HOW TO USE 
THE 
MICROSCOPE 
BEING 
PRACTICAL HINTS ON THE SELECTION AND 
USE OF THAT INSTRUMENT. 
INTENDED FOE BEGINNERS. 
JOHN PHIN, 
EDITOR OF THE “AMERICAN JOURNAL OP MICROSCOPY.” 
FIFTH EDITION. 
THOROUGHLY REVISED AND GREATLY ENLARGED. 
Illustrated with Six Plates and Numerous Figures in the Text. 
NEW YORK: 
THE INDUSTRIAL PUBLICATION COMPANY. 
COPYRIGHT SECURED 
1882. TO 
lilrs. iCucji (3. U3inton, 
OF HAVANA, N. Y., 
IN MEMORY OF MANY PLEASANT HOURS SPENT OVER THE MICROSCOPE WITH 
DEAR ONES WHO ‘ HAVE GONE BEFORE, ” THIS LITTLE BOOK 
IS DEDICATED, 
BY HER SINCERE FRIEND, 
THE AUTHOR. OOKTEKTS. 
Dedication. - - - - - - , - - -iii 
Preface. --------- vii 
Introduction. --------- xi 
The Microscope. 
What it Is; What it Does; Different Kinds of Microscopes ; Prin- 
ciples of its Construction, and Glossary of Terms; Essential 
Parts of the Microscope; Names of the Different Pai’ts, - 15 
Simple Microscopes. 
Hand Magnifiers, with One, Two, and Three Lenses; Doublets; 
Power of Tavo or More Lenses When Used Together; Watch 
Makers’ Eye-Glasses—Single Lenses and Doublets; Engravers’ 
Glasses; Linen Provers; Stanhope Lens; Stanhope Collecting 
Microscope; Coddington Lens, Achromatic Doublets and Trip- 
lets; Twenty-five Cent Microscopes—Their Construction, and 
How to Make Them; Penny Microscopes, to Show Eels in Paste 
and Vinegar; Craig Microscope; Novelty, Globe, etc., - 28 
Dissecting Microscopes. 
Essentials of a Good Dissecting Microscope; Cheap Stands for 
Simple Microscopes; Excelsior Microscope; Raspail’s Micro- 
scope , Compact Dissecting Microscope; Binocular Dissecting 
Microscope, ---------40 
Compound Microscopes. 
Cheap Foreign Stands; French Vertical Microscopes; Conversion 
of Vertical Microscope into Collecting Microscope; the Ross 
Model; The Jackson Model; The Continental Model; The New 
American Model • Cheap American Stands; The Binocular Mi- 
croscope ; The Binocular Eye-Piece; The Inverted Microscope; 
Lithological Microscopes; The Aauarium Microscope; Micro- 
scopes for Special Purposes; “Class” Microscopes, - - 46 
Objectives. 
Defects of Common Lenses; Spherical Aberration; Chromatic 
Aberration, Use of Diaphragms; Corrected Objectives; Defining 
Power, AchromatismAberration of Form; Flatness of Field; 
Angular Aperture; Penetrating Power; Working Distance; Im- 
mersion and “Homogeneous” Lenses; Lens Systems; Duplex 
Fronts, French Triplets; Focal Length of the Numbers used to 
Designate Objectives by Naehet, Hartnack and Gundlach, - 61 IV 
CONTENTS. 
Testing Objectives. 
General Rules; Accepted Standards—Diatoms, Ruled Lines, Arti- 
ficial Star; Podura; Nobert’s Lines; Hollers Probe Platte; Table 
of Diatoms on Holler’s Probe Platte, with the Number of Lines 
to the Inch on the Several Diatoms; Methods of Testing for Flat- 
ness of Field, Penetration, etc., 84 
Selection of a Microscope foe Practical Purposes. 
Must be Adapted to Requirements and Skill of User; Microscopes 
for Botany; For Physicians; For Students; Magnifying Power 
Required; The Stand; The Stage; Mechanical Stages; Revolving 
Stage; Stages for Special Purposes; Diatom Stage, Safety Stage, 
etc.; Sub-Stage; Mirror; Body; Draw-Tube; Adjustments for 
Focussing; The Diaphragm; Objectives; High versus Low 
Angles; Eye-Pieces, - - - - - -95 
Accessory Apparatus. 
Stage Forceps; Forceps Carrier; Object Holder> Plain Slides; 
Concave Slides; Watch-Glasses; Watch-Glass Holder! Animal- 
cule Cage; Large Zoophyte Trough- Small Zoophyte Trough; 
Walmsley’s Zoophyte Trough; The Weber Slide; The Cell- 
Trough ; The Compressorium ;• Gravity Compressorium; Grow- 
ing Slides; Frog Plate; Table; Double Nose-piece, - - J27 
Illumination—Sources of Light. 
Sun-Light; Artificial Light—Candles, Gas, Lamps, Magnesium, 
Oxyhydrogen Light; Parallel, Convergent and Divergent Rays, 143 
Illumination of Opaque Objects. 
Diffused Light: Bulls-Eye Condenser; Side Reflector; The Lieber- 
kuhn; The Parabolic Reflector; Objectives with Tapered Fronts; 
Smith’s Vertical Illuminator; Tolies’Vertical Illuminator. - 147 
Illumination of Transparent Objects. 
Direct and Reflected Light: Axial or Central Light; Oblique 
Light; The Achromatic Condenser; The Webster Condenser, and 
How to Use it; Wenham’s Reflex Illuminator, and Howto Use 
It; The Wenham Prism; The Hemispherical Illuminator; The 
“ Half Button ”; The Woodward Illuminator; Tolies’ Illumina- 
ting Traverse Lens; The Spot Lens; The Parabolic Illumina- 
tor; Polarized Light, ------- 152 
How to Use the Microscope. 
General Rules; Simple Hand Magnifiers; Compound Microscopes; 
Practical Notes on Illumination; White Cloud Illumination; 
Monochromatic Light; Blue Cell; Opaque Objects; Hints to Be- 
ginners, --------- 104 
How to Use Objectives of Large Aperture. 
Illumination; Collar-Correction for Cover-Glass, - - -171 CONTENTS. 
V 
Case of the Microscope. 
Should be Kept Covered; Care of Objectives; Precautions to be 
Used when Corrosive Vapors and Liquids are Employed; To 
Protect the Objectives from Vapors which Corrode Glass; Clean- 
ing the Objectives; Cleaning the Brass Work, - - - 175 
Collecting Objects. 
Where to Find Objects; What to Look for; How to Capture Them; 
Nets: Bottle-Holders: Spoons; Collecting Walking Cane; Water 
Strainer; Wright’s Collecting Bottle; Aquaria for Microscopic 
Objects; Dipping Tubes, - - - - - - - 177 
The Preparation and Examination of Objects. 
Cutting Thin Sections of Soft Substances; Valentine’s Knife; Sec- 
tions of Wood and Bone; Improved Section Cutter; Sections of 
Bock; Knives; Scissors; Needles; Dissecting Pans and Dishes; 
Dissecting Microscopes; Separation of Deposits from Liquids; 
Preparing Whole Insects; Feet, Eyes, Tongues, Wings, etc., of 
Insects; Use of Chemical Tests; Liquids for Moistening Objects; 
Refractive Powers of Different Liquids; lod-Serum; Artificial 
lod-Serum; Covers for Keeping out Dust; Errors in Microscopic 
Observations, - - - - - - - -187 
Preservative Processes. 
General Principles; Preservative Media—Canada Balsam, Solution 
of Balsam, Colophony, Damar Medium, Glycerine, Glycerine 
Jelly, Hantzsch’s Fluid, Glycerine and Gum, Deane’s Gelatine, 
Alcohol, Thwaite’s Fluid, Beale’s Liquid, Goadby’s Fluids, Pa- 
cini’s Fluid, Castor Oil; General Rules for Applying Preservative 
Fluids, - - -- -- -- --198 
Apparatus for Mounting Objects. 
Slides; Covers; Cells; Turn-Tables—Plain, Matthew’s, Kinne’s, 
Cox’s; Cards for Making Cells; Hot-Plate; Lamps; Retort 
Stand; Centering Cards; Mounting Needles; Cover Forceps; 
Slide Holder; Water Bath; Simple Form of Spring Clip, - 206 
Cements and Varnishes. 
General Rules for Using; Gold Size, Black Japan, Brunswick 
Black, Shellac, Bell’s Cement, Sealing Wax Varnish, Colored 
Shellac, Damar Cement, Marine Glue, Liquid Glue, Dextrine, 221 
Mounting Objects. 
Mounting Transparent Objects Dry; Mounting in Balsam; Mount- 
ing in Liquids; Mounting of Whole Insects; How to Get Rid of 
Air-Bubbles; Mounting Opaque Objects; Wooden Cells; Leather 
Discs; Pierce’s Cell; Prof. Smith’s Wax Cell; Deep Cement Cell, 224 
Finishing the Slides. 
Covering with Paper; Varnishing for Preservation; Labeling; 
The Maltwood Finder, - - - - - - - 229 PREFACE TO THIRD EDITION. 
This might with propriety be called the fourth edition—the main idea 
of the work having been embodied in a pamphlet under the same title, 
published in 1873, but long since forgotten. The successive editions 
have reached their present form by accretion, rather than by develop- 
ment; like Topsey, the book has “growed,” rather than been ‘ brought 
up. and just as that young lady exhibited numerous traits which were 
inconsistent with a proper training, so this book shows patch-work and 
inequalities which do not add either to its value or its attractiveness. 
Of all this the author is fully conscious, and if he could possibly have 
secured the necessary leisure he would gladly have rewritten the entire 
volume. But pressing, or rather imperative calls upon his time, have 
px-evented this, and he has, therefore, been compelled to feel satisfied 
with such general revision and additions as were necessary to bring the 
work up to the present state of our knowledge. 
The book is still intended for beginners and has changed nothing of 
its elementary character. It is true that we have inserted a few pages 
relating to the higher class of objectives, and the accessories used with 
them, but those who do not possess such apparatus can easily skip 
these passages. 
That it is suited to the purpose for which it was intended, we have 
evidence, not only in the extended sale which it has secui’ed, but in 
the fact that it has been adopted as an auxiliary text-book in several 
of oxxr schools and colleges. 
New York, January, 1881. 
PREFACE TO SECOND EDITION 
The fact that an unusually lax-ge edition of this work has been sold in 
a comparatively short period, is, to the author, evidence that such a 
work was needed, and that the present volume has, to a certain extent, 
supplied the want. In the present edition, therefore, he has endeavored 
to introduce several important improvements, while at the same time 
the elementary character of the work remains unaltered. With a few 
very slight and unimportant exceptions, the entire matter of the former 
edition has been incorporated in the present, and in addition several 
important subjects, particularly the chapter on objectives, have been 
greatly enlarged. viii 
PREFACE. 
Many important points still remain untouched, but it is believed that 
in its present form most beginners will find” in it all the information 
that they may require upon general topics. 
As the want of all illustrations of the stands of different makers, and 
of many accessories, has been urged as an objection to the first edition, 
and as we have not deemed it advisable to fully supply this omission in 
the present issue, a word of explanation may not be out of place. One 
great object in view in the preparation of this book was the furnishing 
of a cheap manual for those who cannot afford the more expensive books 
of Carpenter, Beale, Frey, etc. To have given anything like a fair rep- 
resentation of the products of the different makers of this country and 
of Europe, would have nearly doubled the size and price of the volume. 
But if the reader will examine the engravings of stands, etc., in the 
books just mentioned, he will find that, even in the best of them, these 
illustrations are mere reproductions of the figures found in the descrip- 
tive lists of the various dealers. As new editions of these lists are being 
constantly issued, and as they may in most cases be obtained without 
cost from those that publish them, we have thought it best to refer our 
readers to these catalogues for information in regard to the construct!c*n 
of the instruments of different makers. For the addresses of the promi- 
nent microscope makers of this country and Europe we refer our 
readers to “ The Microscopist’s Annual.” 
In this, as in the previous edition, we have omitted all descriptions of 
objects, believing that the proper aim of a book on the microscope 
should not be to teach the general principles of botany, zoology or 
histology, but simply the best methods of using the microscope in the 
pursuit of these studies. The proper books in which to find a descrip- 
tion of objects, are those which treat of that department of science which 
takes cognizance of the special subject under consideration. The 
present volume is intended merely as a guide to the best general 
methods of using the microscope. 
It has been a source of great satisfaction to the author to be assured 
by those whom he deems good authority, that this little book has done 
much to foster the use of the microscope in this country, and he hopes 
that the present improved edition will tend to still further increase the 
deep interest which is already felt in an instrument which has done 
more than any other to extend our knowledge of organic nature. 
New York. August, 1877. PREFACE. 
The Microscope and its applications in the Arts, and in general science, 
having deservedly occupied a prominent place in the pages of' The Tech- 
nologist, ob Indhstbial Monthly, a very large number of enquiries in 
regard to the best methods of using and applying this useful instrument 
have been directed to us. It would have been easy to answer these en- 
quiries by a reference to some one of the many treatises that have been 
published on this subject, but as most of these works are expensive, and 
as many of our correspondents desire an answer in a more concise and 
simple shape, we have endeavored to give, in cheap and compact form, the 
information that is most usually demanded. 
It is an unfortunate fact that while the microscope is daily growing in 
favor with those who know anything of its achievements, the operations 
of certain parties, too well known to the public, have brought a certain 
degree of suspicion upon all attempts to popularize this most valuable 
instrument. Microscopes, varying in price from twenty-five cents to two 
dollars and a half have been offered for sale, and the claim made for them 
that they are capable of showing clearly the structure of the more min- 
ute tissues, and that they may be used to advantage by physicians and 
naturalists. To the young student whose means are limited, anfi to the 
country practitioner, whose ability to supply himself with needed books 
and instruments often falls far short of his desires, the offer of a service- 
able microscope for a couple of dollars is a great temptation, and when 
the instrument in question is endorsed by a long list of clergymen, law- 
yers, and even editors, this temptation becomes irresistible. And if the 
purchaser should happen to be unfamiliar with really good microscopes, 
and unable to discriminate between a clear and accurately defined view 
of any object and one that is distorted and incorrect, he may be led to use 
it, and so fall into the most serious mistakes. That this, unfortunately, 
does happen too often must be well known to all who are familiar with the 
subject, and it is within our own knowledge that the most worthless cari- X 
cature of a microscope has been purchased and used under such circum- 
stances. 
PREFACE. 
We indulge a faint hope that the information conveyed in the following 
pages will enable the inexperienced reader to avoid these mistakes, and to 
assign a proper value to the certificates of clergymen and editors who 
vouch for the excellence of articles concerning whose properties and uses 
they are profoundly ignorant. These two classes we single out for repro- 
bation, because—in this respect, at least—they seem to be sinners above 
all other men. 
As stated in the title page, it is intended for beginners, and not for 
beginners in the use of the microscope only, but for those who have had 
little or no experience in the use of instruments of any kind. Hence the 
directions that are given are of the very simplest kind, and all theoretical 
explanations have been avoided, for the reason that any person that is 
desirous of studying the optical principles upon which the microscope is 
constructed will find in the ordinary text books on natural philosophy all 
the information he may want. Our object has been solely to impart such 
information as will enable the reader to make a beginning in the practice 
of microscopy, hoping that the start thus given will lead him to proceed 
with his studies, and ultimately acquire that knowledge, skill and dexter- 
ity which will enable him to avail himself of the extraordinary powers and 
advantages which the use of this instrument confers, both in scientific 
pursuits and in everyday life. Above all things, therefore, we have en- 
deavored to be accurate in our statements and judicious in our directions, 
and the reader is assured that no processes or methods are given which 
we ourselves have not frequently and successfully put in practice. 
New Yorle, January. 1875. 
JOHN THIN. INTRODUCTION. 
Thousands of microscopes throughout the country are at the pres- 
ent day lying idle, simply because their owners do not know how to 
use them. If properly employed they might be made to afford an 
incalculable amount of instruction and amusement; but, as it is, they 
are a drag upon the popularization of science, because they convey 
the idea that the microscope is a difficult instrument to use, and 
that it is not of much account after we have learned to use it. The 
owners of these microscopes have examined all the mounted objects 
at their command, the entire number of which probably does not 
exceed two or three dozen, and they have no information as to the 
best methods of preparing common objects for examination or pre- 
servation. Even the objects that they possess have never been ex- 
plained to them, and are merely pretty toys. The fly’s eye is inter- 
esting because it looks like a piece of netting, aud the butterfly’s 
wing is attractive because it is probably a little more brilliant than 
the most brilliant silk dress, but neither of these objects interests of 
itself and because of its beautiful structure. 
Moreover it often happens that an instrument which, when first 
purchased, was of very fair quality, has, through ignorance and 
carelessness, become so soiled and dimmed that it no longer serves 
the purpose intended. On more than one occasion have we seen a 
fine microscope leave the dealer’s hands in excellent order, and re- 
turn in a week entirely unfit for use. Microscopes in this condition, 
instead of being a source of instruction and pleasure, are an eyesore 
and an occasion of annoyance. They continually serve as reminders 
of awkwardness and failure, of wasted time aud ill-spent money. 
And yet with proper instruction and a due amount of care all this 
might have been avoided. 
It is also a fact to be regretted that heretofore the microscope has 
not been extensively employed in the arts, and in everyday life, 
simply because practical men have not been taught how to use it, 
and consequently have been unable to avail themselves of the advan- 
tages which it offers; but if carefully and judiciously selected, and 
properly handled, it is capable of affording an amount and kind of 
assistance which cannot be safely neglected. It may be made to aid 
in the examination of raw materials, and of the finer kinds of work; 
it will enable us to measure spaces which would otherwise be inap- 
preciable, and this, in an age when even in ordinary machine shops 
the thousandth part of an inch is frequently an important quantity, 
renders it indispensable to the careful and skillful mechanic; on the XII 
INTRODUCTION. 
farm it will enable the agriculturist to examine closely and minutely 
the various noxious insects and forms of fuugi and blight, and thus 
aid him in identifying them and applying the proper remedy; and 
in the examination of minute seeds, such as timothy, clover, etc., it 
will prove a very valuable assistant, enabling him to detect any in- 
feriority in the quality, or any impurity or adulteration. Frequently 
the agricultural seeds offered in market contain minute seeds of of- 
fensive weeds, many of which are so small that they are not easily dis- 
covered by the naked eye. 
Every farmer and mechanic knows the value of a good pair of 
eyes, and he also knows that an agent which doubles or trebles our 
power in any given direction at once confers upon us in that respect 
a superiority over our fellows. Very few men are twice as strong as 
their comrades; still fewer have three times the strength of ordinary 
men, and it may be safely affirmed that no man possesses the power 
of ten ordinary men. But a microscope of very ordinary capacity at 
once multiplies our powers of sight by ten, twenty, or even a hun- 
dred times, while those of the better class enable us to see things 
with a keenness and clearness which, when compared with that af- 
forded by the naked eye, is as more than a thousand to one. 
There are four distinct and important directions in which a mi- 
croscope may be made to serve us: 1. It is capable of affording the 
most refined and elevating kind of pleasure by the exhibition of ob- 
jectsof extreme beauty and interest. There are few more splendid 
sights than the gorgeous colors displayed by some objects when 
viewed by polarized light, and even the tints of certain minerals, 
and the brilliant scales of certain insects, when viewed as opaque 
objects, by means of a good condenser, surpass anything that is 
familiar to us in our ordinary experience. On the other hand the 
exquisite beauty of form which is characteristic of most of the ob- 
j ects with which the microscopist concerns himself can be fully ap- 
preciated only by those who have seen them. As a source of inno- 
cent amusement and pleasure, therefore, the microscope has few or 
no equals; for it may be safely affirmed that a five-dollar instrument 
is capable of affording gratification of greater variety and intensity, 
and of longer continuance, than that yielded by anything else of 
the same cost. This arises chiefly from the fact that most other in- 
struments, when once exhibited, with their slides or fixtures, lose 
their freshness and interest, and become old. While for the micro- 
scope, a few fibres of wool from the carpet, a few grains of sand from 
the sea-shore, or a handful of wild flowers from the field, yield ob- 
jects of surpassing beauty. Everything in nature and in art may be xiix 
subjected to inspection by it, and will then disclose new beauties 
and fresh sources of knowledge. Under it the point of the finest 
cambric needle looks like a crow-bar, grooved and seamed with 
scratches; the eye of the fly is seen to consist of thousands of eyes; 
and the dust on the butterfly’s wing appears to be what it really is, 
scales laid on with all the regularity of shingles or slates on a house; 
while to prepare and examine these simple objects requires no great 
skill and no elaborate apparatus. 
INTBODTJOTION. 
2. As a means of imparting instruction to the young, the micros- 
cope has now become indispensable. The changes which of late 
years have taken place in the views held by our ablest men in regard 
to the best education are too well known to need even mention. 
No education that does not include a knowledge of natural science 
is now regarded as complete, and there is a very wide range of the 
most essential and practical knowledge that can be reached only 
through the microscope. Thus, when we look at a leaf with the 
naked eye, we see but a green mass of matter, possessing a certain 
beautiful form, it is true, bnt disclosing none of those organs which 
render it more complicated and wonderful than anything ever pro- 
duced by our most skilful mechanics. Looked at by the micro- 
scope, however, this same leaf is found to be made up of innumer- 
able parts, each one of which is highly complex and beautiful; it is 
furnished with mouths for breathing, with cells for storing, digest- 
ing and assimilating nutriment, and with ribs for strengthening its 
structure; and all this, which is perfectly invisible to the unassisted 
vision, becomes distinct and obvious when we call to our aid a 
microscope of even moderate power. It is true that much of this 
may be taught by means of books, engravings and verbal descrip- 
tions, but every one knows that for distinctness and impressiveness 
the very best engravings fall far short of a view of the real object. 
