the alloying  metals are removed by the action of the nitric
acid, which is liberated  by the nitre.   Cementation is some-
times employed by goldsmiths to  refine the surface of articles
in which gold is alloyed with baser metals.
  Alloy.—There is a  peculiar language  established  in  com-
merce, and often referred to by writers, to denote the purity of
gold, or the degree of  its alloy with other metals.   The mass
is supposed to consist of  24  equal parts, these  imaginary parts
being termed carats.   If perfectly pure or unalloyed, it is said
to be gold 24 carats fine; if alloyed  with one part of any other
metal, or mixture of metals, it is said to be 23  carats fine.   In
this  way the  proportion of alloy is expressed.   The  standard
gold coin of the United  States and  Great Britain, is 22 carats
fine, or contains one twelfth part of  alloy.
  Gold, when perfectly  pure, is not so fit for coin, on account
of its softness, in consequence of  which the impression is soon
obliterated, and  it sustains  loss from friction.   Hence it is al-
ways alloyed to give it hardness.  The metals that have been
used for  this purpose,  are silver  or  copper.   Gold  made
standard  by  an  alloy  consisting  of  equal  parts  of silver and
copper, has a  color approaching more  to  that  of pure gold
than any other  alloy.   This color also remains uniform,  while
that with  copper,  after  a certain degree of  wear, becomes
unequal. *

  * Mr Hatchet with Mr Cavendish, subjected the different  alloys that have
been used as  coin to friction, as similar as possible to that to which they must
be subjected in the course of circulation.  The loss was by no means consid-
erable, and it appeared as the general result, that the present standard of gold,
or an alloy of one p^rt in 12, is, all circumstances considered, the best,
or at least, as good  as any that could be chosen.   If the  copper be in larger
proportions, more loss is sustained from friction.  The same alloy is employed
in the fabrication of plate, and of trinkets, and lace, and,  by other additions,
various shades of color are obtained.  Its alloy with a  fifth part of silver,
forms the  green gold of the jewellers, and the addition  of iron gives a
blue tint. 
392
ARTS  OF METALLURGY.
   Working.—Common  goldsmith's  work is performed  by
casting in moulds, beating with  hammers, and rolling between
polished steel  rollers.   Works that have  raised or embossed
figures, are commonly cast in moulds and afterwards polished ;
or they are struck in dies, cut for the purpose.   Vessels  both
of gold  and silver, are  beat out from flat plates.  When the
form is difficult, they are made of several plates and soldered
together.  The solder used  for this purpose is an alloy of gold
with silver, copper, or  brass.  Small ornamental works are
commonly executed by enchasing.   This process is performed
upon thin plates of gold,  with a block and hammer.  It consists
in driving in portions of the metal on one  side in such a manner
that they stand in relief, forming the figures required on the
opposite  side.   Many small  articles are  also made from gold
wire, variously wrought  and  ornamented.
   Gold  Beating.—The great utility  of gilding in the arts, in
furnishing an incorruptible covering to various substances, has
given rise to an extensive consumption of gold  leaf,  which is
formed, by  beating  the  metal to a state  of extreme  tenuity.
The gold is first forged into plates on an anvil, and then reduc-
ed, by passing  it between polished steel rollers, till it becomes
a ribband as thin as paper.   This ribband is divided into small
pieces, which are again  beat upon an anvil till they are  about
an inch  square, after which  they are thoroughly annealed. *
Two ounces of gold make  150 of these  squares.   All  these
squares are interlaid with leaves, first of vellum, and afterwards
of gold  beater's skin, a  thin  membranous  substance, obtained
from the intestines of animals.   The whole is then beaten with
a heavy  hammer till the gold is extended to the  same size as
the  pieces of skin.   The gold leaves are then taken out, and
each cut into four parts,  and  the 600 pieces thus produced, are
again interlaid in the same manner with skins, and the beating

  * The process of annealing is applied to metals and some other substances
to diminish their brittleness, or increase  their flexibility and ductility. It
is performed by heating the  substance,  and  suffering it to cool in a very
gradual manner. 
ARTS OF  METALLURGY.
393
repeated with a lighter hammer.  They are  afterwards  redi-
vided as before, and  formed into parcels which are separately
beat, at one or more  operations, until the leaf has attained the
requisite thinness.   The use of the membranes  which are in-
terposed between the leaves, is to prevent them from cohering
together, at the same  time that they are permitted to expand ;
and also to soften the blows of the hammer.   Notwithstanding
the vast extent to which  gold is beaten between these skins,
and the great tenuity of the skins themselves, yet they are said
to sustain  continual repetitions of the  process for a  long  time
without receiving injury.  The kind of leaf  called party gold,
is formed  by laying a thin  leaf of gold, upon a thicker one of
silver.   They are  then heated  and  pressed together till  they
unite and cohere,  after which they are beaten  into  leaves  as
before.
   Gilding  on  Metals.—Gilding  on copper is commonly
performed  with an  amalgam of gold  and mercury.   The
surface of the copper, being freed from oxide, is covered
with the amalgam, and  afterwards exposed to heat  till the
mercury is driven  off,  leaving a thin  coat  of gold.  It is also
performed by dipping a linen rag in a saturated solution  of
gold, and burning it to tinder.  The black  powder thus obtain-
ed is rubbed on the metal to be  gilded, with a cork  dipped in
salt water, till the gilding  appears.  Iron or steel, is  gilded by
applying gold leaf to the metal, after the surface has  been well
cleaned, and heated until it has acquired the blue color, which
at a certain temperature it assumes.  The surface is previously
burnished, and the process  is  repeated when the gilding is re-
quired to be more  durable.  It  is also performed by diluting
the solution of gold  in  nitro-muriatic  acid,  with  alcohol, and
applying it to the clean surface. *

  * This last process has been improved by Mr Stoddart. A saturated solution
of gold in nitro-muriatic acid, being mixed with three times its weight of sul-
phuric ether, dissolves the muriate of gold,  and the solution  is separated
from the acid beneath.  To gild the steel, it is merely necessary to dip it, the
surface being previously well polished  and cleaned, in the ethereal solution,
                50 
394
ARTS  OF METALLURGY.
   Gold Wire.—The common  gold  or gilt wire, is in reality
 silver  wire covered  with gold.   In  making it, a silver  rod is
 enclosed in thick leaves of gold.  It is then drawn successive-
 ly through  conical holes of different sizes, made  in plates of
 steel, in a  manner  similar to that pursued in making iron wire.
 The wire  may thus be reduced to an extreme  degree of fine-
 ness, the gold being drawn out with the silver, and constituting
 a perfect coating to the  wire.   When it is intended to be used
 in forming  gold thread, the wire is flattened by passing it be-
 tween rollers of polished  steel.  The coating of gold remains
 unbroken,  though so far reduced by these processes  as not to
 occupy the millionth part of an inch in thickness.   The gold
 thread  commonly  used  in embroidery, consists of threads of
 yellow silk, covered by flattened gilt wire, closely wound  upon
 them by machinery.

                           SILVER.

   Extraction.—Silver is  in general  extracted without  much
 difficulty.   When native, it is separated  from the earthy matter
 by washing, and amalgamation with mercury; the  latter being
 separated again by distillation.   When  alloyed with antimony,
 or arsenic, or when mineralized, the ore is roasted to expel these
 metals, with the sulphur, or other volatile principles; and the
 residual matter is fused with  lead,  and refined by  cupellation,
 in a  manner  similar to  that  described under  the  head of
 gold ;  the  alloy of lead  and   silver being exposed to heat on
 the hearth  of the  refining furnace, the lead being  oxidized
 along with  the foreign metals,  the oxidizement and  vitrification
 of which it promotes, and the vitrified oxide being in part ab-
 sorbed, and in  part  driven off by the  blast  of the bellows.
 The appearance of a vivid incandescence, or brightening, de-
 notes when the silver has become sufficiently pure.   It retains
 a little gold in combination, but this does not alter its qualities,

for an instant; and on withdrawing it, to wash it instantly by agitation in wa-
ter. By this method steel instruments are very commonly gilt. 
ARTS  OF METALLURGY.
395
and the quantity is seldom such, as to render its separation, by
the operation of parting, an object of importance.
   If the ore which is wrought contain only a small portion of sil-
ver, the previous operation of eliquation is sometimes performed
on it.  This consists in adding a certain portion of lead to the me-
tallic matter which remains after  roasting and fusing the ore.
This alloy is then exposed to a degree of heat just sufficient to
melt the lead, which runs out, and from its affinity to the silver,
carries it along with it, leaving the copper, or other metals with
which the silver had been combined.  The alloy of silver and
lead is then subjected to the usual refining process.
    Working.—Silver is cast into bars, or ingots, and afterwards
wrought by hammering and rolling.   The bars are beaten up-
on anvils, being heated from time to time to render them more
ductile.   The hammering is conducted while the heat is below
redness.  They are then passed between polished steel rollers,
until they are reduced to plates of a suitable thickness.  To
form utensils of different kinds, these plates are hammered in
moulds till they acquire the proper shape.  Vessels are often
made in pieces, which are afterwards united by soldering.   The
solder used for silver, consists of an alloy of silver with more
than an equal part of copper  or  brass.  Figures  which are
raised upon the silver, are  produced by hammering the metal
upon  steel dies, in which  the figure is cut, or  by passing  it
through engraved  rollers.   Silver is polished by burnishing  it
with steel instruments, or with hard  polished stones; and by
 rubbing it with the oxide of iron called colcothar, in fine powder.
    Silver,  in the  arts, is usually alloyed  with a little  copper,
 which increases its  hardness,  and renders it more sonorous
 without debasing its color.   The standard silver of the British
 corns contains 18 pennyweights of copper in a pound Troy of
 silver; and in the United States 1664 grains of  silver contain
 179 grains of copper.
    Coining.—The coining of  silver, and other metals, was
 originally performed by the hammer, in matrices, or dies, en-
 graved for  the purpose.   At  the present day, coins of every 
396
ARTS  OF METALLURGY.
description are  more commonly milled.   In coining by the
mill, the bars, or ingots, of gold or silver, after having been cast,
are taken  out of the moulds and their surfaces cleaned.  They
are then flattened by rollers, and  reduced to the proper thick-
ness to suit  the species of money  about  to be coined.  To
render the  plates more  uniform,  they  are sometimes wire
drawn, by passing them  through narrow holes in a steel plate.
The plates, whether of gold, silver, or copper, when  reduced
to their proper  thickness, are next cut  out into round pieces
called  blanks or planchets.  This  cutting is performed by a
circular steel punch of the size of the coin, which is  driven
downward by a powerful  screw, and passes  through a corres-
ponding  circular hole,  carrying  before  it the  piece  of metal
which is punched  out.   The  pieces which  are thus cut, are
brought to the standard weight, if necessary, by filing  or rasp-
ing ; and  the deficient pieces, together with the  corners and
pieces of  the  plates left  by the  circles, are returned  to the
melter.
   The milling, by which the inscription, or other impression, is
given to the edge of the coin, is performed  by rolling the coin
edgewise, between two plates of steel, in the  form of rulers,
each of which contains half of the engraved edging.   One of
these plates is fixed, and  the other is moveable by a rack and
pinion.   The  coin, being placed  between  them, is carried
along by the motion of the rack,  till it has made half a revolu-
tion and received the  whole impression on its edge. The most
important part of the coining  still  remains to be done,  and
consists in stamping both sides with the appropriate device,  or
figure in relief.   For this purpose, the circular piece is  placed
between two steel dies upon which the figures to be impressed
are sunk,  or  engraved in the manner of an intaglio.  The two
dies are then forcibly pressed together, by the action of a pow-
erful screw, to which  is attached a heavy  transverse  beam,
which  serves the purpose of a fly, and concentrates the- force
at the  moment of the impression.   The  coin is now finished
and is  thrown out when the screw rises. 
ARTS  OF METALLURGY.               397
  In the coining machinery erected by Boulton and Watt, and
introduced at the mint in England, the process is performed by
steam power,  and both the edges  and faces of the money are
coined at the same time. *   By means of this machinery, eight
presses  attended by boys, can  strike 19,000  pieces of money
in an hour, and an exact register is kept by the machine of the
number of pieces struck.
  For the coining of medals the process is nearly the same as
for  that of money.  The principal  difference consists in this,
that money having  but a small relief,  receives its impressions
at  a single stroke  of the  engine;  whereas  in  medals, the
high relief makes several strokes necessary; for which purpose
the piece is taken out from between the dies, heated, and re-
turned again.   This process for  medallions  is sometimes re-
peated as many  as a dozen or more  times  before the full im-
pression is given  them.  Some medallions, in a very high re-
lievo, are obliged to be cast in  sand, and afterwards perfected
by  being sent  to the press.
  Plating.—The great value of silver, and  the useful property
which it possesses of resisting oxidation, has  given  rise to the
art  of plating, in which  vessels and utensils of other  metals,
but chiefly of copper, are covered with a thin coating of silver,
so  as to protect  them  from the influence of the  atmosphere.
Plating  is sometimes executed  by heating  the articles  which
are to be coated, and  rubbing on them portions of leaf silver,
with a steel burnisher, till it adheres.   But it is performed in a
better manner, by plating solid ingots of copper, and  afterwards
working these into  any shape  desired.   The ductility of the
coating of silver causes it to be extended, and drawn out with
the copper, so that the latter metal never appears at the surface.
The copper  used in  plating,  is  alloyed with a little brass.
Great  care is taken in casting, to form the ingots sound, and
free from pores  or flaws.   The surface of the ingot is cleaned
with  a  file,  and  a thin  plate of silver  is  applied  to one,

  * A particular  account of this machinery is given in  the London Mechanic's
Magazine, vol. hi. 
398
ARTS  OF METALLURGY.
 or to both sides,  according to the  article to be manufactured.
 A saturated solution of borax is then insinuated between the
 edges, the object of which is to protect the  copper from oxi-
 dation, which would otherwise prevent the silver from adher-
 ing.  The ingot is then carried to the furnace, and exposed to
 heat until the metals adhere to each other.   Their adhesion is
 owing to the formation of an alloy between the silver and cop-
 per, which being fusible at a lower temperature than either of
 the metals, acts as a solder to unite them  together.   The ingot
 is then rolled into sheets, by passing it repeatedly between iron
 rollers, annealing it from time to time, as  it becomes hard and
 brittle.
   The plated sheets which are thus obtained, are formed into
 articles of different kinds, by hammering them in moulds cor-
 responding to the  intended  shape.   When  vessels are  to be
 made, they are  formed in pieces of a  convenient shape, and
 these are  soldered together with an alloy of silver, copper, and
 brass.   Mouldings,  and other ornamental parts, are made by
 hammering  the  metal in steel  dies, or rolling it between steel
 rollers, upon which the pattern is cut.   As the edges of plated
 ware are most liable to be injured by wear, they are commonly
 protected  by what are called silver  edges.  These are formed
 of a shell  of silver, rolled out, or hammered in dies, and having
its inside  filled up with  a mixture of tin and lead.  When fin-
 ished, these edges are soldered  to the vessel.   The  handles,
 feet, and  solid  parts of vessels, are often  made in the same
 way.   Plated baskets and other light articles are made from
 copper cylinders covered with silver, and  afterwards drawn in-
to wire.
   Plating on iron, as it is used for the buckles of harnesses
 and  other ornaments, is executed  by first covering the iron
 with a coating of tin, and then  applying closely to the surface
a thin  plate of silver.   The union  is  effected by a moderate
heat,  sufficient to melt  the tin, and form an alloy;  and it is
aided by the use of a resinous flux. 
ARTS  OF METALLURGY.
399
                          COPPER.

   Extraction.—The various sulphurets of copper are the most
abundant of its ores, and of these the most so is copper pyrites.
The malachite, red copper ore, and others,  are generally  asso-
ciated with these in small quantities.  Copper mines are wrought
in many countries, but those of  Sweden are said  to  furnish
the  purest  copper of commerce.   The sulphurets  are the
ores from which copper is usually extracted.   The ore is roast-
ed by a low heat, in a furnace with which flues are connected,
in which the sulphur, that is volatilized, is collected.  The re-
maining ore is then smelted in contact with the fuel.   The iron
present in the ore, not being so easily reduced, or fused, as, the
copper, remains in the scoria, while the copper is run out.  It
often requires repeated fusions, and even  after these, it may be
still  alloyed with portions of metals,  which are not  volatile,
and  are  of easy fusion.   Hence  the copper of commerce is
never altogether pure, but generally contains a little lead, and
a smaller portion of antimony.
   The  carbonates of copper reduced by   fusion,  in  contact
with  the fuel,  afford a purer  copper, as  does also the solution
of sulphate of copper which is met  with in some mines, the
copper  being precipitated in its metallic state,  by  immersing
iron  in the solution.   The precipitate which is thus formed, is
afterwards fused.
   Working.—Copper, being  ductile and  easily wrought, is
applied to many useful purposes.  It is formed into  thin sheets
by being  heated  in  a  furnace,  and  subjected to pressure
between iron rollers.  These  sheets being both ductile and
durable,  are applied to a variety of uses, such as the sheathing
of the bottoms of ships, the covering of roofs and domes, the
constructing of boilers and  stills of a large  size,  he  Copper
is also fabricated  into a variety of household utensils,  the use
of which, however, for preparing or preserving articles of food,
is by  no means  free  from  danger, on account of the oxidize- 
400
ARTS  OF METALLURGY.
ment, to which copper is liable.   It has been attempted to ob-
viate this danger, by tinning the copper, or applying to its sur-
face a thin  covering of tin.   This method answers the purpose
as long  as the coating of tin remains entire.
   Copper  may be forged  into any  shape,  but will not bear
more than a red heat, and of course requires to be heated of-
ten.   The bottoms of large boilers are frequently forged with
a large  hammer worked by machinery.   The bolts of copper
used for ships, and other purposes, are either made by the
hammer, or cast into shapes and rolled.  The copper cylinders
used in  calico printing, are either  cast solid upon an iron axis,
or are cast hollow and fitted upon  the axis.   The whole is af-
terwards turned, to render  the surface true.
   Brass.—Brass is an  alloy of copper and  zinc.  The  pro-
portions of these two  metals  differ  in almost every place  in
which  brass  is manufactured,  and the  proportion of zinc  is
found in different specimens to vary from 12 to 25 parts in a
hundred.   The alloy is commonly made from the ores of zinc
mixed  with copper, and with a sufficient  quantity of charcoal
to reduce them to a metallic state.  The volatility of the zinc
gives it  a tendency to escape in vapor, on which account the
combination is effected at a lower  heat than that which would
be necessary to melt the copper.  Several other alloys of the
same  metals, are also  known in the  arts, differing in the  pro-
portions of the ingredients ; such  as pinchbeck, prince's metal,
tombac,  Bath metal, he
   Manufactures.—The  value of brass in the arts, consists in
its bright color, in its being more fusible than copper, and in its
being more easily wrought with common tools.  In the working
of brass, the  larger  articles, as well as  those of complicated
forms, are  cast in moulds.   When it is intended, for economy
of the  metal, that the article shall be hollow, as in the case of
andirons, &c., it is cast in  halves, or pieces, which  are after-
wards  soldered together,  and  turned  in a lathe, or otherwise
polished.   Brass  is also rolled into thin sheets,  and drawn
into wire.    A  variety of figured and ornamental  articles 
ARTS  OF METALLURGY.
401
are made by stamping it in dies or moulds.  Brass knobs and
similar implements, if large,  are made in pieces,  and solder-
ed.  The wheel work of  timepieces, and of other machinery
which is not subjected to great strain or wear, is usually made
of brass.   The  comparative  softness of this  alloy,  permits it
to be cut with thin saws, and to be turned in  a lathe, with much
greater ease than iron.
   Buttons are either struck out of* sheets of brass with a cir-
cular punch, driven by  a  fly press, or they  are cast in large
numbers at once in a mould, or flask of sand.  The  eye, or
shank, of  the button is made separately by a machine, and
soldered on, if the  button has been cut out  by the punch.   If
the  button is cast, the eye is  previously placed in the  mould,
so that its  extremity is immersed in the centre of the  melted
metal.  If the button is to be plain, its surface is planished by
the  stroke of a smooth die ;  and if figured, it is stamped with
an engraved die.  The edges are afterwards turned off in a
lathe.   The gilding of brass buttons is performed by covering
them with an amalgam of gold and  mercury, from  which the
mercury escapes when  heated, and leaves  the gold.   White
metal  buttons are made of an alloy of brass and tin, and sub-
sequently  coated with  tin.   The' brass eyes of pearl  buttons
are inserted by drilling a conical  hole, which is largest on the
inside, in the mother of pearl, or shell, of which  the button  is
 made.  The eye, having an extremity like a hollow cone, is
then driven in, till it spreads and fills the  cavity.
   Pins are made of brass wire cut into proper lengths.  The
 pieces are pointed by turning them with the fingers, upon
 stones, or steel mills.   The heads are cut from a spiral coil  of
 wire, in pieces of  a suitable  length ; and  after  being placed
 upon the pins, are  shaped and fastened by the stroke of an  in-
 strument like a hammer.   Several machines have been invent-
 ed  for this manufacture, one  of which makes a  solid head
 from the body of the pin  itself.   Pins are whitened by immers-
 ing them  in a vessel containing tin and  lees of wine, and are
 polished by agitating them with bran in a revolving  cask.
                51 
402
ARTS OF  METALLURGY.
   Bronze.—A series of alloys is formed from the combination
of copper with tin.   The  combination  appears to have a ten-
dency to form in certain proportions, regulated in some meas-
ure by the specific  gravities and fusibilities of  the metals;  for
when kept in fusion, and allowed to cool without agitation, two
alloys  are formed, the under part of the mass being one of
copper with a small portion of tin, and the upper part tin with
a small proportion  of copper, while between these there is
probably a gradation.   By agitation,  this separation  is counter-
acted.  In  general, tin lessens the ductility of copper, while
it renders it more hard, rigid, and sonorous; these qualities be-
ing possessed in various degrees by the different alloys, accord-
ing to their proportions, the  hardness  and brittleness being
greater as the tin predominates.   The density of the compound
is  also always  greater than  the mean density; the contraction
from the combination being about  one eighth.   The principal
of these alloys, are bronze, gun metal, from which pieces of
artillery are cast, bell metal, and speculum metal which has been
used  for  the mirrors of reflecting  telescopes.   Bronze is one
of those in  which the proportion of  tin is least, not exceeding
10 or  12  parts in 100.   It is of a greyish yellow color, harder
than copper, less  liable to • rust,   and more fusible, so  as to
be  easily  cast in  moulds.   Hence it is  employed in  the
casting of statues.   The metal from which  pieces  of  artillery
are cast, is of a similar composition,  containing rather less tin.
It appears  that an alloy very similar  to bronze,  was much
in use among the ancients;  and swords, darts, and  other war-
like instruments were formed of it, as were also various utensils.*

  * According to Dr Pearson's experiments made on various instruments of
this kind, the alloy appears to have  consisted of about eight or nine parts of
copper, with one of tin, and, as he justly  remarks, this alloy still affords the
best substitute for iron or steel.  While the art,  therefore, of manufacturing
malleable iron was imperfectly known, and difficult to be practised, it must
have been much used.  The hardness of this alloy observed in ancient arms,
had even given rise to an opinion, that the ancients were acquainted with  a
method of hardening copper, which had been lost. Of this alloy, medals and
coins were also often formed, as appears from the experiments of Dize, on
several Greek, Roman, and Gallic coins, which consisted of copper and tin alone. 
ARTS OF  METALLURGY.
403
   When  the proportion of tin is increased, the alloy is render-
ed more  brittle and elastic, and at the same time highly son-
orous.  Bell metal is an alloy of this  kind, in which  the  pro-
portion of tin varies from one third to one fifth of the weight
of the copper,  according to  the size of the bell, and the sound
required.
   When  the proportion of  tin is still greater, an alloy is form-
ed called speculum metal,  which is  of  a white color, and which
from the  closeness of its texture, and  its susceptibility of a fine
polish, exceeds most metals in the  property of reflecting light.
Hence it is used in forming  the  speculum of reflecting  teles-
copes.  It has also the advantage of not being liable to tarnish
on exposure to the air.  The  proportion  in which these  quali-
ties were best attained, appeared, from the experiments of Mr
Mudge, to be a little less  than one part of tin, with  two  parts
of copper. *   The Chinese pakfong, or white copper, which
is sometimes imported  from that country, is an alloy,  according
to Dr Fyfe, of copper, zinc, nickel, and iron.

                             LEAD.

   Extraction.—Lead  mineralized by  sulphur, forms  by  far
 the most  abundant ore of the  metal, and  has been long known
 to mineralogists  by the  name of galena.   This is the ore
 which is generally wrought, and from which nearly all the lead

   * Mr Edwards,  by an extensive series of experiments on the proportions of
 these metals, and the effects of different additions, succeeded in forming alloys
 much superior in  brightness to those that had been before used.  That which
 he preferred, was composed of 32 ounces of copper, 15 or 16 oz. tin, according
 to the purity of the copper, to which were added brass, arsenic, and silver, of
 each one ounce ;  the copper and the tin being melted in separate crucibles,
 when in fusion, the one being added to the other, and the composition, when
 well stirred, being poured into cold water. The other metals are added in a
 second  fusion.  The arsenic appears to give a greater degree of density and
 compactness to the alloy, the brass more tenacity, and the silver adds to the
 whiteness. According to the more recent experiments of Mr Little, the best
 composition, is 32 parts of bar copper, four parts of brass, sixteen and a half
 parts of tin, and one and three quarters of arsenic. 
 ^U4              ARTS OF  METALLURGY.

 of Commerce is procured.  The ore, after being pounded, and
 freed from the admixture of any stony matter by washing, is
 fused in a furnace, with the addition of lime, which combines
 with the sulphur of the sulphuret; the lead is melted, and run
 out by an aperture towards the bottom of the furnace.  When
 the native salts of lead are found with the galena, so as to ren-
 der it of  importance to work  them, they are selected until a
 sufficient quantity be obtained.  They are then roasted to expel
 the volatile  matter, and are  afterwards fused in contact  with
 the fuel,  with an addition of lime.  The lead obtained  from
 galena, sometimes contains so much silver as to be subjected
 to  an additional process to  separate the silver.   In  this  case
 the lead is oxidized in a furnace, a current of air being direct-
 ed on its  surface  when in fusion, by  bellows.   Towards the
 end of the operation, the silver remains with a small portion of
 lead, from which  it is freed by cupellation ; and  the oxide of
 lead is either applied to the purposes for which it  is used, or is
 reduced to the metallic  state.
   Manufacture.—Lead, being fusible at a low temperature, re-
 quires only to be cast in smooth moulds, to form  weights, bul-
 lets, and other articles of  small size.   The linings of cisterns,
 and the coverings of roofs,  gutters,  he are made  of  sheet
 lead ;  pumps, and aqueducts,  of leaden pipes.
   Sheet lead, of the  thicker  kinds, is cast upon large tables
 covered with sand,  and having an elevated  rim.   The melted
 lead is poured upon the  surface  out of a box which moves
 upon rollers across the table, and is spread out with a uniform
 thickness, by passing over it a straight piece of wood, called a
 strike.  The sheets thus cast  are afterwards rendered thinner,
 by  reducing them between rollers.  The sheet lead with which
 tea  chests are lined, is an alloy of lead and tin, and is made
by the Chinese, by suddenly  compressing the melted metal
between flat, polished stones.
   Lead pipes, for  conveying  water,  may be made in various
ways.   They were at first formed of sheet lead  bent round a
cylindrical bar, or mandrel,  and soldered;  but these pipes are 
ARTS  OF METALLURGY.
405
liable to crack and leak, especially when bent.  A second me-
thod is to cast a short tube of lead in a cylindrical mould with
a core.   This tube, when cold, is drawn  nearly out of the
mould, and a fresh  portion of melted  lead  poured in at  aper-
tures in the sides of the mould.  The melted lead unites with
the tube previously  formed, so as to increase its length, and by
repeating the process, any length of  pipe  may be produced.
But pipes cast in this manner are found to  have imperfections
arising from flaws and air bubbles.   A third method, which is
now most commonly practised, is to cast a short, thick tube of
lead, upon one  end of  a long, polished iron cylinder, or man-
drel, of the size of the bore of the intended pipe.   The lead
is then reduced in size, and  drawn out in length,  either  by
drawing it on the mandrel, through  circular holes, of different
sizes, in a steel plate; or by rolling it between contiguous rol-
lers, which have a semi-circular groove cut  round the circum-
ference of each.  A fourth mode  invented by Mr Bramah,
consisted in forcing melted lead, by means of a pump, into one
end of a mould ; while it was  discharged in the form of a pipe
at  the  opposite  end.  Care was   taken  so to  regulate the
temperature, that the lead should  chill, just before it left  the
mould.
   Leaden shot, consist of drops of  metal which are discharg-
ed  in a melted state  from small orifices, and cool  in falling.
The  best shot  are  cast in high  towers  built for the purpose.
The lead is previously alloyed with a portion of arsenic, which
increases  the  cohesiveness of its particles, and causes it  to as-
sume more readily  the globular form.  It is melted  at the top
of the tower, and poured into a vessel, which is perforated at
bottom with numerous small  holes.   The  lead, after running
through these perforations, immediately  separates into drops,
which cool in falling through  the height of  the tower, and are
received in a reservoir of water at bottom, to break  the  force
of the fall.   The shot are then proved by rolling them  down
an  inclined board.   Those, which are irregular in shape, roll
off at the sides, or stop, while the  spherical ones continue to 
406
ARTS  OF METALLURGY.
the end.  They are then assorted by passing  them  through
wire sieves of different fineness.  The glazing is given by agi-
tating them with small quantities of black lead.
   Shot is sometimes  made mechanically by cutting sheets  of
lead into cubes, and agitating these for a long time in a cylin-
drical vessel turned upon an axis.  The attrition thus produc-
ed, communicates a globular form to the cubes.