3. As an instrument of research, the microscope now occupies a 
position which is second to none. There is hardly any department 
of science in which a student can hope to reach eminence without a 
familiarity with the microscope. Botany and Zoology have been 
developed almost wholly by its aid, and so necessary is it in the 
study of these sciences, that Schleiden, one of the most successful 
of investigators says of it: “ He who expects to become a botanist 
or a zoologist without using the microscope, is, to say the least of 
him, as great a fool as he who wishes to study the heavens without a 
telescope.” In chemistry its services have been very important, and 
in geology and mineralogy it has opened up new fields of research 
which almost promise to revolutionize these sciences. Medicine has xiy 
INTRODUCTION. 
long acknowledged the microscope as one of its most efficient as- 
sistants, and in the practice of the best physicians it is regarded as 
an indispensable means of diagnosis in some diseases. 
4. As an assistant in the arts. Its importance in this department 
is but just beginning to be recognized, and in a former paragraph 
we have endeavored to point out a few of the subjects to which it 
may be applied with good hopes of success. 
These important and obvious advantages are not difficult to secure, 
provided we avoid two mistakes which are very commonly made by 
beginners. One of these consists in supposing that it is only by 
means of very expensive and complicated instruments that anything 
of value can be accomplished in microscopy. Now while it is cer- 
tain that, in some departments of study, none but the very best 
microscopes are of any value at all, it is equally certain that a very 
wide range of study and of practical work can be thoroughly culti- 
vated by means of apparatus of very moderate cost, and of great 
simplicity of construction. The great discoveries of Ehrenberg, 
which opened up entire new fields of research and of thought, were 
made with a microscope which at the present day would not com- 
mand $25. Indeed some of the French instruments that are sold 
for $15 will show a very large proportion of the objects that are 
figured in his earlier works. Most of the great anatomical and 
botanical discoveries were made with simple microscopes of no great 
power, and it is not many years since one of the most successful 
workers in the field of botany gave it as his opinion that a power of 
300 diameters is capable of showing everything that is of impor- 
tance in this science. 
The other error is of precisely the opposite kind. It is not at all 
unusual to meet persons who seem to think that all that is necessary 
in order to become a microscopist is to buy a microscope and place 
objects under it! Such people always entertain an exaggerated idea 
of the power of the microscope as an instrument of research. For 
example, they think that in order to detect adulteration all that is 
.necessary is to place a sample under the microscope, when all im- 
purities will at once stand out conspicuously! To their imagination 
every blood corpuscle is clearly marked with the name of the animal 
from which it was obtained! 
Truth lies between these extremes. No progress can be made 
without steady application and persistent labor, but any person of 
fair average ability and a moderate degree of perseverance can soon 
learn to follow the beaten track at least, if not to branch out into 
original research. THE SELECTION AND USE 
OF 
THE MICEOSCOPE. 
Wliat is a Microscope ?—The microscope is an instru- 
ment which enables us to see either very minute objects or 
very minute parts of large objects. It is a very popular idea 
that the name microscope is applicable only to complex instru- 
ments of considerable power; but this is clearly wrong. A ten 
cent magnifying glass has as good a right to the name micro- 
scope as has a complicated binocular instrument with all the 
latest improvements. By common consent, however, the small 
hand instruments, without stands, are generally called magni- 
fiers. An attempt has been made to introduce the foreign word 
loupe as an equivalent of magnifier. The word loupe is, how- 
ever, superfluous, and is used only by ostentatious pedants, and 
by foreigners who are ignorant of English. 
Wliat tlie .Microscope Does.—It is well known that 
the further off any object is, the less it appears. A house at a 
distance appears less than a man who is close by, and the dis- 
tinctness with which an object is seen depends largely upon its 
apparent size. Thus, at a distance, a house not only appears 
very small, but the windows cannot be distinguished from the 
rest of the building. As we draw nearer it becomes apparently 
larger, and the different parts become more distinct. First the 
windows are seen clearly, then the individual of glass, 
then the bricks, and finally the grains of the material of which 
the bricks are made. When, however, we approach too closely 
we again find it impossible to see distinctly, as may easily be 16 
SELECTION AND tTSE 
proved by a very simple experiment. Place some fine print, 
such, for example, as the present page, at a distance of six feet 
from the eye, and gradually move closer to it. At six feet the 
letters will be indistinguishable; at two feet they will be quite 
distinct; at one foot still more distinct; at three inches they 
will be quite blurred. There is, therefore, a limit to the degree 
of closeness with which we can approach any object for the 
purpose of examining it, and the object of a microscope is to 
enable us to get close to it, as it were, without blurring our 
view. If, without changing the distance of the eye from the 
paper (three inches) we introduce between the two a lens of one 
inch focus, and bring it into proper position, we will find that 
the indistinctness formerly complained of disappears, and the 
object is now not only seen clearly, but appears very much 
magnified. That objects appear large in proportion to their 
nearness to the eye may be thus shown: Take two slips of 
paper printed with type of the same size (two clippings from a 
newspaper answer well) and place one at a distance of ten 
inches from the eye and the other at a distance of five inches— 
the edge of the upper slip being placed so as to lie about the 
middle of the lower one. In this way we can readily compare 
the apparent sizes of the type on the two slips, and one will be 
found to appear just twice as large as the other, though, of 
course, we have the evidence of our senses to prove that they 
are precisely of the same size. Moreover, as the usual distance 
for distinct vision is about ten inches, in persons of middle 
age, it will be found that a lens which enables us to view any 
object clearly and distinctly from a distance of,one inch, will 
enable us to see it just ten times larger and ten times more dis- 
tinctly than we could do when looking at it from a distance of 
ten inches. A consideration of these facts led the late Dr. 
Goring to propose the name engiscope as a substitute for the 
word microscope—the word engiscope signifying to see things 
at a very short distance. 
The facts which we have just detailed must, however, be re- 
garded as illustrations, rather than explanations of the action of 
the microscope. It is evident that the power of a lens to in- 
crease the distinctness with which any object is seen, depends 
not only upon the action of the lens upon the rays of light, but 
upon the influence which such modified light exerts upon the OF THE MICROSCOPE. 
17 
organs of vision. Now, the eye, considered merely as an optical 
instrument, is in reality a small camera ohscura in which the 
cornea, crystalline lens, and other transparent portions, combine 
to throw upon the retina an image of external objects. That 
the transparent portions of the eye do in fact act as a lens, and 
throw a real image upon the retina or posterior portion of the 
eye, is easily shown by taking the fresh eye of an ox and grad- 
ually shaving off the coating at the back until it becomes 
transparent. If the eye, so prepared, be then held towards 
a window or any very bright object, a distinct but inverted 
image of the window or other object will be seen on the coat 
of the eye. 
The action of the eye in this case is the same as that of a 
lens, and the general mode of action of lenses under such cir- 
cumstances may be easily illustrated by means of a common 
hand magnifier or even a spectacle glass. If the reader will 
hold before a window, at a distance of, say, six feet, a sheet of 
white paper, and will place a magnifier in front of the paper, 
then by properly adjusting the distance between the magnifier 
and the paper, a picture of the window will be thrown on the 
latter. If the magnifier and paper be now removed to a dis- 
tance of twelve feet from the window, the picture of the latter 
will be only half as large as it was in the first place, and it will 
also be found that the distance of the lens from the paper will 
have to be readjusted and made less. 
That the eye possesses this power of adjustment we are all 
conscious, for we feel that if, when the eye is adjusted for the 
distinct vision of distant objects, we suddenly look at those 
which are near, the condition of the eye requires to be changed 
before a distinct view can be had, and to make this change 
requires an effort of which we are perfectly conscious. 
When a lens is held in front of a sheet of paper, so as to 
throw on the latter a distinct image of the objects in front of 
it, the distance between the paper and the lens is called the 
focal distance or focal length of the latter. This, as we have 
just seen, varies with the distance of the object which gives the 
image. In order, therefore, to secure a standard in this 
respect the object selected is always one whose distance is so 
great that it may be practically regarded as infinite. ' 18 
SELECTION AND USE 
When we examine an object, first at a distance, and then 
close at hand, we see it through the medium of two different 
sets of rays, those in the latter case entering the eye in such a 
direction that the image thrown on the retina is larger than the 
image produced when the object is more distant. The lens acts, 
however, by bending the rays so that the same set, which, if 
allowed to pursue their natural direction would not produce a 
distinct image, are caused to enter the eye in such a direction that 
the image is large and clear. The manner in which the lens acts 
to produce these effects is not difficult to understand. It is true 
that the ultimate causes which produce these phenomena are 
beyond our knowledge, but in this respect the ablest philos- 
opher has very little advantage over the veriest tyro. It may 
be difficult also for the general reader to follow the mathe- 
matical demonstrations of the action of lenses. There are, 
however, a few simple facts which are easily understood, or at 
least demonstrated and accepted as facts, and which, when 
clearly and firmly grasped by the mind, render the construction 
of the microscope comparatively easy of comprehension. 
There are two ways in which the subject may be studied. 
We may examine the facts experimentally, by using lenses 
and actual eyes in the way we have described, or we may fol- 
low the course of the rays as laid down in any good book on 
optics. A combination of both methods will of course give 
the clearest views on the subject, and we would therefore ad- 
vise the reader to provide himself with a few lenses of various 
degrees of curvature, and consequently of various magnifying 
powers, and test all the statements made in the text. He will 
thus acquire such a practical knowledge of the action of lenses 
as can be obtained in no other way. For this purpose the 
cheapest lenses are good enough. One or two cheap magni- 
fiers and a few glasses from old spectacles will serve every pur- 
pose. The simplest methods of arranging such lenses will be 
found in a note on a subsequent page, and although very ac- 
curately made tools are required for the construction of ser- 
viceable optical instruments, it will be found that a very 
large number of simple but valuable experiments may be 
worked out with the aid of a few wooden rollers and a little 
paper and paste. OF THE MICROSCOPE. 
19 
While the magnifying power of lenses depends upon their 
focal length, this in turn depends upon the material of which 
the lens is made, and also upon the curvature given to its sur- 
faces. Lenses of precisely the same form, and made respect- 
ively of diamond, flint glass, crown glass and Canada balsam 
would possess different magnifying powers; the diamond mag- 
nifying most, the flint glass next, crown glass next, and Canada 
balsam least of all. On the other hand, of two lenses composed 
of the same material, that which has the sharpest curvature to 
its surfaces will magnify most. Now, on reflection, it will be 
evident to even the least mathematical mind that lenses which 
have very sharp or quick curves must of necessity be small. 
Suppose the curve which bounds the figure of a lens has a 
radius of half an inch, it is evident that the largest lens which 
could be made with this curve would be one inch in diameter, 
and then it would be a perfect sphere. Most lenses, however, 
resemble thin slices off the spheres, or in some cases two such 
slices joined together, so that the diameter of the lens is in 
general greatly less than the radius of the curves which form 
its surface. Therefore, we see that all lenses of high power are 
of necessity small, and when lenses are required of very high 
power they become so minute as to be handled only with great 
difficulty. Indeed, before the modern improvements in the 
microscope, many of the lenses used by scientific men were 
nothing more than little globules of glass, brought to a round 
form by fusion. 
We have made this lengthened explanation of a very simple 
matter because we have found amongst beginners in micro- 
scopy a very general idea that large lenses are the most power- 
ful. “ Send me one of your largest and most powerful mag- 
nifiers,” is an order with which every optician is familiar, and 
yet such an order contains a contradiction in terms. A lens 
cannot possibly be large and magnify greatly at the same time. 
The Different Kinds of Microscopes.—Microscopes 
are divided into two classes—simple and compound—the dif- 
ference between them being purely optical, and not mechanical; 
for a simple microscope may be very complex and expensive, 
while, on the other hand, a microscope may be compound and 20 
SELECTION AND USE 
yet contain very few parts. Thus the little vertical French 
microscopes, which cost only $2,50, are compound, although 
very simple in construction, while a simple microscope, if bin- 
ocular, and provided with all desirable adjustments, might be 
a very complicated affair. The difference between simple and 
compound microscopes is this: in the simple microscope we 
look at the object directly, while in the compound microscope 
we look at a magnified image of the object. In the simple 
microscope, objects are always seen in their natural position, 
while in the compound microscope they are inverted, and right 
becomes left, and left becomes right. This makes it very diffi- 
cult for beginners to work upon objects under the compound 
microscope; and hence simple microscopes are almost always 
used for dissecting and botanizing. 
It is true that by adding more lenses, and making the instru- 
ment still more compound, we can again invert the image, and 
thus bring it back to its original and natural position, and 
almost all the very expensive microscopes are furnished with 
these extra lenses arranged in a piece of accessory apparatus 
technically known as an erector. The distinguishing feature of 
the compound microscope remains, however, the same. Certain 
forms of the microscope, in which concave lenses are substi- 
tuted for the usual convex form, also give erect images, but 
this does not affect the general truth of the statement just 
made. 
Simple microscopes frequently consist of more than one 
l,ens. Thus, in using the ordinary pocket magnifiers with two 
or three lenses, it is usual to employ all the lenses at once, look- 
ing at the object through two.or three lenses at the same time 
when a high power is required. In this case, however, the two 
or three lenses are placed close together and act in the same 
way as a single lens, with surfaces more sharply curved than 
those of any of the lenses forming the combination. Under 
such circumstances the image is not inverted, but if we now 
separate the lenses sufficiently, we will find that on again bring- 
ing the object into focus, the image is inverted and greatly 
enlarged. Moreover, it will be found that the magnifying 
power may be greatly increased by increasing the distance be- 
tween the two lenses, and it will also be found that as the dis- OF THE MICROSCOPE. 
21 
tance of the two lenses from each other is increased, the dis- 
tance at which the combination is placed from the object must 
be made less and vice versa.* 
The early forms of the compound microscope consisted of 
little more than the two lenses we have just described, but the 
modern instrument, even in its simplest form, is a vastly more 
complicated arrangement. In the best forms, for the lens next 
the eye there is substituted an eye-piece consisting of two lenses 
with a diaphragm between them, while the objective, or lens next 
the object, is composed of from four to ten different pieces of 
glass, forming two or more lenses, which are so arranged that 
each shall correct the defects of the others, and this optical 
combination is mounted on a stand which is sometimes a mar- 
vel of mechanical ingenuity. 
*The student who possesses a little mechanical genius and a desire to 
become experimentally acquainted with the properties of lenses and the 
construction of the microscope, would do well to procure a couple of cheap 
lenses, say one of half inch focus, and one of about two inches focus, and test 
by actual trial the statements made in the text. Such lenses may be con- 
veniently arranged in a tube formed of writing paper and gummed on the 
edges. All the most important properties and defects of lenses may be thus 
illustrated and studied. By means of a little extra care, two such lenses, ar- 
ranged as we have described, in tubes blackened on the inside, and mounted 
on a little wooden stand, the focus bBing adjusted by sliding the tube hold- 
ing the lenses within another tube, also of paper, will give not only a very 
fair view of such objects as the wing of a fly, the scales on a butterfly’s wing, 
and even the barbs on the sting of a bee, but it will show the globules of 
blood quite distinctly, and we have even given a very interesting exhibi- 
tion of the circulation of the blood in the foot of a frog by means of a 
temporary arrangement of this kind, which we put together for the pur- 
pose of explaining to a little girl the construction of the microscope. We 
would not recommend any one to use such a microscope for purposes of 
work or study, because the fallacies to which it may give rise are too 
numerous and too serious. But any boy, or even girl, who will undertake 
the construction of such an instrument, cannot fail to obtain thereby an 
amount of information which the perusal of volumes would not give. As 
hints towards aiding our young friends, we may remark that our tubes 
were made of the best stiff paper, rolled up tight and pasted only along 
the outer edge. The lenses were secured in their places by being attached 
to the bottoms of pill-boxes, holes being punched through to admit the 
light. Pill-boxes with holes were also used for diaphragms to reduce the 
effects of aberration. A piece of mirror reflected the light, and the sides 
etc., of an old cigar box furnished material for the stand. Fifty cents 
covered all expenses. 22 
SELECTION AND USE 
Essential Parts of the Microscope.—When a good 
lens is held steadily at a certain distance from an object which 
is properly illuminated, this distance depending upon the form 
and material of the lens, we are enabled to see the object clearly 
and distinctly. When, however, this distance is either in- 
creased or diminished, the object becomes blurred and indis- 
tinct. The point at which vision is most distinct is called the 
focus* of the lens, and when we are able to see it clearly the 
object is said to be in focus; when the distance is either in- 
creased or diminished, it is said to be out of focus. An object 
is said to be within the focus when the lens is too near it, and 
beyond the focus when the lens is too far away. 
The performance of any lens depends greatly upon the ac- 
curacy with which it is adjusted to the correct focal distance, 
and the steadiness with which it is held there. For all ordi- 
nary purposes, lenses which do not magnify more than ten 
diameters may be very conveniently held in the hand without 
any special means of support; but when the power is much 
greater than this, or where, as in the compound instrument, 
the microscope is bulky and heavy, it becomes necessary to use 
some mechanical contrivance which will hold the microscope 
steadily in its position in relation to the object, otherwise the 
view becomes indistinct, Thus’h good lens, magnifying from 
thirty to forty diameters, will very readily show the individual 
corpuscles or globules in the blood of the frog, provided it is 
arranged on a steady support and accurately adjusted for focus. 
But if the lens be merely held in the hand, without any firm 
support, it will be impossible for the observer to see the 
corpuscles. 
Another important point is the illumination of the object. 
Unless the object be properly illuminated it cannot be dis- 
* It is scarcely necessary to inform the reader that the focus described 
in the text is not precisely the focus of the lens itself, but the focus of a 
compound lens of which the eye forms one element. Hence the focal 
distance varies with different eyes, and so does the apparent size of ob- 
jects. To short-sighted people objects appear of larger size than they do 
to persons of ordinary eye-sight. In working with the compound micro- 
scope we frequently find that different people require a different focal 
adjustment. OF THE MICKOSCOPE. 
23 
tinctly seen, and consequently all microscopes, except the 
simplest forms of hand magnifiers, are provided with means 
for throwing the light upon the object, and for regulating the 
amount wdiich shall either fall upon it or pass through it. 
Hence the importance of providing efficient means for ad- 
justing the focus and holding and illuminating the object, and 
the purpose which the stand is intended to fulfil, is to furnish 
these means in a compact and convenient form. Every micro- 
scope, therefore, of a grade above a hand magnifier, whether 
it be simple or compound, must possess : 
1. Suitable means for supporting the object, and placing and 
maintaining it in proper position. 
2. Means for illuminating the object, either by throwing the 
light upon it when it is opaque, or transmitting the light 
through it when it is transparent. 
3. Means for transmitting to the eye an enlarged image of the 
object. 
The different parts which are employed for securing these 
several ends, have been constructed of an almost endless va- 
riety of forms, according to the fancies of the different makers 
and the requirements of different microscopists. As it is im- 
portant that the student should familiarize himself with the 
names of these different parts, we give a definition of them, 
and in order that there may be no opportunity for mistake or 
misapprehension, we have also engraved an outline of one of 
the ordinary forms of the microscope, and on this we have 
marked the names of the different parts. 
NAMES OF THE DIFFERENT PARTS. 
The following are the names of the essential parts of a com- 
pound microscope of ordinary construction. The names of the 
different parts of the simple microscope are the same as those 
of the compound microscope, but the latter has several parts 
which do not exist in the former. 
The Stand is the name properly applied to the entire frame 
used for supporting and illuminating the object, and for carry- 
ing and adjusting the optical part, the latter consisting of the SELECTION AND USE 
24 
Fig. 1.—DIAGRAM SHOWING THE DIFFERENT PARTS OP THE MICRO- 
SCOPE, AND THEIR NAMES. OF THE MICBOSCOPE, 
25 
eye-piece and the objective. Stands are frequently sold separ- 
ately, or furnished with eye-pieces only—the purchaser making 
such a selection of objectives and other accessories, as may best 
suit his special needs. 
The Base or Foot is that part which supports the rest of the 
stand. 
The Body is the tube to which the eye-piece and objectives 
arc attached. 
A Draw-tube is a secondary body which receives the eye-piece, 
and slides within the main body like the draw of a telescope. 
It enables us to increase the distance between the eye-piece and 
the objective, and thus to change the magnifying power, as 
explained in a previous paragraph. 
A Collar is a short tube through which either the body, the 
draw-tube, or the eyc-jhece slides. 
The Arm is that part which carries the body. 
The Stage is the plate upon which the object is placed for 
examination. 
Clips are springs attached to the stage for the purpose of 
holding in place the glass slide or plate carrying the object. 
A Sub-stage is furnished with some instruments. It is used 
for holding and centering various means of illumination. No 
sub-stage is shown in the diagram, Fig. 1. The sub-stage, with 
its centering arrangements, is shown very clearly in the Koss 
model, Plate I. 
Sub-stage Ring.—Instead of being provided with a sub-stage, 
many cheap microscopes are furnished with what is known as 
a sub-stage ring or tube. This serves to receive the polarizer, 
paraboloid, etc. 
The Object-Glass or Objective is the lens or lenses which are 
placed next the object. The term Object-glass is sometimes 
applied to the glass plate or slide upon which the object is 
placed, but this use of the word is entirely wrong, and tends to 
produce confusion. 
The Society Screw is a screw of a certain standard size for con- 
necting the objective to the body. In microscopes furnished 
with a screw of the Society’s standard, the. objectives of any 
American or English maker may be used. The makers on the 
continent of Europe have now very generally adopted the So- 
ciety Screw. In this country the Society Screw has been uni- 
versally adopted, but as it has been found too small for low- 
power objectives of wide angle, another screw, named the 26 
SELECTION AND USE 
Broad Gauge, is sometimes used in addition to the Society 
Screw. 
In all microscopes, means are provided for moving the objec- 
tive to and from the object, so as to bring the latter into focus, 
as it is called. According as the device used for this purpose 
acts coarsely but rapidly, or slowly but delicately, it is called 
a coarse or a fine adjustment. The best microscopes are provided 
with both kinds, so that the object is first brought approxi- 
mately, but rapidly, into focus by one, and then adjusted more 
slowly, but with great accuracy, by the other. 
Tlie Coarse Adjustment has several forms. In Fig. 1 it consists 
of a rack and pinion. In some cases it is a chain movement; 
very often it is effected by merely sliding the body np and 
down through a tubular collar by hand, as in Fig. 12. 