                            TIN.

   Native oxide of tin, or tinstone, as it is commonly named,
is the only ore that is  wrought to obtain this metal.  Being
freed by washing, from the intermixture of any stony matter,
it is roasted,  and then fused in contact with the fuel, by a mod-
erate heat.   The tin  of Cornwall is supposed  to be purer than
the German  tin, though it is still inferior to the tin from India.
   Block tin, consisting of the  metal  in its solid state, is used
for vessels which are not exposed to  a temperature much ex-
ceeding that of boiling water.  Vessels of this kind, being not
readily tarnished, form a cheaper substitute for silver and plated
ware.   A kind of  ware denominated Biddery  ware, consists
of tin vessels alloyed with a little copper, and having their sur-
face made black by the application  of substances containing
nitre, common  salt, with sal  ammoniac.   Tin foil is made  by
rolling, in the same way as the plates for tinned iron  hereafter
described.  It  is also sometimes hammered.   The most ex-
tensive use, however, to which metallic tin is applied, is to form
a coating for other metals, which are  stronger than itself, but at
the same time more liable to oxidation by exposure to the air.
   Tin  plates,  which constitute the material of the common  tin
ware, so extensively used, are thin sheets of iron coated with
tin.  The mode of rolling these sheets will be described under
the head of Iron.   To  prepare them  for  tinning,  they   are
steeped in water acidulated  with muriatic acid,  and then heat-
ed, scaled, and rolled,  to remove all  oxide, and enable the tin
to adhere to the iron.  The tin is kept melted  in oblong, rec- 
ARTS  OF METALLURGY.
407
tangular  vessels, and to preserve its surface from oxidation, a
quantity of melted  fat and oil is kept floating  upon  it.   The
iron plates are taken up with  pincers, and immersed in the tin
for some  time.   When  withdrawn they are found to have ac-
quired a bright coating of the tin, which adheres closely, ow-
ing to the formation of an intermediate alloy.   The dipping is
repeated twice, or  more times,  according to the thickness  of
the coat intended to be given, and also to produce a smooth
surface, and between these  processes the tin is equalized with
a brush.  *
   Various other  articles of iron, such as  spoons, nails, bridle
bits, small chains, he are coated with tin, by immersing  them
in that metal while in a state of fusion.  From the affinity be-
tween tin and copper, a thin layer of the former metal can be
easily applied to the surface of the latter; and this practice of
tinning, as it is named, is often employed to prevent the erosion
or  rusting of  copper vessels, and the noxious impregnation
which they would  otherwise  communicate to liquors kept  in
them.   The surface of the copper is polished so as to be quite
bright; sal ammoniac is applied to it, when hot, by which the
oxidation appears to be prevented;  or pitch is sometimes used
for the same purpose.   The  melted tin, or sometimes an alloy
of tin and lead, is then  applied to the surface of the copper,
to which it readily adheres.
   Silvering of Mirrors.—The  surfaces best  adapted for re-
flecting  light,  are  those of polished metals.   To constitute a
good reflector, it is necessary that a metal  should be suscepti-
ble  of an equal, unbroken, and exquisite polish, and  that it
should retain  this polish, without being tarnished by the atmos-
phere.  Speculum metal is  chiefly employed for reflecting
surfaces in telescopes,  but  for  common purposes an amalgam
of tin and mercury is used  in a state of adhesion to  glass.
The use of the glass is, in the first place, to produce a smooth
surface in the amalgam; and afterwards to protect it from oxi-
dation by the atmosphere.
   * For a full account of the  present mode of manufacturing  tin plate, see
 Parkes' Chemical Essays, vol. ii. 
408
ARTS  OF METALLURGY.
   In the silvering of plain looking  glasses,  a flat, horizontal
 slab of stone, is  used as a table.   This  is smoothly covered
 with paper, and  a sheet of tin foil, equal to the size of the
 glass, is extended over it.  A quantity of mercury is then laid
 upon the  tin foil, and  immediately spread over it with a roll of
 cloth, or  a hares  foot.  Afterwards, as much mercury as the
 surface will hold,  is poured on.  While this mercury is yet in
 a fluid state, the  plate of glass is slid on  at  the  edge of the
table, so as  to  pass over the tin  foil, driving the superfluous
 mercury before it.   In this way any bubbles of air and  particles
 of dust are prevented from getting between the glass  and the
 metal, and  an uninterrupted coating is formed.   In order to
 force out the  remaining liquid mercury,  the glass is placed
 in a sloping position, to allow  the  mercury to drain off,  after
 which  heavy  weights are placed  upon the glass, and  suffered
 to remain for some time.  The portion which is left,  amalga-
 mates  with  the tin, and  forms a permanent reflecting  surface,
the smoothness and perfection of which, depends upon the
degree of regularity and polish which the  glass possesses.
  In silvering concave and convex mirrors, instead of a stone
table, the  tinfoil is spread upon  a plaster mould, previously cast
on the surface  of the glass itself.   The inside of glass globes
is silvered by pouring  into them a fusible alloy of tin, lead, bis-
muth, and mercury, the heat of which, when liquid, is not suf-
ficient to break the glass.  By turning the globe about, a thin
metallic coating is deposited on the whole interior surface.

                           IRON.

  The properties which iron possesses in its various forms,
render it the most useful of all  the metals.  The toughness of
malleable iron, adapts it to purposes where  great  strength is
required; while its combination of difficult fusibility with the
property  of softening  by heat, so as to admit of forging and
welding,   renders  it capable of being  easily   worked, and  of
withstanding an intense  heat.  Cast iron, from its cheapness, 
ARTS  OF METALLURGY.
409
and the  facility with which its form is changed by fusion, is
made  the  material  of  numerous structures  and  machines.
Steel, which is the most important compound of iron, exceeds
all other metals in the combination of hardness  and tenacity;
and hence it is particularly adapted to the fabrication of cutting
instruments. * It is  equally superior in  elasticity,  a quality
by which it is suited to be the  spring of motion in various
machines.
   Smelting.—The principal ores which  are wrought for the
extraction of iron, are the different species of the  native ox-
ides.   The process is somewhat different, as carried on in dif-
ferent countries, and as adapted to different ores ; but the fol-
lowing is the general outline of it, as it is conducted on the
haematite, bog ores, and  other oxides of iron.
   The ore is first roasted with a strong heat, to expel the car-
bonic acid, and any portion of sulphur, or other volatile matter
that may be present.   The remaining ore is put into a furnace
of a conical form with charcoal, or with coke, and exposed  to
a heat  rendered sufficiently  intense by  a blast of air  urged
through the furnace.   A quantity of lime is at the same time
added to the ore, and fuel; the advantage of which appears to
be, that in combination with the argillaceous and siliceous sub-
stances  generally contained in the iron ores, it acts as a flux,
to vitrify the foreign  matter, and  thus  facilitate the  sepa-
ration of the melted metal.  The proportions of these are ex-
tremely various,  according to the nature of the ore.   When
the furnace is once  charged, the  charge is renewed at the up-
per part, as fast as the  materials sink, and the  process is car-
ried on for a long time without interruption.   During this pro-
cess, the oxygen of the oxide of iron unites with one portion
of the carbon, and the metal with another, producing carbonic
acid, and  carburet of iron; while the earthy  substances,  to-
gether with a little oxide of iron,  enter into combination,  form-
ing a vitreous substance called slag or scoria, and which  being
lighter  than the  metal,  rises  upon  its  surface.   The slag  is
drawn off by  an  opening, and the melted  metal is collected in
               52 
410
ARTS  OF METALLURGY.
a cavity at bottom, from which, as it accumulates, it is convey-
ed off at intervals into moulds.
   Crude  Iron.—The metal  thus obtained, is named pig iron,
and crude, or cast iron.   It is far from being pure, containing
always more or less oxygen and carbon ; and  often several oth-
er heterogeneous ingredients,  such  as mangarfese,  and the
metallic bases of lime, clay,  and silex, with  portions of unre-
duced ore, and  charcoal.  The  oxygen is partly a portion of
what  was  originally combined with the metal in the ore, and
partly perhaps, derived from the blast  of air, which is driven
through the furnace, and necessarily presented to the metal in
a state of fusion.  Hence  the  qualities of cast iron are very
various, according as on£ or other of the principles predominate.
  Iron  in this state, is  readily capable of being fused,  and
cast  into  moulds.   It is,  however,  much more  brittle than
when pure,  and cannot be wrought, or  flattened  under the
hammer.   Hence it  is altogether  unfit for many purposes, to
which pure, or malleable iron is, from its tenacity, and softness,
well adapted.
   Casting.—Iron, as well as brass, and other metals which melt
at temperatures above ignition, is cast in moulds made of sand.
The  kind of sand most employed is loam, which possesses a
sufficient portion of argillaceous matter,  to render it moderate-
ly cohesive, when damp.  The mould is formed by burying in
the sand a wooden pattern, having exactly the shape of the ar-
ticle to be cast.   The sand is most commonly  inclosed in flasks,
which are square frames resembling wooden boxes open at top
and bottom.  If the pattern be  of such  form  that it can be
lifted  out of the sand,  without  deranging  the form  of the
mould, it is only necessary to  make an impression of the pat-
tern in one flask; and articles of this kind are sometimes cast
in the open sand upon the floor  of the foundry.   But  when
the shape  is such that the pattern  could not be extracted with-
out breaking the mould, two flasks  are  necessary,  having half
the mould formed in each.   The  first flask is filled with sand,
by ramming it close, and is  smoothed  off at the  top.  The 
ARTS  OF METALLURGY.
411
pattern  is separated into halves, one half being  imbedded in
this  flask.   A quantity of  white  sand,  or  burnt  sand,  is
sprinkled over the surface to prevent the two flasks from  co-
hering.   The second flask is then placed upon the top of  the
first, having pins to guide it.   The other half of the pattern, is
put in its place, and the flask is filled with sand, which of course
receives the impression of the remaining half of the pattern on
its under side.   After  one or more holes are made in the top,
to permit the metal to be poured in, and the steam and air to
escape, the  flasks are separated and  the pattern withdrawn.
When the  flasks are again  united,  a perfect cavity, or mould,
is formed, into which the melted metal is poured.
  The  arrangement of the  mould is of course varied for dif-
ferent articles.  When the form of the article is complex and
difficult, as in some hollow vessels, crooked  pipes, he,  the
pattern is made in three or more pieces, which are put together
to form the mould, and afterwards taken apart to extract them.
In some other irregular articles, as andirons, one part is cast
first, and afterwards inserted in the flask which is to form  the
other part.
   The  metal for small  articles is usually dipped  up with iron
ladles, coated with clay, and poured into the moulds.  In large
articles,  such as cannon, the mould is  formed in a pit dug in
the earth near the furnace, and the melted metal is conveyed
to it in a continued stream, through a channel  communicating
with the bottom of the furnace.
  Cannon  balls  are sometimes cast in moulds made of iron,
and to prevent the melted  metal from adhering, the inside of
the mould is covered with powder of black  lead.   Rollers for
flattening iron are also cast in iron cases.   This method is cal-
led chill casting, and  has for its object the hardening of  the
surface of the metal, by the sudden reduction of  temperature,
which takes place in consequence of the superior  conducting
power of the iron mould.   These rollers are afterwards turned
smooth in a powerful lathe, which has a slow  motion, that  the
cutting tool may not become heated by the friction. 
412
ARTS  OP METALLURGY.
   Malleable Iron.—To obtain pure iron, that is, to free crude
iron from the  oxygen, carbon, and other foreign substances
contained in it, it is subjected to two operations,—melting, and
forging.   The fusion is performed in different furnaces.  The
melted metal is in some cases run out to free it from the scoria
which has  separated ; and  this  process is repeated  until the
iron attains a degree of consistence sufficient to be submitted
to the action of the forge hammer.   But more commonly the
metal  is kept  in fusion in a reverberatory furnace,  called a
puddling furnace, where it is raised  to a very high temperature.
The liquid is stirred frequently to facilitate  the combination of
the carbon and oxygen.  At  length a lambent blue flame ap-
pears on its surface, probably from the formation and  disen-
gagement of carbonic oxide,  and after  some time  the  fluidity
of the metal diminishes, until it at length assumes the consist-
ence of a stiff paste.   It is  then  subjected to the  action of a
very large hammer, or to the  more equable pressure of rollers,
by which a  portion of oxide  of iron, carbon, and other hetero-
geneous  substances not consumed during the fusion, are forced
out.   The iron in this state, is no longer granular in its texture,
but is soft, ductile, and malleable, and much less fusible.   It is
then named wrought  iron, forged, or bar iron, as it is general-
ly formed  into  long  bars.   A considerable  loss of weight at-
tends the process from the dissipation of the foreign substances
contained in the crude iron, and from the oxidation of the sur-
face of the  metal.   The  operation is generally  performed on
the varieties called white, or grey crude iron.
   Forging.—Forging  consists in changing the  form of iron
and other  malleable  metals, by percussion applied  to  them,
while they  are  softened by heat.   Iron when exposed to the
action of great heat, becomes highly malleable and ductile.   It
is also capable  of welding, at a sufficiently high temperature.
Most other metals have their malleability improved  by a cer-
tain degree of heat,  but become brittle if the  heat is carried
near  to  their fusing point.   The  strength and quality of iron,
on  the contrary,  are improved  by forging at a strong  white 
ARTS  OF METALLURGY.
413
heat, since the parts become  consolidated, and the flaws oblit-
erated, by hammering at a welding temperature.
  The joint action of the  heat and  current of air, used  in
forges, tends to oxidate rapidly  the surface of iron.  The ox-
ide  which is formed has some  tendency to vitrification  when
combined with siliceous matter.  Hence it is a common prac-
tice  among  workmen, to immerse the  iron in sand, when it is
near to a welding  heat.  A vitreous coating is by this  means
formed, which protects the surface of the iron from further oxi-
dation.   This coating would  prevent the different pieces from
uniting by welding, were it not  that its fluidity causes it to es-
cape, while  under the action of the hammer.
  The  forging at the furnaces,  of large masses of iron, called
blooms,  is performed by the aid of tilt hammers,  as is also
that  of  anchors  and various other massive implements and
parts of machines.   Bars of iron are  commonly  rolled, and
when heavier articles, such  as anchors,  are to be made, a suffi-
cient number of bars for the purpose are welded together.
  A tilt  hammer of the  kind used in iron  works, is shown in
PI.  IX.  Fig. 2.   A B is the hammer, which turns upon the
fulcrum C.   At D is a wheel or cylinder furnished  with wipers,
ab c, he each of which as it passes, strikes the end A of the
helve, and causes the hammer end B  to rise.   The hammer
then descends with its own weight, and is accelerated  by the
recoil of the end A, from the fixed obstacle E.   The  wipers
may be  indefinitely varied  in  number and position, and  are
sometimes applied on the other side of the  fulcrum.  The re-
coil  likewise, is sometimes  produced by a spring  placed  over
the   end  B of the  hammer.   The  motions of these engines is
extremely rapid, and is commonly regulated by a fly wheel.
  Rolling and Slitting.—Malleable iron is commonly wrought
into  those shapes which have flat, parallel surfaces, by submit-
ting it to compression between rollers.   Bars, plates, and sheets
of iron  are formed in this  way.  A pair of heavy  cylindrical
rollers, made of iron, chill  cast, and  turned smooth, are con-
nected  together by strong iron  bearings, a space being left be 
414
ARTS  OF METALLURGY.
tween them equal to the intended thickness of the metal which
is to  be rolled.  This distance is varied  by adjusting it with
powerful screws.   The iron which is to be rolled, is prepared
by  heating it red hot,  and in this  state it is presented to  the
rollers.   As soon as any part has entered so as to fill the space
between the rollers, the friction, or adhesion, becomes sufficient
to draw in the remainder, in opposition  to the force with which
the metal resists compression.   The  iron in passing through, is
compressed into a  uniform plate of equal  thickness, and is at
the same time  extended in length, but is very little increased
in breadth.   As the rollers usually move with considerable ve-
locity, the  heated  iron may be passed  several times  between
different pairs of rollers, before it cools.   To prevent the  rollers
from  becoming heated, a continual stream of water is let fall
upon  their surface.
  As the principal extension, which plates  receive, is in a longi-
tudinal  direction, it is necessary to  vary their  position when it
is desired to increase their width.   This is sometimes done by
passing  them  in an oblique direction, but in making sheet iron
and wide plates, it is necessary to  pass the pieces through the
rollers in the direction of their breadth, as well as length, that
they  may be  extended in both  directions.  Very thin plates,
like those  used for tinned  iron, are  repeatedly  doubled,  and
passed  between  the rollers, so that in  the  thinnest plates  16
thicknesses are rolled together, care being taken to change their
relative  positions, and to interpose oil  to prevent them from co-
hering.   The last  rollings are performed  while the metal is
cold.   Bars which  are square, round, and of  various other
shapes,  are  formed between  rollers  which have grooves cut
upon  their  circumferences, corresponding in shape to half the
bar to be made.  Even rails of malleable  iron,  for rail roads,
have  lately been made between rollers formed for the purpose.
And at  some furnaces where malleable iron is made, the forge
hammer is dispensed with, and reliance is placed on the rollers
ak^ne to consolidate and equalize the masses of metal. 
ARTS  OF METALLURGY".
415
   Slitting rollers, or those intended for dividing plates of iron
into  narrow  rods, are formed  with  elevated  rings upon their
circumferences, which reciprocally enter between each other,
their  edges being angular and passing in close  contact with
each other, so as to cut like shears.  These rings are separate-
ly made, so that  they can be removed from the rollers for the
purpose of sharpening them, when necessary.
   Wire Drawing.—The manufacture of wire  consists in draw-
ing a piece of metal  through a conical  hole, in a steel plate,
which forms it into a regular cylindrical filament.   The size of
this filament may be reduced, and the length, extended, indefi-
nitely, by passing it through successive  holes, which gradually
diminish in diameter.
   To prepare the iron for drawing,  it  is first subjected to the
action of the hammer, till it is reduced to a size, that will admit
of its being  drawn through the plate.  Sometimes the iron is
prepared  by rolling,  but  the  best  wire  is produced when the
metal has been thoroughly hammered.
   The rod of iron which has  been prepared  in this manner is
next drawn  through one of the larger holes in the steel plate.
Various machines are  employed  to  overcome  the. resistance
which the plate  opposes to the compression and passage of the
wire.  In general, the end of the wire is held by pincers, and
as fast as the wire is drawn through the plate, it is wound upon
a roller by the action of a wheel  and  axle,  or  other power.
Sometimes a rack and pinion is employed for this purpose, and
sometimes a lever which acts at intervals,  and takes fresh hold
of the wire each time that the force is applied.
   The finer kinds of wire are made from the  larger by repeat-
ed drawings, each of which  is performed through a smaller
hole than the preceding.  As the metal becomes stiff and hard
by the repetition of this process, it is necessary  to anneal  it
from  time to time, to restore its ductility.  It is also occasion-
ally immersed in an  acid liquid, to loosen the  superficial  oxide
which is  formed  in the process of annealing. 
416
ARTS  OF METALLURGY.
   Nail Making.—Nails are made both by hand, and by ma-
chinery.   Wrought nails are made singly at the forge and an-
vil, by workmen who  acquire  from practice great despatch in
the operation.  Machines have been  made for making these
nails perfectly, and with rapidity; yet they have not come into
general use, owing to the cheapness of the product by manual
labor.   Cut  nails are made  almost wholly by machinery, in-
vented in this  country.   The iron, after having been rolled
and slit into rods, is flattened into plates of the thickness intend-
ed for the nails, by a second rolling.  The end of this plate is
then presented te  the nail machine, by a workman, who turns
the plate over once for every nail.  The machine has a rapid
reciprocating motion, and cuts off at  every stroke  a wedge
shaped piece of iron, constituting a nail without a head.  This
is immediately caught near its largest end, and compressed be-
tween gripes.   At the same time a strong force is applied to a
die at the extremity, which spreads the  iron sufficiently to form
a head to the nail.  Some nails are made  of cast iron,  but
these are always brittle, unless  afterwards converted into mal-
leable iron by the requisite process.
   Gun Making.—Cannon, carronades, he whether of iron
or brass, are cast in sand, and afterwards  bored.  Muskets and
fowling pieces are forged from bars of malleable  iron.  The
bar is first  flattened by hammering, till it attains the  requisite
width.  It is then  made  into a tube by turning it over  a man-
drel, or cylindrical  rod, of a size which is smaller than that of
the intended bore.   The edges are made to overlap each oth-
er about half an inch, and are  firmly welded  together.  The
whole is then consolidated and strengthened, by hammering it
for some  time  in  semicircular grooves on a swage, or anvil,
which  is furrowed for  the  purpose.   To render the barrel
smooth on the inside, and perfectly true, it is afterwards bored
out with an instrument somewhat larger than the mandrel,  and
several such  instruments of  different  sizes are employed in
succession.  The  breech of the  barrel  is closed  by  a strong
plug which is firmly screwed in at the  extremity.   The pro- 
ARTS  OF METALLURGY.
417
jecting  parts of the  barrel, such as the  sight, and  the  loops
which confine it to the stocks, are soldered on.  The construc-
tion of  the lock, and  other  appendages, is readily understood
from inspection.
   Steel.—When malleable iron is recombined with carbon in
a much smaller proportion, it forms steel.   Different methods
are  followed to form  this  combination.   The product varies
according to the method pursued, and is also affected by the
introduction  of other  substances into  the  combination.   The
best steel is made from Swedish and Russian iron.
   The general method of forming steel, is by the  process of
cementation.   A furnace is  constructed of a conical  form, in
which are two large cases, or troughs, of fire brick, capable of
holding some tons of  iron.   Beneath  these is a long grate, on
which the fuel is placed.  On the bottom of the case is placed a
layer of charcoal dust; over this a layer of bars  of malleable
iron ; over  this, again, a layer of charcoal  powder;  and the
series of alternate layers of charcoal  and  iron, is thus raised
to a considerable  height.  The  whole is covered with clay to
exclude the air, and flues are carried through the pile from the
furnace, so as to communicate the heat more completely and
equally.  The fire is kept up for eight  or ten  days.   The
progress  of  the cementation is  discovered  by withdrawing a
bar, called the  test  bar, from an aperture in the  side.  When
the conversion  of iron into  steel, appears to be complete, the
fire is extinguished, the  whole is left to cool for  six  or  eight
days longer, and is then removed.
   The iron prepared  in this manner, is named blistered  steel,
from the blisters which  appear on its surface.  To render it
more perfect, it is subjected  to the action of the hammer, in
nearly  the same manner which is practised  with forged  iron ;
it is beat very thin, and is thus  rendered more firm in its tex-
ture, and more convenient in its  form.   In this state it is  often
called  tilted  steel.  When the bars are exposed to heat in a
furnace sufficient  to  soften  them, and afterwards  doubled,
drawn  out, and welded, the product is called shear steel.   Cast
                53 
41S
ARTS OF  METALLURGY.
steel is made by fusing bars of common blistered steel  with a
flux of carbonaceous and vitreous substances, in a large cruci-
ble, placed in a wind furnace.  When the fusion is complete, it
is cast into small bars or ingots.   Cast steel is harder and more
elastic, has a closer texture, and receives a higher polish, than
common steel.   It is  capable of  still farther improvement by
being subjected to  the action of the hammer. *
   Steel is generally prepared from malleable iron.  It can also
be formed from crude cast  iron, as in Mr Lucas' method here-
after described.   Several varieties of cast iron have  been used
for this purpose.   The  crude iron  from  certain ores, as the
sparry iron ore, is  capable of this conversion.   The steel thus
obtained, is named natural steel, but is inferior to  that obtained
by cementation.
   Alloys of Steel.—Messrs Stodart and Faraday, have succeed-
ed  in  making  some useful alloys of steel with other metals, f
Their experiments induced them  to believe that the  celebrated
Indian steel called  wootz, is an alloy of steel with small quanti-
ties of silicium and aluminum ; and they  succeeded in preparing
a similar compound, possessed  of all the properties of  wootz.
They ascertained  that silver  combines  with steel,  forming an
alloy, which, although it contains  only 1-500th of its weight of
silver, is superior to wootz, or to the best cast steel in hardness.
The alloy of steel with 100th  part of platinum, though less
hard than that with silver, possesses a greater degree of tough-
ness, and is therefore  highly valuable when tenacity as well as
hardness is required.   The alloy of steel  with rhodium even
exceeds the two former in hardness.  The compound of. steel
with palladium, and of steel with iridium and osmium, is like-  _
wise exceedingly hard ;  but these alloys cannot be applied to

  * Writers differ in regard to the proportion of carbon contained in cast steel.
Mr Buttery, in Ure's Dictionary, states that the amount is less thin in common
steel, and that no charcoal is added in making it.  He also states that it does
not melt at a welding temperature, but  falls to pieces like sand,  under the
hammer, and the parts refuse to become  again united.
  f Philosophical Transactions, for 1822. 
ARTS  OF METALLURGY.
419
useful purposes, owing to the rarity of the metals of which they
are composed.  M. Berthier has also produced a useful alloy
by combining with the steel a small portion of chromium.
   Case Hardening.—The process of case hardening consists
in converting the surface of iron into  steel, and is used for giv-
ing a superficial hardness to various instruments.   It is effected
by inclosing the article which is to be case hardened, in a box
with some carbonaceous substance, usually  animal charcoal,
and exposing it to heat, until the surface is converted into steel.
The same term is sometimes improperly applied  to the method
of chill casting, which has been already mentioned.
   Tempering.—The most remarkable, as well as the most useful
of the properties of steel, is the power which it has of changing
permanently  its degree  of hardness, by  undergoing  certain
changes of temperature.  No  other metal, says Thenard,  is
known to possess  this property, and iron itself acquires  it only
when it is combined with a minute portion of carbon.   If steel
is  heated to redness, and suddenly plunged in eold  water, it is
found to become  extremely hard, but at the same time, it is too
brittle for use.  On the other hand if it be suffered to cool very
gradually, it becomes more soft, and ductile, but is deficient in
strength.   The process of  tempering is  intended  to give  to
steel instruments  a quality intermediate between brittleness and
ductility, which shall insure them the proper degree of strength
under the uses to which they are exposed.  For this purpose,
after the  steel has  been sufficiently hardened, it is partially
softened, or let down to the  proper temper, by heating it again
in a less degree,  or  to a particular temperature, suited  to the
degree  of hardness  required;  after  which it is again plunged
in cold  water.
   Different  methods have been pursued, for determining the
temperature  proper for giving the requisite temper to different
instruments.   One  method  is to observe  the  shades of color
which  appear on the  surface of the  steel, and  succeed each
other as the  temperature increases.   Thus at 430 degrees of
Fahrenheit, the color is pale, and but slightly inclining to yellow. 
420
ARTS  OF METALLURGY.
 This is the  temperature  at  which lancets are tempered.   At
 450 degrees, a pale straw color appears, which is found suita-
 ble for the best razors and surgical instruments.  At 470 de-
 grees a full yellow is produced, suitable for penknives, com-
 mon  razors, he   At 490 degrees, a brown  color  appears,
 which is  used  to  temper shears,  scissors, garden  hoes,  and
 chisels  intended  for  cutting cold  iron.  At 510  degrees  the
 brown becomes dappled  with  purple spots, which  shows the
 proper heat for tempering axes, common  chisels, plane irons,
 he   At  530 degrees a purple color is established,  and at this
 degree  the temper is given to table  knives  and large shears.
 At 550 degrees, a bright blue  appears, used for swords  and
 watch springs.   At 56Q degrees the color is a full blue, and is
 used for fine saws, augers, &c.  At 600 degrees a  dark  blue
 approaching to black, has  become settled, and is attended with
 the softest of all the grades of temper,  used only for the larger
 kinds of saws.
   Another method of giving the  requisite temper  has been
 practised upon  various articles.  The pieces of steel are cov-
 ered with  oil or tallow, or put into  a vessel containing either of
 these ingredients, and heated over a moderate  fire.   The ap-
 pearance of the smoke from the oil or tallow, indicates the  de-
 gree of heat.   If the  smoke just  appear, the temper  corres-
 ponds with that indicated  by the straw color when the metal is
 heated alone.   If so much heat is applied that a black smoke
 arises, this points out a different degree  of hardness;  and so on,
 till the vapor catches flame.  By this method a number of pieces
 may be done at once, with comparatively little trouble, and the
 heat is also more equally  applied.
   A still more  accurate method of producing any desired  de-
 gree of temper, is to immerse the steel in some fluid medium,
the temperature of which is kept regulated by the thermome-
ter.   Thus oil, which boils at about 600 degrees, may be used
 for this purpose at any degree of heat which  is below  that
number of degrees.   Mr Parkes has recommended the em-
ployment of metallic  baths, chiefly composed of lead and tin, 
ARTS  OF  METALLURGY.
421
in different proportions, whicli pass into fusion at definite tem-
peratures, and which can be used  for tempering steel, as soon
as they arrive at their melting points. *    f

  * The following table of metallic baths is given in Parkes' Chemical Essays,
Appendix to vol. ii.
  No.    Edge Tools to be tempered in the various
                     Baths.
  1     Lancets, in a Bath composed of
  2     Other surgical instruments
  3     Razors, &c.
  4     Penknives and some implements of
             surgery
  5     Larger penknives, scalpels, &c.
  6     Scissors, shears, garden  hoes, cold
             chisels, &c.
  7     Axes, firmer  chisels, plane irons,
             pocket knives, &c.
  8     Table knives, large shears, &c.
  9     Swords, watch springs, &c.
  10     Large springs, daggers, augers, small
             fine saws, &c
  11     Pit saws, hand saws, and some  par-
             ticular springs
  12     Articles which require to  be still
             somewhat softer

   t Formerly, no man in Great Britain knew how to temper a sword in such a
 way that it would bend for the point to touch the heel and spring back  again
 uninjured, except  one Andrew Ferrara,  who resided in the  Highlands of
 Scotland.  The demand which this man had for his swords was so great, that
 he employed workmen to forge them, and  spent all his own time in tempering
 them;  and found it necessary, even in the day time,  to work in a dark cellar,
 that he might be better able to observe the progress of the heat, and that the
 darkness of his workshop might favor him in the nicety of the operation.
   The swords  which  were formerly in  the highest repute, were made at
 Damascus in Syria.   The method by which these were made, has long been
 lost, or perhaps it was never thoroughly known to Europeans ; but from their
 striated appearance, it has been supposed  that they were formed by alternate
 layers of extremely thin plates of iron and steel, bound together with iron
 wire, and then firmly cemented together by welding.  These weapons never
 broke, even in the hardest conflict, and retained so powerful an edge, as to be
 capable of cutting through armour.  Various other  explanations have  been
 given in regard to the character and structure of the  Damascus,  or damasked,
 steel.
Composition of the Bath.	Temper. Fahren.
7 lead 4 tin	420°
1\ lead 4 tin	430
8 lead 4 tin	442
8£ lead 4 tin	450
10 lead 4 tin	470
14 lead 4 tin	490
19 lead 4 tin	509
30 lead 4 tin	530
48 lead 4 tin	550
50 lead 2 tin	558
Boiling linseed oil	600
Melting lead	612
 
422
ARTS  OF METALLURGY.
   Cutlery.—Under  the  head of cutlery,  are comprehended
numerous instruments, designed  for cutting or penetration, and
which  are made of  steel, mostly by the  processes of forging,
tempering, grinding,  and polishing.  The  inferior  kinds of
cutlery are made of  blistered steel  welded to iron.   Tools of
a better quality are manufactured  from  shear steel, while the
sharpest and most delicate instruments, are formed of cast steel.
   The first part of the process consists in forging, and is varied
according to the kind of  article to be formed.  Common table
knives, have the  blade forged of steel, and welded to  a piece
of iron, out of which the shoulder, and part which  enters the
handle, are made, the shape being given to them by hammering
in a die  and  swage.  They are  afterwards tempered  and
ground.   Forks are  made by forging the shank, and  flattening
the other end to  the  length intended for the  prongs.  The
prongs are  made by stamping the  metal at a white  heat, be-
tween two dies, the uppermost of which is attached to a heavy
weight, and falls from a  height.   The shape is thus given to
the fork, leaving, however, a  flat thin piece of metal between
the prongs, which is afterwards cut out with a fly press.   They
are subsequently filed, bent, hardened, and  polished.
   Blades of penknives are  forged  from  the end of a rod of
steel, and cut off, together with metal enough to form the joint.
The small  recess in  which  the nail is inserted  to  open the
knife, is made with  a curved chisel, while  the  steel  is hot.
Razors are forged from cast steel, much in the same  manner
as  knives.  The  anvil is commonly a little rounded  at the
sides, for  the purpose of making the sides of the razor a little
concave, and the edge thinner.   In forging scissors,  the shape
is given to the different parts, by hammering them upon differ-
ent indented surfaces, called bosses.  The bows, which  receive
the finger and  thumb, are  made by punching a hole in the
metal,  and  enlarging it by hammering it round a tool, called a
beak iron.   The halves are finished by filing and grinding, and
afterwards united by a joint.   Saws are made from steel plates
rolled for the purpose, and have  their teeth  cut,  and  finished 
ARTS  OF METALLURGY.
423
by filing, and set by a suitable instrument.   Axes, adzes, and
other large tools, are forged from iron, and have a steel  piece
welded on, of the  proper size to form the edge.
  To enable the steel to be wrought, it is brought to its softest
state, but after the shape is given to the instrument, the steel is
hardened and tempered by the methods already  described.
The  remaining  part  of the manufacture  consists in grinding,
polishing, and setting the instrument, to produce a smooth sur-
face and a sharp edge.   The grinding is performed upon stones
of various  kinds, among which freestone is perhaps  the most
common.  These stones are made to revolve by machinery,
and move with prodigious velocity, so that the surface, in some
cases, passes over six or seven  hundred  feet in a second,  and
stones have  been burst by their own centrifugal force.   For
grinding flat surfaces, like those of saws, the largest stones are
used; while for concave surfaces, like the sides of razors, smaller
stones are used on account of their greater convexity.   The
internal surfaces of scissors, forks, he which cannot be applied
to the stone, are ground with  sand  and emery, applied with in-
struments of wood, leather,  and  other elastic  substances.   The
last polish  is given by the impure oxide of iron, called colcothar,
crocus,  and by the French  Rouge  d' Angleterre.   The  edges
are lastly  set  with  hones  and whetstones,  according  to  the
degree of keenness  required.  The  test used  by cutlers for
determining the goodness of the edge and point of a  lancet, is,
that it shall pass through a piece of soft leather without sensible
resistance.   JSeedles are polished by tying them in large bun-
 dles with emery and oil, and  rolling them  under a heavy plank
till  they become smooth by mutual  attrition.   The shape is
 previously given,  and the eye made with a steel punch.
    A process  has been  invented by Mr  Lucas, for  converting
 edge tools, nails, &c,  made of cast iron, into good  steel.  It
 consists in stratifying the  cast  articles,  in cylindrical metallic
 vessels, with native oxide of iron, and  then submitting the
 whole to a regular heat in a furnace built for the purpose.  It
 is not, however, necessary  that the oxide  employed  should be
 a native oxide, any artificial oxide being equally effectual. 
424
ARTS of  metallurgy.
   The cast iron, of which this cutlery is made, is brittle in the
first instance, like other cast  iron, in consequence of the carbon
contained in it; but the great heat  which it undergoes, aided
by the pulverized oxide, separates a part of the carbon.   This
uniting with the oxygen of the ground oxide of iron, is dissipated
in the  state  either of carbonic oxide, or carbonic acid gas, and
the articles are then converted into a state nearly similar to that
of good  cast  steel  cutlery.   They  do not, however, receive
so fine an edge, and do not bear  hardening and tempering in
the common manner.
  Murray's  System of Chemistry, 4  vols,  8vo. 1806;—Parkes's
Chemical Essays, 2 vols, 8vo. 1823;—Gray's Operative Chemist, 8vo.
1828;—Dumas, Traiti. de Chimie Applique1 e aux Arts, &c. 4 torn.  8vo.
1828-9;—Fourcroy, Systeme des Connaissances Chimiques,  11  torn.
1801;—Aiken's Dictionary of Chemistry and Mineralogy, 2 vols, 4to.
1807;—Martin's Circle of Mechanic Arts, 4to. 1818 ;—Emporium of
Arts and Sciences, Philadelphia, 1812-14;—Franklin Journal, Phila-
delphia, 1826, and  after;—Rees's Cyclopedia,  various  heads;—
Ure's Dictionary of Chemistry;—Thenard, TraiUde  Chimie,5torn.
8vo. 1824;—Works of Bergman, Klaproth, Lewis, &c. 
CHAPTER XVIII.
    arts of communicating and modifying color.

  An extensive branch of industry has for its object the effect-
ing  of changes in the natural colors of bodies.   The  artificial
modifications, produced in color, may be either mechanical and
superficial,  or chemical and intrinsic.   In painting, gilding, and
similar processes, the original color of  a substance is not alter-
ed,  but it is  mechanically concealed by another substance which
covers  it from view.   On  the  other hand, in bleaching  and
dyeing, the color of the whole substance is intrinsically chang-
ed,  by a chemical action.   This  difference of character has
given rise to distinct arts  in coloring, the processes of  which
are  for the  most part dissimilar.

            of  applying  superficial color.

  Painting.—Common painting, when disconnected  with de-
sign, has for its object to produce a uniform and permanent coat-
ing  upon surfaces, by applying to them a compound,  which  is
more or less opaque.   In many cases  painting is applied only
for  ornament, but it  is more frequently  employed to protect
perishable substances from the changes to which they are liable
when exposed to the atmosphere, and   other decomposing
agents.   The effect and  durability of  different coverings em-
ployed in this  way, depends upon the  kind of pigment used,
and still more upon the vehicle, or uniting  medium, by the in-
tervention of which it is applied.
  Colors.—The  coloring substances,  employed by  painters,
comprise a great variety of articles derived from the  mineral,
vegetable,  and animal kingdoms.   They  are  employed in  a
              54 
426
ARTS OF  COMMUNICATING
 state of minute subdivision, and commonly mixed with a fluid
 which  is more or  less viscid and  tenacious.   When applied
 upon the surface of canvass, wood, or other bodies, they com-
 municate their  color, by covering and  concealing the original
 color of the surface, while  they substitute  their  own in stead.
 Those  which are perfectly opaque,  are  called body colors, such
 as white lead, and vermilion;  while those which are partially
 pellucid, are called  transparent  colors, as prussian blue, terra
 di sienna, and lake.   Transparent colors  do not wholly conceal
 the  colors  beneath them,  but produce the combined effect of
 the two.   The process called by painters glazing, consists in
 laying a transparent color over one  of a different tint.   Trans-
 parent  colors are sometimes mixed with a white earth to give
 them a body, where  it is necessary to cover entirely  the  pre-
 vious surface.  Common  whiting is usually  employed for this
 purpose.
   The following list  comprises the  principal coloring  substan-
ces, used  as paints,  exclusive of  those which  belong  only
to the art of dyeing.

   Blues.— Ultramarine is the richest and most durable of all the blues.
 It is not altered by time, and  bears  exposure to a red heat without
 changing  its color.   It is made only from the  lapis lazuli, a stone
brought from several parts of Asia,  which bears an extremely  high
price.
  Prussian blue is a strong and durable color.  In the present language
of chemistry, it is a ferrocyanate of the peroxide of iron.  It is made
from blood, and other animal matters, dried and heated to redness with
an equal weight of pearl ash.  The residue, which consists  chiefly of
cyanuret of potassium, and carbonate of potass, is dissolved in water,
and after being filtered, is mixed with a solution of alum and proto-
sulphate of iron.  A greenish  precipitate ensues, which, by exposure
to the atmosphere, passes through different shades, till it arrives at a
fine blue color.
  Blue verditer is a nitrate of copper combined with hydrate of lime.
It is made by adding  quicklime to a solution of copper in nitric  acid,
and mixing the precipitate with a small  portion more of lime.  It is a
full blue, much used in paper staining, but is liable to grow dull. 
AND MODIFYING COLOR.
427
  Smalt is a powdered glass,  which derives its  blue  color from the
oxide of cobalt.  It is chiefly used by strewing it on a ground of some
other color.
  Bice  consists of smalt finely levigated.  It is rather lighter, and
very durable, but not extensively used.
  Indigo is the deepest  of all  the  blues in common use.   It is very
durable, but more used in dyeing (which see) than in painting.  Stone
blue, Fig  blue, Queen's blue, &c, consist of indigo reduced by starch.
  Reds.— Vermilion is  a bisulphuret  of mercury, formed by  fusing
sulphur with about six times its weight of mercury, and subliming in
close vessels.  The product is called cinnabar, and when powdered,
vermilion.  It is of a bright scarlet color, and stands tolerably well.
  Red lead, otherwise called minium, is a deutoxide of lead, formed by
exposing lead, or litharge, to heat in a furnace, in open vessels,  with a
Current of air passing over it.   The metal is gradually converted into
an oxide of a bright orange red.  Red lead is extensively consumed
in the manufacture of flint glass.  As a pigment, it is brilliant at first,
but liable  in time to turn black.
  Chrome red is a fine  scarlet,  formed by boiling  carbonate of lead
with an excess of chromate of potass.   By Dulong's method, 67 parts
of white lead are boiled with 82 parts of chrome yellow, in water.
  Colcothar, also called crocus martis, and rouge rf' angleterre, is  an im-
pure brown  red oxide of iron which remains after the distillation of
the acid from sulphate of iron.  It forms a durable color, but is most
used by artists in polishing glass and metals.
  Ochres.—The ochres  are various earths containing iron in a greater
or less degree of oxidation.  Venetian red is  a coarse ochre of  a dark
red color.  Indian red is an ochre brought from the East  Indies, and
has a shade inclining to purple.   Red ochre is formed from yellow ochre
by exposing  it to heat.   Burnt sienna is made from the raw terra
di sienna by exposure to  heat, by which process its color is changed
from yellow  to red.  Bole is a fine clay, colored by oxide of iron, of
which there are many varieties, from yellowish red to brown.
  Carmine, the most beautiful  of all the reds, is an animal substance
made from the cochineal insect, or coccus cacti.   It is deposited from
a decoction of powdered cochineal in water, to which alum, carbonate
of soda, or oxide of  tin is added ; but the preparation of the finest va-
rieties is kept secret by the manufacturers, and probably depends much
upon the   delicacy of the manipulations.   A fine color is said to  be
made by adding acetic acid to a solution of carmine in ammonia.
  Lakes of various  shades are formed from cochineal precipitated by
salts of tin, and other agents.   Beautiful lakes are also prepared from
madder, by a process of Sir H. Englefield, in which the coloring sub- 
428
ARTS OF COMMUNICATING
stance is precipitated from an infusion of madder, by adding solutions
of alum, and carbonate of potass.  The lake called rose  pink, is an
extract of Brazil wood, mixed with whiting and alum.
  Rouge  is made from  the flowers  of the  Carthamus tinctorius or
Dyer's saffron,  also called safflower;  by dissolving an alkali in the in-
fusion, and  precipitating the  coloring  matter by lemon juice.  It is
very fugacious.  Under the same name other pigments are also used.
  Yellows.— Gamboge is the concrete juice of a tree growing in the
East Indies, (Stalagmitis cambogioides.)   It is  externally of a  dull
orange  color, but becomes of a  bright yellow, when wet, or thinly
spread upon a white surface.  It is partially soluble in water and alco-
hol, and is chiefly used in water colors.
  Orpiment is  a sulphuret (sesquisulphuret) of arsenic.   The paint
called  kings yellow, is made from this substance, or from its constitu-
ents.   It is a brilliant, but not very durable color, and its use is in
some cases dangerous to the health.
  JVdples yellow is prepared by exposing lead and antimony with po-
tass, to the heat of a reverberatory furnace.  It stands tolerably well,
but turns  black upon  the contact of iron.   A native pigment of this
kind is also obtained from a species of lava.
  Yellow ochre is a native earth, the finer particles of which, are sepa-
rated by washing, as in similar substances.  Although not very bright,
its cheapness and durability have caused it to be extensively used.
  Terra di sienna is also an ochre, of a deeper and brighter yellow,
than most of the  others.
  Massicot, or masticot, is the protoxide of lead, prepared by collecting
the gray film which floats  upon  the  surface of melted lead, and ex-
posing it to heat and air until it assumes a yellow color.
  Chrome yellow is a chromate of lead.  It is precipitated by adding
chromate of potass in solution, to a solution  of nitrate, or  acetate, of
lead.   It forms one of the  most  brilliant yellows, and is extensively
manufactured in this  country, from the chromate of iron  found near
Baltimore.
  Turpeth mineral is a subsulphate of mercury, or rather a sub-bisul-
phate.  It is a pale yellow,  and moderately durable.
  Patent mineral yellow is a fused muriate of lead, made by decompos-
ing common salt by means of litharge, triturating the product with
water, washing away the soda, and drying  and fusing the muriate.
  Dutch pink  is a cheap  color used  by paper stainers, composed  of
whiting  colored by a decoction of dyers wood, quercitron, or French
berries, with alum.
  Greens.— Verdigris is an acetate  of copper, or strictly, an impure
acetate of the peroxide of copper-  It is manufactured in the south of 
AND MODIFYING COLOR.                429
France by covering plates of copper with the refuse of the  grapes
after making wine.  It may also be formed by exposing copper to the
vapor of vinegar.
   Terra verte is a native blue-green ochre.  It is semitransparent and
durable, but not very bright.
   Brunswick green, called also mineral green, is an ammoniaco-muriate
of copper, much  used for paper hangings, and  occasionally in  oil
painting.
   Sap green is the  inspissated juice of the  berries of the buckthorn,
{Rhamnus catharticus.)   It  is semitransparent, and chiefly used in
water colors.
   Many of  the greens in common use are compound colors, made by
the admixture of blue with yellow.
   Browns.— Umber is a light brov/n ochre.  Burnt umber is the  same
substance, having its color darkened by exposure to heat.  It is  dura-
ble in both states.
   Spanish brown is a coarse durable ochre, its color inclining to red.
   Bistre is prepared from common  soot of wood, by pulverizing and
washing.   The soot of the beech is said to afford the best.
   Asphaltum is prepared from the bituminous substance of that name.
When dissolved in oil of turpentine, it is  semitransparent, and is used
as a glaze.
   Ox gall consists of the biliary  concretions found in the gall bladder
of cattle.  It is not soluble in water or alcohol, but dissolves readily in
 a solution of potass.  It is of a yellowish brown,  and is much valued
 for the brightness and  permanence of its tint.  The liquid ox gall is
 used by painters to facilitate the laying on of colors.
   Blacks.—Lamp black is a light carbonaceous substance, thrown off"
 during the  combustion of resinous and oily substances.  The chips of
 fir and pine trees are burnt under tents, to the inside of which the
 lamp black adheres.
   Frankfort black.  This is a charcoal made from the lees of wine.  It
 is used in the  ink of copper plate printers.
   Ivory black, called also Cologne black, is made  from the shavings
 and dust of ivory, heated in covered iron pots.  Various other carbo-
 naceous colors are made from cork, vine twigs, peachstones, &c, con-
 verted into charcoal.
   Indian ink is said to be made from different sorts of lamp  black,
 mixed with water and glue.   The black is obtained from the smoke of
 oil, of fir wood, or of  horse  chesnuts.  A solution of lac with borax,
 in water, is said to be the vehicle of the lamp black in some kinds.
   Sepia is the black liquid  obtained  from the cuttle fish.  It is of a
 viscid consistence, and is preserved by drying it upon saucers or shells. 
430
ARTS OF  COMMUNICATING
  Whites.—White lead, formerly ceruse, is a carbonate of lead, pre-
pared by exposing coils of sheet lead, in earthen pots, to the vapor of
vinegar for several weeks. It is sometimes also formed by precipita-
tion with carbonic acid from a solution of acetate of lead in water.
  Flake white consists of the  densest and thickest scales, which are
separated in making the foregoing article from sheet lead.  It is very
pure, whereas the white lead of commerce is adulterated with chalk.
  Pearl white is the subnitrate of bismuth, formerly called magistery
of bismuth, precipitated by water from its solution in nitric acid.  It
has been used as a cosmetic, but grows yellow by age and light.
  Whiting.—Common chalk separated in the form of an  impalpable
powder by washing.  Blanc de Troyes is similar to whiting.
  Zinc white is the oxide of zinc.  It  does not work easily, but is
thought very durable. Various marls and clays from Bougival, Rouen,
Moudon, &c, are used for white pigments.

   Preparation.—Coloring  substances, before  being used  in
painting, require to be reduced to a  state of extreme  fineness.
For this  purpose they  are ground in a color mill,  and  levi-
gated  with a stone  and muller.   In many  cases colors which
are insoluble in water,  are  separated  by washing, the water
being first made turbid  with the coloring  substance, and left
to stand a short time, till  the coarser  particles have subsided.
The  upper part of the fluid with the finer  particles in suspen-
sion is then  poured  off,  and  the  second   deposit  which
takes place from this is sufficiently  fine  for  mixing.   When a
greater degree of tenuity is required, the washing is repeated.
   Application.—As colors are first prepared for use by simply
reducing  them to powder,  it is necessary that some  tenacious
fluid should be introduced to make their particles adhere to the
surface on which they are  spread.   To effect this end various
fluids are employed, and the difference of  the material  used,
with the  method of employing it, has given rise to the  modes
of painting in water, in oil, in fresco, in distemper, he
   Crayons.—The  most simple mode  of applying colors  is by
the  use of crayons.  Crayons are  cylinders, or sticks of dry
colors, cemented into a friable mass like chalk, by  the assist-
ance of gum or size, and sometimes of clay.   They are  used 
AND MODIFYING COLOR.
431
by simply rubbing them  upon paper, and  afterwards blending
and softening the shades  by means of a stump, or small roll of
leather, or paper.   But drawings in crayons and  chalks, have
always the disadvantage  that they do not adhere to the paper,
but are rubbed off, and defaced, with the slightest attrition. In
this state they can be safely kept and examined only in frames
under  glass.  Various modes have been practised for fixing
crayon  drawings upon paper, so as not to be liable to deface-
ment.   Among other means, this end may be  effected by
brushing  the  back of the paper with a strong solution of isin-
glass, or by passing  the  drawing through a powerful press, in
contact with a moist paper.
   Water  Colors.—The most common mode of painting on
paper, is by the use of water colors.  These are formed into
hard cakes or lozenges  with a larger quantity of gum, than is
employed for crayons.   When  used, they  are  rubbed down
with water upon glass,  or a glazed surface, and applied while
wet with  a camels' hair  pencil.   The  gum with which they
are  mixed  causes them  to adhere so closely to the paper that
they cannot be rubbed off.
   Distemper.—Painting in  distemper is used for works to be
 executed upon a larger  scale, such as stage  scenery, the walls
 of apartments,  &c.  The colors are used in the form of pow-
 der, and are mixed with water rendered  glutinous by size, or
 other   solutions  of animal  glue.  The  mixture requires, in
 many cases, to be used warm, as the solution becomes stiff upon
 cooling.   Skimmed milk also serves as a vehicle for painting
 in distemper, and its tenacity is increased by adding small por-
 tions of lime, and of linseed or poppy oil.  The mixture dries
 speedily,  the oil being  converted  into a soap by the  lime.
 Distemper in badigeon  is employed by the French to restore
 the original color to stone walls which have  become brown by

   -This method is highly recommended by Ting.y who gives the following
 recipe  Skimmed milk 4 pounds ; lime newly slaked 6 ounces ; linseed, nut
 or poppy oil 4 ounces;  Spanish white (white clay) 3 pounds. 
432
ARTS  OF COMMUNICATING
time ; and consists in washing them with  powder of the same
kind of stone,  properly  mixed.   Chipolin is a varnished dis-
temper.
   Fresco.—Paintings in fresco are executed upon walls recent-
ly plastered, before they  have become  dry.  The coloring
substance mixed with water being applied  while  the wall is
wet, sinks in and incorporates itself with the  grain of the mor-
tar, so as to become very durable.  When a  wall is to be done
in fresco it is covered  with a coating of stucco or fine mortar,
which is applied in successive portions, no more being put on
at once  than  can be painted  before it is  dry.   This mode of
finishing by piecemeal,  renders  it necessary that the artist
should have his whole design  either drawn upon paper, or thor-
oughly digested in his mind before he begins.   The  drawings
which are  executed upon large paper to serve as patterns for
fresco paintings, are called cartoons.  They are transferred to
the walls by puncturing through the outlines with a sharp point. *
Many of the greatest  works of the most  eminent Italian mas-
ters are executed in  fresco, upon the walls and ceilings of the
different churches and  cathedrals.
   Encaustic Painting.—The  ancients made  use  of a mode
denominated encaustic painting, the knowledge of which at
the present  day is lost.   From the writings of Pliny it appears
that the material with which the colors were incorporated, was
wax,  and that  this was applied by the assistance of heat.   It
is represented as having been very brilliant and durable, though
no specimens of it remain  at this  day.   The principal paint-
ings which have been discovered upon the walls at Herculaneum
and Pompeii, appear to have been done in fresco.
   Oil Painting.—Painting in oil,  which on many  accounts
has a great superiority  over other methods, was first applied to
the execution of designs about the year  1410, by John  Van
Eyck, in Flanders.  The oils used for painting must be of the
class  denominated  drying  oils.   Of these, linseed oil is  the
* Cartoons are also used as patterns in tapestry and mosaic. 
                   AND MODIFYING COLOR.              433

 kind most  commonly  employed, and  its tendency  to  dry is
 increased by its being boiled.   Its color renders it sometimes
 injurious  to light tints, so that  in delicate pieces it is  better
 to  employ nut  oil,  or poppy  oil,  which  are  nearly  trans-
 parent, and do not turn  dark in drying.   The drying of paint
 is owing, not so much to evaporation, as to a chemical combi-
 nation of the oil with the pigment,  especially when  the latter
 is a metallic oxide, or other substance, having a direct affinity
 for the oil.  The  oxygen of the atmosphere appears also to
 enter  into this  combination.   The drying will be frustrated if
 a small quantity of any fat pil be present.  Hence in painting
 old surfaces, which have been exposed to contract any greasi-
 ness, it is necessary first carefully to  cleanse them, or to wash
 them  with lime in  water, or  with  some  alkaline  solution,
 which combines  with the oil.   The  latter method is practised
 by house painters.
   Oil paintings  of designs  are  executed either  on  canvass,
 on wood, or on  copper.  When the colors used are chiefly
 of the kind denominated body colors,  each  successive  layer
 conceals those beneath  it, so  that the work may be height-
 ened, amended, or altered, at pleasure  during  any  stage  of
 the  process.  Paintings in oil are  very durable, and acquire
 a mellowness from  age which improves rather than injures their
 effect, provided permanent colors have been used.
   Painting in the large way, with uniform  colors mixed  in oil,
 is employed not so much for ornament,  as for the protection of
 perishable  substances from decay.   Thus  wood may be pre-
 served from decomposition, and metals from  oxidation, for an
 indefinite time, by keeping them covered with a thick coating
 of paint, which is impervious to air and moisture.
   Varnishing.—The name  of varnishes  is  given to certain
 compounds,  chiefly  solutions  of resinous  substances,  which
 after being  spread  over surfaces, and dried, possess the quali-
ties of hardness,  brilliancy, and transparency.  They are em-
ployed to give lustre  and smoothness to painted surfaces, and
to defend them from the action of the air.
               55 
434
ARTS OF  COMMUNICATING
   The principal substances which form the basis of varnishes,
are  copal,  mastic, anime, sandarac, lac, benzoin, amber, and
asphaltum.  Of these, copal'is a hard, shining, transparent resin,
of a light citron color, originally brought from Spanish America,
and  erroneously considered  as the product of the Rhus copal-
linum. *   True copal is soluble in oil, but is difficult of  solu-
tion  in alcohol.   It is  commonly made into varnish by dissolv-
ing it in hot linseed oil,  rendered drying by  quicklime, and
diluting the solution with oil of turpentine.   By mixture with
camphor, it becomes soluble in alcohol, or in oil of turpentine.
Mastic is a resinous substance, in the  form of tears, of a pale
yellow color, brittle and semitransparent.  It comes from the
Levant, and is produced by  the Pistacia lentiscus.  A greater
part of it is soluble in  alcohol and in oil of turpentine.  Anime
is  brought  from  Spanish America,  and is said to be obtained
from the Hymencea courbaril.   It resembles copal very much
in its appearance, but  is easily soluble in alcohol,  while copal
is not.  It is often sold under  the name of copal.  Sandarac
is the resin of the  Thuya articulata which grows in Barbary.
It  resembles mastic, but is rather more transparent and brittle.
When chewed, it crumbles to powder, whereas mastic softens
in the mouth.  It is soluble in alcohol, and oil.  Lac is depos-
ited  on certain trees in  the  East Indies, by an  insect called
 Coccus lacca.   The  substance  in its natural state  incrusting
the  twigs, is called stick lac; when broken off and boiled in
water, till it loses its red color, it is termed seed lac, and  when
melted and reduced to a thin crust, it is called shell lac.   Stick
lac has a deep red color, and yields to  water a red  substance
which is used as a dye.   Lac is soluble in alcohol.  Benzoin
is  the product of the Styrax  benzoe,a.iree growing in Sumatra.
It is a solid, brittle substance, in yellowish  white  tears, joined