The Fine Adjustment usually consists of a fine screw, some- 
times called, improperly, a micrometer screw, which moves either 
the entire body or the lower part of it, called the nose-piece. 
In some cheap stands, the fine adjustment is effected by moving 
the stage towards the objective. 
The Nose-piece is a short tube, which fits into the lower end 
of the body, and carries the Society screw at its lower end. 
Sometimes it is made to slide out and in, and thus forms part 
of the fine adjustment. In the instrument figured in the dia- 
gram, it is immovable. The term nose-piece is also applied to 
certain accessories which enable us to attach different pieces of 
apparatus to the microscope, as, for example, two or more ob- 
jectives at one time, the analyzer of the polariscope, etc. 
A Diaphragm is usually a thin plate of metal pierced with a 
hole, the size of which regulates the diameter of the pencil of 
rays that pass through. There is a diaphragm in the eye-piece 
which contracts the field of view, and cuts off those x-ays which 
tend to confuse the images, and all good microscopes have a dia- 
phragm attached to the stage, whereby the amount of light 
2iassing through the object to the objective may be regulated. 
Instead of a thin plate of metal, an arrangement known as the 
“Iris diaphragm” is used in the microscope shown in the 
diagram. 
The Eye-piece or Ocular is the short brass tube, with its lenses, 
which is next the eye. The eye-piece contains an Eye-Glass, 
which is that next the eye ; a Field-Glass, placed next the 
objective, and a Diaphragm, consisting of a brass plate with a 
hole through it, and so arranged as to cut off the outer rays of 
light. The tube in which these lenses are secured is in almost 
all eases removable, and the best microscopes are furnished OF TICK MICROSCOPE. 
27 
with several eye-pieces of different powers, wliicli may be 
changed at pleasure. We may here remark that where a mi- 
croscope is furnished with several eye-pieces, the shortest eye- 
piece gives the greatest magnifying power. 
The Cap is a cover which fits over the top of the eye-piece. 
It is pierced with a hole, to allow the rays which pass through 
the instrument to reach the eye. This cap is sometimes covered 
with a second cap, which has no hole, but which is intended 
to exclude dust from the eye-lens, and which is removed when 
the instrument is in use. 
The Mirror reflects the light, and causes it either to fall 
upon the object or to pass through it, so as to render it 
visible. 
The Mirror-bar is a bar attached to the stand and carrying 
the mirror. It is usually made to turn on a pivot, and in the 
microscope shown in Fig. 1, it consists of two parts sliding 
upon each other, so that it may be shortened or lengthened, as 
circumstances require. 
Accessories are those parts of the microscope which are used 
only for special purposes, such as the paraboloid, the camera 
lucida, stage forceps, etc. 
The Object is that which is subjected to examination. It is 
usually mounted upon 
A Slide, or plate of glass, which is laid upon the stage. 
All these parts will he fully described in a subsequent part 
of this volume, and their utility and importance explained. It 
is greatly to be desired that the young micro,scopist should 
familiarize himself with the terms employed, so that he may 
always use them accurately. Anything that he may say or 
write will then be clearly understood by all who have given 
careful attention to the subject. So important does the author 
deem this matter, that he has in an advanced state of prepara- 
tion an extended glossary or dictionary of microscopical terms. 28 
SELECTION AND USE 
SIMPLE MICEOSCOPES. 
The simple microscope is an indispensable assistant to those 
who nse the compound instrument, as well as to those who rely 
upon it alone for the examination of flowers, seeds, minerals, 
textile fabrics, etc. We shall therefore devote some space to 
a consideration of its various forms, though even then we shall 
be unable to do more than describe certain typical models 
which, however, afford variety enough for all practical pur- 
poses. 
Hand Magnifiers.—These are so generally useful and 
applicable that they are used by all who wish a cheap and yet 
efficient aid to natural vision. They are found in market in a 
great variety of forms, styles of mounting, and price, and are 
too well known to need minute description. Large lenses, 
magnifying two or three times, are mounted singly, and used 
chiefly for the examination of pictures, and as reading glasses ; 
the smaller sizes of the same style serve for the examination of 
fine engravings. Very small lenses of considerable power, and 
simply mounted in a frame, are also sold by most opticians. 
They are known as “watch-charms,” and magnify about fifteen 
diameters. We have also seen a very powerful magnifier 
mounted in a little ring attached to a pair of eye-glasses. 
For the purpose of the student and naturalist, a very ex- 
cellent form is that shown in Fig. 2. It consists of a lens of 
suitable magnifying power set in a frame, which folds into a 
case, just as the blade of a jmcket knife folds into its handle, 
thus allowing the instrument to be carried in the pocket with- 
out liability to injury. Similar magnifiers are made with two, 
three, and even four separate lenses, as shown in Fig. 3. The 
lenses are usually of different powers—a 2 inch, 1 inch, and 
£ inch, forming a very'useful combination. Each lens may be 
used separately, or two may be used together, or all three may OP THE MICROSCOPE. 
29 
be used at once, a considerable range of magnifying power 
being thus secured. 
Fig. 2.—HAND MAGNIFIER—SIMPLE LENS. 
The magnifiers shown in Figures 2 and 3 are furnished 
with what are called diaphragms—that is to say, each one has a 
thin plate of some opaque material, having a hole of suitable size 
through its centre. This plate is placed over the lens when 
Fig. 3.—HAND MAGNIFIER—THREE LENSES. 
but one lens is used, and between the lenses when two or more 
are employed. It serves to cut off the marginal rays which do 
not give a clear image, and in this way it greatly improves the 
definition of the object. 
Two or more lenses, properly adapted to each other, and used 
together, give results greatly superior to anything that can be 30 
SELECTION AND USE 
obtained from a single lens, at least so far as clearness and 
accuracy of definition is concerned. But when used as a work- 
ing or dissecting microscope, they are open to the objection 
that the distance at which they must be placed from the object 
is very small, and hence it is frequently inconvenient to use 
them for working upon objects. Tints, if we have a plano- 
convex lens of a quarter of an inch focus, and one of three 
quarters of an inch focus, and place them at a distance of a six- 
teenth of an inch from each other, we will have a very good 
magnifier which will enlarge objects about fifty times, but avc 
must place it at but a very short distance from the object. If 
Ave separate the lenses a little, the definition Avill be improved, 
but the working distance, as it is called, Avill be diminished. 
Those Avho haAre studied optics are quite familiar with these 
facts, but the ordinary reader does not always think of them, 
and yet they are very important Avhen Ave come to choose a mi- 
croscope for Avorking or dissecting purposes. 
Whore tAVo or more simple lenses are used together (without 
being combined so as to form a compound microscope) the 
power of the combination is always equal to the sum of the 
poAvers of the separate lenses. Thus if we have a lens of half 
an inch focus and one of one inch focus, one magnifying ten 
and the other twenty diameters, the resulting power is thirty 
and not tAvo hundred times. In the compound microscope, on 
the other hand, the combination of an objective magnifying 
tAventy diameters Avith an eye-piece magnifying ten diameters, 
gives a magnifying poAver of tAvo hundred diameters. 
Watch-Makers? Eye-Glasses.-Those are Avell known, 
and may be obtained of almost any power within the useful 
range of a singe lens. They are called “eye-glasses"’ because 
when in use they are held by the muscles around the orbit oi 
the eye, and consequently require no extraneous support 
Fig. 4 shows the bell-mouthed form of the frame, which enables 
us to secure this result. The eye-glass ordinarily used by 
watch-makers magnifies about eight times, but glasses magnify- 
ing twenty diameters are not uncommon. Glasses of the latter 
poAver are usually doublets, that is, they consist of tAvo lenses, 
arranged together, one being of much longer focus than the OP THE MICROSCOPE. 
31 
other. If well made they give excellent definition and a large 
field, and, when mounted on a stand, are very serviceable as 
dissecting microscopes, especially in working upon coarse objects, 
and picking out shells, the larger foraminifera, etc. Their 
form enables us to support them by means of a small wire 
ring, arranged as in a retort stand, and the large bell-mouth of 
the frame prevents any light from entering the eye, except that 
which has passed through the lens. They are very cheap, and 
any intelligent boy can make a tolerable stand for one. The 
same stand will answer for several glasses of different powers. 
Fig. 4.—WATCH-MAKERS’ GLASS. 
Fig. 5. 
The eye-glass shown in Figure 4 is a doublet, the front lens 
of which is set in a separate piece, shown in Figure 5. When 
the latter is removed, the remaining part forms a very service- 
able low-power glass ; when both are used together, the com- 
bination forms an excellent high-power magnifier. This form 
is one made by the Bausch & Lomb Optical Co. 
.Engravers’ Glasses.—These are mounted in frames, 
similar to that of the watch-makers’ eye-glass, but as they are 
larger, and are therefore not so readily held in the eye, after the 
fashion of the latter, they are always used with a stand of some 
kind. Those of the best quality are, in general, doublets, con- 
sisting of two plano-convex lenses, and as they give a large 
field of view, with very good definition, they are altogether the 32 
best microscopes for examining bank bills, fine engravings, and 
similar objects, Tlie general form is shown in Fig. 6. 
SELECTION AND USE 
Fig. 6.—engravers’ glass. 
Linen Provers.—These are a very old form of the simple 
microscope, and being in very general nse, they are manufac- 
tured in large quantities, while as it is necessary that they 
should be of good quality they afford an opportunity ol getting 
a good magnifier at a moderate price. The general form is 
shown in Fig. 7, in which the instru- 
ment appears as in use. The upper 
plate carries the lens, and the length of 
the upright is such that when the base 
is placed upon any flat surface, that 
surface will be in focus. ’ The base is 
pierced with a hole one quarter of an 
inch square, and when placed on a 
piece of cloth the lens enables us to 
count the number of threads which oc- 
cupy that space. This indicates the 
fineness of the fabric. 
Fig. 7.—LINEN PROVER. 
The Stanhope Lens consists of a cylinder or rod of 
glass, one end of which is rounded so as to form a lens, while 
the other end is either flat or slightly curved. The distance OS' THE MICROSCOPE. 
33 
between the lens and the flat surface is exactly equal to the 
focal distance of the lens. Transparent objects, such as the 
scales of insects, animalcuhe in water, etc., are simply placed 
on the flat surface of the glass cylinder, and when looked at 
through it, they appear greatly magnified. It is easily used, 
but can not well be employed as a working microscope. It is 
this kind of lens that is used in the construction of those watch 
charms in which a large picture is seen on looking through a 
very small hole. The picture is a photograph attached to the 
flat end of a small glass rod, the other end of the rod being- 
formed into a lens of exactly the right focal length required to 
show the picture clearly and considerably magnified. Lenses 
and photographs of this kind are usually mounted as miniature 
opera-glasses. 
The Stanhope lens seems to be a favorite in France, where it 
is manufactured very extensively, and sold under the name of 
the Stanhoscope. One advantage claimed for it is that no adjust- 
ment for focus is required, the flat surface of the lens being 
Fig. 8.—STANHOPE COLLECTING LENS. 
exactly in the focus of the curved surface. This feature, while 
presenting some slight advantages, has also the great disad- 
vantage that objects covered with thin glass cannot be ex- 
amined by such lenses, and neither can objects having a 
sensible thickness. The feature which we have just mentioned 
is imitated in some cases by placing a piece of thin glass in 
front of a small lens, and at such a distance that the outer sur- 
face of the thin glass will be exactly in focus, as is hereafter 
described when speaking of the Craig microscope. 
There is one purpose, however, to which this form of lens is 
applied with good effect, and that is to the construction of a 
“ collecting lens ” as it is called—that is, a lens for examining- 
drops of water when searching for diatoms, algrn, animal cube, 
etc. Fig. 8 shows a lens of this kind made by Jas. W. Queen 
& Co., of Philadelphia. The lens is set in a brass frame, pro- 34 
SEMCTION AND tTSE 
vided with a handle, and after a drop of water has been placed 
on the flat surface of the lens, the cap, c, is screwed on, and the 
object examined by simply holding the instrument up to the 
light. 
A very excellent collector’s microscope will also be found de- 
scribed amongst the compound instruments. 
The Coddington Lens.—This lens was devised by Sir 
David Brewster, but having been made by a London optician 
for Mr. Coddington, it was called by his name, which has stuck 
to it ever since. It consists of a cylinder of glass, the two ends 
of which have been ground so as to form portions of the surface 
of the same sphere. A deep groove is cut around the cylinder, 
midway between the ends, and a diaphragm is thus formed 
between the two lenses. In Figure 9 is shown a very neat 
and convenient method of mounting the Coddington. 
This form of lens gives very sharp definition, so that when- 
ever a power greater than twenty diameters is required for 
examining objects, a Coddington, if well made, will be found to 
be the best lens in use, always, of 
course, excepting the carefully 
corected doublets and triplets 
hereafter described. The price 
of the latter, however, is in 
general four to eight times that 
of a good Coddington. But it 
has this defect, that the working 
focus is very short, and therefore 
for a dissecting microscope a 
doublet is to be preferred. In using a Coddington lens, great 
care must be taken to secure good illumination of the object, 
and the shortness of the focus makes this difficult to those who 
have had no experience. 
Those who desire to acquaint themselves with the structure 
and peculiarities of the most important simple microscopes, 
will find this subject very fully and very clearly treated in the 
article contributed by Andrew Boss to the “ Penny Cyclopaedia,” 
published by the Society for the Diffusion of Useful Knowl- 
edge. This article has been republished in book form. 
Fig. 9.—CODDINGTON LENS. OF THE MICROSCOPE. 
35 
Achromatic Doublets and Triplets.—Magnifiers, 
composed of two or more lenses, are to be had of two very 
distinct kinds. The lenses may either be simply united in one 
frame, without any special adaptation to each other, or the in- 
strument may consist of two or more achromatic lenses com- 
bined together in a fixed and accurately determined relation. 
Examples of the former are found in the ordinary two and three 
lens magnifiers we have just described ; the latter are not so 
common, since they are somewhat expensive when well made. 
They are known as achromatic doublets and triplets, and one 
maker in this country, Mr. Tolies, of Boston, has long been 
noted for the excellence of the simple achromatic microscopes 
of this class made by him. 
The advantages possessed by lenses of this kind are the larger 
field of view which they give, thusenabling ns to obtain a clear 
view of objects of considerable size ; and the wonderfully in- 
creased sharpness of definition which they afford, owing to their 
wide angular aperture. They are usually mounted in the same 
style as the Coddington (Fig. 9), but are readily distinguished 
from the latter by the absence of any diaphragm. The lenses 
of which these magnifiers are composed are so constructed and 
combined that the field is perfectly flat and well defined in all 
its parts, so that a diaphragm is not necessary. Mere common 
lenses, put together so as to resemble these achromatic doublets, 
and without a diaphragm, would give such a misty view of ob- 
jects that they would be at once condemned. 
With the exception of the low and medium-power achromatic 
objectives used with the compound microscope, these doublets 
and triplets, when well made, are altogether the most satisfac- 
tory simple microscopes in use, and several firms now make a 
specialty of their manufacture. Amongst others we may name 
the Bausch & Lomb Optical Company, Messrs. E. & J. Beck, 
Browning, whose magnifiers of this kind are known as Platy- 
scopic lenses, and Steinheil, of Munich. 
To some it may appear that we have devoted more space to 
the simple microscope than its importance demands. Our 
excuse is that simple microscopes, of the different kinds we 
have just described, are not in such general use as they ought 
to be. This, however, seems to be the case even in France, the 36 
SELECTION AND USE 
country of Raspail, who was the great advocate of the simple 
microscope, for Chevalier, in his work, says : “It is a matter of 
regret, from a scientific point of view, that the simple micro- 
scope is not more extensively used in France than it is, because 
in minute dissections it is capable of rendering immense 
service.” 
Twenty-five cent Microscopes.—Before leaving this 
subject it may be well to say a few words about those very cheap 
microscopes which have been so extensively advertised. We 
frequently see in the papers an advertisement in which some 
person offers to send for twenty-five cents a microscope which 
will show animalcules in water, globules of blood etc., etc., and 
the question naturally arises, Are these microscopes good for 
anything, or is the advertisement a swindle—the advertiser 
taking the money and sending nothing in return? 
As a general rule, those who send to such advertisers, receive 
in return, a plate of brass or lead, with a glass bead fastened 
in a hole in Uie centre. The glass bead is formed by fusion and 
is frequently ground flat and polished on the side by which it 
was attached to the thread or rod of glass from which it was 
made, forming in such cases a hemispherical lens. Such 
lenses are very easily made by any one. Take a strip of flint 
glass, such as a piece of flint glass tubing, or a piece of glass 
rod, draw it out to a thread in the flame of a spirit lamp, 
fuse the end and allow it to gather into a drop. Give plenty of 
time and a good strong heat, so that the surface of the little 
globe may become well-fused and truly round. The best re- 
sults are always obtained by holding the thread perpendicularly, 
as when held horizontally the globule is apt to become dis- 
torted. Make one or two dozen of these, and in separating 
them from the glass rod leave about an eighth of an inch of 
the latter attached to each globule, to serve as a handle, in the 
next step of the process, which consists in inserting them to 
about half their depth in a plate of cement, consisting of 
shellac thickened with very dry and finely powdered pumice- 
stone. To form such a wax plate, melt some shellac in a ladle 
or large iron spoon, mix it carefully with as much powdered 
pumice-stone as can be conveniently stirred in, remove it from OF THE MICKOSOOPE. 
37 
the fire, stir well until it begins to stiffen, and then pour it out 
on a flat metal plate—the surface of a smoothing iron answer- 
ing very well. The plate of cement should be from one-half to 
three-quarters of an inch thick, and the little globules are easily 
fastened into it by seizing them by the small handles left on 
them, holding them by a pair of forceps in a lamp flame until 
they are hot enough to melt the cement, and then pressing 
them in to about half their depth or a little more. When quite 
cold they will be very securely held. The little handles, or tails, 
are now nipped off with a pair of cutting pliers, and the glo- 
bules ground all at once on a fine grindstone, or still better on 
a metal plate charged with emery. When they have been re- 
duced nearly to the surface of the plate of cement, they should 
be ground with emery of the finest kind, and as soon as all 
coarse scratches have been removed they should be polished on 
a buff leather with crocus martis or putty powder. When finely 
polished they may be removed from the cement by means of a 
small chisel, and any cement that adheres may be dissolved off 
by means of alcohol. They are then mounted in thin plates of 
lead, brass, or, what is better still, vulcanite. Out of two dozen 
such globules, carefully made and well polished, three or four 
may be obtained that will give satisfactory definition, and it 
was with such lenses that the early microscopists made many of 
their discoveries. These men, however, took great pains in 
making and polishing them, and rejected hundreds as unfit for 
use. The objections to the microscopes of this kind, that are 
ordinarily sold, are that they are badly made, and that good 
and bad are sold together without any selection being exercised. 
But, even if well made, they are very difficult to use, and very 
unsatisfactory in their results, even in the hands of persons of 
great skill. The polish of a fused surface never equals that of 
a surface finely cut and polished, as every housekeeper that is 
familiar with common, and with cut glass, very well knows. 
The fused surface of these little globes is, therefore, always 
more or less, covered with striae or very minute ridges which 
interfere with their defining powers, and we have described 
thus minutely the process of their manufacture, rather for the 
purpose of giving our readers such information as will enable 
them to understand how they can be sold so cheaply, than in 
the hope that they will endeavor to make them for themselves. 38 
SEIiECTlON AND USE 
Penny Microscopes.—A few years ago a man in London 
made a living by selling through the streets a microscope which 
would show the eels in paste and vinegar, and of which the 
price was only one penny, (equal to two cents.) These micro- 
scopes were thus made: In the bottom of a pill-box he punched 
a small hole and then blackened the inside of the box. In this 
hole was placed a drop of Canada balsam or damar varnish, 
which was allowed to dry. When hard, the balsam formed a 
very tolerable lens. 
A drop of water, balsam, or varnish, laid on the under side 
of a slip of clear glass will often enable us to extemporize a 
microscope capable of doing good service in the hands of a 
skillful observer. The outline of the drop should be perfectly 
round, and the glass plate should be held as level as possible. We 
have derived great assistance from such a lens, when better 
could not be had. 
The Craig Microscope.—This microscope at one time 
attained an unprecedented degree of popularity, not on account 
of its merits, but because of the extensive puffing and adver- 
tising which it received. It consists of a vertical frame, some- 
what like that of the cheap French microscopes, having a 
mirror, but no sliding tube, as there is no occasion for any. The 
slide which holds the object is slipped through a horizontal slit 
cut in the stand, and the lens with its frame is laid on it. 
The lens is a fused bead of glass set in a little frame, to the 
under side of which is attached a thin plate of glass, whose 
lower surface is exactly in the focus of the bead, so that when 
a drop of water or vinegar is placed on the glass plate, or such 
objects as insects’ scales, wings, etc., are laid on it, they are ex- 
actly in focus. Hence, this microscope is said to require no 
adjustment for focus. This is true when the objects to be ex- 
amined are actually in contact with the glass plate, but when 
we wish to examine objects that are covered with thin glass (as 
all valuable preparations should be) or objects having a percep- 
tible thickness, it is impossible to adjust it for focus, and hence 
it is impossible to examine such objects satisfactorily. Besides 
this, nine-tenths of the microscopes of this pattern in market, 
are very badly made, and distort objects to such an extent that OF THE MICROSCOPE. 
39 
one 'who lias been accustomed to employ a good microscope 
cannot recognize them. It has unquestionably done a great 
great deal to impede the progress of microscopy in this country, 
and we have been led to give this extended description of it, 
chiefly because so many editors and clergymen have praised it 
in the highest terms. It has even been patented, although the 
principle upon which it is constructed is very old; but then we 
must remember that under our present administration the 
patent office seems to be conducted rather for the discourage- 
ment than the encouragement of progress and invention, We 
daily see patents issued for old and worthless devices, while it 
is well-known that the author of a really meritorious inven- 
tion will have the hardest work to obtain protection. 
Of the Novelty, Globe, and other similar microscopes, it is 
unnecessary to speak. In all the microscopes of this kind that 
we have seen, the optical part is utterly worthless. The lenses 
are mere fused globules of glass, and they distort beyond recog- 
nition the image of any object. 