   * The Rhus copallinum is a common shrub in the United States, and is not
known to produce any substance resembling  copal.  According to Hernandez
 the copal of Spanish America is obtained from various trees.  I am informed
that the copal used in this country comes almost wholly from the East Indies.
It is  probably the produce of the Eleocarpus copalifera. 
AND MODIFYING COLOR.
435
together by a brown substance, and is sometimes wholly brown.
It is a balsam, and affords benzoic acid.   Amber and asphaltum
are mineral substances, already mentioned in the first chapter.
  Varnishes are  divided  into three kinds, according  to  the
menstruum in which the resinous substance is dissolved.  These
are spirit varnishes, in which the solvent is alcohol; essential
varnishes in which a volatile oil, commonly oil of turpentine, is
used ; and oil varnishes, which consist of a resin dissolved in a
drying oil.  Some vegetable juices may be applied in their
liquid state.  Thus the  viscid juice of the Rhus vernix affords
the celebrated black varnish used in Japan.  The same shrub,
which  grows  in  this country, affords a whitish juice,  which,
upon boiling,  yields a strong, glossy black varnish. *
   An elastic  varnish may be made by dissolving caoutchouc
in linseed oil  and oil of turpentine ; but this preparation dries
slowly.   Besides the solvents mentioned in the first chapter of
this work, it  is  found  that  the naptha of coal tar dissolves
 caoutchouc readily, and on  drying leaves its properties  un-
 altered, f
    Japanning.—Japanning is the  art  of  varnishing in colors,
 and is therefore a species of painting.   It is most easily exe-
 cuted upon wood and metal, or  such other substances as retain
 a determinate form, and are capable of sustaining the operation
 of drying  the  varnish.   Paper and   leather, when wrought
 into  forms in which  they remain stretched, stiff,  or  inflexible,
 are common  subjects for japanning.
    The article to be japanned is first brushed  over with two or
 three  coats of seed lac  varnish, to form  the priming.   It is
 then covered  with varnish previously  mixed with a pigment of
 the tint  desired.  This is called the groundcolor;  and if the
 subject  is to exhibit a design,  the objects are  painted upon
 it, in  colors mixed with varnish, and used in the same  manner as
 for oil painting.   The  whole is then  covered with  additional

   * See American Medical Botany, vol, i. p. 101.  The shrub is poisonous to
  many persons.
   t Annals of Philosophy, vol. xii, 
436
ARTS  OF COMMUNICATING
coats of transparent  varnish, and all  that remains to be done,
is to dry and polish it.
  Japanning requires to be executed in warm apartments, and
the articles are warmed before the varnish is applied to them.
One  coat of varnish, also, must be dry before another is laid
on.   Ovens  are employed to hasten the drying of the work.
  The same pigments which  are  employed in oil or water,
answer also in varnish.  For painting figures, shell lac varnish
is considered best, and easiest to work ; it is therefore employ-
ed in most cases where  its color permits.   For the  lightest
colors, mastic varnish is employed, unless the fineness of the
work admits the use  of copal dissolved in alcohol.
  Polishing.—Pictures,  and other  subjects, to which only a
thin  coat or two of varnish is given, are generally left to the
polish which the varnish naturally possesses, or are brightened
only by rubbing them with a woollen cloth when dry.  But when-
ever  several coats of varnish or japan  are laid on, a more
glossy surface can be produced, by  means similar to those
which are used to  polish  metals; the surface having first been
suffered to  become  completely dry  and hard.  Where the
coat of varnish is very thick, the surface is first rubbed with
pumice  stone and oil, till it becomes uniformly smooth ; the
pumice having been  previously reduced to a smooth flat face,
by  rubbing it on freestone.   The japanned  or varnished  sur-
face may  afterwards be  rubbed  with pumice reduced  to an
impalpable powder, the workman using oil  and leather to lay
on the powder.   The finishing  may be given by oil and  a
piece of woollen only.
  Where  the varnish is thinner, and of a more delicate nature,
it may be rubbed  with tripoli, or rotten stone, in fine powder,
finishing with oil as before.   Where the ground is white, putty,
or Spanish white, finely washed, may be used instead of rotten
stone, of which the color  might have  some tendency to injure
the ground.
   Lacquering.—Lacquering consists  in  the application  of
transparent varnishes to metals, to prevent their tarnishing, or 
AND MODIFYING COLOR.
437
to give them a more agreeable  color.  When the color of the
metal to be  lacquered is to be  changed, the varnish is tinged
with some coloring matter ; but where preservation from rust,
or tarnish, is the sole object, any of the transparent varnishes
will answer, the best and hardest being used where the greatest
durability is required.   Shell  lac is the most common basis of
the varnishes used in lacquering.   An  imitation of gilding is
effected  by covering the surface of tin or lead with a clear
varnish tinged  with  annotto,  turmeric,  or gamboge.   The
Chinese  gilt paper appears to be made in this manner.
   Gilding.—The process of gilding on  metals, described in a
former chapter,  depends on a chemical union, or alloy, between
the gold  and the  metal to which it is applied.   But gilding as
it is commonly performed upon  wood,  leather, he, is a me-
chanical  process,  and  consists in  cementing  gold  leaf upon
surfaces, for which it has no affinity.   In common oil gilding,
the surface to be  gilt is covered  with an adhesive  coating of
paint or gold size, composed of  yellow  ochre ground  in  oil.
When this  is partially dried, so as to feel  adhesive,  the  gold
leaf is laid upon it and pressed down with cotton wool.  When
the whole surface is covered, it is left to dry, and the superflu-
ous gold  leaf brushed  off.   In burnish gilding, the surface to
be gilt is first  covered  with a mixture of whiting and  size,
prepared by boiling  shreds  of parchment  or skins, in water.
This is rubbed smooth and covered with a gilding size contain-
ing a little  ochre  or Armenian bole.  This is suffered to dry
and is rubbed  smooth  with a linen rag.   The gilding is then
performed  by moistening successively the parts of  the  sized
surface with water, and applying the gold leaf before it becomes
 dry.   When  the  work has become firm, it is burnished  by
 rubbing  it with a hard polished substance,  such as agate, dog's
 tooth, or steel.
   Gilding on leather and on paper may be performed by ap-
 plying gold leaf with gum arable  or size.   The edges of paper
 and  of  books  are gilded with a size composed of  whites  of
 eggs, beaten with three or four times their quantity of water, 
438
ARTS  OF COMMUNICATING
and mixed with a little Armenian bole.   Bookbinders gild the
leather of books by coating it two or three times with whites of
eggs,  and  suffering it to dry.   A minute  quantity of tallow is
then rubbed on and the gold leaf laid loosely upon the  surface.
The stamps and letters are cut in brass; or printing types are
used.  These are  moderately heated, as much as the leather
will bear, and are then pressed upon the gold  leaf, by  which a
portion of gold corresponding to the letters is made to  adhere ;
after which the superfluous gold leaf is brushed off.
   Shell  gold is prepared by grinding up gold leaf with honey
until it is completely subdivided ; the honey  is  then  washed
away with water and the gold powder mixed with gum water
or some  other adhesive fluid.  It is usually  kept for use  on
shells, and is applied with a pencil  or brush in the manner of
common painting.

              OF CHANGING INTRINSIC  COLOR.

   The processes  considered in the previous part of this chap-
ter,  are  used to  produce  an external modification  of color,
and consist in mechanically covering the surfaces upon which
they are applied.   The remaining  division includes those arts,
which depend more exclusively upon chemical processes, and
which, by operating on the  internal texture of bodies, produce
a total and intrinsic change of color.   Of this  kind are the
arts of bleaching, dyeing, and calico printing.   The operations,
however, which belong to these arts, are too extensive to be
considered in all their details in this place.
   Bleaching.—Bleaching is the process by which fibrous tex-
tures, such as linen, cotton, silk, he are deprived of their col-
 or, and  rendered white.  The  coloring matter,  which is inhe-
 ent in vegetable fibres, appears to be of a resinous character, and
the  effect of the operation  of bleaching is to dissolve, or dis-
charge it.  In manufactories of linen  and cotton goods,  the
yarn or  cloth passes through a number of successive processes,
the principal of which  are the steeping, in which the goods are 
AND MODIFYING COLOR.
439
fermented in an acescent liquid at a temperature of about 100
degrees, Fahrenheit—the bucking and boiling, in which a hot
alkaline ley is made to percolate through  them for some time—
the souring, performed  with  diluted  sulphuric  acid—the
bleaching with  chlorine, in which the stuff is exposed to the
action of some  compound of that substance,  usually chloride
of lime, called bleaching salt.  Various mechanical operations,
washings, and repetitions of the processes, are  commonly prac-
tised to complete the discharge of the color.   Formerly the
process of bleaching  was  very tedious, and  was  effected by
alkaline leys and by exposure to the sun and air, with frequent
irrigations, for many weeks.   The discovery of the bleaching
power of chlorine,  has greatly  abridged  and  simplified the
process.
   Chemists explain  the  effect of chlorine in bleaching, * by
supposing  that it unites  with the hydrogen  of the coloring
matter, and  forms muriatic  acid, which again acts upon the
color in its  altered state.   The acid may be detected in the
altered coloring matter.   In bleaching which is performed by
 exposure to the air  and  moisture, it is supposed  that oxygen
 combines  with the coloring  matter, and  renders a portion of it
 more easy  of solution, during the  other parts of the  process.
   The  fibres of wool and   silk are not  bleached  by  chlo-
 rine, but after being deprived of the saponaceous, or gummy
 matter, which adheres to them, are exposed to the  fumes  of
 burning sulphur to discharge their color.
    Dyeing.—The art of  dyeing consists in impregnating cloths
 and other  flexible fabrics, with coloring substances, in such a
 manner, that the acquired color may remain permanent  under
 the common exposures, to  which the stuffs may be liable.   It
 is effected  by producing  a chemical  union between the material
 to be dyed and the coloring matter.  It is found that different
 materials not  only possess  different attractions for dye stuffs,

    * Gay Lussac,  Cours de Chimie, Lee. 30, p. 21.—Ure's Notes to BerthoU
  let, ii. 344. 
440
ARTS  OF COMMUNICATING
but that they absorb the coloring matter in different proportions.
Wool appears in this respect to have the greatest  attraction for
coloring substances; silk  comes next to it, then  cotton, and
lastly hemp and flax.
  Mordants.—The coloring substances  used in  dyeing, have
been divided by  Dr  Bancroft into substantive  and  adjective
colors.   Substantive colors are those which communicate their
tint immediately to the material to be  dyed, without the  aid of
any  third substance.   Adjective  colors require the intervention
of a third substance, which  possesses a joint attraction for the
coloring matter and the stuff to be dyed.   The substance  ca-
pable of thus fixing the color, is called a mordant,  and by Mr
Henry, a basis.
   The agents which  are  capable of acting in some way as
mordants, are very numerous, including many oxides and salts.
But those which are principally employed in practice, are the
acetate  of alumina,  the  sulphate or acetate of iron,  and the
muriate of ti?i.  The substance to be dyed is first  impregnated
with the  mordant, and then  passed through a solution of the
coloring matter.   The mordant fixes the color, and, in  many
cases, alters or improves and heightens its tint.
  Dyes.—The coloring substances capable of being  used  as
dyes, are very numerous, but a few of the most important have
in practice  taken precedence of the rest.   Indigo,  madder,
quercitron, and some of the woods are consumed  in vast  quan-
tities by dyers, and are capable of producing an  indefinite va-
riety of tints,  under the action of different mordants.   They
are somewhat differently treated according as the substance to
be dyed is of wool, silk, or cotton.

  Blue Dyes.—Indigo is the chief substance employed  for giving  the
blue  dye.  The best indigo is obtained from a plant cultivated in warm
climates, the indigqfera tinctoria. The plant is cut a short time  before
its flowering, and is put into large vats covered with water, when fer-
mentation spontaneously  ensues, during which the indigo subsides in
the  form of  a pulverulent, pulpy matter.  Its color is  at first  green,
but by exposure to the air, it absorbs oxygen and becomes blue. 
AND MODIFYING COLOR.
441
  Indigo is a light brittle substance, of a deep blue color, and without
either taste or odor.  At 550 degrees Fahrenheit it sublimes, forming
a violet vapor with a tint of red, and condensing into long flat acicular
crystals, which appear red by reflected, and blue by transmitted light.
The process of subliming indigo is one of considerable delicacy, owing
to the circumstance that the temperature at which it  sublimes, is very
near that at which it is decomposed.  Indigo in its dry state, may be
preserved without change; but when kept under water it is gradually
decomposed.  It is quite insoluble in water and alcohol, and is attack-
ed by the alkalies in a partial manner.  Its only proper solvent is con-
centrated sulphuric acid.  When indigo is put into this acid, a yellow
solution is at first formed,  which, after a few hours, acquires a deep
blue color.  If the indigo is pure,  sulphurous acid is not generated,
nor is the acid decomposed ; but the indigo undergoes a change, for it
is rendered soluble in water.  To the indigo thus modified, Mr Crum
has applied the name cerulin, and he regards it as a compound of one
atom of indigo and four atoms of water.   This solution properly diluted
with water, is employed by dyers for forming what is called the Saxon
blue.  Mr Crum has  also described another compound of indigo and
water, under the name of Phanecin, because it acquires a purple  color
on the addition of a salt.  It appears to consist of one atom of indigo
and two atoms of  water.
  When indigo, suspended in water, is brought into contact with cer-
tain deoxidizing agents, it is deprived of oxygen, becomes green, and
is rendered soluble in water, and still more in the alkalies.  This effect
is produced for  example, by sulphuretted hydrogen, by the hydrosul-
phuret of ammonia,  by the protoxide of iron, precipitated by lime or
potass, or by a solution of the  sulphuret of arsenic in potass.  On
dipping cloth into a solution of deoxidized indigo, it receives a green
tint, which becomes blue by exposure to the air.  This is the  usual
method of dyeing blue  by means of indigo, a color which adheres per-
manently to cloth without the intervention of a basis.
   Wood is  prepared from the leaves of the  lsatis  tinctoria,  a  plant
cultivated in Europe.  Gay Lussac, and others, consider it chemically
as a species of indigo.  It is prepared by grinding,  and several pro-
cesses of fermentation.  Cloth dyed in woad liquor  is at first green,
but turns blue on  exposure to the air, in the same manner which takes
place with indigo.
  Red Dyes.—The chief substances which are employed for giving a
red dye, are madder, cochineal,  archil, Brazil wood, logwood, and saf-
flower, all of which are adjective colors.
  Madder,  which is one of the most  valuable drugs  in the art of dye-
ing  is the root of the Rubia tinctorum, a plant extensively cultivated 
442
ARTS OF COMMUNICATING
in Europe, and  particularly in Holland.   It is properly classed  with
red dyes, but by the use of different mordants, it is made to produce
every shade of red, purple, and even black.  In calico printing a piece
may be stamped  with several mordants, which  are  bases of different
colors; and upon immersing it in a madder bath, as many colors will
appear, as there  are mordants used.  The quality of" madder is said to
be improved by age, provided it is kept packed in casks which exclude
the air.  Its quality is also affected by the mode of cultivating, and
curing it, and the judgment which  is used in separating the samples.
   Cochineal is obtained from an insect already mentioned, which feeds
upon the leaves of several species  of the cactus, and which is suppos-
ed to derive this coloring  matter  from its food.  It is very soluble in
water, and is fixed on  cloth by means of alumina or the  oxide of tin.
Its natural color  is crimson, but when the bitartrate of potass is added
to the solution, it yields a rich scarlet dye.  Cochineal  according to
Pelletier and  Caventou, is composed  of, 1. Carminium,  which is the
name  given to the coloring matter. 2.  A peculiar animal matter. 3. A
fatty substance.  4. Salts of lime and potass.
   Archil.—The  dye called archil, is obtained from a kind of lichen,
(lichen roccella) which grows  chiefly in the Canary Islands, and is em-
ployed by  the Dutch in forming  the  blue pigment  called litmus or
turnsol.  The coloring ingredient  of litmus is a compound of the red
coloring  matter of the lichen and an alkali; and hence, on the addition
of an acid, the coloring matter is set free, and the red  tint of the plant
is restored. Litmus is not  only used as a dye, but  is  employed by
chemists for detecting the presence of a free acid.
   Logwood is a dense,  heavy wood, derived from the Hozmatoxylum
Campechianum,  which  grows  in  the tropical  parts of America.  A
decoction  made  from this wood,  is of a fine red, inclining a little to
violet or purple.   This, if left to  itself, becomes in  time  yellowish,
and at length black.  The violet  color of logwood is fixed by alum,
and a blue is obtained from it by verdigris.  But the  great consump-
tion of logwood  is for blacks, to which it gives a peculiar depth, and
velvety lustre.   The coloring principle of logwood has been procured
in a separate state by M.  Chevreul, who has applied to it the name of
hematin.   It is obtained in crystals by digesting the  aqueous extract of
logwood in alcohol, and allowing  the  alcoholic solution to evaporate
spontaneously.
   Brazil wood is the heart, or central part of  the Ceesalpinia echinata,
a large tree of Brazil.  It produces very lively and beautiful red tints
with solutions of alumina and tin, but they are deficient in permanency.
Sappan  wood brought from the East Indies, and Nicaragua wood, or
Peachwood, from Central America, are also said to be species of Cae- 
AND MODIFYING COLOR.
443
salpinia,  and resemble Brazil wood in their properties, but yield a
smaller amount of coloring matter.   Braziletto and Camwood, are
among the poorest of the red dyes.
  Saffiower is the dried flowers of the Carthamus tinctorius, and affords
a bright but fugitive red.   See Rouge.
  Yellow Dyes.—The chief yellow  dyes are the quercitron bark, tur-
meric, hickory, weld, fustic, and saffron.  They are all adjective colors.
  Quercitron bark, which is one of the most important of the yellow
dyes, is an extract made from the bark of the Quercus tinctoria, or
common black oak of the United  States, and was introduced into no-
tice by Dr Bancroft.  With a basis of alumina, the decoction of this
bark gives a bright yellow dye.   With  the oxide of tin it communicates
a variety of tints, which may be made  to vary from  a pale lemon color
to deep orange.  With the oxide of iron it gives a drab color.
  Hickory.—Several species of  American  walnut or hickory, particu-
larly the Juglans, or Carya alba, yield a yellow dye from their  bark,
leaves, and rinds, resembling quercitron, but less abundant in quantity.
   Weld is derived from a European plant, Reseda luteola.   When fixed
with a basis of alum, it gives a lively and permanent yellow.
  Fustic is the wood of the Morus tinctoria, a tree of the  West In-
dies.  It affords, with an aluminous  basis, a less brilliant,  but  more
durable  yellow, than the preceding articles.  It is also employed to
produce certain greens and  drab colors.
   Annotto, otherwise called Rocou, is a soft  substance prepared from
the seeds of the Bixa  orellana, a shrub of tropical America.   The
coloring matter is combined with a resin which renders it difficult of
solution in water,  An alkali facilitates the solution  and  improves the
color.
   Turmeric  is the root of the  Curcuma longa, a native of the East
Indies.  Paper, stained with a decoction of this substance, constitutes
the turmeric or curcuma paper employed by chemists a,s  a test of free
alkali; by the action of which it receives a brown stain.
   Saffron.—The coloring ingredient of saffron (Crocus sativus) is solu-
ble in water and alcohol, has a bright yellow color, is rendered blue
and then  lilac  by sulphuric acid, and receives a  green tint on the
addition of nitric acid.   From the  great diversity of colors which it is
capable of assuming  under different  circumstances, M.  M.  Bouillon,
Lagrange, and Vogel, have proposed for it the name of Polychroite.
   French  Berries.—The unripe berries of the Rhamnus infectorius,
 afford a lively but fugitive yellow.
   Black Dyes.—The black dye is made of the same ingredients  as
 writing  ink, and therefore contains usually a compound of  the oxide 
444
ARTS  OF COMMUNICATING
of iron with gallic  acid and tannin.  From the addition of logwood
and acetate of copper, the black receives a shade of blue.
   Galls.—The common nutgall is an excrescence produced upon an
Asiatic species of oak, (Quercus infectoria) by the puncture of an in-
sect, a species of cynips.   It contains tannin, gallic acid, and accord-
ing to Dr Bancroft,  a coloring matter distinct from these.  Galls pro-
duce a black color with salts of iron, well known as the basis of writ-
ing ink.
  Maple.—The common red maple of this country  (Acerrubrum) when
applied with the sulphate or acetate of iron, produces,  according to
Dr Bancroft, a more intense and perfect black than any of the common
vegetable  dyes.  With the aluminous basis, it produces a lasting cin-
namon color, both on wool and cotton.   Both the bark and leaves may
be used.
  Butternut.—The bark of the butternut (Juglans cathartica) affords
a durable brown upon cotton with an aluminous basis, and upon wool
without any mordant.

   By the dexterous combination of the four leading colors,
blue, red, yellow,  and black, all other shades of color may be
procured.   Thus  green is  communicated by forming  a blue
ground  with indigo, and then adding a yellow  by  means of
quercitron bark.
   One  of the  latest  improvements  in the art of dyeing, con-
sists  in the  employment of colors  derived from the mineral
kingdom.   Prussian blue,  orpiment,  chromate  of lead,  and
other mineral compounds, have by appropriate processes been
made to communicate  their colors to different stuffs.   An ab-
stract of the processes  is given in Ure's  notes to Berthollet on
dyeing.
   Calico Printing.—Calico printing is a combination  of the
arts  of engraving and  dyeing, and  is used  to produce upon
woven fabrics, chiefly of cotton, a variety of  ornamental com-
binations, both of figure and color.   In  this process the whole
fabric is  immersed in  the  dyeing liquid, but  it is previously
prepared in  such  a manner, that the dye  adheres only to the
parts intended for the  figure, while  it leaves the  remaining
parts unaltered.   In  calico  printing, adjective colors are most
frequently employed.   The cloth is  prepared  by  bleaching and 
AND MODIFYING COLOR.
445
other processes, which dispose it to receive the color.   It is
then printed with the  mordant, in a manner similar to that of
copperplate printing, except that the figure is engraved upon a
cylinder, instead of a plate.  The cylinder, in one part of its
revolution, becomes  charged  with  the mordant mixed to a
proper consistence with starch.   The superfluous part of the
mordant is then scraped off by a straight steel edge, in contact
with which the cylinder revolves, leaving only that part which
remains in the lines of the  figure.   The cloth then passes in
forcible contact with the other side of the cylinder, and receives
from it a complete impression of the figure in the pale color of
the mordant.   The cloth is then passed through the coloring
bath, in which the parts previously printed become  dyed with
the intended color.   When it is afterwards exposed, and wash-
ed,  the color  disappears from those parts  which are not im-
pregnated  with the mordant, but remains permanently fixed to
the rest.  When additional colors are required, they are print-
over the rest  with different mordants,  suited to the color in-
tended to be produced.  This secondary printing  is in most
instances performed with  blocks, engraved in the  manner of
wood cuts,  and applied by hand to the successive parts of the
piece.
   In some  articles, white  spots upon a dark ground are pro-
duced by covering  the parts  with wax, tallow, pipe clay, or
other materials, which prevent the contact of the color.  Some-
times the color is discharged in places by the application of
chlorine.  A preparation of one of the salts of copper, applied
in spots, or figures, has the effect to oxygenate indigo, so as to
render it insoluble, and consequently incapable of dyeing these
spots, when the stuff is immersed.   To these and similar pro-
 cesses, the name  of resist work has been given.

   Fast Colors.—The  following  are the  dye stuffs used by the calico
printers for producing fast colors. *  The mordants are thickened with
 gum, or calcined starch, and  applied with the block, cylinder, plates,
or otherwise.
                        * Ure's Dictionary. 
446
ARTS OF COMMUNICATING
  1. Black.  The cloth is impregnated with  acetate  of iron  (iron
liquor) and dyed in a bath of madder and logwood.
  2. Purple.   The preceding mordant of iron, diluted ; with the same
dyeing bath.
  3. Crimson.  The mordant for purple, united with a portion of ace-
tate of alumina, or red mordant, and the above bath.
  4. Red.  Acetate of alumina is the mordant, and madder is the dye
stuff.
  5. Pale red of different shades.  The preceding mordant diluted
with water, and a weak madder bath.
  6. Brown or Pompadour.   A mixed mordant, containing a somewhat
larger proportion of the red than of the black: and the dye of madder.
  7. Orange.  The red mordant; and a bath first of madder, and then
of quercitron.
  8. Yellow.  A strong red mordant; and the quercitron bath, whose
temperature should be considerably under the boiling point of water.
  9. Blue. Indigo, rendered soluble and greenish yellow colored, by
potash and orpiment.  It recovers its blue color, by exposure to air,
and thereby also fixes firmly on the cloth.  An indigo vat is also made,
with that blue substance, diffused in water with quicklime and copperas.
These substances  are supposed to deoxidize  indigo, and at the same
time to render it soluble.
  Golden-dye.   The  cloth is immersed  alternately in a solution of
copperas and lime water.  The protoxide of iron precipitated on the
fibre,  soon passes by  absorption  of atmospherical oxygen,  into the
golden-colored deutoxide.
  Buff.  The preceding substances, in a more dilute state.
  Blue vat, in which  white spots are left on a blue ground of cloth,
is made, by applying to these points a paste composed of a solution of
sulphate of copper and pipe clay;  and after they are dried, immersing
it stretched on frames for a definite number of minutes, in the  yellow-
ish-green vat, of one part of indigo, two of copperas, and two  of lime,
with water.
  Green.  Cloth dyed blue, and well washed, is imbued with the alum-
inous acetate, dried, and subjected to the quercitron bath.
  In the  above cases, the cloth, after receiving the mordant paste, is
dried, and after some preparation, put into the dyeing vat of copper.
  Fugitive Colors.—All these colors are  given,  by making decoc-
tions of the different coloring  woods;  and receive the slight degree
of fixity  they  possess, as well as  great brilliancy, in consequence of
their combination or  admixture with the  nitro-muriate of tin.
  1. Red is frequently made from Brazil and Peach wood.
  2. Black.  A strong extract of galls, and deuto-nitrate of iron. 
AND MODIFYING COLOR.
447
  3.  Purple.  Extract of logwood and the deuto-nitrate.
  4.  Yellow.  Extract of quercitron bark, or French berries, and the
tin solution.
  5.  Blue.  Prussian blue and solution of tin.
  Fugitive  colors are thickened with gum tragacanth, which leaves
the cloth in a softer state than  gum senega! ; the goods being some-
times sent to market without being washed.
  Tingry's Painter  and Varnisher's Guide, 8vo. translated 1816 ;—
Elmes' Dictionary of Fine Arts,  8vo. 1826;—James's Panorama of
Science and Art, 2 vols, 8vo. 1816;—Bancroft on Permanent Colors,
2 vols, 8vo.  1814;—Berthollet, Elements of the Art of Dyeing,
translated by Ure, 2 vols, 8vo. 1824;—Gay Lussac, Cours de Chimie,
2 vols, 8vo. 1828 ;—Brande's  Chemistry, 1820 ;—Turner's  Chemis-
try, 1828;—Parkes's Chemical Essays, 1823;—Ure's Dictionary;—
Vitalis, Cours eUmentaire deteinture, 1823. 
CHAPTER XIX.
                  ARTS OF VITRIFICATION.