Strange to say, however, even this fact has been used as an 
argument to sell them. They have been sold chiefly by news- 
dealers and stationers, and as the purchasers did not know how 
any given object ought to appear, the fact that it looked so very 
different from what they expected was considered an evidence 
of the power of the microscope !! 
In regard to all microscopes in which fused globules are 
used, it must be remembered that the lower the power of the 
lens the more apt it is to be imperfect. No lens of this kind, 
magnifying from 100 to 150 times, (according to the estimates 
of those who deal in them, which, however, is in fact only from 
ten to twelve times, as measured by proper methods), can be 
good for anything. On the other hand, it must be borne in 
mind that when we attempt to examine objects under high 
powers, obtained by the use of very small single lenses, we 
subject our eyes to an almost destructive strain. 40 
SELECTION AND USE 
DISSECTING MICROSCOPES. 
The term Dissecting Microscope is applied to all microscopes 
used for working upon objects under moderate magnifying 
powers. They are used not only for dissecting, properly so 
called, but for the study of botany, mineralogy, etc., as well as 
for numerous investigations in the arts. A good microscope of 
this kind is absolutely indispensable to those wdio hope to do 
more than merely look at objects prepared by others. 
For ordinary purposes of examination, the different magni- 
fiers previously described serve very well when merely held in 
the hand, but their performance is greatly improved when they 
are mounted on appropriate stands, which not only enable us 
to adjust the focus with great accuracy, but which hold the 
lens steadily in relation to the object, and thus prevent any 
necessity for that constant adjustment of the eye itself, which 
always occurs when a lens trembles, and which is so fatiguing 
and injurious to the sight. A complete dissecting micro- 
scope should, therefore, be furnished with stand, mirror, 
etc., and if the student can afford it, there should be some good 
mechanical means of adjusting the focus. The importance of 
dissecting microscopes being generally recognized, even if the 
instruments themselves have not come into general use, nearly 
every manufacturer of microscopes has devised a stand of his 
own, some of which are very complete, and as a consequence 
very expensive. We shall, therefore, rest content with de- 
scribing a few of the simpler forms. 
The microscopist can easily construct a dissecting microscope 
for himself, by means of a cork and some wire, for whenever a 
piece of apparatus is to be supported steadily, while at the 
same time it is necessary that it should be easily moved and 
adjusted, nothing serves so well for a temporary expedient as a 
fine cork sliding on a smooth wire. Consequently a very 
serviceable stand for a simple microscope is easily extemporized OP THE MICROSCOPE. 
41 
as follows: Procure a good sound wine cork, and bore two 
boles through it, the holes being at right angles to each other, 
and to the axis of the cork. The holes should be of the right 
size to slide easily, but firmly, on a wire rather more than the 
sixteenth of an inch in diameter. One piece of such wire is 
stuck perpendicularly in a wooden foot, and serves as a stand 
upon which the cork slides up and down; another piece of wire, 
having a ring at one end for holding the magnifier, is thrust 
through the second hole in the cork, and is supported by it in 
a horizontal position. The horizontal wire should be so long 
that there will be no danger of injury to the eye or face from 
the upright wire. A piece of white paper makes the best 
mirror, as it gives sufficient illumination with low powers, and 
besides this, it diffuses the light very equally over the object. 
This, of course, is for use with transparent objects ; when 
opaque objects are under examination a condensing lens must 
be employed. 
The Excelsior Microscope.—The accompanying en- 
graving gives a very clear view of this microscope, which is 
constructed as follows: 
To one end of the lid of a small wooden case or box, is at- 
tached one of the ends of the box; and when the lid is reversed 
and turned upside down, it may be slid into the groove which 
usually receives it, and then forms a stand for the lenses and 
glass stage, as is shown in engraving. The lenses and stage are 
supported by a steel rod, D, the lower end of which is hinged 
to the lid, so that it may be turned down and lie in a groove 
provided for it. When raised into the position shown in the 
figure, it is held very securely in place by means of the button, 
E; and this button also serves to retain it in the groove when 
it is turned down. The glass stage, G, which is fitted into a 
frame of hard rubber, slides easily on the stem, D, so as to be 
readily adjustable for focus, while at the same time it may be 
firmly fixed, by means of a set-screw, at any desired height, 
and will then serve as a stage for dissecting purposes. The 
frame which holds the lenses fits on to the top of the stem. A 
mirror, H, is fitted into the case, and is readily adjustable by 
means of the button shown on the outside, so that light may 42 
SELECTION AND TTSE 
be reflected up through the stage when the objects to be ex- 
amined are transparent; and when they are to be viewed by re- 
flected light there is a dark ground of hard rubber (not shown 
in the engraving) which is also carried by the stem, D, and 
may be turned under the stage, so as to cut off all transmitted 
light. Dissecting needles (K and L), with neat handles, fit 
into appropriate grooves. When the lenses and stage are re- 
moved from the stem they are readily packed in the case; the 
Fig. 10.—THE EXCELSIOR MICROSCOPE. 
stem is then turned down and held in its groove by the button, 
E; the lid is drawn out of the groove, turned over, and re- 
placed so that the vertical piece (0) closes the open end of the 
box, and the whole thing is packed into a compass which readily 
admits of its being carried in the vest po ket. 
The lenses are well made, and being provided with a proper 
diaphragm, great clearness of definition is secured. Two styles OF THE MICBOSCOPE. 
43 
of frame are sold, one containing two, and the other three 
lenses, the latter being altogether the cheapest, in proportion 
to the power furnished. The magnifying powers are about as 
follows: With the lens of longest focus, five diameters; with 
the lens of medium focus, eight diameters; with the lens of 
shortest focus, ten diameters. When the lenses of shortest and 
medium foci are combined the magnifying power is about 
eighteen diameters; all three lenses together give a power of 
twenty-five to thirty diameters. 
In using a combination of two or more lenses, the lens of 
shortest focus should always be placed nearest to the object. 
As a dissecting microscope for botanical, entomological, and 
physiological work, this instrument is very efficient and con- 
venient. The glass plate is fitted into the stage so as to form 
a cell capable of holding water, so that dissections may be 
carried on under that liquid, or aquatic animals may be kept 
alive and examined at leisure. The stege may also be turned, 
so that the flat side will be up when so desired, in which posi- 
tion it is most convenient for some purposes, such as dissec- 
tions and the teasing out of tissues by means of needles. The 
only serious defect in the Excelsior microscope is that it is not 
sufficiently steady for ordinary work, the case which forms the 
base or foot being, for portability’s sake, made quite small. 
This difficulty is, however, easily remedied by screwing the 
case to a piece of pine board six inches long, four inches wide, 
and three-quarters of an iuch thick. A single small screw, 
which does not deface the instrument, is sufficient, and when 
the microscope is to be carried in the pocket it is easily de- 
tached from its temporary stand. Its low price, $2.75, is a 
strong recommendation. 
Raspail’s Microscope.—This was the instrument so 
largely used by lias pail in his investigations into the structure 
of plants, and having been fully described by him, it has been 
called by his name, though Chevalier tells us that it was really 
invented by Cuff, of London, and ought to be called the Cuff 
microscope. It consists of a pillar which screws into the to]} 
of the box in which the whole instrument packs when the micro- 
scope is not in use. This pillar carries the mirror, and also a u 
fixed stage. It is hollow, and in it slides a rod which may be 
moved up and down by means of a rack and pinion, so as to 
adjust for focus. This rod carries a horizontal arm, into one 
end of which the lenses fit, and the arm itself may be moved 
back and forth across the top of the vertical rod, so as to bring 
the lens over any part of the object. The great objection 
to this microscope, as usually constructed, is its Avant of 
steadiness, and this is a vital defect. 
SELECTION AND USE 
Tke Compact Dissecting Microscope —Those who 
desire a really serviceable and substantial microscope for dis- 
secting purposes, will find that several manufacturers have 
recently endeavored to supply the demand for an instrument 
Fig. ll.—TaE COMPACT DISSECTING AND MOUNTING MICROSCOPE. 
of this kind at a moderate price. We select one by the same 
firm that manufactures the Excelsior Microscope—theBausch & 
Lomb Optical Co. It is called the “Compact Dissecting and OF THE MICROSCOPE. 
45 
Mounting Microscope,” from the fact that it may be folded 
together so as to occupy very little space, and may then be 
packed in the case which contains the compound microscope, 
or carried in its own little box. It is capable of receiving 
lenses of long focus, as the rod which carries the horizontal 
arm slides up and doAvn in a tube upon which a rack is cut. 
This sliding movement senses for a coarse adjustment, the rack 
and pinion just mentioned serving for the fine adjustment. 
The mirror is hung Avith all necessary movements, and the arm 
Avhich carries the lenses is provided Avith the Society screAv, so 
that ordinary achromatic objectives may be used—thus saving 
the expense of extra lenses. 
The engraving fails to sIioav an important feature Avhich is 
provided by the makers. This is a joint in the arm, Avhich, in 
connection with the rotation that may be given to the rod to 
Avhich the arm is attached, enables the operator to place the 
lens over any part of the preparation. We call this an im- 
portant feature, for Ave hold it to be essential to the convenient 
use of the dissecting microscope that the preparation should 
remain stationary and firm during the processes and operations 
to Avhich it is subjected. This is just the reverse of Avhat is 
found to be most convenient and efficient in the compound 
microscope. There the objective should be immoveable (hori- 
zontally), and the object should be adjusted to a proper posi- 
tion in relation to it. 
Rests for tlie arms, when, using the dissecting microscope, are 
easily improvised out of books or blocks of wood. We prefer, 
to anything else, good-sized blocks of wood, having the form of 
a wedge with the point cut off. They are clumsy, it is true, 
but very comfortable. Small rests may be fitted like wings to 
each side of the stage, and these are furnished at a slight extra 
cost by the makers of the microscope just described. 
Cheaper forms of this microscope are also made. In these 
the instrument is not made to fold up, and there are a few 
other points (not essential to the efficiency of the microscope) 
in Avhich expense is avoided. But as improvements are being 
constantly introduced, those avIio require a good dissecting 
microscope should procure the catalogues of all the various 
dealers before they decide. 46 
SELECTION AND USE 
Binocular Dissecting Microscope.—The binocular 
principle, when applied to the dissecting microscope, is of the 
greatest value, as it enables us to estimate accurately the posi- 
tions, vertically, of the several parts, and we can thus direct 
needles, knives, scissors, etc., to the exact point that we wish to 
operate on with an accuracy that is impossible with the monocu- 
lar dissecting microscope. Nachet and Beck manufacture very 
excellent binocular dissecting microscopes, and the only thing 
to be regretted is that the price is necessarily somewhat high. 
PRINCIPAL FORMS OF THE COMPOUND 
MICROSCOPE. 
The variety of models, styles, or patterns which have been 
devised for the stands and for the general arrangement of com- 
pound microscopes, is almost infinite, and as they are con- 
tinually changing, it would be a hopeless task to attempt to 
give a description of all, or even of any large number of them. 
Fortunately, from motives of self-interest, the manufacturers of 
these instruments promptly publish full descriptions and en- 
gravings of new styles as soon as they bring them out, and 
therefore the best plan for those who dcsire to make a judicious 
selection, is to procure the catalogues of as many manufacturers 
as possible, and carefully compare the several advantages of the 
different forms. The addresses of all the prominent manufac- 
turers are published from year to year in the “ Microscopist’s 
Annual,” a cheap little volume devoted to statistical informa- 
tion of this kind. 
Clieap Foreign Stands.—A few years ago, the only 
stands attainable by those who could not afford an expensive 
article, were the cheap French and German microscopes. 
These were imported in large numbers by dealers in optical 
goods, and were distributed to different parts of the country 
through the agency of watchmakers, jewellers, booksellers, and 
those who dealt in spectacles and opera glasses, and conse- 
quently were called “ opticians.” Fortunately the production 
of really good and clieap American microscopes has almost 
driven this class of instruments out of market, but as they are 
still to be found on sale, a few words in regard to them may be OF THE MICEOSCOPE. 
47 
necessary. One of the most common models is that shown in Fig. 
12. This form, although modern when compared with the micro- 
scopes of Adams, Baker, etc., is one of the oldest in use. It 
was, we believe, devised by Wollaston, as a stand for his 
doublet, and was afterwards modified by Fraunhofer, whose 
microscopes on this model were almost identical with that 
shown in the engraving. It is now too well known to need 
elaborate description, and the smaller sizes are still sold ex- 
tensively for the use of young peojile. Being manufactured in 
large quantities, they are sold very cheaply, when the quality 
of the lenses is taken into consideration. Therefore, until 
some manufacturer concentrates his efforts upon the produc- 
tion of the more convenient forms, and 
turns them out in very large numbers, 
the vertical microscope will probably 
maintain its place in the market, and 
many beginners will be led into buying 
an instrument which, even in its must 
complete and perfect form, will almost 
certainly be a source of dissatisfaction. 
Aside from any deficiencies which may 
exist in the optical parts of the instru- 
ment, the objections to this model are the 
small size and inconvenient form of the 
stage ; the fact that the microscope can be 
Used only in the vertical position, which, 
although occasionally very useful, is the 
worst position in which the instrument 
can be placed for protracted observations, 
and the arrangement of the mirror, which 
renders the proper management of the illu- 
mination impossible. Therefore, when- 
ever there is a possibility of choice, some 
form other than the vertical should be 
chosen. 
Fig. 12. 
Occasionally microscopes of tliis kind 
are furnished with achromatic objectives of 
pretty fair quality. In such cases the ob- 
jectives and eye-pieces, if they could be 
VERTICAL MICROSCOPE. 48 
SELECTION AND USE 
applied to a better stand, would be worth more than the whole 
microscope in its original form. 
There is, however, one very useful purpose to which cheap 
microscopes of this kind may be applied. They make a very 
convenient and efficient pocket microscope for collecting. The 
stand should be cut off above the mirror, the flat stage being 
left with enough of the tube adhering to it to give it stiffness. 
A drop of water being placed in a cell, and covered with thin 
glass, is laid on the stage and held there with the fingers. To 
illuminate the object the microscope is simply held up to the 
sky. Those who object to holding the slide with the fingers, 
can have a round plate of metal soldered to the under side of 
the stage, so as to make it even. Movable clips, made by 
bending a narrow strip of hard sheet brass, so that both legs are 
even, can then be slipped on so as press on the slide, and on 
the under side of the stage. Such a microscope is very light, 
and may be readily carried in a tubular pasteboard case, which 
any one can make. 
Setting aside these obsolete forms, as well as those models 
which have been devised for special purposes, we find that of 
the stands which are best suited to the purposes of the phy- 
sician, the naturalist, the student, and the family, there are four 
distinct styles, which may be distinguished as follows : The 
Eoss, the Jackson, the Continental, and the New American 
models. In order to give the reader an idea of these different 
models, and to explain the advantages and disadvantages of 
each, we give engravings and such descriptions as will enable 
him to form some idea of the stand best suited to his special 
wants. In selecting illustrations of the different types, we have 
taken the cheaper forms in preference to the more perfect, but 
more expensive models ; and as our object is to describe the 
general features of the stands themselves, and not to detail the 
merits and point out the faults of those parts which may be 
easily changed or altered, Ave have omitted all description of 
diaphragms, eye-pieces, objectives, etc. 
Tlie Ross Model.—The distinguishing characteristic of 
this model is the mode in Avhich the body is supported. By re- 
ferring to Plate I, it will be seen that the body is attached at or THE HICKOSCOPE. 
49 
its lower end to a transverse arm, which in turn is supported 
bj a stout bar, which is moved up and down by means of a 
rack and pinion. This movement constitutes the coarse ad- 
justment, the fine movement being effected by means of a lever 
which is concealed in the transverse bar, and acts upon the 
nose-piece. 
So far as mere questions of convenience and adaptability to 
different kinds of work is concerned, this model is all that can 
be desired, and as made by Boss & Co., the workmanship is so 
perfect, and the finish so exquisite, that it has long maintained 
a high position in public favor. It has, therefore, had numerous 
imitators, and has probably been copied more extensively than 
any other model in existence. At the recent Centennial Exhibi- 
tion there were microscopes on this model from the most widely 
scattered localities. Canada was represented by two micro- 
scopes made after this design. Unfortunately, however, this 
model is one of the very worst that a poor workman can 
attempt to imitate, for unless the workmanship is far above the 
average, the results are execrable. The reason for*1 this is very 
obvious. The body, being supported only at the lower end, 
every vibration causes the upper end to swing through a com- 
paratively large arc, and hence any motion arising from loose- 
ness in the joints is multiplied a hundred fold. And even when 
the joints are firm and without shake, any vibration communi- 
cated to the table on which the instrument stands, fis greatly 
increased in its effects when it reaches the upper end of 
the body. In addition to this, the unsupported part of the 
body acquires, by each movement, a momentum which reacts 
powerfully on the lower part, and consequently on the ob- 
jective. 
These defects have induced Messrs. Boss & Co. to bring out 
a new pattern designed after the Jackson model. This design 
has been carefully worked out by Mr. Wenham, and is certainly 
very beautiful in appearance, and very efficient and convenient 
in use. Our readers will therefore bear in mind, that all micro- 
scopes made by Boss & Co., are not made on the “Boss 
model.” 50 
SELECTION AND USE 
The Jackson Model.—The special characteristic of this 
model lies in the fact that the “ ways ” of both the coarse and 
fine movements are brought as close as possible to the optic axis 
of the instrument. In the Ross model the coarse movement is at 
a considerable distance from this axis, and any lateral motion 
which may take place on the sliding part is greatly magnified 
at the axis of the body—the transverse bar, which supports the 
latter, acting like the long arm of a lever to greatly multiply 
that which at first was very insignificant. Hence the advan- 
tages which this model presents are great steadiness and the 
fact that, in common with the Ross model, it affords abundant 
room underneath the stage for those acessory methods of 
illumination which are indispensable in the highest class of 
work. It is almost impossible to attach to the smaller patterns 
of the Continental model a convenient sub-stage, carrying 
polarizer, achromatic condenser, paraboloid, etc., while the 
model under consideration is specially designed to receive 
these important accessories. 
This model is a very general favorite both with English 
and American makers. Amongst the latter it has been adopted 
as the best for all first-class stands. The engraving, Plate II, 
shows a very excellent form of this model by the Rausch & 
Lomb Optical Company, and known as their Large Student 
Stand. It will be observed that the body of the microscope is 
supported along its whole length by means of a tube attached to 
the arm, which is hung between two pillars, so as to give great 
steadiness. To add to this steadiness, all sharp angles are 
avoided, and the arm is gracefully curved instead of joining the 
body at a right angle, as in the Ross model, and all of those 
made strictly after the so-called Continental pattern. 
Tlie Continental Porn*.—Most of the stands made by 
the better class of French, German, and Austrian microscope 
makers are characterized by a low, compact form, and great 
solidity and simplicity of construction. They are intended to 
be used chiefly in a vertical position, and hence the bodies 
are short, and the space beneath the stage is contracted to the 
last degree. And as a low price is an important feature in these 
microscopes, the coarse movement is generally secured by OF THE MICROSCOPE. 
51 
simply sliding tlie body through a tube or collar. In the higher- 
priced stands the coarse movement is effected by means of a 
rack and pinion, arranged as in the “Jackson ” model, but in 
both styles the fine movement is generally arranged in the 
place where the coarse movement is located in the “Ross” 
stand. These features will be found to characterize the micro- 
scopes of Chevalier, Hartnack, Nachet, Zeiss, and others. 
The term “Continental” model has been applied by our- 
selves and others to any low, compact form of microscope, but 
a careful study of the subject has satisfied us that this is not 
correct. The characters above given are peculiar to what 
ought to be known as microscopes of the Continental model. 
The Continental model has some advantages on the score of 
convenience, and as large numbers of our medical students 
have been educated to its use, it has been such a favorite that 
many of our prominent makers have imitated it to a certain 
degree. Tor the ordinary work of the physician and the his- 
tologist, a low microscope, which may be easily arranged for 
work, and which may be used conveniently in a vertical posi- 
tion, is certainly desirable, but other forms, possessing the 
same advantages and without the objectienable features of the 
Continental model, are now in market, and have taken their 
place. 
The objections to the Continental model as a microscope for 
the higher classes of work, are the want of space below the 
stage tor illuminating accessories, and the liability of the fine 
movement to get out of order. Tor it is obvious that a very 
little wear on the “ ways ” or “slides ” will allow the body to 
have considerable lateral motion, the distance of the “ways” 
from the optic axis of the instrument being very great. Some 
of our American makers, who have adopted this fine motion, 
have gone so far as to use hard steel pins sliding on hardened 
ways as guides, but with all their care lateral motion ensues 
after a time. 
Tl»e New American Model.—The more genera] em- 
ployment of objectives of wide angles of aperture, and of im- 
proved methods of using them, have led American manufac- 
turers to introduce certain improvements in stands of moderate 52 
SELECTION AND USE 
price, and tlie stands wlxicli embody these improvements and 
modifications are so distinct that they form a class by them- 
selves, •which may be designated the “ New American Model.’’ 
None of the individual features found in this model are new} 
the most important of them having been embodied many years 
ago in the English patent of Grubb, while others were used long 
ago by Spencer in this country. But Grubb’s invention, so far 
as we know, never came into use, and it was not until the year 
1875, that the importance of the improvements in question be- 
came generally recognized. Towards the close of that year, and 
the beginning of 1876, four of the prominent microscope makers 
of this country, viz., Bulloch, Gundlach, Tolies, and Zentmayer 
seem to have turned their attention to the subject, and shortly 
after brought out models on the new plan, the distinctive fea- 
tures of which are the swinging of the mirror around a centre 
which lies in the plane of the object ; the combination of a 
swinging with a longitudinal movement in the sub-stage, and 
the use of a very thin stage. Prior to this time, in all the best 
microscopes of English and American make (at least as de- 
scribed in the catalogues of the dealers), the sub-stage was made 
to move only in the line of the optic axis of the instrument; 
the American makers took a new departure, and the new model 
is the result. In its popular forms this model is characterized 
by great simplicity in its working parts, while at the same time, 
being provided with the very best means for adjusting and 
registering the illumination, it is a stand which is sufficient for 
the highest class of work, except, of course, in a few special 
departments. 