   A great number  of earths, and other mineral  bodies, after
being fused, do not resume their original character upon cool-
ing, but pass  into a dense, hard, shining, and brittle state, hav-
ing the character of glass; and are thus said to be  vitrified.
Most of these  substances do not immediately become  hard,
upon the reduction of their temperature, but go through an in-
termediate, or  ductile state, in which a combination of soft-
ness  with tenacity, enables them to be wrought into articles of
use  and ornament.   Of these, common  glass is the most im-
portant,  while enamels, artificial gems, he belong to the same
species of manufacture.
   Glass.—Glass is a compound substance artificially produced
by the combination of siliceous  earth with alkalies, and in some
cases  with other  metallic oxides.   These substances  being
melted together at a high temperature,  unite,  lose their opacity,
and  are fused into a homogeneous mass, which on cooling has
the properties of hardness, transparency, and brittleness.
  Materials. *—The  most  important ingredient, and in fact
the basis of transparent glass,  is silica,  or oxide of  silicium.
This earth  nearly in  a  state of purity,  is found in the sand
of certain situations, and also in common flint, and quartz peb-
bles.  Sand has the  advantage of being already in a state of

  * The term metals,  which appears to be a corruption of materials, is in
common use among glass  manufacturers to express the  ingredients or sub-
stances, upon which their operations are performed.  The same term is em-
ployed in a similar sense by other  manufacturers and artists, and by some
writers on  road making.  The term metal, in the singular, is applied to glass
in a state of fusion. 
ARTS OF VITRIFICATION.
449
minute division, not requiring to be pulverized.  Pure siliceous
sand proper for the glass  furnace, is found in many  localities.
A great  portion of that used in the United States, is taken
from the banks of the  Delaware.  When flints or quartz are
employed, they must be first reduced to powder, which is done
by heating them red hot  and plunging them  in cold  water.
This causes them to whiten and fall to pieces after which they
are ground and sifted, before they are ready  for the furnace.
  An alkaline substance,  either potash or soda, is the second
ingredient in glass.  For  the  finer kinds of  glass, pure pearl
ash is used, or soda procured by decomposing sea salt; but for
the inferior sorts, impure alkalies and even wood  ashes are made
to answer the purpose.   Lime is often employed in small quan-
tities, also borax, a salt which facilitates the fusion of the silica.
  Instead of the common alkalies, the sulphate of soda may
be employed in glass making.   But in this case it is necessary
to liberate the alkali by decomposing the sulphuric acid  of the
salt.  This  may be done  by charcoal, or in flint glass by me-
tallic lead.  Lime is also used with this salt.
  Of the metallic oxides which are added in  different cases,
the deutoxide of lead  (red lead) is the  most  common.   This
substance renders flint  glass more fusible, heavy, and  tough,
and more easy to be ground  and cut.  At  the  same time it
imparts to it a greater brilliancy, and refractive power.   Black
oxide of manganese  in small  quantities,  has  the  effect  of
cleansing the glass, or of rendering it more  colorless and
transparent.   This effect  it seems to produce by  imparting
oxygen to the carbonaceous impurities, thus forming with them
carbonic   acid,  which subsequently escapes.    Common nitre
produces a similar effect.   If too much manganese be added,
it communicates a purple  tinge to the glass,  which,  however,
may be  destroyed by a little charcoal, or wood.   Arsenious
acid (white arsenic) in  small quantities, promotes the clearness
of glass,  but if too much  be  used,  it communicates a milky
whiteness.  Its use in drinking vessels, is not free from danger.
57 
450
ARTS OF VITRIFICATION.
when the glass  contains so much alkali, as to render any part
of it soluble in acids.
   Crown Glass.—Glass is of various kinds, which are named
not only from the  character of their  ingredients, but from the
mode in which they are wrought.   The name of crown glass
is given to the best kind of window glass, that which is hardest
and most free from color.   It is made almost entirely of sand
and alkali, and a little lime, without lead or any other  metallic
oxide, except a  minute quantity of manganese, and sometimes
of cobalt, which are added to counteract the effect of any im-
purities  in giving color to  the glass.   Crown  glass  requires
a greater  heat to melt its ingredients, than  those kinds  which
contain  a larger  quantity of metallic oxide, especially of lead.
   Fritting.—After the materials  have been intimately mixed,
they are subjected to the operation called fritting.   This con-
sists in exposing them to a dull red heat,  which is not sufficient
to produce  their fusion.   The use of this process is to drive
off the carbonic acid, and  other gaseous and volatile matters,
which would otherwise prove troublesome by causing the ma-
terials to swell up in the glass pots.  The heat is gradually in-
creased, and the materials constantly stirred for some  hours,
until  they unite  into a soft, adhesive  mass,  the  alkali having
gradually combined with the siliceous earth.   The reason why
the fritting is conducted  at a low  heat, is,  that if a high tem-
perature were  applied at once, the alkali would be driven off,
before it had time to combine with the silica.
   Melting.—The homogeneous mass, or frit, is next transfer-
red to the glass  pots of the melting furnace.  These  are cru-
cibles made of the most refractory clays and sand.  A quantity
of old glass is commonly placed  upon the top of the  frit, and
the heat of the furnace is raised to its greatest height, at which
state it is  continued for 30  or 40 hours.  During this  time the
materials  become  perfectly united,  and  form a transparent,
uniform mass, free from specks and  bubbles.  The  whole is
then suffered to cool a little, by slackening the heat of the fur-
nace, until it acquires sufficient tenacity to  be wrought. 
ARTS OF VITRIFICATION.
451
  Blowing.—The  formation  of window  glass is effected by
blowing the melted  matter, or  metal, as it is called, into hollow
spheres, which are afterwards made to expand  into  circular
sheets.  The workman is provided with a long iron tube, one end
of which he thrusts into the melted  glass, turning it round until
a certain quantity sufficient for the purpose, is gathered, or  ad-
heres to the extremity.   The  tube  is then  withdrawn from  the
furnace,  the lump  of glass, which adheres, is rolled upon a
smooth iron table,  and the workman blows strongly with his
mouth through  the tube.   The glass, in  consequence of its
ductility, is gradually inflated, like  a bladder, and is prevented
from falling off by  a rotary motion  constantly communicated to
the tube.   The inflation is assisted by the  heat, which causes
the air and moisture of the breath to expand with great power.
Whenever the glass becomes so stiff from cooling, as to render
the inflation  difficult, it is again held over the fire to soften it,
and the blowing is repeated until the globe is expanded to the
requisite  thinness.   It is then received by another  workman,
upon an iron rod,* while the blowing iron is detached.  It is
now  opened at its  extremity,  and by means of the   centrifugal
force acquired from its rapid whirling, it spreads into a smooth
uniform  sheet,  of equal  thickness  throughout, excepting  a
prominence at the  centre, where the  iron rod was attached.
   Annealing.—After the  glass has  received the shape which
it is to retain, it is  transferred to a hot chamber, or annealing
furnace, in which its temperature is gradually reduced until it
becomes cold.  This process is indispensable to the durability
 of  glass, for if it is cooled too suddenly, it becomes  extremely
 brittle, and flies to  pieces upon the slightest touch of any hard
 substance.   This effect is shown in the substances  called Ru-
pert's drops, which  are made  by  suddenly cooling  drops of
 green glass, by letting them fall into cold water.  These drops
 fly to pieces with an  explosion, whenever their smaller extrem-
 ity is broken off.   The Bologna phials, and some other vessels
* Called a punt, or punting iron. 
452
ARTS OF VITRIFICATION.
of unannealed glass, break into a thousand pieces, if a flint, or
other hard and angular substance, is dropped into them.  This
phenomenon seems to depend upon some permanent and strong
inequality of pressure, for when these drops are heated so red
as to be soft,  and left to cool gradually, the property of burst-
ing is lost, and the specific gravity of the drop is increased.
   Broad Glass.—This is a coarser kind of window glass, and
is  made from sand with kelp and soap boilers' waste.  It is
blown  into hollow cones, about a foot in diameter, and these,
while hot, are touched on one side with a cold iron  dipped in
water.    This produces a crack which runs through the length
of the  cone, nearly in a right line.  The glass then expands
into a sheet, in its form, resembling somewhat  the shape of a
fan.   This appears to have been one of the oldest methods of
manufacturing glass.
   Flint  Glass.—Flint glass, so  called from its having been
originally made of pulverized flints, differs from window glass,
in containing  a large  quantity of  the red  oxide of  lead.
The proportions of its materials differ, but in round numbers, it
consists of about three parts of fine sand, two of red lead, and
one of pearl  ash, with small  quantities of nitre, arsenic, and
manganese.  It fuses at a lower temperature than crown glass,
has a beautiful  transparency, a great refractive power,  and a
comparative  softness,  which enables it to be cut and polished
with ease.   On  this  account it is much used for glass vessels
of every description, and especially those which are  intended
to be ornamented by cutting.   It is also employed for lenses,
and  other  optical glasses.  Flint glass is worked by blowing,
moulding, pressing, and grinding.   Articles of complex  form,
such as lamps and wine glasses, are formed in pieces, which
are afterwards joined by simple contact, while the glass is hot.
It appears  that the  red lead  used in the manufacture of flint
glass, gives up a  part of its oxygen, and passes to the state of
a  protoxide.
   Bottle Glass.—Common green glass, of which bottles are
made, is the  cheapest kind, and formed of the  most ordinary 
ARTS OF VITRIFICATION.
453
materials.  It is composed of sand with lime,  and sometimes
clay, and alkaline ashes of any kind, such as kelp,  barilla, or
even wood ashes.  The green color is owing to the impurities
in the ashes,  but chiefly to oxide of iron.  This  glass is hard,
strong,  and  well  vitrified.   It is less subject  to corrosion by
strong acids than flint glass, and is superior to any cheap mate-
rial for the purposes to which it is ordinarily applied.
   Cylinder  Glass.—The  plates of crown glass which are ob-
tained in the common manner  by blowing them in circular
plates, afford the common  material for window glass, being cut
into squares by first marking the surface deeply with a diamond
and then breaking the glass in the same  direction, the crack
always following the exact course of the incision made by the
diamond.  But there is always a loss or waste in cutting squares
from  a circular  plate, besides which, they can never be very
large, owing to the protuberance, or bull's eye, which fills the
centre of the plate, so that a square can never be larger than
can be described within less than half the circle.   To remedy
this disadvantage, plates for looking glasses, and others of large
size,  are executed in a different way,  either by blowing them
in cylinders, or by casting them in plates at first.
   Cylinder glass is blown at first in spheres like window glass.
These are elongated into spheroids by a swinging motion which
the workman gives to his rod.   The ends of this spheroid are
successively perforated, thus converting it into an irregular cylin-
der.   One side of this cylinder is cut through  with shears, and
the glass is laid  upon a  flat  surface, where  it expands into
a uniform plate, without any protuberance.  It is then annealed
by diminishing the heat in the common way.   When the plates
 are intended for looking glasses, the finest materials are used,
 and the heat kept at its greatest height for a long time, to dissi-
 pate all impurities and remove any specks or bubbles.
    Plate Glass.—Looking glass plates may be blown in cylin-
 ders when they do not exceed about four feet in length.  But
 they cannot well be blown of a larger size than this, from such
 a quantity of glass as the  rod will take up, without becoming 
454
ARTS OF VITRIFICATION.
too thin to bear  polishing.   Plates, however, may be made of
more than double this size, by another process which is called
casting, and which is the only mode by which very large plates
are produced.
   When glass is to be cast, it is melted in great quantities in
large pots, or reservoirs, until it is in  a state of perfect fusion,
in which state it is kept for a long time.  It is then  drawn  out
by means of iron cisterns of considerable size, which are low-
ered  into the furnace, filled, and  raised  out by machinery.
The glass  is poured out from  these cisterns, upon tables of
polished copper of a large  size, having a rim elevated as high
as the  intended  thickness of the plate.  In order to spread it
perfectly, and to make the two surfaces parallel, a heavy roller
of polished  copper, weighing 500 pounds, or more, is  rolled
over the plate, resting  upon the  rim at the edges.  The  glass,
which  is beginning  to  grow stiff, is pressed down and spread
equally, the excess being driven before  the roller till it falls off
at the  extremity of the table.   The  plate is then ready to be
annealed.
   As the plates which are cast  for looking glasses  are always
uneven  and dull  at their  surface,  it  is  necessary to grind
and polish them, before they are fit for use.   The process  em-
ployed for  producing a perfectly even and smooth  surface, is
very similar to that employed in polishing  marble, except  that
the  glass being the  harder  substance,  requires more labor
and nicety in the operation.  The plate to be polished  is  first
cemented to a table of wood, or stone,  with plaster  of  Paris.
A  quantity  of wet  sand or emery is spread  upon it, and  an-
other glass plate similarly cemented to another wooden surface,
is brought in contact with it.  The two plates are then rubbed
together until the surfaces have  become mutually smooth  and
plane.   The emery which is  first used  is succeeded by  emery
of a finer  grain,  and the last  polish  is given  by  colcothar,
or putty.   When  one  surface has become perfectly polished,
the cement is removed, the plate turned, and the opposite side
polished in  the  same manner. 
ARTS OF VITRIFICATION.
455
   As the grinding of glass causes an expenditure of a consid-
erable portion  of its substance,  a great  waste of glass takes
place when foreign materials are employed in the manner which
has been described.   To prevent this loss, a more economical
mode  has been  introduced, in which the glass is ground with
pure  flint reduced  to  powder.   The  mixture of glass and
flint, which is left after  the operation, is valuable  for  forming
fresh glass.
   Moulding.—A variety  of ornamental  forms are  produced
upon the surface of glass vessels, by impressions given  to them
with a metallic mould, while the  glass is in a hot state.  Flint
glass is the kind, which is used for articles intended to possess
much brilliancy, but coarser kinds, even of colored glass, are
also subjected to the same process. The simplest manner in
which the operation  is conducted, consists in blowing the glass
into the mould,  till  it receives the impression on its  outside.
For this purpose a quantity of glass, sufficient to form the in-
tended vessel, is taken up  on the end of a pipe and inserted at
the  top of the  mould.   The workman then  blows  with his
mouth  till a  hollow  portion of glass is driven into the mould
and expands, so as to fill every part, and receive an impression
on its outside.   The mould is usually  made of copper, with
the  figure cut  on its inside, and opens with hinges to permit
the glass to be inserted, and taken  out.   As the mould is
of necessity much colder than the  glass, the latter  substance
is chilled at  its surface, as soon  as it comes in contact with the
copper; hence its  ductility is  impaired, and the impression
given is never so sharp, as that which is obtained with  substan-
ces, which  are nearly at the same temperatures.   Moulded
bottles, phials,  decanters, he are made in this way.
   Pressing.—An improvement has been made in the  process
of moulding glass, by subjecting the  material to pressure, on
the inside and  outside at the same time, by different parts of a
mould, which  are brought suddenly together  by  mechanical
 power.  This process has been carried to great perfection in 
456
ARTS OF VITRIFICATION.
several of the manufactories in this  country, * and  produces
specimens  which  compare  with cut glass in the accuracy and
beauty of the workmanship.   It is applied only to solid articles,
and  to vessels  which  are  not contracted  at top.   The hot
glass being dropped into the mould, a part called the follower,
answering to the inside  or top of the  vessel, or other article, is
immediately pressed down  upon it by a lever, and the glass is
thus stamped with a very distinct impression of the figure on both
sides at once.  The glass vessel is sometimes transferred from
the mould to another receptacle called the receiver, in order to
preserve its shape  till it is cool enough to stand.
   Cutting.—The  name of cut glass, is given in commerce to
glass which is ground and polished in figures with smooth sur-
faces,  appearing as if cut by  incisions of a sharp instrument.
This operation is chiefly confined to  flint glass, which,  being
more tough,  soft,  and  brilliant  than  the other  kinds, is more
easily  wrought,  and produces  specimens of greater lustre.
An  establishment for cutting glass contains a great number of
small wheels of stone,  metal, and wood, which are made to
revolve rapidly by a steam engine, or other power.   The cut-
ting  of the glass consists entirely in grinding away successive
portions, by holding them upon the surface  of these wheels.
The first, or rough cutting, is  sometimes given by  wheels of
stone, resembling grindstones.    Afterwards wheels of iron are
used, having their edges covered with sharp  sand, or  with
emery  in different  states of  fineness.   The last polish is given
by brush wheels covered with putty, which is an  oxide of tin
and  lead.   To  prevent the friction  from  exciting  so much
heat as to endanger the glass, a small stream of water continually
drops upon the surface of the  wheel.
   Stained  Glass.—The name of staining has been applied to
the process by which painting  with vitrifiable  colors,  is execut-
ed upon the surface of  glass.   The pigments used are chiefly
metallic oxides, which  do not exhibit their full color, until they
* Particularly at Lechmere's Point, and Sandwich. 
                  ARTS OF VITRIFICATION.              457

have been exposed to the heat of the  furnace.  This art has
been repeatedly described as being no  longer known ; but this
is  not  the fact, except in  respect to  some particular colors
which are found in the windows of the ancient cathedrals.
   The  metallic oxides used in staining glass, are  difficult of
fusion, on which account it is necessary to  mix them with a
flux, composed of glass, with  lead or borax.   This renders
the oxide  fusible  at a temperature, which does not injure its
color ; also by enveloping the particles, it causes them to adhere
to the glass, and afterwards protects them from the atmosphere.
   A very beautiful violet, but liable to  turn blue, is made from
a flux composed of borax and flint glass colored with one sixth
part of the  purple of Cassius, precipitated from muriate of
gold by protomuriate of tin.
   A fine  red is made from red oxide of iron, prepared by
nitric acid and heat, mixed with a flux of borax and a small
proportion of red lead.
   A yellow, equal in beauty to that produced  by the ancients,
may be  made from  muriate of silver, oxide  of zinc,  white
clay, and the yellow oxide of iron, mixed together without any
flux.   A powder  remains  on the  surface after the glass has
been baked,  but this is easily cleaned off.
   Blue is produced by oxide of cobalt, with a flux  composed
of fine sand, purified pearl ash, and red lead.
   Black is produced by mixing the composition for blue, with
the oxides of manganese and iron.
   To  stain  glass green, it may be painted blue on one  side,
and yellow on the other.
   The colors  ground with water  being laid  upon the glass,
must be exposed to heat under a muffle, so as to  be heated
equally until the color is melted upon the surface.  To prevent
the panes of glass from bending, they  are placed upon a bed
of bone ashes, of  quicklime,or of unglazed porcelain.  Abed
of gypsum has been recommended, but the sulphuric  acid ex-
haling from it is apt to injure the glass.
58 
458
ARTS OF VITRIFICATION.
  Among ancient specimens of  painted  glass,  some  pieces
have been found in which the colors  are found to penetrate
through the glass, so that the figure  appears in any section
made parallel to the  surface.   It is supposed  that such pieces
can only have  been made in the manner of mosaic, by accu-
mulating transverse filaments of glass of different colors, and
uniting them by heat, the  process being  one of great labor.
They are  described by Winckelmann, and Caylus, from some
specimens brought from Rome.
  Enamelling.—Enamels are compositions of various substan-
ces which when  vitrified  upon the surface of opaque bodies,
communicate their colors, and produce the effect of painting.
Enamels differ  from stained glass, as a  common picture differs
from a transparency, the  former  producing its  effect when
viewed by reflected, and the latter by transmitted light.   En-
amels are  executed upon the surface of copper and other me-
tals,  by a method  similar  to painting.  One  coat, or color,
often  requires to be  vitrified before another is  laid upon it,
and  thus  the  plate to be enamelled  is obliged to be exposed
to heat several successive times.
  Transparent  enamels are usually rendered  opaque, by add-
ing putty,  or the white oxide of tin, to them.  The basis of all
enamels is therefore a transparent and fusible glass.   The ox-
ide of  tin renders this of a beautiful white, the perfection of
which is greater when a small quantity of manganese is  like-
wise added.  If the oxide of tin be not  sufficient to destroy
the transparency of the mixture,  it produces  a semiopaque
glass, resembling the opal.
  The metals employed as coloring materials are;—1. Gold.
The purple of Cassius imparts a fine ruby  tint.  2.  Silver.
Oxide or phosphate of silver gives a yellow  color.   3. Iron.
The oxides of iron produce green, yellow,  and brown, de-
pending upon the state of oxidizement and quantity.   4. Cop-
per.   The  oxides  of copper give a  rich green;  they also
produce a red, when mixed with a small  proportion of tartar,
which  tends partially to reduce  the oxide.  5. Antimony im- 
ARTS OF VITRIFICATION.
459
parts a rich yellow.   6.  Manganese.   The black oxide of this
metal,  in  large quantities, forms  a  black glass;  in smaller
quantities,  various  shades of purple.  7.  Cobalt, in the  state
of oxide, gives beautiful blues of various shades ; and with the
yellow of antimony, or lead, it produces green.  8. Chrome
produces fine  greens and reds,  depending upon its  state of
oxidizement.
  Artificial  Gems.—The great value of  the precious stones
has led to artificial imitations of their color  and lustre, by com-
positions in glass.   In order to approximate as near as possible
to the brilliancy and  refractive power of native gems, a basis,
called a  paste, is made from the finest flint  glass, composed of
selected  materials, combined in different proportions, according
to the preference of the  manufacturer.   This is mixed  with
metallic  oxides capable of producing the   desired  color.   A
great number of complex recipes are in use among manufac-
turers of these articles.
  Devitrification.—It is found that if certain kinds of glass be
exposed  to heat sufficient to keep them in a soft state for some
hours, and are suffered to cool gradually, they lose their trans-
parency, and pass  into the state of an opaque substance, of a
greyish white color.  M. Dartrigues, * who has examined the
cause of this change, asserts that it is owing to a real crystalli-
zation of the vitreous silicate.   Common  bottle glass is most
easily changed  in  this manner,  while those  varieties which
contain  neither  lime nor alumina, are the  most difficult to de-
vitrify.   In all cases, glass which has undergone this  change,
requires  a stronger  heat to melt it than before.
  Reaumur's Porcelain.—-It has been frequently observed that
during the annealing of green glass,  some  parts of it become
white and  opaque.   M. Reaumur  made  experiments on this
apparent devitrification of glass, and found it was owing to the
alkali flying off by the too long continuance,  or too great  de-
gree of the heat, and that  the opaque changed  glass had ac-

       * Journal de Physique, 1804.—Thenard, Chimie1, ii. 473. 
460
ARTS OF VITRIFICATION.
quired the quality of bearing sudden  transitions of heat and
cold as well as the best porcelain.
   For the purpose of making vessels of this  kind,  common
bottle glass is chosen, and blown into the proper form.  The
vessel is then to  be filled  to  the top with a mixture of white
sand  and gypsum,  and  is  set in a large  crucible upon a
quantity of the same mixture,  with  which  the  glass vessels
must also be surrounded, and covered  over, and  the whole
pressed down rather hard.  The crucible is then to be covered
with a lid, the junctures well  luted, and put into a potter's kiln,
where it remains during the whole time that the pottery is bak-
ing, after  which the glass will be found  changed  into a milk
white porcelain.
   An imitation of porcelain which is lately introduced into  our
shops,  and which combines  whiteness with a beautiful semi-
transparency,  is  made of flint  glass,  containing a portion  of
white arsenic, on which its opacity depends.
   Crystallo-Ceramie.—This name is given to an elegant,  but
difficult, species  of manufacture, in which medallions, portraits,
and other subjects executed in an opaque  material, are inclosed
or incrusted,  with  glass.   This art was  first attempted by in-
closing in glass small figures  made of a peculiar kind of  clay;
but these experiments  were but in few instances  successful,
owing  to  the  unequal  expansion  and contraction  of the two
substances,  and  their consequent  fracture.  More  recently a
composition has  been employed for the  opaque figure, which
is less  liable to these accidents.   It is necessary that the sub-
stance employed in these devices,  should be less fusible than
glass, incapable  of generating air, and at the same  time, sus-
ceptible of expansion and contraction, as the  glass becomes
hot or cold.   The  ornamental figures are introduced into  the
glass while hot,  and thus become incorporated with it.
   Glass  Thread.—The  great  ductility of glass, is one  of
its most  remarkable properties.   When  heated to a sufficient
degree, it may not  only  be  moulded  into  any possible form
with the utmost  facility, but  it can be drawn out into the finest 
ARTS OF VITRIFICATION.
461
fibres.  The method of spinning glass  is very simple.   The
operator holds a piece of glass  over the flame of  a lamp  with
one  hand,  he then fixes a hook to the  melted mass, and by
withdrawing it, obtains a thread of glass attached to the hook.
The  hook is then fixed in the  circumference of  a cylindrical
drum, which  can be turned  round by the  hand; and a rapid
rotary motion  being given to the drum, the  glass is drawn in
the  finest  threads from the fluid mass, and coiled round the
cylindrical circumference.   M. Reaumur supposed, with great
reason, that the flexibility of glass increased with  the  fine-
ness of the threads, and he therefore  conjectured, that if they
were  drawn to a sufficient degree  of fineness, they might be
used in the  fabrication of stuffs.   He succeeded in making
them as fine as a spider's web, but he was never able to obtain
them of a sufficient length, when their  diameter was so much
reduced.   The circumference of these threads is generally a
flat  oval, about three or four  times as broad as it is thick.  By
using opaque and transparent  glass, of different  colors, artists
have been able to produce many beautiful ornaments.
   Remarks.—Pure glass possesses the remarkable property of
 suffering  no  change by the application of  an intense  heat.
 The effect of  great heats is only to melt the glass, or to dissi-
 pate it in vapor ; but as long as any of the glass remains,  it still
 preserves  its transparency, and other distinguishing properties.
   Of all the solid substances whose expansibility has been ac-
 curately examined, glass possesses the property of being least
 affected by heat or cold.  Its  expansion, according to General
 Roy, with an increase of heat  equal to 180 degrees of Fahren-
 heit's thermometer, is  only  0.000776,  while that of platina is
 0.000856, and that of hammered zinc, 0.003011.  On account
 of  this property, glass is peculiarly fitted for containing  fluids
 whose expansions are under examination, as its own change of
 form may in ordinary cases be neglected.   For the same reason
 it is better than any other substance for the simple  pendulum
 of a clock. 
462
ARTS OF VITRIFICATION.
  The invention of glass seems to have been extremely ancient,
and imperfect specimens  are found in the sarcophagi of Egyp-
tian mummies.   Glass windows appear not to have been in use
among the Romans of the Augustan age ; though  vessels  and
plates of glass, are found  at Herculaneum and Pompeii.  Most
of the important improvements in the manufacture of this sub-
stance, have been made by the moderns.
  Parkes's Chemical Essays, 8vo. vol. ii.;—Loysel, Essai sur VArt
de la Verrerie,  8vo. 1800;—Brogniart,  Art de VEmailleur, Annates
de Chimii, torn. ix. and other works;—Franklin Journal, v. 80;—Article
Glass in Rees' Cyclopedia, and in the Edinburgh Encyclopedia;—
Chaptal,  Chimie"  Applique"t  aux  Arts, 4 vols, 8vo. 1806;—Gray's
Operative Chemist, 8vo. 1828;—Thenard, Traite de Chimie", vol. ii. ;—
Brande's Chemistry;—Beckman's History of Inventions, 4 vols,8vo.
translated 1797;—Works of Neri, Blancourt, Kunckel, Reaumur,
&c. 
CHAPTER XX.
             ARTS OF INDURATION BY HEAT.