So far as our knowledge goes there are at present before the 
public four stands of comparatively low price, which may be 
relegated to this class They are : The “Acme” of J. W. Sidle 
& Co. ; the “Biological” of Bulloch ; the “ Histological ” of 
Zentmayer, and the “Investigator” of the Bausch & Lomb 
Optical Company. The large stands of the Bausch & Lomb 
Optical Co., of Beck, Bulloch, Boss, Tolies, Zentmayer, and 
others, are of course quite as efficient as the small stands we 
have named, but the price is greater, and the convenience of 
the small stands, when used as working microscopes, is in their 
favor. At the end of this volume the reader will find plates OF THF MICltOSCOPF. 
53 
of tlie “Acme,” the “Biological,” the “Histological” and the 
“Investigator” stands, and we would recommend the reader 
to study carefully their several special features. 
The “Acme ” will be described in its binocular form, and we 
therefore pass, in alphabetical order, to the “Biological” stand 
of Mr. Bulloch, which is shown in Plate III. 
It will be seen at once that this stand is substantial and firm 
in all its parts. The coarse movement is by rack and pinion, 
and the body is supported, as in the Jackson model, along 
nearly its entire length. The fine movement acts upon the 
entire body, the coarse movement included, so that the distance 
between the eye-piece and the objective is not affected by it. 
The stage is thin, but substantial, and is so cut away at the 
well-hole that light of great obliquity can be used. The stage- 
plate rotates in a ring, and may be clamped when necessary by 
means of the small screw seen in front. By loosening this 
screw the plate may be entirely removed, and then, when the 
body stands upright, a simple plate of glass may be used for a 
stage, and thus all danger of injury from acids is avoided. The 
ring in which the stage-plate rotates is held in place by two 
capstan-headed screws, and when these are slacked it is easy 
to adjust the stage so that it shall be concentric with the optic 
axis. The sub-stage is arranged for adjustment in the same 
way. It is adapted to carry the standard size accessories, and 
is furnished with an adapter which has the Society screw, so 
that ordinary objectives may be used as condensers. Mr. 
Bulloch also furnishes a diaphragm of peculiar form (shown in 
the engraving), which we have found very efficient, both with 
direct and oblique light. The special feature of models of this 
class is, however, shown in the method of hanging the mirror 
and sub-stage. These are attached to separate bars, which 
rotate on an axis, the plane of which is a little above the level 
of the stage. A stop is also provided, whereby they may both 
be placed precisely in the line of the optic axis. Both mirror 
and sub-stage may be moved towards the stage and from it, and 
the movements of both are entirely independent. The conse- 
quence is that the various forms of illuminating apparatus have 
a range of adjustment that cannot be obtained with the older 
models. 54 
SELECTION AND USE 
The instrument, as shown in the cut, is about two-fifths of 
the real size. When the draw-tube is out, the body has the 
standard length of ten inches, and it is furnished with the 
“broad-gauge” screw, to which is fitted an adapter carrying 
the standard Society screw. 
The first stand placed in market at a moderate price, and em- 
bodying the special features of the new American model, was 
the Histological stand of Mr. Zentmayer, •which is shown in 
Plate IY. The base and uprights of this stand are one piece, 
of a peculiar shape, of great rigidity, to which the bell-metal 
bar is attached by a joint, allowing the use of the instrument at 
any angle of inclination ; the perpendicular and horizontal po- 
sitions are indicated by stops. The coarse adjustment is by a 
rack and pinion, or in cheaper forms by a sliding tube. 
The fine adjustment is by a concealed lever, acted upon by a 
delicate screw, and moving the entire body, which is fitted 
to the grooved bar, giving a steady and delicate movement. 
The arrangement of the swinging sub-stage and mirrors is 
easily understood from the engraving. 
The removable sub-stage carries the diaphragms, ■which can 
be shifted up close to the object. 
The stage is a modification of the glass stage, and consists of 
a glass bar kept down by two spring clips, against which the 
object rests. By this method the object may be moved in the 
latitude, the longitudinal movement being accomplished by 
hand. The spring clips may be used independently for hold- 
ing anything in a fixed position, by simply placing them in the 
extra holes provided for that purpose. 
The “Investigator” stand is shown in Plate Y, and also 
presents the special features which we have mentioned. The 
mirror-bar is swung so that its axis of motion lies in the plane 
of the object, and it carries the sub-stage, which may thus be 
inclined to any angle with the plane of the stage, or it may be 
brought entirely above the latter. The mirror is attached to 
the mirror-bar by means of a secondary bar, which thus permits 
the use of the mirror independently of the sub-stage, and both 
mirror and sub-stage may be moved to and from the object. 
The sub-stage may be removed entirely when desirable. 
In order to secure the convenience of the low Continental OF THE HICKOSCOPE. 
55 
tnodel, this microscope is provided with two draw-tubes, sliding 
one within the other, so that the body may be shortened as 
much as possible when desired. The first draw-tube has the 
Society screw at the lower end, so that low-power objectives of 
very great working distance may be used ; and as, by means of 
the second draw, the draw-tube may be made of the usual 
standard length (ten inches), it may be used as the body for 
any objective, and quickly focussed by sliding it in the outer 
tube, the same as in instruments without rack and pinion ad- 
justment. The “ broad-gauge ” screw has been added, so that 
low-power objectives of wide angle may be used to the greatest 
advantage. 
Cheaper Stands.—The stands which we have just de- 
scribed, are, of necessity, somewhat expensive, because, unless 
the workmanship is of the very best, the performance is quite 
unsatisfactory; and as a stand alone is of no use, an outfit 
which includes such a stand is frequently beyond the means of 
students and others. To meet the wants of such persons, the 
various manufacturers we have named, together with Klein, 
Pike, Schrauer, and others, have brought out stands, which, 
when complete, with case and objectives, are sold for about 
the price of the stands we have described. For the study of 
elementary botany, histology, etc., many of these cheap micro- 
scopes answer a very good purpose. They enable us to follow 
the descriptions given in the books, and the view of any object 
which we obtain from even the poorest of them, is infinitely 
better than any representation which can be given by an en- 
graving. The better class of these microscopes answer well for 
the ordinary purposes of the physician, and, as they are simple 
and easily used, they are frequently preferred to more expensive 
and more complicated instruments. 
The Binocular Microscope.—More than two hundred 
years ago, attempts were made to construct binocular micro- 
scopes, and yet a good and efficient binocular is a thing of 
yesterday. The first really efficient binocular microscope was 
constructed by Prof. Riddell, of New Orleans, about the year 
1853, and to this fact Mr. Wenham has borne free and generous 56 
SELECTION AND USE 
testimony in a letter addressed to the English Mechanic. To 
Mr. Wenham, himself, however, is due the honor of having 
devised a form of the binocular which is at once efficient 
and of moderate price. Mr. Wenham’s form has been adopted 
by all the American and English makers that manufacture bi- 
noculars, and he has, therefore, laid all microscopists under 
deep obligations, not only by devising such simple and efficient 
means of accomplishing a most desirable result, but by giving 
the use of his invention freely to the world. 
Of the value of the binocular, there is a wide difference of 
opinion, some regarding it as a mere toy, altogether beneath 
notice as an instrument of scientific research, while others con- 
sider it a most important addition to our means of investiga- 
tion. Since, however, it will almost always be found that those 
who place a high value on the binocular are those who have 
used it most, while those who decry it know absolutely nothing 
of its merits, and in some cases are even ignorant of the man- 
ner of using it, the reader will have but little difficulty in de- 
ciding on which side the truth lies. In England, where cheap 
and good binocidars are common, this form of instrument has 
become a great favorite with all the noted microscopists, and 
we refer not merely to men who own microscopes as a means of 
amusement, but to those, who, like Carpenter and others, have 
enlarged the boundaries of knowledge by their researches. At 
present the binocular is gaining rapidly in favor in this country, 
and very excellent instruments are now turned out by several 
of our American microscope makers. 
There are, of course, certain limits to the range of usefulness 
of the binocular microscope. As at present constructed, it is 
most efficient in the use of the low powers, and hence, there 
are certain classes of work to which it is peculiarly applicable, 
while in other branches, particularly certain departments of 
histology, it is of comparatively slight advantage. And it will 
in general be found that the principal opposition to the binoc- 
ular has come from continental histologists, who, because they 
found it of little use to themselves, concluded that it could not 
possibly be of use to any one else. 
The advantages presented by binocular instruments are two- 
fold ; the relief to the observer arising from the ability to use OF THE MICBOSCOPE. 
57 
both eyes is very great, and the view which is obtained of any ob- 
ject is so much clearer and more realistic, that we at once per- 
ceive, by our mere sense of vision, those features which we would 
otherwise have to work out by tedious mental processes. It has 
been said by some that the binocular is apt to exaggerate the 
stereoscopic effects, and give false views. This is certainly not 
the case under ordinary circumstances, and we doubt much if 
it ever occurs. 
We have selected as an illustration of the binocular micro- 
scope, one of moderate cost, which combines the binocular 
feature with those peculiar to the new American model—the 
“Acme,” made by J. W. Sidle & Co., of Lancaster, Pa. This 
instrument, in its monocular form, was, we believe, arranged by 
Prof. J. Edwards Smith, and the details of its construction were 
worked out with special reference to the use of objectives of 
high angles. So far as this purpose is concerned, the “Acme” 
has many points in common with the “Biological” stand of 
Mr. Bulloch, the “Histological” of Zentmayer, and the “In- 
vestigator” of the Bausch & Lomb Optical Co., the differences 
being chiefly in details of construction, which leave room for 
choice on the part of intending purchasers. We therefore turn 
to the binocular feature as being that with which we are now 
more immediately concerned. 
The binocular in general use, being that in which the Wen- 
ham prism is used, consists of a main body through which the 
half of the rays transmitted by the objective pass directly to the 
eye-piece. In the figure (Plate YI) this body is the one nearest 
to the reader, and connected with it is another body, through 
which the other half of the rays pass—they being diverted in 
this direction by the prism, which, when in place, cuts the cone 
of rays from the objective in two. The frame which carries 
this prism is seen just above the point at which the objective is 
attached, and it is so arranged, that when desirable it may be 
drawn out, and thus the prism becomes inoperative, and the in- 
strument is practically converted into a monocular one. This 
is one of the important advantages which are peculiar to the 
Wenham prism. In some forms of the Acme binocular the 
entire fittings of the prism may be removed, so as not to inter- 
fere with wide-angle lenses of low power. 58 
SELECTION AND USE 
As eyes differ greatly in their distance apart, tlie eye-pieces 
in the binocular are made variable in this respect by being 
pushed out or in, either by a lever or a rack and pinion. As 
the bodies are not parallel, but form an angle with each other, 
it is evident that the further the eye-pieces are drawn out the 
wider apart do they become. 
Binocular Kye-Piece.—A very valuable and efficient 
means of converting an ordinary monocular microscope into a 
binocular, has been devised by Mr. Tolies. The one which we 
possess gives excellent results with objectives of higher power 
than those available with the Wenham prism as ordinarily con- 
structed, and it is greatly to be regretted that its high price 
($80) places it beyond the reach of those for whom this work 
is chiefly intended. It has been copied extensively in Europe, 
but we believe that it is now definitely settled that the honor of 
the invention belongs to Mr. Tolies. 
The Inverted Microscope.—Some years ago, Professor 
J. Lawrence Smith devised a microscope specially adapted to 
chemical investigations. In this instrument the stage is placed 
over the objective, which is inverted, and the rays from the 
object, after being reflected down through the objective, enter 
a prism, which so changes their direction that they pass up the 
body to the eye-piece, and thence to the eye of the observer. 
Eor very many investigations the inverted microscope is a very 
useful instrument. 
Lithological Microscopes.—The application of the 
microscope to petrology, or the study of rocks, has now become 
such an important department of scientific research that micro- 
scopes specially adapted to this purpose are manufactured by 
several makers. These microscopes possess several very im- 
portant conveniences, which are almost indispensable for such 
work, but which the limits of the present volume forbid us to 
describe at length. 
The Aquarium Microscope.—The importance of the 
compound microscope in the examination of small portions {in 
situ) of large objects, 'without any preparation whatever, has led OB’ THE MICEOSCOPE. 
59 
to the construction of microscopes consisting simply of a body 
with its adjustments for focussing arranged on the simplest 
kind of a support—usually a rod and foot somewhat like a re- 
tort stand. Such microscopes have been used largely for exam- 
ining objects in aquaria, and hence the name. They are also 
applicable to the examination of writing, the sheet of paper 
being simply spread out on a table and the microscope placed 
on it; to the examination of portions of the surface of the 
human body in various cases of skin disease, and, in short, to 
the examination of any object which cannot be conveniently 
placed on the stage of an ordinary microscope. 
Microscopes for Special Purposes.—In addition to 
the microscopes which we have described, some of which have 
been devised with a special view to certain particular lines of 
research, it often happens that a microscope is needed for a 
single purpose, and for no other. Thus, for example, in Ger- 
many, a few years ago, microscopes were made and sold for the 
sole purpose of examining flesh for trichinae. These micro- 
scopes were very simple, and when their quality was considered, 
they were very cheap—the cheapness being due, in a great 
degree, to the fact that no provision had been made for a 
multiplicity of conveniences, which, in the case of these special 
instruments, would never be of any use. As the microscope 
becomes more generally used, and the people at large become 
more thoroughly acquainted with the extraordinary aid which 
it is capable of rendering to those avIio are engaged in the arts, 
it is probable that the numbers of these cheap microscopes will 
increase, in which case we may expect to see the price greatly 
reduced in proportion to the quality. 
‘4 Class” Microscopes.—When a number of objects are 
to be shown to a class or to a scientific meeting, it is desirable 
to avoid the inconvenience arising from each individual having 
to go to the instrument, and this is unavoidable Avhere ordinary 
microscopes are used on fixed tables. Prof. Quekett got over 
this difficulty by having his class-room or theatre fitted up with 
rails upon which the microscopes with their lamps were passed 
from one to another, and Avhere the company is small, the com- 
mon revokving table meets every requirement. But Avhere the 60 
SELECTION AND USE 
class or meeting is large, tlie best device is that of Prof. O. W. 
Holmes, whose class microscope, as made by Messrs. J. W. 
Queen & Co., is shown in Figure 13. This instrument is of the 
simplest construction, so as to reduce the cost as much as 
possible, and it is made largely of wood, so as to be light and 
easily held in the hand. The objects are viewed by direct light, 
without the intervention of a mirror. The lamp used is a flat- 
wicked one, the edge of the wick being turned towards the 
object when high powers are used, and the flat side of the wick 
when the powers are low. 
For opaque objects, the lamp is raised to the top of its stand, 
and its rays allowed to fall upon a small concave mirror at- 
tached to the iron frame by a universal joint, whence they are 
reflected upon the object. The coarse adjustment is effected by 
sliding the body through a short split tube, and the fine move- 
ment by means of a delicate screw, which acts on the stage. 
The entire height of the instrument is about twelve inches, size 
of base twelve by four inches. 
Fig. 13.—holmes’ class microscope. OF THE MICROSCOPE. 
61 
OBJECTIVES. 
The modern Compound microscope owes almost all its value 
to the high degree of perfection which has been attained in the 
construction of the objectives used with it. Some of the old 
microscope stands were quite as elaborate, and quite as costly, 
as anything that can be found in the workshops of our modern 
opticians, but from the fact that the objectives were defective, 
their value as instruments of research was of a very low degree. 
In these old microscopes even the highest power objectives were 
simply bits of ground glass, such as with our modern appliances 
might easily be produced for ten cents apiece, while a modern 
objective of the same power, by any of our first-class makers, 
would cost at least one hundred dollars. In mechanical exe- 
cution the modern objective approaches more nearly to theo- 
retical perfection than any other instrument made by man, but 
the reader must not infer from this, as some have done, that 
it has reached the limit of perfection, and that nothing more 
is to be expected. This was said ten, twenty, and thirty years 
ago, and in each case the words had hardly been committed 
to paper before some optician proved their falsity by accom- 
plishing that which had just been declared to be impossible ! 
Within the past few years the most wonderful improvements 
have been effected, and from present indications it would seem 
that we are on the eve of still more startling developments. 
Since, then, the objective is really the most important part of 
every microscope, seeing that the quality and trustworthiness 
of the work done must depend to a very great extent upon its 
efficiency, it is of some importance to the microscopist that he 
should have at least a fair understanding of the causes to which 
the superiority of modern objectives is due. 
When we use a simple glass lens as an objective for a com- 
pound microscope, we find, on attempting to examine objects 
under powers of more than one hundred diameters, the following 
defects and difficulties : The field of view is so dimly illuminated 
that objects are seen with difficulty ; the outlines of the different 
parts, instead of being sharp and clear, are thick and hazy ; 
several of the lines are fringed with brilliant colors, but colors R‘2 
SELECTION AND USE 
which do not belong to the objects, and finally, if the outlines 
of the object should happen to be straight lines, and be known 
to be such, it will be found that they will appear to be curved 
and distorted. It is evident, therefore, that a simple lens can- 
not be used as an objective in any important work; its indica- 
tions are unreliable, and the imagination is allowed full scope, 
so that the eye is enabled to see whatever the mind desires 
to see. 
The defects which we have just detailed, and which are found 
in every simple glass lens, whose surfaces are bounded with 
curves that are parts of circles, are largely due to what is called 
spherical and chromatic aberration. As these terms are probably 
not familiar to many of our readers, we will give as full and 
simple an explanation of the subject as can be done without 
the formal aid of mathematics. 
Spherical Aberration.—The enlarged image formed at 
the focus of any lens, and rendered visible on a screen or sheet, 
is produced in this way; The rays proceeding from the object, 
and passing through the lens, are, by the action of the glass, 
bent from the path they would otherwise pursue. The object 
may of course be supposed to consist of an infinite number of 
points, and from these points rays proceed in every direc- 
tion, and consequently through every part of the lens. If the 
lens were perfect, all the rays from any one point would be 
brought together at a second point corresponding with the 
first. Unfortunately, however, the ordinary lens does not do 
this; the central portions of the lens and the outer por- 
tions act differently; the one brings the rays to a focus at 
a point a little nearer to the lens than the other, and, con- 
sequently, although we move the screen to a slightly greater 
or less distance, we skill get an image of about the same 
degree of distinctness. It is obvious, therefore, that when 
placed at any distance within certain limits, the screen will 
receive not one image, but a series of layers of images as it 
were, and this consequently gives an indistinctness to the 
resulting image. 
Our readers will find no difficulty in thinking out this 
matter for themselves, and when they have arrived at clear OF THE MICROSCOPE. 
6B 
ideas upon the subject, they will see that spherical aber- 
ration is caused by the difference between the extent of the 
refraction produced at different parts of the lens, and this 
applies not only to all the rays proceeding from each in- 
dividual point, but to the several pencils which proceed from 
different points. 
It is evident that if some parts of the lens bring the rays to a 
focus at a shorter distance than others, these parts must magnify 
more, and such is in reality found to be the case. But if one 
part of an object is magnified more than another, the image 
will be distorted, and hence we have what is sometimes known as 
aberration of form. This distortion is easily seen by examining a 
piece of muslin with a magnifier of high power and large 
diameter. The threads in the centre of the field of view* will 
appear to be straight, while those at the outside will appear to 
be curved.f 
Chromatic Aberration.—This is a defect of ordinary 
or uncorrected lenses, whereby they not only act as magnifiers, 
but as prisms, decomposing the light, and causing objects seen 
through them to appear with a fringe of color. Common hand 
magnifying glasses, used in the ordinary way, do not exhibit 
this defect to a very marked degree, but when the images formed 
by lenses of this kind are again magnified, as is done in the 
compound microscope or telescope, the color becomes very dis- 
agreeably perceptible. 
* By field of view is meant that portion of the object which is visible 
through the magnifier. 
fin ordinary lenses and microscopes, in which this defect is not cor- 
rected by the structure of the glasses themselves, the effects of spherical 
aberration are lessened by contracting the field of view, so that only those 
parts of the object which are seen through the centre of the lens or objec- 
tive are looked at. This contraction is usually effected by means of dia- 
phragms, or round plates of metal pierced with a central hole, which are 
so placed as to cut off the rays which pass through the edge of the lens, 
and leave only those that are central. This plan, however, is only the 
substitution of one defect for another, for by lessening the field of view of 
the lens, we are prevented from seeing more than a very small portion of 
the object, and in addition to this Ihe light is so much reduced that the 
object is seen only with very great difficulty, and not at all clearly. u 
SELECTION AND USE 
Corrected Objectives.—The defects which we have just 
described have been the chief difficulties in the way of perfect- 
ing both the microscope and the telescope. In the case of the 
latter, however, it was long ago found that very excellent re- 
sults could be obtained by forming the lenses of two or more 
pieces of glass of different kinds, and numerous attempts were 
made to apply the same principles to the construction of the 
microscope, but without marked success. The small lenses 
used for the microscope seemed to defy the skill of the practi- 
cal opticians of those days, and resort was had to such devices 
as lenses made of precious stones, and the use of light which 
could not be decomposed—mono-chromatic light as it was 
called, or light of one color. Such light is readily procured by 
the combustion of alcohol mixed with common salt, and when 
illuminated solely by such a light, a brilliantly colored painting 
looks exactly like a plain black and white engraving. But 
although the use of such a light lessens the evils caused by 
chromatic aberration, they introduce another which is quite 
serious—objects which are really colored, appear in black and 
white only. Moreover, such a light cannot easily be obtained 
of a brilliancy sufficient to afford good illumination, and in 
addition to this all the defects due to spherical aberration still 
remain in full force. 
The first attempts made to perfect the object-glasses of micro- 
scopes, consisted in the use of doublets and triplets, it having 
been found that the spherical aberration is greatly lessened, 
when the total refraction is divided up amongst several surfaces 
of moderate curvature, instead of one surface in which the curva- 
ture is excessive, and this plan is still pursued in the construc- 
tion of what are known as French triplets, which will be de- 
scribed hereafter. About the year 1829, however, Mr. J. J. 
Lister, of London, England, published an elaborate paper 
upon the subject, and it was from the principles laid down in 
this paper, that all the important improvements in the modern 
objective took their rise. These principles were embodied in 
the practical construction of objectives by Andrew Ross, who 
suggested the important improvement known as the adjust- 
ment for thickness of cover. To Lister and Ross, therefore, 
it may be justly said that we owe that optical wonder, the OF THE MICROSCOPE. 
65 
modern objective, for although, great improvements have been 
made within the past few years, it is upon the results of their 
labors that these improvements have been based. And yet, 
notwithstanding this well-known fact, the names of these 
distinguished microscopists are not so much as mentioned 
in this connection in the recent work of Dr. Frey, which has 
been lately translated into English, and extensively circulated 
in this country ! 
In estimating the quality of an objective, there are certain 
features to which especial attention must be given. Aside 
from magnifying power, which, of course, cannot be regarded as 
affecting the quality of an objective, these points are: 1. Defin- 
ing power; 2. Achromatism; 3. Freedom from aberration 
of form; 4. Flatness of field; 5. Angular aperture; 6. Pene- 
tration; 7. Working distance.* 
Defining Power.—This is undoubtedly the most impor- 
tant quality to be sought for in objectives. A glass that is 
deficient in this point is absolutely worthless. Want of de- 
fining power is shown by a general haziness and thickening of 
the outlines, together with a want of clearness in the details. 
It arises from the presence of either spherical or chromatic 
*The authors of the Micrographic Dictionary enumerate the following 
points as those in which object-glasses differ from each other: 1. Magni- 
fying power. 2. Defining power. 3. Penetrating power. 4. Their cor- 
rective adaptations. The functions attributed to “ defining power ” are 
the same as those given by other writers; “penetrating power” seems to 
be equivalent to what is generally called “resolving power;” “corrective 
adaptation” is merely the presence of a means of adjusting for thickness 
of glass cover. Frey distinguishes two attributes of object-glasses, viz., 
defining power, and penetrating or resolving power—penetrating power 
and resolving power being considered by him to be the same thing. 
Carpenter enumerates four distinct attributes of object-glasses, viz., 
“ (1) Defining power, or the power of giving a clear and distinct image of 
all well marked features of an object, especially of its boundaries; (2) its 
penetrating power or focal depth, by which the observer is enabled to look 
into the structure of objects; (3) its resolving power, by which it enables 
closely approximated markings to be distinguished; and (4) the flatness 
of the field which it gives.” We cannot regard any of these classifica- 
tions, as strictly logical. Beale makes no formal statement, but gives 
some very excellent practical directions in regard to the selection of ob- 
jectives. 66 
SELECTION AND USE 
aberration, or both. It might be caused by a want of finish oil 
the surfaces of the lenses, but this is seldom the case in prac- 
tice, except where the objective has been exposed to some cor- 
roding fumes or liquids. Old objectives that have been very 
excellent in their day, sometimes fail in defining power, from 
the fact that the surface becomes covered with a greasy deposit, 
very slight, it is true, but just enough to destroy the efficiency 
of the glass. Objectives in this condition should be returned 
to the makers to be cleaned. In one case we found that in a 
lens which failed to show anything clearly, the difficulty arose 
from the fact that the cement used for uniting the glasses of 
the combination had become affected. The objective was by a 
well-known maker, but was over twenty years old 
Achromatism.—When an objective shows much color, it 
fails to define well except by monochromatic light, such as that 
obtained by passing sunlight through a cell filled with the blue 
solution of copper in ammonia. A very slight degree of color 
is not regarded as objectionable, and indeed it has been found 
almost impossible to secure the requisite angular aperture and 
absence of spherical aberration without leaving a little color. 
Some of the best objectives, therefore, show such objects as 
the P. angulatum with decided colors, and yet well resolved. 
Aberration of Form.—An objective may appear to de- 
fine an object perfectly, and yet give a very distorted figure of 
it, just as a cylindrical mirror gives a perfectly definite, though 
very distorted, image of objects seen reflected in it. Aberra- 
tion of form may arise either from over or under correction of 
the spherical aberration, or from want of homogeniety in the 
glass used for making the lenses, or from a want of perfection 
in the workmanship—the surfaces of the lenses not being per- 
fectly spherical. Sometimes this defect is shown very clearly 
on one side of an objective, while the other side is not affected, 
and this fact may give rise to very curious results when the 
objective is tried on different stands, and with oblique light. 
Owing to a variation in the point at which the screw threads 
begin in the different stands, the objective, when fairly screwed 
up, may have a different position in each, as regards the direction OP THE MICROSCOPE. 
67 
from ■which the illumination comes. The consequence is, that 
an objective which may give excellent results on one stand, 
may fail on another. An easy way of testing this fact, is by 
means of a rotating adapter. Of course the best test for aber- 
ration of form is the artificial star, though in the hands of the 
beginner, a micrometer, ruled into squares, is probably the 
most available test. Any trace of the defect under consider- 
ation will be shown by the lines being curved. 
When the lines appear curved, from the fact that the spherical 
aberration has not been properly corrected, the nature of the 
error may be determined as follows: When the micrometer 
lines are widest apart at the centre (like the lines on a map of a 
hemisphere) the spherical aberration has been over-corrected. 
It is under-corrected when the reverse is the case. 
Aberration of form is one of the worst faults with which a 
lens can be affected, and experience has shown us that it is the 
one which is least apt to be detected by a beginner. An objec- 
tive may give a “beautiful” image, and yet be worthless 
because affected with this defect. 
Flatness of Field.—If, when we examine a perfectly flat 
object, every part included in the field of view is clearly in 
focus, the objective is said to have a flat field. Want of flat- 
ness of field is shown by some parts of a flat object being 
clear and well-defined, while other parts are out of focus. In 
general it happens that where this defect exists, the centre and 
circumference of the objective do not act together. 
Angular Aperture.—This subject has given rise to some 
of the most vexatious questions connected with microscopy, for 
a discussion of which wo must refer our readers to the pages of 
the microscopical journals published during the past few years. 
The views which have been promulgated by the two schools into 
which microscopists have been divided on the questions affect- 
ing angular aperture, have been of an extremely opposite 
nature, and few scientific disputes have been waged with more 
bitterness and personalities than that which has been called the 
“Battle of the High and Low Angles.” Now that the smoke 
has in a measure cleared away, and that we are able to take a 68 
SELECTION AND USE 
calm view of the actual results which have been attained, there 
is little room for doubting that the wide angles have gained the 
victory in all the most important points. In a subsequent 
section we shall give our view in regard to the circumstances 
Fig. 14. 
Fig. 15. 
DR. GORING’S FIGURES ILLUSTRATING ANGULAR APERTURE, 
which ought to influence the beginner in the selection of ob- 
jectives of high or low angles ; at present wo shall confine our- 
selves to a discussion of what angular aperture is, and its 
influence upon the working qualities of the objective. 
The reader who will carefully look over the pages of the 
microscopic journals published during the last few years, will OF THE MICROSCOPE. 
69 
probably find that amongst the combatants even the definition 
of angular aperture seems to be undecided, all of which is, of 
course, very puzzling to a beginner. We do not propose to 
decide this vexed question, but the following statement will, 
wo hope, enable our readers to form a clear idea of what the 
older writers meant by this term. 
It Avas Dr. Goring, we believe, that first pointed out the 
special advantages of high angles, and suggested the use of 
test objects, and the figures on the preceding page were used by 
him to define and explain what he meant by angular aperture. 
In these figures, L L and L' L' are two lenses of the same 
magnifying power, but different angular apertures. It will be 
seen that the cone of rays proceeding from O, is substantially 
the same as that from O', but that the lens L L takes in a larger 
part of the cone from O, than the lens L' 1/ does of the cone 
from O'. The angles L O L and L' O' L' are the respective 
measures of the angular apertures of the two lenses. 
The definition of angular aperture, 
given by Goring, has been followed 
by all subsequent writers, the ac- 
companying figure being that used 
by Dr. Carpenter for the purpose of 
explaining and defining the same 
thing. In this figure the compound 
lenses, 1, 2 and 3, are parts of an 
achromatic objective without its 
brass mounting. The line, a c, is 
the front of the objective, and b is 
the object. In this case the angle, 
a b c, is the angle of aperture, and it 
is evident that if a c had been made 
of a larger diameter, or if the curva- 
Pig. ig, 
tures of the lenses, 1, 2 and 3, had been such that the distance 
of a c from b had been lessened, the angle, a b c, would have 
been increased. The points that Ave have mentioned as govern- 
ing the angular aperture are in general controlled by the 
character of the glass used, and by the formula (as regards 
curves, distance, etc.) employed by the optician, and he cannot 
deviate from them without an entire change of design. 70 
SELECTION AND USE 
Dr. Goring' devised several practical methods of measuring 
the angular aperture of different objectives, and he gives a very 
full and clear description of an arrangement adapted to his own 
instrument, in which the foot was made to rotate on a carefully 
centered and graduated base, and modifications of this plan 
have since been adopted by several of our prominent micro- 
scope makers. It has been pointed out, however, that, as 
usually employed, the angle which is measured by this method 
is not the angle a b c, and although the angle which is actually 
determined may be of great value in determining the qualities 
of an objective, it can hardly be denied that to apply the term 
angular aperture to any other angle than the one that has been 
described, must tend to introduce a confusion of terms, and is 
altogether wrong. But in order to be strictly accurate, this 
statement presupposes a condition which is unfortunately too 
frequently overlooked, and that is that all the proportions and 
curves of the different parts of the objective are perfect. To 
make this clear, let us assume that Fig. 16 truly represents an 
objective of which the diameters, curves, and distances apart of 
the several lenses, are absolutely correct for the kind of glass 
used. It is obvious that by slightly increasing the diameter of 
lens 1, or by changing the relations of the three lenses, the ap- 
parent angular aperture might be considerably increased. We 
would soon find, however, that this increase was of no advan- 
tage, because after passing a certain degree the back combina- 
tions would fail to utilize the additional rays admitted, and the 
result would be that the performance of the lens would be in- 
jured rather than improved. Therefore, although in a properly 
constructed lens the angle a b c shows the true angular aperture, 
this will not be the case if the optician has made the front, a c, 
larger than it ought to be in relation to the other parts of the 
objective.* 
It is an unfortunate, but an indisputable fact, that this very 
mistake is frequently committed by makers of objectives, who 
either have not studied, or do not appreciate the qualities of 
lenses of wide angles. They therefore make objectives which 
* The reader who desires to pursue this subject will find it fully dis- 
cussed in Dr. Blackham's paper ou Angular Aperture, which has becu 
published in a separate form. OF THE XIICKOSCOPE. 
71 
admit widely divergent pencils, but which fail to give distinct 
and sharply-defined images. Such lenses, when measured by 
the older methods, indicate extraordinarily large angles, and 
yet fail to have a resolving power at all commensurate with 
the aperture claimed. Indeed, when such objectives are 
diaphragmed down to moderate angles, their performance is 
frequently greatly improved. The action in this case is similar 
to that of the diaphragms in the hand magnifiers, shown in 
Figures 2 and 3. In these simple lenses, it is found that by 
cutting off the outer rays, which do not come to the same focus 
as the central ones, the definition is greatly improved. 
It is a fact no longer open to dispute, that the efficiency of 
an objective, supposing it to be properly corrected, may be 
more nearly expressed by its angular aperture than by its focal 
length. For example, if we have two objectives, one of one- 
fifteenth of an inch focal length, and 150° angular aperture, and 
another of one-fifth of an inch focal length, and 180° angular 
aperture, the latter, although magnifying only one-third as 
much as the other, will actually show more of the more delicate 
structural features of any object; and if its magnifying power 
be increased by suitable eye-pieces until it is equal to the mag- 
nifying power of the one-fifteenth, it will give a better image 
than the latter. Our own experience has long since convinced 
us of the truth of this, and we believe that it is the opinion 
held to-day by all who are familiar with glasses of both kinds. 
Prof. Abbe, who is, perhaps, the highest living authority on the 
mathematics of the microscope, goes so far as to say that the 
angular aperture of an objective is an exact expression of its 
power, and ho gives a table in which he lays down the number of 
lines to the inch which may be resolved by any given aperture. 
It is not difficult to give a practical demonstration of the im- 
portance of a comparatively wide angle of aperture, for as we 
have just said, object-glasses possessing this feature are capable 
of giving important results, which cannot be obtained by means 
of lenses of lower angle. Thus, when we examine, by means 
of a superior French triplet of one-sixth of an inch focus, 
the silicious remains of certain very minute plants of the species 
Plaurosigma Balticum, we are able to see certain lines or mark- 
ings which exist upon their surfaces. That we may be able 72 
SELECTION AND USE 
to see these lines, it is necessary that the 
stand be a good one, and that the light 
be very carefully managed, but, even 
with the most perfect arrangements or- 
dinarily used, we cannot, with such an 
objective, discover similar markings upon 
the Pleurosigma Angulatum, although 
they exist there in great perfection. But 
if for the French sixth we substitute a 
first-class objective of less than half its 
magnifying power, but of wider angular 
aperture, we shall be able to see the lines 
quite distinctly. We have now before us 
an objective of four-tenths of an inch 
focus, which does not correct for.thick- 
ness of cover, but which, with any ordi- 
nary thickness of covering glass, is capa- 
ble of resolving the lines on the Angu- 
latum perfectly, and we have seen objec- 
tives of even lower magnifying power 
which would accomplish the same thing. 
That the effect depends here chiefly 
upon angular aperture, was shown very 
clearly by Dr. Goring, from whose work 
we take the following figures, engraved 
from seven drawings showing the ap- 
pearances presented by the scale of a 
butterfly’s wing, viewed with the same 
magnifying powers, but different angular 
apertures. A well corrected lens of wide 
aperture showed the scale as in G; re- 
ducing the aperture, while all else re- 
mained the same, the appearance was as 
shown in F, and by successive reduc- 
tions the stages shown in E, D, C, B, 
and A, were reached. The slightest ex- 
amination shows that features which were 
quite distinct under a high angle, became 
invisible when the angle was reduced. 
Fig. 17. 03? THE MICROSCOPE. 
73 
This quality of objectives of large angles, whereby they 
are capable of showing distinctly delicate lines or dots placed 
very closely together, is known as resolving power. In the early 
days of microscopy, it was called penetrating power, the term 
genetrating having been applied to that quality of the telescope 
by which it is enabled to show separately the individual stars 
of which the nebulae are composed. In the telescope this was 
supposed to depend upon space-penetrating power as distin- 
guished from mere magnifying power, and this space-penetrat- 
ing power was found to depend very largely upon angular aper- 
ture. In the case of the microscope, however, it is now gene- 
rally agreed that what was called penetrating power in the 
telescope, shall be called resolving power, while to the term 
penetrating power an entirely different meaning has been given. 
Mere resolving power, however, or the power of showing 
separately lines placed very closely together, is not the only 
valuable feature of well-corrected object-glasses of high angles. 
They show delicate lines and fibres, and enable us to make out 
differences of structure which are entirely invisible to lenses 
of low angles. Thus, for example, it has been found during 
recent researches, that the delicate flagella of certain monads 
can be seen perfectly with high angle lenses, while with very 
excellent glasses of low angular aperture they are quite invis- 
ible, The same fact, probably, holds true in regard to the ulti- 
mate fibres of nerves and similar objects. 
The researches of Lister and Ross formed, as we have just 
stated, the first great step in the direction of better correction and 
increased angular aperture. "Whereas, 40° to 65° had previously- 
been regarded as very high angles, even in objectives of the 
shortest focal distance, Ross, in his objectives, soon attained 
an aperture of 132° to 135° and, working with the glass at that 
lime available, this was pronounced the highest attainable 
angle. Attempts had previously been made to obtain a higher 
angle by the use of the glass which Faraday devised for optical 
purposes, and which is in fact a borate of lead. But this com- 
pound is so easily tarnished and disintegrated, that it was 
found impracticable to use it. It happened, however, that 
a young American backwoodsman, Charles A. Spencer, of 
Oanastota, N. Y., a gradxxato of Hamilton College, had his 74 
SELECTION AND USE 
attention called to tliis subject, and after careful study, he con- 
cluded that if he could only procure a durable glass of greater 
refracting power than that ordinarily attainable, the angular 
aperture might be greatly increased. He at once went to work, 
and after many experiments he succeeded in producing a glass 
which enabled him to attain immediately an angular aperture 
of 146°. As early as 1857 he had produced a l-12th with an 
angular aperture of 178°. His objectives had corresponding ex- 
cellence in other directions, and from that time forward this 
country has been noted for the excellence of its objectives, and 
especially for their great resolving power. We may note, in 
passing, that glass of great refractive power, combined with 
sufficient hardness and durability, is now produced as a regular 
article of commerce. 
Penetrating Power.—As previously stated, penetrating 
power, in the early days of microscopy, meant precisely what is 
now understood by resolving power. Now, however, penetra- 
ting power is usually understood to mean the extent to which 
an object-glass shows the depth or thickness of an object. It 
is obvious that such a result can only be produced by the lens 
showing several layers of images, all of which are equally in 
focus, and consequently equally visible at the same time. In 
other words, instead of bringing only one given point sharply 
to a focus, the lens, which has great penetrating power, will 
bring several other points lying above and below this point 
equally to a focus. Hence, as Dr. Pelletan well observes in his 
work, “ Le Microscope ” : “ From a purely theoretical point 
of view, an objective with penetration is in reality a defective 
objective. ” 
As this subject is one of great importance, we have intro- 
duced the two engravings, Figures 18 and 19, for the purpose 
of making it clear to our readers. In Figure 18 we have shown 
a small lens of half-inch focus, and with a very narrow angle. 
Figure 19 shows a lens of the same focal length, but with an 
angle of 90°. The points at which the lines a c and h c in Fig. 
18, and a' c' and V c' in Fig. 19 cross each other, ai’e the respec- 
tive foci of the two lenses at the centre of the field of view. 
Across the points where the lines a c and b c, and a'o' and V d OP THE MICROSCOPE. 
75 
Cross, we have drawn these lines, which may he supposed to 
represent respectively three layers of cells in a section mounted 
for microscopical examination. If the reader will examine the 
relation of these lines to the crossing lines in Fig. 18, he will 
find that the lines a c and b c coincide completely between the 
upper and under lines, and even outside of them, forming, in 
fact, a single line. In Figure 19, on the other hand, it is only 
the middle line that passes through the point at which the lines 
coincide ; at the point where the upper and lower lines pass, 
Fig. 18. 
Fig. 19. 
the lines, a' d and b'd, have already separated to such an extent 
as to form distinct lines. If we regard the lines, a h, b c and 
a' b', V d, as rays of light, it is evident that while those in Fig. 
18 will form images of the upper and lower lines, those in Fig. 
19 cannot do so.* 
Until within a few years it has been accepted, as a thoroughly 
demonstrated fact, that penetrating and resolving power always, 
of necessity, exist in inverse ratio to each other, for it is always 
found that, other things being equal, resolving power increases 
with the angle of aperture, while penetrating power decreases. 
Of late, however, it has been claimed that certain lenses 
of great resolving power possess considerable penetrating 
power. 
* Those who wish to examine this subject more closely,'would do well 
to examine an article on “ Penetration in Objectives,” by Dr. Geo. E. 
Blackham, published in the American Journal of Microscopy, for July, 
1880, and the discussions which follow in succeeding numbers. 76 
SELECTION AND USE 
In attempting to reach a sound conclusion on this point, it 
must be borne in mind that resolving power does not depend 
wholly upon angular aperture. Two objectives of the same 
angle may have very different powers of resolution, on account 
of the degree of perfection to which the corrections have been 
carried, and it is quite possible that a lens of great resolving 
power may have a lower angle than another objective which it 
excels in this respect. In this case the lens of greatest resolving 
power might also have the greatest penetration. We confess, 
however, that we cannot see how great penetration can be com- 
bined with very high angular aperture, and in this view we be- 
lieve that we are in accord with the majority of our best micro- 
scopists. Want of penetration has been urged against objec- 
tives of high angular aperture as a serious defect in many in- 
vestigations in histology and natural history. The advocates 
of high angles claim that the best way to avoid this difficulty 
is to use objectives of less magnifying power, and to combine 
them with high eye-pieces. It is claimed that in this way the 
same amplification and penetration may be obtained as with 
low-angled objectives, and with greatly increased distinctness 
and improved definition. 
Where stereoscopic effect is required by means of the ordin- 
ary binocular, low-angled objectives give better results than 
those of higher angle—one reason for this being that the 
corrections of such objectives are not so easily disturbed as 
those of the others. But it is a curious fact +hat low-power 
objectives of high angle, when used monocularly for examining 
opaque objects, frequently give an impression of stereoscopic 
effect which is startling. We feel certain that no one that has 
his attention once called to this point can ever forget it. 
The late Henry J. Clark, in an article contributed by him to 
Sillimaris Journal, many years ago, suggested another meaning 
for the term “penetration” in objectives. He referred to the 
power which objectives of high angle and perfect correction 
have of pasing through and ignoring, as it were, the various 
layers of cells or other elements which lie above the special 
layer in focus, which latter, when seen by a high-angle lens, is 
clear and distinct, while all the others are invisible. Mr. Stod- 
der, who has recalled my attention to this article, which I had OS' THE MICROSCOPE. 
77 
read many years ago but had forgotten, suggests that this be 
called the penetration of high angles in contradistinction to the 
penetration of low angles as understood by Dr. Carpenter, 
Drey, and others. Where the latter kind of penetration obtains, 
all the layers are visible at once, as we have previously 
explained. 