  Common  clay,  with  its varieties, consisting essentially  of
alumina  and silica;  also the artificial  imitations of clay, into
which these earths enter, possess  properties adapted to render
them highly useful in the arts.  When mixed with water, they
form a ductile and tenacious  paste, capable of being  moulded
into  various forms, and of acquiring, when exposed to the heat
of a furnace, a durable and stony hardness.   These com-
pounds  are used in  different states, to form the materials both
for the largest structures, and  the  most delicate ornaments;
and  they are surpassed by few  substances in the power  of
resisting the effects of exposure and time.  Bricks, tiles, terra
cotta, pottery, and porcelain, are  the most noticeable products
of the branch of industry, in the operations of which indurated
clay is the material.
  Bricks.—The use of bricks in building, may be traced to
the earliest ages, and they are found among the ruins of almost
every ancient nation.  The walls of Babylon, some of the an-
cient structures of Egypt and Persia, the walls of Athens, the
Rotunda of the Pantheon, the temple of Peace, and the Ther-
mae, at Rome,  were all of brick.  The earliest  bricks were
dried in the sun, and were never  exposed to great heat, as ap-
pears from the fact that they contain  reeds and straws, upon
which no mark of burning is visible.   These bricks owe their
preservation to the extreme  dryness of the climate  in  which
they have  remained, since the earth of which they are made,
often crumbles to pieces when immersed in water, after having
kept its shape for more than two  thousand years.   This is the
case with some of the   Babylonian  bricks, with inscriptions in 
464
ARTS OF INDURATION BY HEAT.
the  arrow headed character, which have been brought to this
country.  The ancients, however, at a later period, burnt their
bricks, and it is these chiefly which remain at the present day.
The  antique bricks  were larger than those employed by the
moderns, and were almost universally of a square form.   Be-
sides bricks  made of clay, the ancients  also employed a kind
of factitious stone, composed of a calcareous mortar.*
   Modern bricks receive their hardness from exposure to heat
in the process of burning.   The common  clay of which  they
are made, consists of a mixture of argillaceous earth and sand.
Most of  our  common clays contain also oxide of iron, which
causes the bricks to turn red in burning.  Pure  clays  become
white in  the furnace, such as that of which pipes  are made,
and  common crockery ware.   Clay, after it is taken from the
earth, requires to be thoroughly mixed, incorporated, and mel-
lowed, before it is fit for  the manufacture of bricks.   For this
purpose, it is  to be dug in the  summer, or fall, and exposed to
the influence of the  frost through the winter.   It  should be
worked  over repeatedly with  the spade, and not  made into
bricks till the ensuing spring, previously  to  which, it is well
tempered, either by treading it with  oxen, or by a horse  mill,
till it is reduced to a tough,  homogeneous paste.  In  propor-
tion  to the labor bestowed on this process, the bricks  become
solid, hard, and strong.   The  clay,  after being thus prepared,
is forced into moulds  to receive the shape of bricks,  and after-
wards dried in the sun.
   Pressed bricks, which are  used to form the facing of walls
in the better  kinds of structures, are  finished in a  machine.
The  roughness and change of form to which common bricks
are liable, is owing in part  to  the evaporation of a  portion of
the water which the clay contains.   To  remedy  the difficulty
arising from this cause, the bricks after being moulded in the
common  manner,  are exposed to the sun till they are nearly
dried, retaining, however, sufficient plasticity to be still capable
  * Some travellers have even advanced an opinion that the  Pyramids of
Egypt are constructed with an artificial stone. 
ARTS OF INDURATION BV HEAT.
465
of a slight change of form.   In this state they are placed in
an  iron  mould  and subjected to a strong pressure, by which
they become regular in shape, and  very smooth.   A machine
usually  contains a number of moulds  arranged in a circle, or
otherwise, so that the power is applied to them in succession,
and the bricks pressed with rapidity.
   The burning  of bricks is commonly performed in this coun-
try,  by  forming them  into  large  square  piles,  denominated
clamps, or with  us, kilns, having flues or cavities at the bottom
for the insertion of the fuel,  and interstices between the bricks
for the fire and  hot air to penetrate.  A fire is kindled in these
cavities,  and gradually increased for the first twelve hours, after
which it it is kept up at a uniform  height for several  days and
nights, till the bricks are  sufficiently burned.  Much care  and
experience are necessary in  regulating the fire, since too much
heat  vitrifies them, and too  little  leaves them soft and friable.
In some  places the burning of bricks is conducted in permanent
kilns erected for the purpose.
   Tiles.—Tiles are plates of burnt clay, resembling bricks in
their composition, and manufacture, and  used for the covering
of roofs.  They  are necessarily made thicker  than  slates or
shingles, and thus  impose  a  greater weight upon the roofs.
Their tendency to  absorb water,  promotes the  decay of the
wood work beneath them.   Tiles are usually shaped in such a
manner  that the edge of one tile receives the  edge of that  next
to it, so  that water  cannot percolate between them. *   Tiles,
both of  burnt clay and marble, were used by the ancients, and
the former continue to be employed in various parts of Europe.
Floors made of flat tiles are used in many countries, particu-
larly in  Italy.
   Terra Cotta.—-The  Italian name  terra cotta, in  French
terre cuite, in its most general sense, implies clay indurated by
heat.  In the  arts, however, its use seems to be restricted to
the finer clays,  in which ornamental designs have been  execut-
   * For different forms of tiles used at Florence,  Trieste,  &c. see Cadell's
Journey in Italy and Carniola, Plate X.
                59 
466
ARTS OF INDURATION UY HEAT.
ed, both by the ancients and moderns.  Not only vases, but
imitations of sculpture, and architectural decorations, are suc-
cessfully made from this material.  Among other things, a
complete restoration of the Choragic monument of Lysicrates,
at Athens, has been made from  terra cotta in the court of the
Louvre, at Paris.   From the facility with  which it is moulded
into any form, this  substance would be of great use in archi-
tecture, were it not for the unequal shrinking of the clay from
heat,  and  the difficulty of preserving  accurately the original
proportions.
   Crucibles.—Crucibles, melting pots, and other vessels in-
tended for use in the furnace, require to be made of substances
which sustain  a high temperature without  fusion.  When they
are made of about one part of  pure clay,  mixed with three of
sand, and slowly dried and annealed, they are found to bear a
great heat, and will retain most of the metals which are melted
for use in the arts.   Such crucibles, however, are liable to be
acted upon, and destroyed at high  temperatures, if the metals
are suffered to become oxidized, or if saline  fluxes are used.
To prevent this accident, some  crucibles are made  entirely of
 clay, which is burnt, coarsely powdered, and mixed with fresh
 clay.   These are found very refractory in the furnace.  Cru-
 cibles are also made of plain Stourbridge clay, of Wedgewood's
 ware, of graphite, and of platina.
    Pottery.—In  manufactures of vessels  from argillaceous
 compounds, the different degrees of beauty and costliness de-
 pend upon the quality of the raw material used, and upon  the
 labor and skill  expended in  the operation.  The  cheapest
 products of the  art, are  those  made of common clay, similar
 to that of which bricks are formed, and which, from the iron it
 contains,  usually turns red in  burning.   Next to  this is  the
 common crockery ware, formed of the purer and whiter clays
 in which iron exists  only  in  minute quantities.   Porcelain,
 which is  the most beautiful and  expensive of all, is formed
  only from argillaceous minerals of extreme delicacy, united
  with siliceous earths capable of communicating to them a semi-
  transparency, by means of its vitrification. 
ARTS OF INDURATION BY HEAT.
467
   Clay, although it is a compound body, and  possesses more
silica than  alumina,  nevertheless  derives characters  from the
latter, which abundantly distinguish it from minerals which are
more purely  siliceous.   The  processes  of its  manufacture
are in most respects the reverse of those applied  to glass, that
substance being softened by heat, and wrought at a high tem-
perature, whereas  the  clay is wrought while  cold, and after-
wards hardened by heat.
    Operations.—Though  the various  kinds  of  pottery  and
porcelain, differ from each other in  the  details of their manu-
facture, yet there are certain  general principles and  processes
which are common to them all.   The first belongs to the pre-
paration of the  clay, and consists in dividing  and washing  it,
till it acquires the requisite fineness.  The quality of the clay
requires by the intermixture of a certain proportion of siliceous
earth,  the  effect  of which  is  to increase  its firmness,  and
render  it less liable to shrink and crack, on exposure to heat.
In common clay, a sufficient  quantity of sand exists in a state
of natural  mixture,  to answer this  purpose.  But in the finer
kinds,  an  artificial  admixture  of  silica  is necessary.  The
paste which is thus formed, is thoroughly beaten and kneaded
to render it ductile, and to drive out the air.   It is then ready
to receive  its  form.  The form of the  vessel intended to  be
made,  is given to the clay either by turning  it on a wheel, or
by. casting it in a mould.  When dry it is transferred to  the
oven or furnace, and there burnt till it acquires a sufficient de-
gree of hardness  for  use.   Since, however, the clay is still
porous, and of course  penetrable  to water,  it is necessary to
 glaze it.   This is done by covering the surface with some vit-
 rifiable substance, and  exposing it  a second time to heat, until
 this  substance is converted into a coating of glass.
    In the coarse earthen ware^which is made  of common clay,
 the clay, after being mixed  and  kneaded until it has acquired
 the  proper ductility, is transferred  to a sort of revolving table,
 called  the wheel.   A  piece of  clay of sufficient  size,  being
 placed in the centre of this table, a rotary motion is communi- 
468           ARTS OF INDURATION BY HEAT.

cated to it by the feet.   The potter  then begins to shape it
with his hands, which are previously wet  to prevent its adher-
ing to the fingers.   The rotary motion gives it a circular form
and  it is gradually wrought up to the intended shape, a tool
being occasionally  used to  assist  the  finishing.  The vessels
are now set aside to dry, after  which they  are baked in the
oven, or kiln.  The glazing of this kind of pottery is given by
metallic oxides,  which  vitrify at a low heat.   A yellow glaz-
ing is communicated by the oxide of lead, black by the oxide
of manganese, and white by the oxide of tin.   Unglazed ware
is porous and permeable to water, as is seen in common flower
pots and coolers.
   Stone Ware.—The  kinds of  pottery  denominated  stone
ware, may be formed of the clays which are used for other ves-
sels, by applying to them a much  greater  degree  of heat, the
effect of which  is to increase very much their strength and
solidity.   These vessels do not require to be glazed with any
metallic  oxides,  but afford the material of their own  glazing by
a vitrification of their  surface.  When the  furnace in which
they are burnt has arrived at its greatest heat, a quantity of
muriate of soda, or common salt, is thrown  into the body of
the  kiln.  The  salt rises in vapor and envelopes the hot ware,
and by the combination  of its alkali with the siliceous particles
on the surface of the ware, a perfect vitrification is produced.
This glazing, consisting of an earthy  glass, is insoluble in most
chemical agents, and is free from  the  objections to which ves-
sels glazed with lead are liable, that of communicating an un-
wholesome quality to liquids contained in  them, by the solution
of the lead in common acids, which they frequently contain.
   White Ware.—The better sorts of earthen ware are made
of white clay, or of clay containing so little oxide of iron that
it does not  turn red in burning, but on the contrary, improves
its whiteness in the furnace.  This  kind,  commonly  called
pipe clay, is found very pure in  Devonshire and Dorsetshire, in
England.   In the manufactory of Mr Wedgewood, to whose
industry and ingenuity, the public are indebted for some of the 
               ARTS OF INDURATION BY HEAT.           469

finest specimens of  the art,  the  clay  is prepared by first
bringing it to a state of minute division, by the aid of machin-
ery.  This  machinery consists of  a  series of iron blades or
knives  fixed to an upright axis, and made to revolve in a cy-
linder,  and intersecting or  passing between another set of
blades  which  are fixed to the cylinder.  The clay, by the
continual  intersection of these blades, is minutely divided, and
when sufficiently fine, is transferred to a vat.   It  is here agitat-
ed  with  water until it assumes  the consistence of a pulp, so
thin,  that the coarser or stony particles can subside to the bot-
tom after a little rest, while the finer clay remains in suspension.
This last is poured  off and  suffered to subside,  after which it
is passed  through  sieves  of different fineness,  and  becomes
sufficiently attenuated for use.
   To this clay is added a certain quantity of flint reduced to
powder by heating it red hot, and  throwing it into cold water
to diminish the cohesion of its parts.  Afterwards it is pounded
by  machinery, ground in a mill, sifted and washed precisely as
the clay is treated, and made into a similar pulp.  In this state
the  two  ingredients are intimately  mixed  together  in such
quantities that the clay bears to the flint the proportion of about
five to  one.
   The object of adding flint to the clay, is twofold.   It lessens
the  shrinking of the clay in the  fire, and  thus  renders it less
liable to warp and  crack in  the  burning.   At the same  time,
by its partial  fusion, it communicates to the ware that beautiful
translucency  which is so much admired in porcelain, and  of
which the simple clay wares are destitute.
   The fine   pulp of flint  and clay being intimately mixed, is
then exposed to evaporation by a gentle heat, until the super-
fluous  water  is dissipated  and the mass  reduced to a proper
consistency to work.  To produce a uniformity in the thick-
ness of the material, it is taken out in successive pieces which
are repeatedly divided, struck, and pressed together, till every
part becomes blended with the rest. 
470
ARTS'OF INDURATION BY HEAT.
   Throwing.—The  formation of circular vessels  is done  by
the process  called throwing, performed on the potter's wheel,
in the manner already described, except that in large manufac-
tories the wheel is not turned by the operator  himself, but by
an assistant, or a steam  engine.  The handles and similar ap-
pendages, are made by forcing the clay with a piston, through
an aperture of the size and  shape which it is desired to pro-
duce.  When  formed, the handles  are cemented to the ware
by a thin mixture of the clay with water, which the  workmen
call slip.   The vessels, when complete, are  dried with a grad-
ual heat, in a room  heated to 80 or 90 degrees, and after be-
ing smoothed  from any irregularities of surface, they are con-
veyed to the kiln.
   Pressing.—The only vessels  which  can be made in the
wheel or lathe, are those of a circular form.  When the form
is different, the  vessel must be made either by press  work or
casting.  The  press work  is  executed in  moulds  made of
plaster of Paris, one half the figure being on one side of the
mould and the other half on the  other side.  These fit accu-
rately  together.  The clay is first made into two flat pieces of
the thickness of the articles ;  one of these is pressed  into one
side of the mould,  and the  other into the  other side.  The
superfluous clay being cut away, the two sides of the  mould
are  brought together to  unite the  two halves of the vessel.
The mould is now  separated from the clay, and the article is
finished as to form.  When  dry, it is completed  by the  addi-
tion of handles, or other parts belonging to it.  All vessels of
an oval  form, or which have flat sides, may be  made in this
way.
   Casting.—In the third method called casting, the clay is
used in the state of pulp, sufficiently thin to flow.   It is poured
into moulds made of plaster, by which the  superfluous water
being  rapidly absorbed,  the  clay is deposited, and acquires
sufficient solidity  to preserve the  shape communicated by the
mould.  It is then taken out and  dried, and transferred to the
kiln. 
               ARTS OF INDURATION BY HEAT.           471

  Burning.—All vessels, when formed, are in a very tender
and  frangible  state,  before  they  are  submitted  to the ac-
tion of fire.   The burning, or hardening, is performed in kilns,
and to preserve the ware from injury, it is inclosed in cases, or
boxes, of burnt clay, called saggars, in which it is heated red
hot, by the  flame circulating  among the cases.  The fire is
kept up from 24 to 48 hours, and the saggars  suffered to cool
before  they are  removed.   The ware is then found to have
acquired great hardness,  and is converted into a dry, sonorous,
and extremely  bibulous  solid.   In this state  it is called the
biscuit.  It adheres strongly to the tongue, and absorbs water
in such quantities, that vessels in this state are  used as coolers,
being  kept saturated with water, which, as it passes constantly
to the outer surface, generates cold by its evaporation.
   Printing.—When  colors, or  designs, are to be impressed
upon  the vessels, it is necessary in  most cases, that it should
be done  before the  ware is glazed.   In China, the  drawings
on the surface of porcelain, and other wares,  are executed by
hand, with the  pencil,   and the same method is pursued in
Europe,  in  elaborate pieces of workmanship.   But  in  the
common figured white ware, the designs are first engraved upon
 copper, and an impression taken on thin paper, in  the common
 mode of copperplate  printing, except that  the color is a me-
 tallic  oxide.   The paper  is then  moistened, applied  closely
 to the biscuit, and rubbed on, by which process  the  coloring
 matter is absorbed,  in  consequence  of the  porosity of the
 earthen material.   The paper is then  washed off, leaving the
 printed figure transferred to the sides of the vessel.   Blue and
 white ware is printed with oxide of  cobalt, * and a black color
 is imparted by an admixture with the oxides of manganese
 and iron.
    Glazing.—To prevent the penetration of fluids, it is neces-
 sary that vessels should be glazed, or covered, with a vitreous

   * Mr Parkes informs us that such improvements are made in the manufac-
 ture of this article, that the Chinese potters are now supplied from England,
 with all the cobalt they consume. 
472
ARTS OF INDURATION BY HEAT.
 coating.  The  materials of common glass  would afford  the
 most perfect  glazing to crockery ware, were it not that the ra-
 tio of its expansion and  contraction is not the same with  that
 of the clay, so that a glazing of this  sort is liable to cracks
 and fissures,  when  exposed  to  changes of temperature.   A
 mixture of  equal  parts of oxide of lead  and ground flints is
 found to be a durable glaze for the common cream colored
 ware, and is generally used for that purpose.   These materials
 are first ground to an  extremely fine  powder, and mixed with
 water to form a thin liquid.   The ware is dipped into this fluid
 and drawn out.  The moisture is soon absorbed by the clay,
 leaving the  glazing particles upon the surface.  These are af-
 terwards  melted by the heat of the kiln, and constitute  a  uni-
 form and durable  vitreous coating.
   The English and French manufacturers find it necessary to
 harden their vessels by heat, or bring them to the state of  bis-
 cuit, before they are glazed ; but the  composition  used by  the
 Chinese, resists water, after it has been once dried in the  air,
 so as to bear dipping in the glazing liquid, without injury.  This
 gives them a great advantage in the economy of fuel.
    China Ware.—The Chinese porcelain excels other kinds
 of  ware, in the  delicacy of its texture, and  the partial  trans-
 parency which it exhibits when  held  against the light.   It  has
 been long known and manufactured by the  Chinese, but  has
 never been successfully  imitated in Europe, until  within  the
 last century.   In China, porcelain is  made by the  union of
two earths, to which they give the name of petuntze and kaolin,
the former  of which is fusible in the  furnace,  the  latter not.
Both these  earths are varieties of feldspar, the kaolin  being
feldspar in a state  of decomposition, and which is rendered in-
fusible by having lost the small quantity of potass which origi-
nally  entered into its composition.   The Petuntze is feldspar
undecomposed.  These earths  are reduced to an impalpable
powder, by processes similar to those already  described, and in-
timately blended together.  When exposed to a strong heat the
petuntze partially melts and enveloping the infusible kaolin com- 
               ARTS OF INDURATION BY HEAT.           473

municates to it a fine semitransparency.  The glazing is pro-
duced by the petuntze alone, applied in minute powder to the
ware, after it is dry.
  European Porcelain.—Since  the nature  of  the Chinese
earths has been understood, materials nearly of the same kind,
have been found in different  parts of Europe, and the manu-
facture of porcelain has been carried on in several countries,
but particularly at Sevres, in France, with great success.   The
European porcelains, in the elegance and variety of their forms
and the beauty of the designs which are executed upon them,
excel  the manufactures  of  the  Chinese.   But   the Oriental
porcelain has not  yet  been  equalHfil  in hardness,  strength,
durability,  and the permanency of its  glaze.  Several of the
processes which are successfully practised by the Chinese, re-
main  still to be learnt by Europeans.   The manufacturers in
Saxony, are said to have  approached most nearly  in their pro-
ducts, to the character of the Asiatic porcelain.
  The porcelain earths are found in various parts of the United
States, and  will doubtless hereafter  constitute the material of
important manufactures.
  The finer and  more  costly kinds of porcelain, derive their
value, not so much from the quality of their material, as from
the labor bestowed on  their  external decoration.   When  the
pieces are separately painted by hand, with devices of different
subjects, their value,  as specimens of art, depends upon  the
size of the  piece, the number and brilliancy of the colors em-
ployed, and more especially upon the skill and finish, exhibited
by the artist in.the  design.  The manual part of the operation
consists  in  mixing the  coloring oxide  with a fluid medium,
commonly an  essential  oil,  and applying it with  camels'  hair
pencils.  The  colors used are the same as those employed in
other kinds of enamelling.   When  one color requires to be
laid over another, this is performed by a second operation; and
it often happens  that a piece of porcelain  has to  go into  the
enamel kiln, four or five times, when a  great variety of colors
is contained in the painting.
               60 
474           ARTS OF INDURATION BY HEAT.

  Gilding upon porcelain is performed by applying the gold
after its solution in  nitro-muriatic acid, ground up  with oil of
turpentine, and mixed with a flux.  When exposed  to  heat,
the oxygen,  if any is present,  escapes, and a coating of metal-
lic gold remains  fixed to the porcelain.   This has at first the
appearance of dead gold, but is subsequently burnished with an
instrument of  polished steel, or with an agate, or blood stone.
  The articles called lustre ware, are of two kinds.   The first
of these, called gold lustre, is made of red clay, and is brush-
ed over with a thin coating of gold obtained  from  its solution
in nitro-muriatic acid, the acid being driven off by heat.  The
other kind is called silver  lustre,  and is made of the  cream-
colored ware, covered in trie same manner with a film of pla-
tinum.
  Etruscan Vases.—This name is given to a kind  of  painted
antique vases, of great  beauty, lightness, and delicacy, which
are dug up  in the graves of lower  Italy.  Many of them are
supposed to  be of Grecian, and not of Etruscan origin.   Some
of these vases are entirely black, and in this case  there is no
separate glazing, but the interior of the mass has the same ap-
pearance with the outside.  Other  vases  are  furnished with a
simple black coating, but unlike the modern glazing.  It appears
from  analysis, that this black  color is produced by  a carbona-
ceous substance, perhaps bitumen;  but the art of applying it is
unknown to the moderns.
  The  celebrated  Portland  vase,  discovered in the tomb of
Alexander  Severus, and for which the Dutchess of Portland
paid a thousand guineas, is said to be made,  not of porcelain,
but of glass.  The body of  the  urn consists of a  deep blue
glass, over which is applied a coating of white semitransparent
glass.   The white covering appears to have been cut away by
the lapidary, in the  same way as the subjects of antique cameos
on  colored  grounds.  Mr Wedgewood,  at  a great expense,
produced imitations of this vase in porcelain.
   Among the curiosities of this  art, may be mentioned the
magic porcelain of the  Chinese.   The figures upon  the sur- 
               ARTS OF INDURATION BY HEAT.            475

face of this ware, are executed in such a manner that they are
said to be invisible  when the vessels are empty, * but become
apparent when the  vessels are filled with water.

  * See the article Porcelain, in the Edinburgh Encyclopedia, ascribed to M.
Brogniart.
  Parkes's Chemical Essays, vol. ii.;—TIees' Cyclopedia and Edin-
burgh  Encyclopedia, articles Pottery, Porcelain,  &c.;—Chaptal,
Chimii  Appliquie aux  Arts, torn,  iii.;—Gray's Operative  Chemist,
8vo. 1828. 
CHAPTER XXI.
    ON THE PRESERVATION OF ORGANIC SUBSTANCES.

  Decomposition.—The  compounds which are spontaneously
formed by organic bodies, both vegetable and animal, are of a
different nature from those which exist in unorganized matter.
They are the peculiar results of vital processes, and neither
their structure nor composition, can  be imitated by art.   Dur-
ing life, the  elements of organic  bodies  are held together by
vital affinities, under the influence of which they were originally
combined.   But no sooner does life cease, than these  elements
become subject to the laws of inert  matter.   The original af-
finities, which had been  modified, or suspended, during life,
are brought into operation; the  elementary atoms react upon
each other,  new combinations are formed, and the organized
structure passes sooner or later into  decay.
   The  rapidity with which decomposition  takes place in or-
ganic  bodies, depends upon the  nature of the particular sub-
stance, and upon  the circumstances under which it is placed.
Temperature, moisture,  and  the  presence  of  decomposing
agents, greatly  affect both the period, and extent of this pro-
cess.   By regulating,  or preventing, the operation  of these
causes, the duration of most substances may be prolonged, and
many materials are rendered useful,  which, if left to themselves,
would be perishable  and  worthless.   The preservation of tim-
ber, of fibrous  substances, of leather, of food, and of various
objects of art, are subjects of the highest importance,  and have
received, at various times, much attention from  scientific ex-
perimentalists.
   Temperature.—The influence of temperature, in accelerat-
ing, or retarding, the  decay of organized substances, is generally 
      ON THE PRESERVATION OF ORGANIC SUBSTANCES.  477

known.   Cold tends to check the progress of destructive fer-
mentation,  and when it extends so far as to produce congela-
tion, its preservative  power is complete.   Bodies of men and
animals  have been found  frozen, in situations where they had
remained for years, and  even  ages; and the recent discovery
of an elephant in the ice of Siberia, shows that the period of
this  preservation is unlimited.   On the other hand, in warm
seasons  and in hot climates, everything tends to corruption and
decay.   Both animal and vegetable substances, pass rapidly
into the putrefactive fermentation; alimentary  substances  are
difficult to preserve, and when moisture is combined with heat,
ships, houses, and other structures of wood, as well as  cordage,
canvass, and clothing, have the period  of their duration greatly
abridged.
   Dryness.—Although   certain  degrees  of  heat, especially
when combined with moisture, tend greatly to promote decom-
position, yet if the degree of heat, and the circumstances under
which it  acts, are such as to produce a perfect dissipation of
moisture, the further progress of decay  is arrested.  The exer-
tion of chemical affinities usually requires that one of the agents
at  least should  be in a fluid state.  And  while a body is  in a
state of perfect  dryness, no internal chemical change is likely
 to  befall it.   The beams and furniture of houses, often remain
 entire for centuries.  In the arid caverns of Egypt,  the wood
 of sarcophagi appears to have undergone no  alteration in the
 lapse of two or three thousand years, the fibres of linen  tex-
 tures are  found  distinct  and  perfect, though weakened  in
 strength, and the dried flesh of the mummies  themselves dis-
 cover no  marks of decomposition.  In  cabinets  of Natural
 History, the specimens, so long as they are kept perfectly  dry,
 undergo  no alteration  from spontaneous decay.  They  are,
 however,  extremely liable to the depredations of insects, from
 which  they require to  be protected,  either by impregnating
 them with poisonous substances, or by inclosing them in cases
 which are hermetically tight. 
478
ON THE PRESERVATION
   Wetness.—Some materials, especially wood, are capable of
lasting for a  long time, if kept continually  immersed in water,
especially at low  temperatures.   Thus the lower part of a
pump log is  much  more durable than the upper, if kept always
under water.  The effect of pure water is  to dissolve and car-
ry off the soluble parts, leaving the fibrous structure in a state
less liable to fermentation than before.   Some animal substan-
ces, likewise, such as  leather, hear immersion  in water for a
considerable time.   It must be  observed, however,  that  the
effect of wetness upon  most organized bodies, is to soften their
texture, and render them  less able to support mechanical vio-
lence, than when dry.   Wood, after having been long immers-
ed, if taken out and   dried, is found  to be more brittle than
it was before.
   But the state which most rapidly promotes decay, is that of
alternate  moisture and dryness, attended with exposure to the
atmospheric air.   It appears in  regard  to  wood, that in each
wetting, a sensible portion of substance is  dissolved, and that
in each drying, a new portion of soluble matter is formed.   In
a  ship,  under common  circumstances, the parts  which first de-
cay, are those which  are situated between wind and water, or
are subjected to alternate dryness and moisture.  So also  in a
post standing in the earth, the part which first decays, is usually
that which is nearest the surface of the ground.   Exposure to
the  vicissitudes of weather, is also one of the  most  common
and  active causes  of decomposition.
   Antiseptics.—A certain class of  substances has received the
name of  antiseptics, from their power, when present, of  resist-
ing putrefaction in organic bodies, as well  as in their products.
Such are charcoal, tannin, resins, camphor, bitumen, sugar, chlo-
rine, alcohol, oils,  acids, and salts of various kinds.  The man-
ner in which they exert their preservative agency, is not fully
understood.  It appears, however, that in some cases they com-
bine with the substance to be preserved, forming a less perisha-
ble  compound, as in the instance of leather; and probably in
 other instances they  unite with and qualify the decomposing
agents, which are present. 
OF ORGANIC SUBSTANCES,
479
   Timber.-—A vast expense is every year created by the pre-
mature decay of wood, employed in ships and other structures,
which are exposed to vicissitudes of weather, and especially if
they are subjected to the influence of warmth combined with
moisture.   Trees of different species, vary greatly in the du-
rability of their wood, yet none of the species commonly em-
ployed, are capable of withstanding for many years, the effect
of unfavorable exposures and situations.  The  decay of tim-
ber is sometimes superficial, and sometimes  internal.   In  the
former  case, the outside of the  wood first perishes and crum-
bles away,  and successive strata are decomposed, before  the
internal parts become unsound.   In the other  species, which
is distinguished by the name of the dry rot, the  disease begins
in the interior substance of the wood, particularly of that which
has  not been  well  seasoned, and spreads outwardly, causing
the  whole  mass to  swell,  crack,  and exhale a musty odor.
Different fungous  vegetables sprout out of its  substance, the
wood  loses its  strength,  and crumbles  finally  into a mass of
 dust.   This disease prevails most in a warm, moist, and con-
fined atmosphere, such  as frequently exists in  the interior of
 ships, and  in the cellars  and foundations of houses.   Its de-
 structive  effects in  ships of war, have given rise of late to nu-
 merous publications.  Some writers consider that the dry rot
 is not essentially different  from the more common kinds of de-
 cay, but  there  seems to be sufficient reason for the distinction
 which  has usually been  drawn.  The prevention of the evil
 has been attempted in various ways, and with some degree  of
 success.
     Felling.__It  is  agreed by  most   writers   that  the  sap
 of vegetables is the great cause of their fermentation and de-
 cay.   Hence it appears  desirable, if there  is  any season,  in
 which the  trunk of a tree is  less charged with sap than at oth-
  ers, that this time should be selected for felling it.  The mid-
  dle'of summer and the middle of winter, are undoubtedly the
  periods when the wood  contains least  sap.  In the months of
  spring and fall, in which the roots  prepare sap, but no leaves 
480
ON THE PRESERVATION
exist to expend it, the trunk is overcharged with sap ; and in
many trees, as the maple and  birch, sap will flow  out  at these
seasons, if the trunk is wounded.   In summer, on the contrary,
when the  leaves are out, the sap is rapidly expended, and in
winter, when the  roots are dormant, it is sparingly produced;
so that no surplus of this fluid  apparently exists.   From rea-
soning a priori, it would seem that no treatment would be  so
effectual in getting rid of the greatest quantity of sap, as to gir-
dle the  tree, by cutting away a ring of alburnum, in the early
part of summer, thus putting a stop to the further ascent of the
sap, and then to suffer it to stand until the leaves should have
expended, by their growth, or transpiration, all the fluid which
could be extracted by them previously to the death of the tree.*
The wood would  thus probably be found in the driest  state to
which any treatment  could reduce it in the living state.   Buffon
has recommended stripping the trees of their bark in spring,
and felling them in the subsequent  fall.  This  method is said
to harden  the alburnum, but the cause is not very apparent, nor
is the success at all certain.
   Seasoning.—At whatever period timber is felled, it requires
to be thoroughly  seasoned, before it is fit for the  purposes of
carpentry.   The  object of seasoning is partly to evaporate  as
much of the sap  as possible, and  thus to prevent its influence
in causing decomposition ;  and partly to reduce the dimensions
of the  wood,  so  that it may  be used without  inconvenience
from its further shrinking.   Timber seasons best, when placed
in dry situations, where  the air has  a free circulation round it.
Gradual  drying is considered a better  preservative of wood,
than a sudden exposure to warmth, even of the sun, for warmth
abruptly applied, causes cracks and flaws from the sudden and
unequal expansion produced in different parts.   Two or three
years' seasoning is requisite to produce tightness and durability
in the wood work of buildings.   It must be  observed that sea-
soning in the common way, only removes a portion of the aqueous