Working Distance.—Considered as a quality of an ob- 
jective, working distance is the distance between the front lens 
and the object, and it is this distance, and this only, which can 
guide us in forming an estimate of the quality of any given ob- 
jective, as regards this particular feature. In practice, this 
distance is diminished by the amount of metal used in setting, 
which projects in front of the lenses, and also by the thickness 
of the cover glass. It is evident, however, that these are mere 
accidental circumstances which can be readily changed, and 
which have nothing whatever to do with the quality of the ob- 
jective as regards its optical characteristics. Some writers 
have defined working distance to be the space between the 
front of the lens and the upper surface of the cover glass ; but 
it is very evident that if Ave accept this definition avc can no 
longer regard “ working distance ” as a quality of the objective, 
since an objective which might be notable for its great Avorking 
distance Avith ordinary cover glasses, would have no Avorking 
distance at all if very thick covers Avere used. 
To avoids this difficulty, the term frontal distance has been 
introduced, and is used by some writers to signify the quality 
heretofore recognized as Avorking distance. But since the term 
“working distance” has obtained a firm foothold in micro- 
scopical literature, as expressing an important quality or feature 
of objectives, we cannot see how any other meaning can be at- 
tached to it than that given above. 
Working distance is a very important feature in all lenses, 
and good Avorking distance is specially valuable to beginners. 
There are many objectives in market that have to be brought 
so close to the object that ordinary covering glass cannot be 
used, and even Avith the thinnest glass, the distance between 
the objective and the object is such that great skill and care are 
required to avoid accidents. Such objectives do excellent work 78 
SELECTION AND USE 
in the hands of experienced microscopists, but beginners will 
find it difficult to use them. Objectives of very high angular 
aperture have in general very short working distances, but there 
are great differences in this respect amongst the products of 
different makers. Working distance does not depend upon 
angular aperture alone. 
Immersion and “Homogeneous” Lenses.—Ob- 
jectives which require a drop of liquid between the front lens 
and the covering-glass of the object, are now in common use, 
and have been deservedly received with general favor. The 
liquid employed serves two important purposes. In the first 
place, it partially extinguishes two of the glass surfaces (the 
front surface of the objective and the upper surface of the 
covering-glass), and thus it prevents, to a considerable extent, 
the loss of light which always occurs at these surfaces ; and in 
Fig. 20, 
the second place, it enables the objective to gather up rays 
which otherwise would pass outside of it. In the ordinary im- 
mersion objective, water is the liquid which is used, and its 
action will be readily understood from an inspection of the 
accompanying diagram, where c is the front of the objective ; 
Y is the cover-glass ; E the space between the front lens and 79 
the cover; o the object, and o o' a ray of light proceeding 
from that object. It is obvious that when the space, E, is 
filled with air, the ray, o o', after passing through the cover- 
glass and suffering refraction within it, will, on emerging, pass 
on in a direction parallel to its original path, and so will pursue 
the line, I d, and pass outside of the objective. But if the 
space, E, be filled with water, it will take the course I c, and so 
will enter the front lens. 
OP THE MICEOSCOPE. 
It is evident that if a fluid of greater refracting power than 
water were used, the result would be still more marked. This 
consideration led to the use of glycerine instead of wrater, with 
notably good results, and finally lenses have been constructed 
in which a liquid of the same refractive and dispersive power, 
as the glass of the thin cover, is used, and such lenses are known 
as “objectives of homogeneous immersion,” or, for short, 
“homogeneous objectives”—the word homogeneous meaning of 
the same hind, and applying to the liquid and the cover-glass. 
An immerson fluid, perfectly homogeneous with the cover- 
glass, would evidently obviate all necessity for what is known 
as “cover correction,” provided certain other conditions in the 
mounting of the object and the construction of the microscope 
always remained the same, and most of the objectives made by 
Zeiss on the homogeneous system have no such correction. 
But since a difference in the quality or thickness of the me- 
dium in which the object is mounted, or a difference in the 
length of the, tube or body of the microscope used with 
the objective, gives rise to serious disturbances, American 
makers have preferred to make their best homogeneous ob- 
jectives “adjustable,” as it is called ; that is, provided with the 
usual means for cover correction. 
It is a general impression that immersion objectives are more 
difficult to use than dry ones ; such is not the case, however. 
Immersion objectives, with the same degree of effort and skill, 
give finer results than dry objectives of the same power, though 
of course for the ordinary rapid work of searching for known 
objects, dry lenses are to be preferred as being less trouble- 
some, for it is undeniable that it is some trouble to apply the 
liquid and clean the lens, and also the cover, and where a large 
number of observations are to be made, even trifling delays 80 
SELECTION AND USE 
must be considered. Some makers have endeavored to avoid 
this difficulty by supplying double fronts (a vet and a dry) to 
their objectives, while others have constructed objectives which 
work either wet or dry, according as the arrangement used for 
the ordinary cover-adjustment is set to the one or the other. 
Lens Systems—Duplex Fronts —Formerly the term 
“system” was applied only to the entire combination forming 
the objective, and we had “immersion systems,” “correction 
systems,” etc. At present the word is used also to denote the 
individual combinations of two or more pieces of glass, which, 
when arranged together, form the whole objective, as will be 
understood from Fig. 16, where 1, 2 and 3 form the separate 
systems, each composed of two pieces of glass. Such a com- 
bination (the figure of which is, of course, only diagramatic) is 
said to form a three-system lens. Very low powers, formed of 
two achromatic lenses, are said to be two-system ; four com- 
binations, four-system, etc. 
Some years ago, Mr. Tolies brought out objectives of remark- 
able power, which were known as “duplex fronts,” or “four- 
system objectives. These objectives wrere so called because a 
second lens (nearly hemispherical) was added to the front com- 
bination, and this additional lens, added to the three already 
in use, made a four-system arrangement. 
French Triplets.—A few years ago these objectives were 
used quite extensively. They are so called because they ori- 
ginated in the country after which they are named, while to 
further distinguish between them and objectives constructed 
according to the principles laid down by Lister, the latter were 
known as the English, form. Good makers of the English form 
are now found in the United States, France, Germany, Austria, 
and Italy ; and the French pattern is made in many of the 
cities of Europe outside of France, although as yet neither the 
English nor the American opticians have been able to manu- 
facture them at prices which can compete with those of 
continental Europe. The best of the so-called French ob- 
jectives consist simply of lenses in which the chromatic aber- 
ration is corrected by the usual plan of making each lens OT? THE MICBOSOOPE. 
81 
of two different kinds of glass, while the spherical aberration 
is corrected partly by the form of the lens, but chiefly by re- 
ducing the aperture, and by properly combining a series of 
single lenses, which, hovever, are never especially adjusted to 
each other, as in the English forms. Each objective, in its 
most perfect condition, consists of three lenses screwed to- 
gether, and in the lower powers these lenses may be separated 
and used either singly or in combinations of two or three. As 
the magnifying power obtained with two lenses is less than 
that obtained by three, the defects of the double combination 
are not as obvious as they would be if the magnifying power 
were equal to that of the triple combination'. As, however, the 
spherical aberration in the case of a single lens, whether it be a 
plain lens or an achromatic combination, is always greater than 
that of a doublet, and the aberration in the doublet greater 
than that in the triplet, it is never a good plan to attempt to 
obtain a low or moderate power by separating the lenses of a 
high power objective, and using them singly or in twos. Any 
person having a few French objectives at hand who will try this 
and attempt to secure the same magnifying power by the use of 
two lenses, and also by the use of three, the latter being a regu- 
larly adjusted combination, will find that the results obtained 
by the use of the latter are far superior to those afforded by the 
former. 
Considering their quality, these French objectives are re- 
markably cheap. Thus a French No. 2, which is nearly equiv- 
alent to the one-fourth objective of the English and American 
opticians, can be bought for $5, while the cheapest student’s 
objective of this power would cost at least double that sum. In 
addition to this, the French objective may be divided so as to 
afford two other objectives of about three-quarters and one 
inch each, and although the performance of these is far inferior 
to English or American objectives of the same power, they are 
*In making such a trial, it is, of course, necessary to use lenses of equal 
quality in both cases, since the quality of the professedly achromatic 
French objectives in market varies very much. We have seen objectives 
of this class of the same magnifying power, one of which would not resolve 
the markings on the scales of the clothes-moth’s wing, while the other 
would resolve the Pleurosigma Balticum. 82 
SET/ECTION AND USE 
capable of showing a great deal that is interesting and instruc- 
tive. Two or three years ago these lenses were the only ones 
furnished with microscopes costing less than $50, and in the 
very cheap instruments the different powers were always 
obtained by the division of one doublet or triplet, which 
was thus made to yield two or three different objectives. 
Those, however, who cannot afford American objectives, and who 
wish to do work that is of some real value, are advised never to 
separate their objectives, or at least never to separate any but 
the very lowest—that is the No. 1, and against even this 
we would protest were it not for the fact that cheap lenses 
of lower power than the half-inch are seldom found in market; 
and therefore, no other course except the division of a No. 1 
is left to us when we wish to use a lens of lower power. But 
this system of dividing is often carried too far, and we find mi- 
croscopes in market which are furnished with No. 2 or No. 
3 objectives which are divided when lower powers are needed. 
This is decidedly wrong. If a power lower than No. 1 be needed, 
it may be admissible to divide this number, because this is in 
general the only course left to us, but a No. 2 should never 
be divided for the purpose of obtaining an objective equivalent 
to a No. 1. 
The value of the numbers assigned to the different French ob- 
jectives varies according to the fancy of the maker, but those 
of the better class usually found in market are about as follows: 
Number • 1 2 3 4 5 6 
Corresponding focus in parts of an inch.... 1-2 1-4 1-6 1-8 1-10 1-12 
Frey, in his recent work on the microsccpa, regards the 
English system, whereby the focus is expressed in inches, as 
“peculiar.” It certainly is “peculiarly ” definite and positive, 
instead of being indefinite and arbitrary, as is the system 
adopted by the French and German opticians. According to 
the English and American systems, an objective of an inch 
focus ought to be the same, no matter by what maker it has 
been constructed, but when designated after the plan which 
Frey seems to prefer, it is impossible to tell what the focus of 
the lens may be, and consequently what its power is. Thus— 
a No. 2 of Nachet has a focus of half an inch, while a No. 
2 of Hartnack has a focus of one inch, and a No. 2 of the OF THE MICROSCOPE. 
83 
ordinary French objectives is about a quarter of an inch in 
focal length. As it is often useful to the microscopist to know 
the powers of the different objectives made by prominent con- 
tinental makers, we give the focal lengths of the objectives of 
Nachet, Hartnack, and Gundlach, premising, however, that 
by so doing we by no means intend to class these objectives 
with ordinary French triplets. 
Number 0 1 2 3 4 5 
Focus in inches 2 1 1-2 1-4 1-5 1-8 
Nachet’s ordinary objectives are as follows: 
The immersion and correction objectives of the same maker 
are as follows: 
Number 6 7 8 9 10 11 12 
Focus in inches 1-10 1-14 1-15 1-20 1-30 1-40 1-50 
Hartuack’s objectives of recent construction are as follows: 
Number 1 2 3 4 5 6 7 8 9 
Focus in inches.... 2 1 3-4 1-2 1-4 1-5 1-6 1-9 1-11 
Hartnack’s new objectives with immersion and correction are 
as follows: 
No. Focus in inches. 
9 1-12 
10 1-16 
11 1-18 
12 1-21 
13 1-25 
No. Focus in inches. 
14 1-28 
15 1-33 
16 1-40 
17 1-45 
18 1-50 
No. Focus in inches. 
1 1 
II 1-2 
III 1-3 
IV 1-4 
V 1-8 
The following is Gundlach’s scale: 
No. Focus in inches. 
Via 1-12 
VI6 1-12 
Vila 1-16 
VII5 1-16 
VIII 1-24 
IX 1-32 
Via and Vila are not adjustable for thickness of cover, 
while VI/> and VII/> are. Vila, VII/;, VIII and IX are immer- 
sion lenses. 
Since taking up his residence in this country, Mr, Gundlach 
has adopted the system of the English and American makers, 
and designates his objectives by their focal length. The 
table given above, however, will prove of service to those who 
either possess or intend to purchase specimens of his earlier 
work, some of which was very excellent. 84 
SELECTION AND USE 
Testing Objectives.—At first sight it would seem to be 
the easiest thing in the world to test an objective, and find out 
whether or not it is capable of doing certain work, but a little 
experience soon teaches those who are not too self-conceited, 
that it is the easiest thing in the world to be deceived. We 
have seen those who considered themselves the most capable 
of judges, condemn lenses that had received the approbation of 
the ablest microscopists in the world—lenses too that had shown 
their efficiency by doing really good work; showing that even 
those who consider themselves very expert, may sometimes arrive 
at wrong conclusions. If this is the case, then, with men of 
training and experience, how can a beginner, who has had no 
experience, hope to be able to form a correct judgment in re- 
gard to the quality of an objective ? 
But while it is difficult, or perhaps impossible, to pronounce 
a positive opinion in regard to the quality of an objective, 
especially those made for some of the higher departments of 
microscopic work, it is in general easy for those who have had 
experience, to form a judgment in regard to ordinary objectives, 
or at least those designed for ordinary purposes. The ability 
to form such a judgment depends rather upon experience and 
a comparison with the work of other glasses than upon a refer- 
ence to any special standard; and therefore, as a general rule, 
we would advise beginners who are about to purchase objectives, 
to obtain the advice and assistance of some skilful friend. 
To those who cannot obtain such assistance, we offer the follow- 
ing hints. 
The great difficulty in the way of arriving at a decision in 
regard to the quality of an objective, is the want of a standard 
with which to judge its performance. When we examine the 
image which an objective gives of any object, it is very difficult 
to decide whether or not that image truly represents the ob- 
ject. Take, for example, the podura scale: wide differences of 
opinion exist as to its structure, and how it ought to look; sup- 
pose, then, that two objectives show entirely different appear- 
ances of this object, who shall decide which one is correct ? 
And if, even in the case of expert microscopists, this holds 
true absolutely, which it does,' how shall a beginner determine 
that the images which he sees throngh an objective are true or OE THE MICROSCOPE. 
85 
false ? In some departments, the most earnest and long-con- 
tinued discussions have been maintained in regard to the ac- 
curacy or inaccuracy of certain images as seen by professional 
microscopists, and, strange to say, these disputes affect the 
very tests most commonly used, viz., the Podura scale and the 
test diatoms. 
Makers of objectives, and skilful microscopists, being aware 
of the fallacies which beset examinations of this kind, resort to 
certain artificial standards of which the construction is posi- 
tively known, and which should therefore give appearances 
conforming to this known structure. Numerous tests of 
this kind have been suggested, but the only ones generally 
accepted are the artificial star* and ruled glass plates. Of the 
latter, ordinary micrometers answer a very good purpose, but 
the most delicate tests are the famous ruled plates of M. Nobert. 
In the examination of objectives, there are a few simple gene- 
ral rules which must be observed by the microscopist if he 
would secure accurate results. 
The first important point, and one to which sufficient attention 
is not generally given, is the health of the observer at the time of 
making the trial. The eye is a very delicate organ, and the 
slightest derangement of the stomach or nerves affects it to an 
extent that few persons realize. We have an object-glass of 
comparatively low power, with which, when in good personal 
health, we find no difficulty in resolving the P. cmgulatum, 
though a very slight disturbance of the digestive organs, ren- 
ders the lines perfectly invisible. 
It must also be remembered that in the case of such delicate 
observations, personal peculiarities, irrespective of health or 
sickness, exert a marked influence, so that it does not follow 
that what one observer sees, all can see. We have frequently 
*The artificial star is a very minute globule of mercury, obtained by 
crushing a small drop by means of a smart tap with a flat slip of iron or 
ivory. This globule is made to act as a small convex mirror, reflecting 
the light of a lamp, candle or window. It is not mentioned by modern 
writers on the microscope (Carpenter, Hogg, Beale, Frey, etc.), but is 
used by some of our best opticians. Dr. Boyston Piggott, has recently 
revived its use. Goring devoted considerable space to an account of the 
nest methods of using it. 86 
SELECTION AND USE 
seen those who could not distinguish lines that were visible to 
others, and we have also met those to whom an objective, in 
which the chromatic errors were very obvious, seemed to be 
perfect. This probably arose from a kind of color blind- 
ness. We have also met eyes which distorted objects, and 
those which saw fringes of color round objects viewed through 
an objective of generally recognized excellence. 
Attempts have been made to get rid of the errors arising 
from personal peculiarities (or what may perhaps be called the 
“personal equation”) by employing photography, it being 
assumed that if a lens will give an image which can be photo- 
graphed, it must give an image that may be seen, and that 
whatever is photographed must of necessity be a real image. 
But from the known fact that the foci of the chemical and 
visual rays do not coincide, and that the corrections required 
in the one case are not those calculated to give the best results 
in the other, we have little faith in photography as the best 
test of the excellence of an objective, except, of course, in those 
cases where photographic work is the chief purpose in view. 
Lenses intended to transmit an image to the eye must be tested 
by the eye, and if certain eyes show peculiarities not possessed by 
the average eye, then lenses must be corrected specially for them. 
It is scarcely necessary to say that when an objective is put 
upon its trial, the stand and means of illumination ought to be 
such as will do it justice. The best stand in the world cannot 
make a good objective out of a poor one, but a poor stand will 
give poor results even with the best objective. The eye-pieces 
also should be of good quality, and if an objective, which the 
microscopist has reason to believe is a good one, fails, it should 
not be condemned until.it has been tried with eye-pieces either 
by the same maker, or of a known standard of excellence. And 
we must also remember that it is not sufficient to examine an 
objective in combination with a shallow eye-piece, or one giving 
a low magnifying power. An objective may perform very well 
if used with low eye-pieces, and utterly fail when a higher 
power is applied. Most makers of objectives test their glasses 
under eye-pieces of very high power—a quarter and even an 
eighth of an inch focus, or what would be equivalent to H or K 
on the usual scale. OP THE MICROSCOPE. 
87 
The room in which the test is made must also be a subject of 
careful selection. Very many of our best microscopes are used 
in our large cities; at least they are very generally examined 
there with a view to purchase. Now, those who are familiar 
with the subject, know that during the day time the buildings 
along the principal thoroughfares in our large cities are in such 
a state of constant vibration, that good results are rendered im- 
possible, and therefore that an objective and stand which, 
under such circumstances, fail to resolve difficult tests, or to 
define clearly, should not on that account be condemned. 
The illumination employed must also receive careful atten- 
tion. An objective which readily resolves the P. angulatum by 
central illumination, when lamp light or good daylight is used, 
may fail when poor daylight is employed. Special directions 
on this point are given under the head of light and ilium1'- - 
tion, and therefore we would merely say here that an objec j 
which has been tested only by the dull blue light of a northern 
sky, cannot be said to be inferior because it has failed either in 
resolving or defining power. 
On the other hand, we must not place too high an estimate 
on an objective which, by the aid of monochromatic light, (the 
blue-cell, for example,) has resolved certain difficult tests. It 
is not uncommon to find that lenses of a quarter-inch focus 
will, with blue light, resolve the Amphipleura pellucida, but 
fail completely with ordinary light. Even eighths and tenths 
by the same makers, and of a grade quite as good as the fourths 
just mentioned, fail to resolve the Amphipleura by ordinary 
illumination, even when well managed. The aid which is 
derived from blue light in the resolution of difficult diatoms is 
unquestionable, but it is not quite so clear that this kind of 
light gives the same assistance in the matter of definition. Our 
own experience leads us to believe that the real assistance de- 
rived in the latter case is very slight. Therefore, we do not 
regard it as a very high recommendation for ordinary work that 
a lens can resolve the Amphipleura by blue light. We have, 
however, seen a fourth which would resolve the Amphipleura by 
the light of an ordinary hand lamp, aided by Wenham’s reflex 
illuminator. The objective was made by Tolies, and manipu- 
lated by him. 88 
SELECTION AND USE 
To determine the quality of an objective it is best to take up 
in succession the several features which we have just detailed, 
and examine its efficiency in each of these directions. First of 
all, the defining power should be carefully tried, this being the 
most important quality that a glass can possess. No special 
test can be named for this, and in fact the formation of a cor- 
rect judgment in regard to it will depend more upon the 
experience of the observer than upon any particular rules that 
can be laid down. As Carpenter well says: “An experienced 
microscopist will judge of the defining power of a lens by the 
quality of the image which it gives of almost any object with 
which he may be familiar.” To which we may add that the 
inexperienced microscopist will in general fail to detect a want 
of defining power, no matter what object he may examine. 
The chief points seem to be that the outlines should be sharp 
and clear, the blacks black, and the other natural colors clear 
and distinct. Frey compares the image given by a good lens 
to a good copper plate, or a print with sharp letters, and no 
illustration could be more to the point. He also states that an 
objective which is deficient in this respect, is best tested with 
a pretty strong eye-piece. In our own experience we have 
found no surer test of excellence than this ; an objective which 
is deficient in defining power, is sure to “break down ” under 
a high eye-piece. Deep eye-piecing does not effect the resolv- 
ing power of a lens to the samo extent that the defining power 
is lessened, and therefore, the fact that a glass shows lines 
under a high eye-piece, is not an absolute demonstration of its 
excellence as regards definition. At the same time, it will be 
found that considerable angular aperture is absolutely neces- 
sary to enable any glass to bear deep eye-piecing, because with- 
out this, the loss of light is so great that nothing can be seen 
clearly. Hence the truth of the somewhat paradoxical state- 
ment, that an objective may be really good under a low eye- 
piece, and yet fail under a high one. 
With the English opticians a favorite test for definition is 
the Podura scale. Unfortunately, however, the structure of 
this scale and even the identification of the scale itself, seem 
to be a matter of doubt. Page after page has been written for 
the purpose of showing how the Podura scale ought to look, and OF THE MIOKOSCOPE. 
89 
still the question seems to be undecided. Carpenter, in his last 
edition (page 702) says: “The sharp and distinct bringing-out 
of the 4 exclamation marks ’of the Podura scale, constitutes, when 
it coexists with the greatest practicable freedom from color, and 
with adequate 4 focal depth ’ or 4 penetrating power,’the most 
valuable proof of the fitness of an Objective of high power for 
the purpose of scientific work.” 