        * See McWilliam on the Dry Rot, pages 151, and 158. 
OF ORGANIC SUBSTANCES.
481
and volatile matter from the wood.   The extractive, and oth-
er soluble portions, still remain, and are liable to ferment, though
in a less degree, whenever the wood reabsorbs moisture.  Such,
indeed, is the force of capillary  attraction, that  wood, exposed
to the atmosphere in our climate, never gives up  all its moisture.
   Preservation of Timber.—When wood  is to be  kept in a
dry situation, as in the interior of houses, no other preparation
is necessary than that of thorough seasoning.  But when it is
to be  exposed to the vicissitudes of weather,  and  still  more
when it is to remain in a warm and moist atmosphere, its pre-
servation often becomes  extremely difficult.   Numerous ex-
periments have been made, and many  volumes written, upon
the preservation of timber, and  the prevention  of the dry rot;
but the subject is not yet brought to a satisfactory conclusion.
The methods which have hitherto been found most successful,
consist in extracting the sap, in  excluding moisture, and in im-
pregnating the vessels of  the wood with  antiseptic substances.
   For extracting the sap, the  process of water seasoning is
recommended.   It consists in immersing the  green timber in
clear  water for about two weeks, after which it is taken out
and seasoned in  the usual manner.  A great  part of the sap,
together with the soluble  and  fermentable matter, is said to be
dissolved or removed, by this process.  Running water is more
effectual than that  which is stagnant.   It is necessary that the
timber should be sunk, so as to be completely  under water,
since  nothing is more destructive to wood, than partial immer-
sion.   Mr Langton* has proposed to extract the  sap by means
of an air pump, the  timber being inclosed in tight cases, with a
temperature somewhat elevated, and the sap being  discharged
in vapor by the operation of the pump.
   It appears extremely  probable,  that if trees were felled  in
summer, and the buts immediately placed in water without re-
moving  the branches, a great part of their  sap would be ex-
pended by the vegetative  process alone, and replaced by water.
It is well known  that branches of plants, if inserted in water,
        * Repertory of Arts, 1826.  Franklin Journal, ii.  and vi,
               61 
482
ON THE PRESERVATION
    continue for some days, to grow, to transpire, and to perform
    their  other  functions.   This they  probably do at the expense
    of the sap, or assimilated fluid, which was previously in them,
    while they replace it by the water they consume.  This state
    of things continues  until the juices are  too far diluted to be
    capable  of any  longer sustaining life.
       The charring of timber by scorching, or  burning its outside,
    is  commonly supposed to increase  its  durability, but on this
    subject the  results of experiment do not agree.   Charcoal is
    one of the most durable of vegetable  substances, but the con-
\    version of the surface of wood  into charcoal, does not neces-
    sarily alter the character of the interior part.   As far, however,
    as it may operate in excluding worms, and arresting the spread-
    ing of an infectious decay, like the dry rot, it is useful.   Prob-
    ably also, the pyroligneous acid which is generated when wood
    is burnt,  may exert a preservative influence.
       The exclusion of moisture by covering  the surface with a
    coating of paint, varnish,  tar, he, is a well known preservative
    of wood  which  is exposed to the  weather.  If  care is taken
    to renew the coat of paint, as often as it decays, wood on the
    outside of buildings, is sometimes made to  last for  centuries.
    But painting is no  preservative  against the internal, or dry rot.
    On the contrary, when this disease is begun, the effect of paint,
    by choking the pores of  the wood,  and preventing the exhala-
    tion of vapors and gases which are formed,  tends rather to ex-
    pedite, than prevent the progress  of decay.  Paint itself is
    rendered more durable, by covering it with a coating  of fine
    sand.  Wood should never be painted, which is not thoroughly
    seasoned.
       The impregnation of wood with tar, bitumen, and  other re-
    sinous substances, undoubtedly  promotes its preservation.  It
    is the opinion of some writers, * that ' woods abounding in re-
    sinous matter, cannot be more  durable than others,' but the
    reverse of this is proved  every year in the pine forests of this

           * Tredgold's Elementary Principles of Carpentry, page 166. 
OF ORGANIC SUBSTANCES.
483
country, where the lightwood, as it is called, consisting of the
knots and  other resinous parts of pine trees, remains entire,
and is collected for the purpose of affording tar, long after the
remaining wood of the tree has decayed.   A coating of tar or
turpentine, externally applied to seasoned  timber, answers the
same purpose as paint in protecting the wood, if it is renewed
with sufficient frequency.  Wood impregnated with drying oils,
such as linseed oil, becomes harder, and more capable of re-
sisting moisture.   It is frequently the custom, in this  country,
to bore a perpendicular  hole in the top of a mast, and  fill it
with oil.   This fluid is  gradually absorbed  by the  vessels of
the  wood, and penetrates the mast to a great distance.   Ani-
mal  oils, in general,  are  less proper for  this purpose,  being
more liable to decomposition.
   The preservative quality of common salt (muriate of soda),
is well known.  An example of its effect is seen in the hay of
salt  marshes, which is frequently housed  before it is dry, and
which often becomes damp afterwards from the deliquescence
of its  salt,  yet  remains  unchanged  for  an indefinite  length
of time.    In the   salt  mines  of  Poland   and   Hungary,
the  galleries are  supported  by  wooden pillars, which are
found  to  last unimpaired  for ages, in  consequence  of being
impregnated  with  the salt, while pillars  of brick and stone,
used for the same purpose, crumble  away in a short time by
the decay of their mortar.  Wooden piles driven into the  mud
of salt flats and  marshes, last for an unlimited time, and are
used for the foundations of brick and stone edifices.   In canals
which have been  made in the salt marshes  about Boston, and
other places, trunks of oak trees are frequently found with the
heart wood entire and fresh, at a depth of five or six feet below
the surface.   At Medford, (Mass.) the stumps of trees are found
standing in the gravelly  bottom of the  salt marsh where the
tide rises in the canals  four or five  feet  above them.   This
bottom must originally  have constituted  the  surface of the
 ground, and must have settled long enough ago for the marsh
mud to have accumulated, as it has done for miles round, ap-
parently since that period. 
484
ON THE PRESERVATION
   The application of salt in minute quantities, is said rather to
hasten, than prevent the decay of vegetable and  animal bodies.
Yet the  practice of docking  timber, by immersing it for some
time in sea  water, after it has been  seasoned, is generally ad-
mitted to promote its durability.   There are some experiments
which appear to show,  that after  the dry rot  has commenced,
immersion  in salt water effectually checks  its  progress, and
preserves the remainder of  the  timber.  *    In  some of  the
public ships built  in the United States, the interstices  between
the timbers  in various parts of the hull, are filled with  dry salt.
When this salt deliquesces, it fills the pores of the wood with
a strong saline impregnation, but it has been said, in some cases,
to render the inside of the vessel uncomfortably damp.   If
timber is immersed in a brine  made of pure   muriate of soda,
without the  bitter  deliquescent salts, which sea water contains,
the evil of dampness is avoided.
   A variety of other substances  besides  common salt, act as
antiseptics  in  preventing the dry rot, and the  growth of the
fungus which  attends it.  Nitre and alum have  been recom-
mended for this  purpose, and some of the  metallic  salts are
considered still more effectual.   Of these  the  sulphates of iron,
copper, and  zinc, have the effect to harden  and preserve  the
timber.  Wood boiled  in a  solution of  the   former  of these,
and afterwards kept some  days in a warm place to dry, is said
to become  impervious to  moisture.   Corrosive sublimate,
which is recommended by Sir H. Davy,  is a powerful preser-
vative of organized substances from decay, and proves destruc-
tive to parasitic vegetables and animals; but its safety, in regard
to the health of crews if used in large quantities about the wood
of a ship, may be  considered as doubtful.

  * The  British  frigate  Resistance, which went down in Malta harbor, and
the Eden, which was sunk in Plymouth  Sound, were both affected with dry
rot. These ships, after remaining many months under water, were raised,
and it was found that the disease was wholly arrested.  Every vestige of
fungus had disappeared, and the ships remained in service afterwards, per-
fectly sound from any further decay.  Supplement to the Encyclopedia Bri-
tannica, iii. 682. 
OF ORGANIC SUBSTANCES.
485
   An opinion has been supported in this country, that the decay
of timber in ships, by dry rot, is owing to the impure atmos-
pheric generated by bilge  water, and that it is to be remedied
by constructing  ships  with a view to their free  and  effectual
ventilation. *
   Preservation of Animal Textures.—The solid and fibrous
portions of organic bodies, such as wood, bone, shell, horn,
hair,  cotton,  he, are most  easy  of  preservation.   But the
soft and succulent parts,  such as the  pulp of vegetables, and
the flesh of animals,  are extremely perishable, owing  to the
decomposing influence of their fluid contents ; and require the
assistance of art to communicate to them  any degree  of dura-
bility.   These substances, when they cannot be dried, are  usu-
ally preserved by enveloping, or impregnating them with anti-
septics.  For alimentary substances the  antiseptics used are
sugar, alcohol, salt, and  the  acetous and  pyroligneous  acids;
while for scientific  specimens and  preparations, alcohol, oil of
turpentine, resinous and bituminous varnishes, alum and corro-
sive sublimate, are found most effectual.
   Embalming.—As the  art of embalming can hardly  be rank-
ed among the useful arts, any further than it can be made  sub-
servient to  the  promotion of  anatomy, or  natural history, it is
not much  cultivated at the present day.  The ancient  Egyp-
tians  converted the dead bodies of their friends into mummies,
by removing the viscera from  the large  cavities  and replacing
them  with aromatic, saline, and bituminous substances, particu-
larly asphaltum;  and also enveloping the  outside of the body
in cloths impregnated with similar  materials.   These  impreg-
nations prevented decomposition,  and excluded insects, until
perfect dryness  took place.   In times comparatively  modern,
embalming has been practised with  great  success, particularly
where bodies have remained at a low and uniform temperature,
and have  been protected  from the access of  the air.   The
body  of king  Edward the First, of England,  appears upon

  * See a pamphlet on Dry Rot by Commodore Barron, Norfolk, 1828. 
486
ON THE PRESERVATION
record to have been  embalmed.  He died in July,  1307, and
was buried in Westminster Abbey.  In 1770,  his  tomb was
opened, and the contents examined, and after this lapse of 463
years, the body of the monarch remained entire.   The flesh
upon the face was a little wasted, but not  putrid.   The body
of Canute, king  of Denmark, who  invaded  England in 1017,
was found very fresh in 1776, by the  workmen employed  in
repairing Winchester  Cathedral.   The bodies of William  the
Conqueror, and of Matilda his wife,  both buried at Caen, were
found entire in the sixteenth century.   In  like manner, the re-
mains  of  various  other  princes, and persons  of note, have
been discovered to be imdecayed,  some  centuries  after their
decease.   In certain  cases,  bodies not embalmed  have been
preserved, merely by the exclusion of air, and  a uniform low
temperature.
   But the  most  perfect of all  the  modes of preserving the
animal body, without continued immersion, appears  to be  a
thorough impregnation with  corrosive  sublimate.   This may
be performed, by saturating the  soft solids with a strong solu-
tion, consisting of about four  ounces of bichloride of mercury
to a pint of alcohol.  This is injected  into  the blood vessels,
and after the viscera are  removed, the whole body is immersed
for three months in the same  solution.  At the end of this pe-
riod it  easily dries, and is afterwards nearly imperishable. *
   In what  are  called by anatomists wet preparations, the  ob-
jects are kept  immersed  in alcohol, and last for an indefinite
time.  Oil of turpentine answers the same purpose, and in the
Museum of Natural History, in  Paris, there is a head prepared
in this  way, more than a  hundred years ago, by the  celebrated
Ruytch, which preserves all the vivacity of its colors.  In cold
weather  the  liquid becomes opaque,  but is again rendered
transparent in the spring.
   Tanning.—The skins of animals, when  prepared  by merely
drying  them, are stiff, incapable of resisting water, and liable
  * See a paper by Dr J. C.  Warren, on Embalming, in the Boston Journal
of Arts, vol.  i. p. 269. 
OF ORGANIC SUBSTANCES.
487
to decay.  If, however, they are impregnated with the tannin
which is found in astringent vegetables, that substance combines
with  the  gelatin of the skin, and forms a durable  compound,
which is no longer soluble in water.  Common tanned  leather
is prepared in this way.   The skins are previously prepared
by soaking them in lime water, which facilitates the separation
of the cuticle and hair.   A slight degree of putrescency assists
the same object.  They are then immersed in the tan pits, in
a  strong infusion of some  astringent vegetable.   Oak bark,
from  its cheapness,  and  the  quantity of tannin it  contains, is
commonly employed in the preparation of leather,  both in this
country, and in Europe.  The  bark of the hemlock  spruce,
and of  the  chesnut, the  leaves of the  different species of su-
mach, and various other astringent vegetables, are used in sec-
tions  of country where  oak is  scarce.   The  strength of the
astringent infusion is increased  from time to time, until the
skin is saturated with tannin.  A portion of extractive matter
likewise  combines with the hide, and to this the brown color,
which is common in leather, is owing.  The presence of this
extractive is supposed to render leather more tough  and pliable.
   When strong or saturated solutions of tannin  are used, the
leather  is formed in a much shorter time, but it is observed
that leather tanned in this way is more rigid and more liable to
crack, than that made in the common manner, with weaker in-
fusions, gradually increased in strength.  But sole leather, the
most important requisites of which are firmness and resistance
to water, is  immersed in an infusion kept  nearly saturated by
alternate strata  of bark.  The full impregnation requires from
 10 to 18 months.
   The  currying of leather is performed by covering  the skin
or leather,  while yet moist, with common oil,  which, as the
 moisture evaporates, penetrates into the pores of the skin, giv-
ing it a peculiar suppleness, and rendering it, to a certain ex-
tent, water  proof.   During the process, it is pared,  washed,
 and rubbed, to increase its flexibility.  The black  color is also
imparted by the currier,  by rubbing the outside with a solution 
4S8
ON THE PRESERVATION
of copperas, or any solution of iron, whicli immediately turns
it black by combining with the tannin in the leather.
   Tawing, is the method by which skins  are dressed of a
white color, and it is performed without the use of hark.   The
skins  are  first prepared  by steeping them in lime water, and
subjecting them  to various processes of scraping and fulling.
They  are  then  fermented   with  wheat bran,  and afterwards
impregnated with a solution of alum and common salt.  Be-
fore being dried, they are fulled with wheat bran and yolks of
eggs,  and  are thoroughly trodden, steeped,  and washed.   In
this process,  the place of  tannin appears to  be supplied  by
some principle extracted from the alum.
   As  examples  of  the foregoing  processes, common sole
leather is simply tanned,  the upper leather of boots and shoes,
is tanned and curried, the white leather for gloves is tawed, and
fine morocco leather is tawed, and  afterwards  slightly tanned
with sumach, and  dyed.   Chamois, and other kinds of wash
leather, are steeped in lime pits, and afterwards fulled with oil.
Before the dressing  is finished, the superfluous oil is scoured
out with an alkaline liquor.
   Parchment.—Parchment used for writing, is prepared from
the skins of sheep and goats.  These, after being steeped in
pits impregnated  with lime, are stretched upon frames and re-
duced by  scraping and  paring, with  sharp instruments.   Pul-
verized chalk is rubbed on with  a pumice stone resembling a
muller, which smooths and softens the skin  and improves  its
color.   After it is reduced  to something less than half its orig-
inal thickness, it is smoothed and dried for use.  Vellum is a
similar substance to  parchment,  made  from the skins of very
young calves.
   Catgut.—The  strings of certain musical instruments,  the
cords of clock weights, and those of some other machines and
implements, are  made of a dense,  strong, animal substance,
among us usually denominated catgut.   It is derived from the
intestines  of different quadrupeds, particularly those of cattle
and sheep.  The manufacture is  chiefly carried on in Italy and 
OF ORGANIC SUBSTANCES.
489
France.   The texture  from which it is made, is that  which
anatomists call the muscular coat, which is carefully separated
from the peritoneal and  mucous membranes.  After a tedious
and troublesome  process of steeping, scouring, fermenting, in-
flating,  he, the material is  twisted, rubbed  with horsehair
cords, fumigated with  burning  sulphur, to improve its  color,
and dried.  Cords of different size, and strength, and delicacy,
are obtained from different  domestic  animals.  The  intestine
is sometimes  cut into uniform  strips with an instrument made
for the  purpose.  To  prevent  offensive effluvia  during  the
process, and  to get rid  of the  oily matter, the French  make
use of an alkaline liquid called  eau de Javelle.
   Gold Beater's Skin.—This delicate membrane is also man-
ufactured from the intestines of animals.  The workman strips
off that  part of the peritoneal membrane which surrounds the
ccecum.   He  then takes about two  feet of it in length,  turns it
inside out, and leaves it to  dry.  It is afterwards  steeped in a
weak solution of potash, cleansed  by scraping, and cut open.
It is then stretched to dry upon wooden frames, and notwith-
 standing the tenuity of  the  membrane  when dry, every piece
 of it  is double or  consists of two  membranes  glued  together.
 It is  finished  by washing it  with a solution of alum, and  coating
 it with isinglass and whites  of eggs, together with some aromat-
 ics to repel insects. *
   Specimens in  Natural  History.—Preparations of  animals
 intended to show their  external form and characters, are made
 by detaching their skins, and  stuffing or mounting these so  as
 to represent the  natural figure and attitudes of the  animal.
 Quadrupeds  and  birds, are  preserved  by extracting the body
 through an opening on the  under side, at the same time invert-
 ing the  skin.  The fleshy parts of the limbs,  are  extracted
 through the same opening, also the neck, brain, and eyes, leav-
 ing the skull, if the  animal be small.   Care is taken not to m-

   » See Franklin Journal, iii. 223, and London Mechanics Magazine, vi. 63.
 also the Prize Essay of Labarraque, 1822.
62 
490
ON THE PRESERVATION
jure the hair, or plumage.  When the fleshy parts are remov-
ed, the inside of the skin is rubbed with some poisonous sub-
stance, usually arsenic, * to prevent insects.   The skin is then
returned to its  natural situation, and filled with cotton or tow,
or  what is still better,  an artificial body,  shaped out of wood,
cork, or dried  clay, may be introduced within the skin.   The
opening is sewed  up, and  wires are passed  longitudinally
through the legs and  neck.    These  are afterwards bent into
the proper  position to  give  the attitude  desired.  Glass eyes
are  inserted, and the hair and  feathers rendered as smooth as
possible, and retained,  while drying, in paper bandages.
   Reptiles, and fishes without scales, are  extracted by careful-
ly separating the bones of the neck through an opening in the
throat, or gills, and inverting the skin.   In serpents, the whole
body is easily extracted through the mouth.  Fishes with scales
cannot be turned  without injury.   It is therefore necessary to
detach the skin carefully, without doubling it.   Insects may be
killed, without hurting their  texture, by the fumes of burning
sulphur, or prussic  acid, or, in  many cases, by pinching the
breast.  They are then secured by pins,  and  placed to dry
with the wings and  legs in the natural attitudes.   Arsenic, or
corrosive sublimate, is generally necessary to secure them from
the  depredations of other insects.
   An Herbarium, or collection of dried plants, is usually form-
ed by subjecting the plants, while fresh, to a sufficient pressure
between folds of paper, to preserve their natural smoothness
and regularity, until they become dry.   The plants should be
gathered at a time  when their characters  are  most perfectly
developed.  A specimen in flower should be preserved, and if
possible, one also in fruit.  The plant must be carefully spread
out on smooth, bibulous paper, so that the  leaves, petals,  he,
may be displayed  as perfectly as possible.  In this situation it
is retained, and another  sheet of paper turned  gradually  over

   * The following is the arsenical soap of Becoeur, much used in France.
 Camphor, 5 ounces, powdered arsenic, 2 pounds, white soap, 2 pounds, salt of
'artar, 12 ounces, lime 4 ounces, melted and triturated together. 
OF ORGANIC SUBSTANCES.
491
it, commencing at one side, till the whole is covered.   Several
sheets of paper are then to be added to each  side, and  the
whole placed to dry under a strong, equal pressure.  In  this
way  many  plants may be preserved without further  trouble,
especially if the  weather be warm  and  dry.  The process,
however, may be expedited by shifting the papers, or by pass-
ing over them occasionally a warm  iron.  These  precautions
are more necessary for succulent plants, or for others in cold
and damp weather.
   Appert's  Process.—A method brought  into notice by M.
Appert, for  preserving articles of food unchanged for several
years, deserves to be noticed among the practical improvements
of the present  century.   This  method was partially known at
a much earlier period, but its most successful modes of appli-
cation were undoubtedly  discovered by M. Appert.  It con-
sists in a very  simple  process.   The articles to be preserved
are inclosed in bottles, which are filled to the top with any li-
quid, for example with the water in which the article, if solid,
has been boiled.   The bottles are closely corked, and cement-
ed, to render them hermetically tight.  They are then placed
in kettles filled with cold water,  and subjected to heat till the
water boils.  After the boiling temperature has been kept up
for a  considerable time, in some cases an hour,  but varying
with  the  character of the article to be preserved, the bottles
are suffered to cool gradually.   In this state, meats, vegetables,
fruits, milk, and other substances, are preserved perfectly fresh,
without any  condiments, for long periods, of from one to six years.
Instead  of  bottles,  tin  cannisters  are sometimes used,  and
rendered  tight by soldering.
   The remarkable  effect of this process has been explained,
by attributing the preservation  of the articles to the total ex-
clusion of atmospheric air.   But as air, in common cases, is
always present in sufficient  quantities to excite fermentation, it
is supposed  that the  application of heat serves to fix the small
portion of atmospheric oxygen which is present, by combining
it with some principle in  the other substances; so that it is 
492  ON THE  PRESERVATION OF ORGANIC SUBSTANCES.

no longer capable of producing the fermentative action, which
in parallel cases leads to decomposition.
  Chapman's Treatise on the Preservation of Timber, 8vo. 1817;—
TREDGOLn's Elementary Principles of  Carpentry, 4to. 1820;—Mc
William, on the Dry Rot,  4to. 1818;—Article Dry Rot, in the Sup-
plement to the Encyclopedia Britannica;—Aiken's Chemical Dic-
tionary, article Leather;—Labarraque, VArt du Boyaudier; Bulletin,
de la Sociitt de VEncouragement pour VIndustrie", 1822 ;—Lf.ttsom's
Naturalist's Companion, 8vo. ;—Taxidermy, or the  Art of Collecting,
Preparing,  and  Mounting  Specimens  in Natural  History, London,
1823;—Appert, Art of Preserving  Animal and Vegetable Substan-
ces, London, translated, 1812;—Edinburgh Review, vol. 23, p. 104, 
INDEX.
Abutments, 120.
Acanthus, 134.
Achmet, Mosque of, 149.
Acroteria, 129.
Aerial Perspective, 85.
Aerostation, 225.
Agate, 13.
Agrigentum, 139.
Air flues, 165.
Alabaster, 11.
Alhambra, 151.
Alloys, 387.
Alloy of Gold, 391.
Alternate Motion, 237.
Amalgam, 21.
Amalgamation, 389.
Amber, 23.
Amianthus, 15.
Amphiprostyle Temple, 136.
Amphitheatre, 143.
Annealing, 392, 451.
Animals, Motion of, 192.
Animal Power, 254.
Anime, 434.
Annotto, 443.
Anthracite, 23.
Anthracite  Grate, 162.
Antimony, 22.
Antiseptics, 478.
Antae, Temple with, 136.
Antoninus and Faustina, 144.
Apollo de Belvidere, 8.
Appert's Process, 491.
Apron, 258.
Aqua Tint# 96.
Aqueducts, 212.
---------, 302.
Arabesque, 147.
Arseo Systyle, 146.
Arbor, note, 371.
Arbor Vita:, 31.
Arcade, 121.
Arch, 118.
Aichil,442.
Archimedes' Screw, 310.
Architecture, 114.
Architrave, 128.
Archivolt, 120.
Argand Lamp, 181.
Arkwright, Richard, 346.
Arsenic, 22.
Asbestus, 15.
Ash, 26.
Asphaltum, 23.
-------, 429.
Assaying, 387.
Astragal, 129.
Astral Lamp, 178.
Atmospheric Engine, 283.
Attic, 129.—Base, 134.
Attrition, 332.
Automaton Lamp, 180.
Axis, note, 371.
Axle, note, 371.
Axletrees, 200.
Azure.  See Ultramarine. 
494
INDEX.
Back Water, 263.
Badigeon, 431.
Balance, 369.
Balbec, Temple at, 146.
Ballast, 220.
Balloon, 225.
Baltimore Monument, 125.
Band, 245.
Band Wheels, 229.
Bark, 25.
Bark Mills, 334.
Barker's Mill, 266.
Base of Columns, 128.
Basilica, 143.
Basis, in Dyeing, 440.
Bass Wood, 27.
Batting, 347.
Battlement, 148.
Bay Window, 148.
Bayonets, 248.
Beams, Shape  of, 50.
Beech, 27.
Bell Metal, 403.
Belt and Segment, 244
Benzoin, 434.
Besant's Wheel, 264.
Bevel  Gear, 232.
Bice, 427.
Biddery Ware, 406.
Birch, 28.
Birds,  Flying of, 193.
Biscuit, 471.
Bismuth, 22.
Bistre, 429.
Bitumen, 23.
Black  Lead, 24.
Black  Walnut, 29.
Blasting with Powder, 300.
Bleaching, 438.
Blowing Glass, 451.
Blue Verditer, 426.
Body Colors, 426.
Boiler, 227.
Bole, 427.
Bologna Phials, 451.
Boltels, 119.
Bone, 39.
Boring, 330.
Boston State House, 125.
Bottle Glass, 452.
Boustrophedon, 53.
Boxwood, 32.
Brake, 210.
Brass, 20.
----, 400.
Brazil Wood, 442.
Breast Wheel, 265.
Bricks, 463.
Bridges, 204.
Bridgewater's Canal, 213.
Broad Glass, 452.
----Wheels, 198.
Bronze, 20.
-----, 402.
-----Casting, 109.
Brunswick Green, 429.
Brush Wheel, 234.
Buckets, 258.
Buhrstone, 13.
Bulk, Limit of, 48.
Bunker Hill Monument, 10.
Burning Pottery, 471.
Burning of Smoke, 175.
Burns' Grate, 162.
Bushnell's Machine, 224.
Butternut Dye, 444
Buttons, 407.
Buttonwood, 28.
Buttress, 148.
-----, Flying, 150.

Calamus,  58.
Calcareous Stones, 7.
Caledonian Canal, 215.
Calico Printing, 444
Cameos, 111.
Cams, 237.
Canals, 211.
-----, size of, 215.
Canal Boats, 215.
Candles, 177.
Caoutchouc, 34, 
INDEX.
495
Capitals of Columns, 128.
Capitol at Washington, 10.
-----------------, 125.
Carats, 391.
Card Ends 349.
Carding, 348.
Carmine, 427.
Carpets, 357.
Carthamus Tinctorius, 428.
Cartoons, 432.
Cartwright's Steam Engine, 241
Caryatides, 135.
Case, 61.
Case Hardening, 419.
Casting, 341.
Cast Iron, 410.
Casting in Plaster, 107.
----- Pottery, 470.
Catenary Arch, 119.
Catgut,  488.
Cathedral, 147, 150.
-------, Milan, 125.
-------, Strasburg, 125.
Cavetto, 130.
 Cedar, 30, 31.
 Cell, 135.
Cementation of Gold, 390.
 Cementing, 338.
 Cements, 15.
 Cerulin, 440.
 Chain Pump, 320.
 -----Wheel, 260.
 Chalk, 12.
 Chamois Leather, 488.
 Charcoal, 155.
 Charring of Timber, 482.
 Cherry Tree, 27.
 Chesnut, 27.
 Chiaro  Oscuro, 82.
 Chill Casting, 411.
 Chimnies, 167, 173,
 China Ware, 472.
 Chinese Style, 132.
 Chipolin, 432.
 Choir, 147.
 Choragic Monument, 140, 141
Chrome Red, 427.
Chrome Yellow, 428.
Church, 147.
Cider Mills, 335.
Circular Saw, 332.
Clay, 14.
Clepsydra, 365.
Clock, Description of, 371.
Clock Work, 366.
Close Hauled, 218.
Close Rooms, 173.
Clutches,  248.
Coal, 23.
----Gas, 185.
----Grate, 161.
Cochineal, 427, 442.
Cockle, 165.
Coffer Dam, 205.
---- Walls, 117.
Cohesion, 328.
Coin, 391.
Coining,  395.
Coin Posts, 214.
Coke, 23.
Coliseum at Rome, 124.
Colcothar, 427.
Colors, 86.
 Coloring, 86.
 Colored Engravings, 98.
 Color Mills, 336.
 Coloring  Substances, 426.
 Column,  115, 128.
 Composing, 61.
 Composite Order, 142.
 Compression, 44.
 Concord, Temple of, 139.
 Condensation of Steam, 274.
 Condensing Engine, 283.
 Cones, Double, 235.
 ----, Geared, 235.J
 Constantine, Arch of, 145.
 Contrast, 87.
 Contrate  Wheel, 233.
 Convoy, 210.
 Copal, 434, 36.
 Copper, 19. 
496
INDEX.
Copper, Extraction of. 399.
-----, Working of, 399.
-----Plates, 90.
Copperplate Printing, 98.
Copying Machines, 59.
Corbel,  149.
Cordage, 344.
Corinthian Order, 134.
Cork, 32.
Cornelian, 13.
Cornice, 128.
Correcting the Press, 63.
Corundum, 13.
Cotton, 33.
-----Gin, 33.
-----Spinning, 346.
Counterpanes, 358.
Couplings, 247.
Covering of Roofs, 127.
Cranks, 235, 239.
Crayons, 430.
Crevices,  169.
Crochets, 148.
Crocus Martis, 427.
Crown Glass, 450.
-----Wheel, 233.
Cross Weaving,  355.
Crucibles, 466.
Crushing, 333.
Crystallo Ceramie, 460.
Culverts,  212,171.
Cupellation, 389,
Cupola, 121.
Curb, 383.
---- Roof, 126.
Currying, 487.
Cutlery, 422.
Cutting, 329.
----- Glass, 456.
----- Machines, 329.
Cuttle Fish Liquor, 429.
Cylinder  Glass,  453.
Cymatium, 130.
Cypress, 30.

Danforth's Speeder, 349.
Davy's Safety Lamp, 1SS
Dead Water, 216.
Decomposition, 476.
Dentels, 134.
Derbyshire Spar, 12.
Designing, 70.
Devitrification, 459.
Dial, 364.
Diameter of a Column, 130,
Diamond, 13.
Diastyle, 137.
Die, 128.
Diocletian's Palace, 151.
Dipteral Temple, 136.
Direction of Light, 83.
Disengaging Machinery, 247
Dishing Wheels, 199.
Distemper, 431.
Dividing of Bodies, 328.
Diving Bell, 222.
Docking of Timber, 484.
Dome, 121.
Doric Order, 133.
Double Fire Place, 160.
Double Speeder, 349.
Double Weaving, 355.
Dovetailing, 337.
Drawing, 70, 130.
Drawing of Cotton, 348.
Dressing, 353.
Drilling, 330.
Drying Oils, 36.
Dry Point, 91.
Ductility, 43.
Dutch Pink, 428.
Dyeing, 439.
Dyes, 440.

Ebony, 32.
Echinus, 130, 133.
Edge Railway, 207.
Egyptian Style, 131.
Elastic Gum, 34.
Elasticity, 43.
Elastic Moulds, 108.
Elephanta, 131. 
INDEX.
497
Elevation, 130.
Eliquation, 395.
Elm, 26.
Embalming, 485.
Embankments, 211.
Emery, 13.
Enamelling, 458.
Encaustic Painting, 432.
Enchasing, 392.
Engaging Machinery, 247.
Engines, Fire, 325.
Engine, Steam, 227, 281.
Engraving, 90.
Engraving of Gems, 111.
Entries, 169.
Entablature, 128.
Entasis, 116.
Epicycloidal Wheel, 242.
Epistylium, 128.
Equalizing Motion, 248.
Erectheum, 141.
Erie Canal, 216.
Essenay, Temple at, 149.
Etching, 93.
Etruscan Vases, 474.
Eustyle, 137.
Expansion Engines, 287.
Expansion of Steam, 275.
Extension, 43.
Extrados, 120.
Eyes of a Portrait, 85.

Fagade, 128.
Fast Colors, 445.
Fat Oil, 35.
Feathers, 37.
Fecula, 36.
Feeders, 211.
Feedpipe, 280.
Feldspar, 9.
 Felling of Timber, 479.
Felting, 361,
Fibres, Combination of Flexible,
Field of Vision, 72.
Fig Blue, 427.
Fillet,  130.
              63
 Filtering Stone.  See Freestone.
 Fire Engines, 325.
 ----in the open air, 156.
 ----Modes of Procuring, 190.
 Fireplaces, 157, 172.
 Firs, 30.
 Fishes, Swimming of, 193
 Flake White, 430.
 Flame, 176.
 Flange, 207.
 Flash Wheel, 326.
 Flat Boards, 262.
 Flax, 33.
 Flint, 12.
 Flint Glass, 452.
 Flue Boilers, 278.
 Fluor Spar, 12.
 Fluxes, 341.
 Fly, 374.
 Flying Buttress, 150.
 Fly Wheel, 250.
 Forces, Moving, 253.
 Forcing Pump, 314.
 Foreshortening, 72.
 Forging, 412.
 Forks, 422.
 Form of Materials, 42, 50.
 Foundations, 114.
 Fountain Lamp, 180.
 Fountains, 324.
 Frankfort Black, 427.
 Franklin Stove, 158.
 Freestone, 10.
 French Berries, 443.
 Fresco Painting, 432.
 Friction, 251.
 Friction of Pipes, 305.
 Frieze, or Frize, 128.
 Fritting, 450.
 Fuel, 153.
 Fugitive Colors, 446.
 Fulling, 360.
:. Fur, 37.
 Furnaces,  163.
 Fusee, 336.
 Fusible Metal, 22. 
498
INDEX.
Fustic, 443.

Gable, 149.
Galena, 403.
Galls, 444.
Gamboge, 12S.
Gangue, 385.
Gas Engines, 294.
Gas Lights, 184.
Gasmeter, 188.
Gasometer, 186.
Gates, 213.
Gauze, 355.
Gear Bevel, 232.
----, Spiral, 231.
Gearing, 230.
Gelatin.  See Glue.
Gem Engraving, 111.
Gems, Artificial, 459.
Generation of Steam, 274.
Generator, 281.
Gilding, 434.
-----on Metals, 393.
-----on Porcelain, 474,
Gin, Cotton, 33.
Glass, 449.
---Blowing, 451.
----,  Broad, 452.
----,  Crown, 450.
----Cutting, 456.
----Cylinder, 453.
----,  Flint, 452.
----,  Plate, 453.
----Shades, 183.
----,  Stained, 456.
----Thread, 460.
Glazing, 426.
------  Porcelain, 471.
Glue, 339, 40.
Gold, 21, 389.
----Beater's Skin, 489.
----Beating, 392.
----Leaf, 392.
Goldsmiths' Work, 392.
Goldthread, 394.
Goldwire, 394.
Gothic Style, 147.
Governor, 248.
Granite, 8.
Graphite, 24.
Grate, Anthracite, 162.
Graver, 91.
Grecian Style, 132.
-------Temple, 135.
Greco Gothic Style, 146.
Grinding, 335.
Grindstone.   See Freestone.
Gristmill, 335.
Groins,  149.
Gudgeons, note, 371.
Gum, 36.
----Tree, 29.
Gun Making, 415.
----Metal, 402.
Gunpowder, 296.
Gun, Properties of, 299.
Guttas, 133.
Gypsum, 11.

Hackmatack, 31.
Hair, 37.
---Spring, 370,381.
Halle du Bled, 122.
Hardness, 43.
Hargreaves, Richard, 346.
Harmony, 87.
Harnessing of Horses, 201
Hanging of Pictures, 182.
Hat  Making, 361.
Heart Wheel, 239.
Heating, 153.
-----  by Steam, 166.
Heddles, 353.
Hematine, 442.
Hemlock, 30.
Hemp, 32.
Herbarium,  492.
Herculaneum Manuscripts, 56.
Hermopolis, Temple of,  10.
Hero's Fountain, 322.
Hickory, 26.
-------Dye, 443. 
INDEX.
499
High Steam, 293.
---- Pressure Engine, 282.
Highways, 202.
Hindoo Architecture, 131.
Hipped Roof, 126.
History of Printing, 68.
Hollow Backs of Fireplaces, 160.
Hcse, 13.
Horizontal Wheel, 265.
--------Wind Mill, 268.
Horn, 39.
Hornbeam,  29.
Hornblower's Engine, 288.
Horology, 364.
Horses, Attaching of, 200.
-----, Power of, 255.
Hubb, 199.
Hungarian  Machine, 321.
Hydraulic Cement, 16.
--------Ram, 323.
Hydreole, 310.
 Hydrostatic Lamp, 179.
---------Press, 316.
 Hypcethral  Temple, 137.

 lchnographic Projection, 80.
 llissus, Temple on the, 140.
 Illumination, 176.
 Imposing, 62.
 Impost, 120.
 Incipient Fracture, 46.
 Inclined Wheel, 242
 Indellible Ink, 59.
 India Ink, 429.
 Indian Red, 427.
 India Rubber, 34.
 Indigo, 440.
 Induration  by Heat, 463.
 Inertia, 194.
 Ink, 58.
 Ink, Printers', 65.
 Inlaid Work, 112.
 Insertion, 337.
 Instrumental Perspective, 77.
 Intaglios, 112.
 Intercolumniation, 137
Interposition, 337.
Intrados, 120.
Intrinsic Color, changing of, 438.
Invention of Letters, 53.
Ionic Order, 134.
Iron, 488.
----; 19.
Isinglass, 40.
Isometrical Perspective, 81.
Ivory, 39.
Ivory Black, 429.

Japanning, 434.
Jasper, 13.
Jenny, Spinning, 346.
Jewelling Watches, 384.

Kaolin, 472.
Karnac, 150.
Keel,  217.
King Posts, 126.
King's Yellow, 428.
Knee  Joint, 247.
Knives, 422.

 Lac, 36, 434.
 Lace, 356.
 Lacquering, 434.
 Lagarousse's Lever, 246.
 Lakes, 427.
 Lambert's Wheel, 264.
 Lamp Black, 429.
 Lamps, 177.
 Lamp without Flame, 188.
 Lancet Arch, 120.
 Languedoc Canal, 215.
 Lanterns, 231, 147.
 Lantern of Demosthenes, 141.
 Lapis Lazuli, 426.
 Larch, 31.
 Lateral Strain, 45.
 Lathe, 331.
 Lead, 20.
 ----, Extraction of, 403.
 ---Pipes 404.
 Leaning Tower at Pisa, 125. 
500
INDEX.
Leather, 486.
Leaves of Pinions, 231.
Lehigh Coal, 23.
Letters, 50.
Lignum Vita?, 32.
Light and Shade, 82.
----, Measurement of, 183.
----, Modes of Procuring, 190.
Lightwood, 483.
Limestone, 15.
Limit of Bulk, 48.
Line Engraving, 91.
Line of Traction, 197.
Linens, 358.
Lintel, 118.
Lithography, 100.
Litmus, 442.
Locks, 338.
Locks of Canals, 213.
Locomotion, 192.
Locomotive Steam  Engine, 210.
Locust, 26.
Logwood, 442.
Loom, 353.
Luni Marble, 8.
Lustre Ware, 474.
Luxor, 150.
Lysicrates, Monument of, 141.

Machinery, 228.
Machine Printing, 67.
Madder, 441.
Magic Porcelain, 475.
Mahogany, 31.
Maison Carree, 144-
Malleability, 42.
Maltha, 18, 23.
Manganese, 22.
Man Hole, 279.
Maple, 28.
-----Dye, 444.
Marble, 7.
Marie del Fiore, St, 123.
Marseilles Quilts, 355.
Massicot, 428.
Mastic, 36, 434.
Materials, estimation of, 42.
Materials for Waiting, 54.
Matrix, 385.
Mc Adam Roads, 203.
Measurement of Light, 183.
Measures, Architectural, 130.
Mechanical Lamp, 180.
---------Perspective, 79.
Medals, 397.
Melting Glass, 450.
Menai Bridge, 205.
Men, Power of, 254.
Mercury, 21.
Metallurgy, 385.
Metals, Extraction of, 385.
Metopes, 133.
Mezzo Tinto, 95.
Mica, 9.
Milan Cathedral, 125.
Mill, Bark, 334.
---, Barker's, 266-
----, Cider, 335.
----, Color, 336.
---, Grist, 335.
----, Stamping,  333.
---, Sugar, 334.
----, Oil, 334.
----, Parent's, 266.
---, Stone.   See  Buhrstone.
Milling of Coins, 396.
Mineral Green,  429.
Mineralizer, 385.
Minaret, 147.
Minerva, Temple of, 140.
------, Polias  Temple of, 141.
Minute Architectural, 130.
Modelling, 106.
Modillions, 135.
Module, 130.
Monopteral Temple, 137.
Moody's Machines, 352.
Moorish Arch, 120.
Mordants, 440.
Mortar, 15.
Motion of Animals, 192.
Morey's Engine, 290. 
INDEX.
501
Mortise, 127
Mortising, 337.
Mosaic, 112.
Moscow, Riding House at, 126.
Mosque of Achmet, 149.
------of St Sophia, 124.
Moulding Glass, 455.
Mouldings, 129.
Moulds, 342.
----- for Casting, 108.
Moving Forces, 253.
Mule Spinning, 351.
Mullions, 148.
Mutules, 133.
Mylassa, Sepulchre at, 145.

Nailing, 337.
Nail Making, 415.
Naples Yellow, 428.
Naptha, 23.
 Natural History, Specimens in,
 Nave, 199, 147.
 Needles, 423.
 Newcomen's Engine, 283.
 New  York Canal, 216.
 ________City Hall, 125.
 Nicaragua Wood, 442.
 Nismes, Temple at, 144.
 Noncondensing Engine, 282.
 Noria, 310.
 Novaculite, 13.

 Oak, 25.
 Obelisk, 124.
 Obelisks, 10.
 Obstruction of Pipes, 306.
 Ochres, 427.
 Ogee, 130.
 -----Arch, 120.
 Ogyve, 149.
 Oil Gas, 187.
 Oils, 34.
  Oil Mill, 334.
 — Painting, 432.
 Opus Reticulatum, 112.
 Orchestra, 138.
Orders of Architecture, 133
Ores, 385.
Oriel, 149.
Orpiment, 428.
Orthographic Projection, 80.
Overshot Wheel, 257.
Ovolo, 129.
Oxgall, 429.

Paddle Wheels, 221.
Paestum, 138.
Pagodas, 132.
 Painting, 71, 425.
------in Distemper, 431.
 ------in Fresco, 432.
         in Oil, 432.
    Paints, 426.
    Pak Fong, 403.
    Pallets, 380, 244.
    Palmer's Rail Way, 208.
489. Palmyra, Temple at, 145.
    Pandroseum, 141.
    Panoramic Views, 72.
    Pantheon at Rome, 124, 144
    Paper, 57.
    Papermaking, 361-
    Pappenheim Limestone, 8.
    Papyrus, 55.
    Parachute, 226.
    Parallel Motion, 240, 290.
    Parapet, 148.
    Parent's Mill, 266-
    Parchment, 57, 488.
    Parthenon at Athens, 140.
    Parting of Metals, 390.
    Party Gold, 393.
    Passings, 209.
    Patent Mineral Yellow, 428.
    Pavements, 202.
    Peachwood, 442.
    Pearl, White, 430.
     Peat, 24.
     Pedestal, 128.
     Pediment, 129.
     Penetration, 330.
     Pencils, Black Lead, 24. 
502
INDEX.
Pendentives, 122, 149.
Pendulum, 368.
Pendulum Spring, 370, 383.
Pentelic Marble, 8.
Pent Roof, 126.
Pepperidge, 27.
Peripteral Temple, 136, 137.
Perkins' Generator, 281
Perkins' Lock, 338.
Perpetual Screw, 233.
Persian Wheel, 309.
Persepolis, 150.
Perspective, 70.
Perspectographs, 79.
Petersburgh, Columns at, 9.
Peter the Great, Statue of, 9.
Petroleum, 23.
Persimmon, 29.
Petuntze, 472.
Pewter, 20.
Philadelphia U. S. Bank, 125.
Phcenicin, 441.
Phosphorus, 41.
Picker, 347.
Pictures, Hanging uf, 182.
Pilaster, 128.
Pillar, 149.
Pine, 29.
Pinchbeck, 400.
Pinion, 231.
Pin Making, 401-
Pinnacles, 148.
Pipes for Water, 303.
Pisa, Leaning Tower at, 125.
Pise, Building in, 117, 118.
 Piston, 289.
 Pitch, 34.
 -----Lines, 231.
 Pivots, note, 371.
 Place of Strain, 46.
 Plan, 130.
 Plate Glass, 453.
 Plaster, Casting in, 107.
 Plaster of Paris, 11.
 Platinum, 22.
 Plating, 397.
Plinth, 128.
Plumbago, 24.
Plying, 348.
Pola, Temple at, 145.
Polishing, 434.
--------Glass, 454.
--------Slate, 14.
--------Steel, 423.
Pompey's Pillar, 9.
Porcelain, 472, 473.
--------, Magic,  471.
Porphyry, 12.
Portable Gas Light, 188.
Portland Stone, 8.
Portland Vase, 474.
Portrait, Eyes of, 85.
Posticus, 135
Pottery, 466.
Power, Maintaining, 367
Powers, Moving, 253.
Precious Stones, 13.
Preservation of Food, 491.
----------of Organic Substances,
     478-
Press, Correction of, 63.
-----, Hydrostatic, 316.
-----, Printing, 65.
 Pressing Glass, 455.
Printing, 59, 66.
-------Porcelain, 471.
-------Press, 65.
 Projections, 80.
Projection of Water, 324.
 Pronaos, 135.
Propylcea at Athens, 139.
 Proscenium, 138.
 Prostyle Temple,  136.
 Prussian Blue, 426.
 Pseudo Dipteral Temple, 137.
 Puddle, 212.
 Puddling Furnace, 412.
 Pulley, Live and  Dead, 248.
 Pulpit, 138.
 Pumice, 14.
 Pump Bag, 317.
 -----, Centrifugal, 313. 
504
INDEX.
Sand Stone, 10.
Salona, Temple at, 146.
Sap Green, 429.
Sappan Wood, 442.
Sapphire, 13.
Saracenic Style,  147.
Satin Wood, 32.
Sawing, 332.
Saw Mill, 332.
Saws, 422.
Savannah Steam Ship, 222.
Saxon Architecture, 146-
Scagliola, 112.
Scapements, 244, 370.
Scarfing, 127, 337.
Scenographic Projection, 80.
Schemnitz Vessels, 321.
Schuylkill Bridge, 205.
Scissors, 420.
Scoop Wheel, 309.
Scotia, 130.
Screwing, 337.
Screw, Archimedes, 310.
-----, Perpetual, 233.
Sculpture, 106, 109.
Sealing Wax, 339.
Seasoning of Timber, 480.
Section, 130,
Sepia, 429.
Serpentine, 11.
Serpents, Motion of, 193.
Shades, 87.
Shades, Glass, 183.
Shadows, 85.
Shaft, note, 371.
----of Columns, 128.
Shafts, 212.
Shape of Timber, 48.
Shearing, 360.
Sheet Lead, 414
Shell Lac, -See Lac, 434.
----Gold, 434.
Shot, Leaden, 405.
Sidelings, 209.
Sienna, Burnt, 428.
-----, Terra di, 428.
Sienite, 9.
Signatures, 63.
Silk, 38.
Silver, 21.
----, Extraction of, 394.
Silvering of Mirrors, 407.
Silver Edges, 398-
Silversmiths' Work, 395.
Singeing, 358.
Sinkicien, Pagoda at, 149.
Single Rail, 208.
Sinumbral Lamp, 183.
Size, 40.
Size of Wheels, 196.
Skins,  37.
Skylights, 169.
Slaking of Lime, 15.
Slate, 10.
Slitting, 415.
Smalt, 427.
Smelting, 386.
-------, 408:
Smoke, Burning of, 175.
Smoky Rooms, 171.
Snail, 374.
Soap Stone, 10.
Soldering, 340.
Sources of Power, 253.
Spalatro, Temple at, 146.
Spandrells,  148.
Span of an Arch, 120.
Speculum Metal, 402.
Spelter, 22.
Spinning, 346, 351.
Spiral Gear, 231.
Spiral Pump, 311.
Splicing, 127.
Spire,  147.
Springs, 200.
Spruce, 30.
Stability of a Ship, 220.
Stamping Mill, 333.
Stained Glass, 456.
Starch, 36.
Steam, 270.
----Boats, 220. 
INDEX.
505
 Steam  Carriages, 295.
 -----  Engine, 277, 281.
 -----  Engine, History of, 291,
 -----  Guage, 279.
 -----■  Gun, 296.
 -----,  Heating by, 166.
 -----  Navigation, 292.
 -----  Power, 270
 Steel, 19.
 ----, 417.
 ----- Engraving, 99.
 Steeple, 147.
 Stereotyping, 66.
 Stiffness, 43.
 St Genevieve's Church, Paris, 1!
 Stippling, 93.
 St Marie del Fiore, 123.
 St Mark's Church, Venice, 124.
 Stone Blue, 427.
 Stones, Lithographic, 101.
 Stone Ware, 468.
 Stoves, 163.
 St Paul's, London, 123.
 St Peter's, Rome, 123.
 Strasburg Cathedral, 125.
 Strain, 42.
 Strength, 43, 46.
 -------of Materials, 42.
 Stress, 42.
 Striking Part of a Clock,  373.
 St Sophia, Mosque of, 124.
 Stucco, 11.
 Stylobate, 128.
 Stylus, 54, 58.
 Styles of Building, 127
 Sublimation, 342.
 Submarine Navigation, 224.
 Sugar Mill, 334.
 Sulphur, 24.
 Sun Dial, 364.
 Sun and  Planet Wheel, 241.
 Surbase, 128.
 Suspension Bridges, 205.
 Swell of Columns, 116
Swimming, 194.
_________Bladder of Fish, 193.
             64
  Sycamore, 28.
  Syphon, 308.
  Systyle, 137.

  Talon, 130.
  Tamarack, 31.
  Tanning, 486.
  Tapestry, 357.
  Tar, 34.
  Tarras, 17.
  Taunton Spindle.  See Danforth.
  Tawing, 488.
  Teazle, 360.
  Teeth of Wheels, 230.
i. Telford's Road, 203.
  Tempering, 419.
  Temple of Vesta, at Tivoli, 124,
  Tenacity, 43.
  Tents, Origin of, Chinese Style,
      132.
  Terra Cotta, 465.
  ----Verte, 429.
  Theatre, Grecian, 137.
  Thebes,  Ruins of, 150.
  Theodori, Tomb of, 8.
  Thermre, 143.
  Theseus, Arch of, 145.
  -------, Temple of, 139.
  Thrasyllus, Monument of,  140.
  Throttle Valve, 289.
  Throwing, 470.
  Throwing Wheel, 326.
  Tie Beam, 126.
  Tiles, 465.
 Timber, 479.
  Tin, 20, 406.
  Tinfoil, 406.
 Tin Plates, 406.
 Toggle Joint, 247
 Tombac, 400.
 Tone, 87.
 Tongueing, 337.
 Toothed Wheels, 230,
 Tophus, 8.
 Torches, 177.
 Torpedo, 225. 
506
INDEX.
Torsion, 48.
Tortoise Shell, 39.
Torus, 129.
Tower, 148.
Tower of the Winds, 141, 364.
Tracery, 149.
Tracing Paper, 92.
Traction, line of, 197.
Trajan's Column, 124.
Tram Road, 208.
Transept, 147.
Transparent Colors, 426.
Transparency of Flame, 183.
Travertino, 8.
Treadwell on Rail Roads, 209.
Triglyphs,  133.
Tripoli, 14.
Triumphal  Arches, 143.
Trundle 231.
Trussing, 126.
Tubes, 46.
Tulip Tree, 27.
Tunnels, 212.
Tupelo, 29.
Turmeric, 443.
Turncap, 174.
Turning, 331.
Turnsol, 442.
Turpeth Mineral, 428.
Turpentine, 34.
Turret, 148.
Tuscan Order, 142.
Twilling, 354.
Twisted Column, 151.
Twisting, Theory of, 343.
Tympanum, 129.
Types, 60,  61.

Ultramarine, 426.
Umber, 429.
Undershot  Wheel, 261.
Union, Modes of, 337.
Universal Joint, 233.
--------Lever, 246.

Valve* of Canals, 214.
Valves of Steam Engines, 2c?8.
Vanishing Point, 75.
Vapors of Low Temperature, 294.
Varnishing, 433.
Vases, Etruscan, 474.
Vaults,  121, 149.
Vehicles of Power, 253.
Vellum, 488.
Velocity, Change of, 235.
Velvets, 358.
Venetian Red, 427.
Ventilation, 170-
Ventilators, 171.
Venus de Medici, 8.
Verandah, 132.
Verdigris, 428
Vermillion, 427.
Vesta, Temple of, 145.
----, Temple of, at Tivoli, 124.
Vitrification, 448.
Volutes, 134.
Voussoirs, 120.

Wall, 116.
Walnut, 26, 29.
Wafers, 339-
Warping, 352.
Washing Ores, 386.
Washington, Capitol at, 125.
Watch,  Description of, 376.
Water Cements, 16.
-----Clock, 366.
-----Colors, 431-
-----, Conveying of, 302.
-----in Fuel, 154.
-----Pipes, 303.
-----Power, 257.'
-----, Raising of, 308.
-----Snail, 311.
Watt's Steam Engine, 284.
Wax, 41.
---Sealing, 339.
Weaving, 353.
Wedgewood's Ware, 468.
Weight of Fuel, 153.
Weirs, 213. 
INDEX.
507
 Weld, 443.
 Welding, 340.
 Westminster Abbey, 150.
 Whalebone, 139.
 Wheels, 195.
 Wheel, Besant's, 264.
 ------, Breast, 265.
 ------, Brush, 234.
 -----, Carriages, 195.
 ------, Chain, 260.
 -----, Contrate, 233.
 -----, Crown, 233.
 -----, Epicycloidal, 242.
 -----, Flash, 326.
 -----, Horizontal, 265.
 -----, Inclined, 242.
 -----, Lambert's, 264.
 -----, Overshot,  257.
 -----, Ratchet, 234.
 -----, Throwing, 326.
 -----, Undershot, 261.
 -----, Window, 149.
 Wheels, Form of, 199.
 Whetstone.  See Novaculite.
 White Cedar, 30, 31.
-----Lead, 430.
-----Pigments, 430.
------Ware, 468.
White Wood, 27.
Whiting, 430.
-------.  See Chalk.
Willow, 31.
Windage, 299.
Wind, Effect of, on Sails, 218.
Windmills, 268.
Windows, 170.
Wind Power, 267.
Wipers, 239.
Wire Drawing, 415.
Woad, 441.
Wood, 25.
Wooden Bridges, 204.
Wood Engravings, 99.
Wool, 38.
Woolf s Engine, 288.
Woollens, 359.
Worm, 233.
Worsted, 359.

Yellow Ochre, 428.

Zinc, 22.
----, White, 430.
Zophorus, 128.
Zurich Machine, 312. 
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