To give our readers an idea of 
how the podura scale ought to look, 
we give a figure copied from the 
engraving published by the late 
Richard Beck, in his work on the 
microscope. The figure shows 
44 the appearance of the Podura 
scale when the adjustment of the 
object glass is correct and the mark- 
ings are in focus.” The objective 
used was a one-eighth, giving a 
magnifying power of 1,300 diame- 
ters. 
Fig. 21. 
It is, we believe, generally conceded that in the present state 
of the art, perfect correction for color cannot be obtained, but 
so long as the residuary chromatic abberration does not inter- 
fere with the defining power of the objective, it cannot be re- 
garded as an objection. And yet we have seen a would-be critic 
reject a very excellent lens because it showed a little color, 
while he was loud in his praise of another lens which, although 
more perfect in this respect was almost worthless otherwise. 
Like specks of dirt on an eye-piece, which do no harm and are 
never even seen by experienced microscopists, slight color and 
want of flatness of field are the bites noirs of beginners. They 
are the defects which are most easily detected, and the detec- 
tion gives the critic an air of knowledge which is to him a 
source of great pride. 
The best English and American opticians now slightly under- 
correct their best objectives, so that the field shows a slightly 
greenish hue, while any prominent markings on the object, 
such as the dots on the Angulatum stand out clear and well de- 
fined and of a very delicate ruby tint. According to Frey the 1)0 
SELECTION AND USE 
majority of continental makers adopt the opposite plan. 
Their lenses are over-corrected, and objects show a bluish 
border. 
A want of correction for color is shown when thin objects with 
many cross lines are examined, especially with slightly oblique 
light. As a test for achromatism in low powers, Carpenter 
prefers a section of coniferous wood, showing the glandular 
dots. He also recommends the tracheae of insects, but almost 
any lined object will answer the purpose. 
The existence of aberration of form is best proved by the use 
of a fine micrometer or a Nobert’s plate. When this defect is 
very marked, it is easily seen in the curved and distorted lines 
of which the image consists, but such a state of things exists 
only in extreme cases. Where this distortion is not very glar- 
ing, it may be necessary to compare the magnified image of the 
lines in the stage micrometer with straight lines ruled on a thin 
plate of glass laid on the diaphragm of the eye-piece—in other- 
words with an eye-piece micrometer in which the ruled lines are 
quite long. 
For testing for flatness of field and aberration of form, Frey 
recommends “ a slide thickly smeared with India ink, in which 
small circles or other figures are scratched with the point of a 
fine needle. * * * If the instrument is adjusted with trans- 
mitted light for such a circle, it should appear sharply 
cut on the black ground, and not surrounded by a halo 
of light. If the circle is then brought out of focus, it 
gradually enlarges, while its sharp borders disappear, with- 
out spreading a strong halo of light either inwards or outwards 
over the black field.” 
The angular aperture of an objective can be determined 
accurately only by measurement, and this is something that 
beginners will hardly attempt. To measure accurately the 
angular aperture of an objective, is a task requiring con- 
siderable skill and knowledge, and most of the appli- 
ances furnished by microscope-makers for this purpose, fail 
to give accurate results. It must be remembered that in 
measuring the angle of an objective, we must comply with 
the same rules that govern the accurate measurement of 
any other angle. Dr. Carpenter, in his work, gives a method OP THE MICROSCOPE. 
91 
■which he calls “ the simplest and most convenient.” We ven- 
ture to say, that none but an expert can obtain by it results 
that are anywhere near accurate, especially with high powers. 
We therefore consider that any directions upon this subject, 
addressed to beginners, would be worse than useless. 
Since, however, the resolving power of an objective depends 
in a large measure upon its angular aperture, we may feel 
pretty certain that an objective which fails to resolve tests 
suited to its magnifying power, is deficient in angular aperture, 
unless, indeed, its inefficiency should arise from want of defining 
power, which may be tested by other means. Of ordinary work- 
ing lenses, the half inch ought easily to resolve the Pleurosigma 
Balticum; the quarter inch should resolve the P. angulatum by 
oblique light, and those of a fifth or sixth inch focus should 
resolve the latter test by axial or central light. An eighth, 
tenth, or twelfth, ought to resolve all the diatoms on the Probe 
Platte below the 17th. It is true that objectives of a quarter 
inch focus have beeh made to resolve everything on the Probe 
Platte, but such glasses cost too much to render it likely that 
they will fall into the hands of ordinary students. Twelfths 
and sixteenths should go through the Probe Platte easily. If 
they cannot do this it would be better to take a lower power of 
better quality, and use it with a higher eye-piece. 
We must also be on our guard against an old source of error— 
the use of lined tests which vary from the accepted standard.* 
Great differences exist in the different specimens of the var- 
ious test objects that are used, some, owing to individual 
characteristics and the methods employed in mounting, being 
much more easily resolved or shown than others. Gonse- 
*“Theproof objects [finely lined insect scales] originally discovered by 
me, are sufficient for that purpose in honest hands, and when used with (he 
precautions I have pointed out. But it is well known that they have been 
shamefully abused, owing to the various facilities of resolution which 
exist between different specimens of lined objects, the external charac- 
ters of which closely resemble each other; so that it may be said that 
there are proof objects to suit the capacities of all microscopes; nay. they 
are actually perverted to the purpose of deceiving the unscientific part of 
the public in a much more effectual manner, than could possibly have 
been done without them.”—Goring. What is true of the scales used by 
Goring is also true, though perhaps not to the same extent, of diatoms. 92 
SELECTION AND USE 
quently, because an objective resolves one specimen of the P. 
Angulaium, it does not follow that it will resolve all others. One 
of the most important steps in the direction of uniformity in 
this respect, at least so far as testing the resolving power of 
objectives is concerned, is furnished by the test-plate (Probe 
Platte) of J. D. Holler. Upon a slide of the usual size, he ar- 
ranges twenty diatoms, carefully selected as to cleanness, and 
also as to resolvability. Those that he has chosen for the pur- 
pose are named in the accompanying table. They are arranged 
on the slide in a line which is about a quarter of an inch in 
length, the beginning and end of the row being marked by a 
specimen of Eupodiscus Argun, Ehrbg. The table on the oppo- 
site page gives the closeness of the lines and the direction of 
the markings in these diatoms according to the best authorities. 
In this connection it must not be forgotten, however, that mere 
closeness is not the only feature which makes a series of lines 
easy or difficult of resolution. Every micrometer maker knows 
that of two sets of lines, both ruled at 10,'000 to the inch, one 
may be much more difficult to resolve than the other. The 
strength of the individual lines has as much to do with it as 
the mere distance at which they are placed apart. Holler’s 
Probe Platte is furnished of two kinds, dry and in balsam, the 
latter being, of course, by far the most difficult test. It is an 
unfortunate fact, however, that even with all the care and skill 
exercised, even the test-plates of Herr Holler do not always 
conform to a standard; and, therefore, were it not for the facts 
just stated, it would seem that the most trustworthy tests are 
the ruled plates of H. Nobert. 
It is not difficult to test an objective of moderate power for 
flatness of field, provided we have on hand a suitable object. 
For this purpose a thin section of wood, or cf an echinus spine, 
is generally chosen. For low powers a very excellent test is 
one of those micro-photographs which are so common. One 
showing a sentence or sentences should be chosen in prefer- 
ence to a picture, since, unless the field of view be flat, the whole 
of the letters will not be clearly readable at once, while in a 
picture the effect known as aerial perspective may give rise to an 
impression of want of flatness of field. In applying tests for 
flatness of field, it is of course obvious that we must make sure OF THE MICKOSCOPE. 
93 
1. Triceratium Favus, Ehrbg 
2. Pmnulana nobilis, Ehrbg 
3. Navicula Lyra, Ehrbg. var. 
Direction of 
Striae. 
. Transverse. 
Smith. 
Strias in 1-1000 of an inch— 
Sollitt. Morley. 
3 06 to 3.08 
10.8 to 12,5 
Others. 
4-5 
10-20 
4. Navicula Lyra, Ehrb" 
5. Pmnularia interrupta, Sm. var 
0. Stauroneis Phoenicenteron, Ehrb" 
' ■ Grammatophora marina, Sm 
8. Pleurosigma Balticum, Sm 
9. Pleurosigma acuminatum (Kg.) Grun. 
10. Nitzschia Amphioxys, Sm 
11. Pleurosigma angulatum, Sm 
12. Grammatophora oceanica, Ehrbg 
(=G. subtihssima.) 
13. Surirella Gemma, Ehrbg 
14. Nitzschia sigmoidea, Sm 
15. .Pleurosigma Fasciola, Sm. var 
16. Surirella Gemma, Ehrbg 
17. Cymatopleura elliptica, Breb 
18. Navicula crassinervis, Breb 
. Transverse. 
. Transverse. 
Transverse. 
. Transverse. 
Transverse. 
Transverse. 
Transverse. 
Diagonal. 
Transverse. 
Transverse. 
Transverse. 
Transverse. 
Longitudinal. 
Transverse, 
38 
52 
85 
64 
40-20 
51-46 
90-50 
lo a to 18.5 
25 0 to 27.1 
26 5 to 26 8 
31 1 to 33 
36 3 
31.5 to 34.3 
42.7 
42.9 to 45.3 
43.8 
61.2 to 61.7 
51.4 to 54.8 
63.0 to 63.3 
55.5 to 56.5 
63.0 to 70.4 
63.3 
79.4 to 82.2 
84.5 to 84.7 
92.7 to 92.9 
16-17 
24-25 
62 
80 
75 
80 
(— Frustuha Saxonica, Babb.) 
19. Nitzschia curvula, Sm 
20. Amphipleura pellucida.. 
(= Navicula Acus.) 
Transverse. 
Transverse. 
130-120 
85 
95 
MOLLEE S TEST PLATE. (PKOBE-PLATTE. ) 94 
SELECTION AND USE 
that the test used is itself flat. Common glass glides are not 
flat, and as they are used for the cheaper kinds of micro- 
photographs, this fact may give rise to errors if we are not care- 
ful in our selections. The best slides are cut from glass plate 
which has been ground and polished so that the sides are per- 
fect planes, and it is this kind only that should be used. Care 
should also be taken to see that the object lies flat on the slide, 
and is not distorted by the cover. We have seen an objective 
condemned because it did not show all the diatoms in the field 
of view in focus at once, when the fact was that the diatoms 
were attached to the cover which was slightly wavy as covers 
often are. WTien it is suspected that the fault is not in the objec- 
tive, but in the slide or cover, the object should be carefully 
passed across the field of view, and the changes in focus noticed. 
This will in general tell where the defect lies, for if the part 
that is apparently foggy should move as the object moves, it 
shows that the object itself is not flat. It has been recom- 
mended by high authority to test objectives for flatness of field 
by strewing some fine powder on a slide and seeing whether all 
the grains are in focus at once. For obvious reasons this is a 
very unreliable method. 
Penetration in low powers is perhaps most readily deter- 
mined by the examination of opaque objects of considerable 
thickness. The round pollen grains of the hollyhock, and the 
rounded forms of the polycystina are excellent tests for objec- 
tives of an inch or inch and a half. Lower powers ought to 
show coarser objects in all their dimensions, while for those of 
medium power the coarser cellular tissue of plants answers very 
well. It is more difficult to indicate a good test for penetra- 
tion in the higher powers, in which, by the way, we have often 
seen want of penetration mistaken for want of flatness of field. 
This arose simply from the fact that scarcely any object is 
absolutely flat, and hence, as explained under another head, 
the curvature of the object is sometimes taken as an indica- 
tion of a defect in the objective. Want of good working 
distance makes itself obvious during the examination of any 
object suited to the objective. OF THE MICROSCOPE. 
95 
ON THE SELECTION OE A MICEOSCOPE FOE PEAC- 
TICAL PUEPOSES. 
The object of all the information given in the preceding 
pages, is to enable the reader not only to understand the con- 
struction of the microscope, but to select one judiciously ; and, 
therefore, in every section we have offered hints bearing in this 
direction. We now propose to give the reader such special in- 
structions in regard to the choice of an instrument as are 
necessary in addition to those previously offered. 
Those who will examine the catalogues of the various makers 
of microscopes, will find the instruments divided into first, 
second, third, fourth, etc., classes, the microscopes in each 
succeeding class in this descending scale being smaller and less 
complete than those in the one preceding it. The first-class 
microscopes of almost all our prominent makers are large, 
beautifully-made instruments. They are provided with me- 
chanical movements in every part, whereby the utmost delicacy 
and precision in making an adjustment, and in recording it, 
may be obtained, and as a natural consequence, such instru- 
ments are quite expensive. Indeed, it will often be found that 
the hanging and adjustment of the mirrors alone, of these fine 
stands, cost as much as an entire microscope of the lower 
grades. 
Second-class stands are usually smaller than those of the first 
class, but they are frequently very complete as regards their 
adjustments and arrangements. Microscopes of the third and 
fourth class are usually much simpler in their construction, as 
well as less in size. In addition to these different classes, most 
manufacturers offer models adapted to special purposes, so that 
in setting out to procure a microscope, the beginner is very apt 
to be bewildered unless he has the guidance of some judicious 
friend. Of course those who are mere dealers always urge the 
purchase of the most complete and expensive microscope which 
the funds of the purchaser will enable him to procure, whereas 96 
SELECTION AND USE 
a comparatively cheap microscope would frequently answer his 
purpose far better. The reader will of course bear in mind 
that by “ dealer ” we do not refer to experienced opticians, such 
as are most of our microscope makers. From these men the 
student will be pretty sure to get sound advice and efficient 
assistance. But, as is well known, every dealer in spectacles 
sets himself up as an optician, and professes to be competent 
to give advice in regard to the purchase of a microscope ; and 
the microscope which these men always advise the purchaser to 
procure is the one that will afford them the largest commissions. It 
is unnecessary to say that this is not always the instrument 
that will afford the greatest amount of satisfaction to the be- 
ginner in microscopy. 
In selecting a microscope, regard must be had, not only to 
the excellence of the instrument, but to its adaptability to the 
purpose for which it is intended, and to the person who is to 
use it. A complicated and expensive compound microscope, if 
placed in the hands of a person having little experience or skill, 
would evidently be worse than wasted, while to attempt to con- 
duct elaborate and delicate investigations by means of a cheap 
non-achromatic instrument, would simply be to throw away 
time, and wantonly incur the risk of serious errors. And yet no 
mistake is more frequently made. A microscope is wanted ; the 
purchaser is liberal with his means, and he is saddled with an 
expensive instrument entirely unsuited to his requirements. 
Or, on the other hand, a physician or student of limited means 
requires an instrument, and, being unable to afford the price of 
a really good one, he is induced to purchase a cheap affair, 
whose indications, when applied to the subjects for which he 
requires it, are entirely unreliable; whereas, he ought to be 
told that if he cannot afford a microscope which is at least pro- 
vided with good objectives, and the necessary facilities for using 
them, he ought to leave microscopy in its applications to medi- 
cine and physiology alone. We feel it the more necessary to 
be emphatic on this point, from the fact that cases involving 
such errors have so often come under our own observation. 
Thus we have seen cheap French instruments, with poor triplets, 
in the hands of physicians, and used in cases where the safety 
of the patient depended upon a correct diagnosis } 97 
OF THE MICROSCOPE, 
The first point to be decided, is the kind of microscope that 
should be procured—that is to say, whether a simple or a com- 
pound microscope is wanted. If the student is desirous of 
working on objects under the microscope—making dissections 
of flowers, etc.—a simple microscope, of any of the kinds de- 
scribed in a previous chapter, will suit his purpose best. It 
should be arranged on a stand, and this he can either do him- 
self, or he can procure one of the many dissecting microscopes 
which he will find described in the catalogues of the manufac- 
turers. For such purposes a simple microscope is indispensa- 
ble, though when we come to examine the results of our work, 
(dissections, etc.) a good compound microscope is equally 
necessary. 
Attempts have been made to combine these two forms of the 
microscope in one instrument, and with considerable success, 
so far as increasing our power to examine our work as it pro- 
gresses is concerned. This is accomplished by so arranging 
the simple microscope that a compound body with its eye- 
piece may be slipped on or off, as required. And by using a 
single concave lens as an eye-piece, we can secure considerable 
magnifying power and great working distance, while at the 
same time the object is seen erect and not inverted, as when 
the ordinary compound body is used. This form is called the 
“Brucke Loupe”—and is too little known in this country. 
But no such makeshift can take the place of a good compound 
microscope, although it may form a useful and convenient ad- 
dition to the student’s outfit. 
The selection of a compound microscope will frequently be 
determined, not only by the wants, but by the means of the 
purchaser. To those who are obliged to put up with a cheap 
microscope, the only advice that we can give is to get the best 
they can for the money, and as newer and better microscopes 
are constantly coming into market, the best thing the student 
can do is to procure the latest catalogues of the different 
dealers, and examine and compare what they have to offer. 
There is no microscope in market to-day that will not probably 
be excelled by something better in less than twelve months 
from this time. 
To those whose means enable them to procure whatever they 98 
SELECTION AND USE 
may require, a word of caution is also necessary. If your 
studies require the employment of the very best instrumental 
appliances, by all means procure either a first-class stand by 
some well-known maker, or a microscope made to suit your 
special requirements. But at the same time do not fail to pro- 
vide yourself with one of what may be called the third-class in- 
struments ; that is, a microscope of moderate size, and destitute 
of those complicated arrangements which are the glory of all 
first-class stands. With such a microscope you will be able to 
do twice, yes thrice as much work as with the large heavy 
stands. The physician or working naturalist that procures a 
very expensive stand for every-day use, makes a great mistake. 
It is very well to have such a stand for special occasions, but 
for “ ordinary work ” the small stand is to be preferred. 
And this leads us to enquire what is or ought to be meant by 
“ ordinary work ? ” The expression is not an uncommon one, 
but it is one to which objection has been made on account of 
alleged indefiniteness. 
If we exclude from consideration the employment of the micro- 
scope for purposes of amusement or of elementary instruction, 
almost all microscopic work may be divided into two classes, 
which may very properly be called, respectively, ordinary work 
and purposes of research. Ordinary work in this sense consists 
chiefly in searching for known forms, and does not demand 
anything like the instrumental perfection which is required for 
work which at all approaches the nature of original research. 
And by original research, we do not mean that research which 
is carried on for the purpose of making important scientific dis- 
coveries, but simply that which has for its end the examination 
of the structure and characteristics of objects which are un- 
known to the individual observer. 
In support of this view, it would be easy to cite numerous 
instances. Thus every one knows, that for the examination of 
different kinds of starch, and the investigation of their peculiar- 
ities, very good microscopes and high powers ought to be used. 
But Hassal, in his work on adulteration, tells us that a quarter- 
inch objective, of ordinary quality, and used on a common 
stand, is sufficient to discriminate between the different starches 
when they are mixed together, OF THE MICROSCOPE. 
99 
The study of the diatoms, in so far as their structure is con- 
cerned, confessedly requires microscopes and objectives of the 
very highest class. And yet we have been told by a gentleman, 
whose name deservedly stands very high in connection with the 
study of these interesting objects, that for the determination of 
species, and for most other points which he has studied, he has 
used a good non-adjusting quarter, on a simple stand, and that 
it is but seldom that he has recourse to better objectives, of 
which, however, he has a full series by the most eminent 
makers. 
By the term “ ordinary work,” then, we may very properly 
designate all such examinations as lead us over ground that is 
well known, while no work that involves the examination of 
unfamiliar structures or the investigation of unknown processes, 
can be so called. But of all the work that is done with the mi- 
croscope, four-fifths (including the work of the physician) is 
“ordinary work.” 
To those, therefore, who have abundant means at their 
command, we would by all means recommend the pur- 
chase of two microscopes—always, of course, getting the cheap 
one first. If, during the course of their “ apprenticeship,” this 
cheap instrument should get injured, the loss will not be very 
great, and by the time the student has learned to use the cheap 
instrument, he will have acquired intelligent views as to his 
special needs in the matter of a more complete one, and will 
not be dependent upon the advice of any one. 
To those who cannot afford two microscopes, we would 
strongly recommend as a stand, one of the New American 
Models, previously described. If we except a few special de- 
partments, such as goniometry, etc., these stands are equal to 
all demands, and will do justice to any objectives or accessories, 
while at the same time they are sufficiently compact and handy 
to allow of the convenient and rapid accomplishment of all 
kinds of simple work. 
To those who cannot afford one of these stands, the only 
advice we can offer is to get the best they can for the amount of 
money they have to spend. 
It would be impossible to give anything like a list of special 
cases in which the different styles of microscopes prove most 100 
SELECTION AND USE 
useful : the reader whose attention is called to this point will 
have little difficulty in deciding the question for himself. We 
merely give the general rule, that where dissections of plants 
and animals are to be carried on, a simple microscope should 
in general be chosen, while the compound microscope fur- 
nished with good objectives, is indispensible whenever high 
powers are required for the examination of objects. 
Having decided upon the kind of microscope that is needed, 
the next step is to determine the individual quality of the dif- 
ferent instruments that may be offered to us. To do this 
thoroughly, it will in every case be found a good plan to take 
up, point by point, all those elements that are necessary or desir- 
able in a microscope, and in this wray subject the instrument 
to the most careful scrutiny. Unless a microscope is made 
specially to order, it will be difficult to find one that will com- 
bine all desirable features, but the plan we suggest certainly 
enables us to decide most readily and accurately as to the pres- 
ence or absence of those points which are desirable for our pur- 
poses. The following are the chief points that demand atten- 
tion: 
Magnifying Power.—We place this first, because usually 
the first question in regard to a microscope that is asked by be- 
ginners is, “ What is its magnifying power? ” Now magnifying 
power, although an important element, is after all but a secondary 
consideration. A microscope magnifying a thousand diame- 
ters could easily be made and sold at a profit for five dollars, 
and a few cents expended in paper and paste will at any time 
double, or even treble, the magnifying power of an ordinary 
compound instrument. The proper question is not how much 
does a microscope magnify, but how much will it show. A 
magnifying power of one hundred diameters, obtained by the 
use of first-class objectives, will enable us to see more of the 
true structure of an object than could be reached by a magni- 
fying power of five hundred, the lenses in the latter case being 
of inferior quality. But, although not the first consideration, 
magnifying power is a feature of sufficient importance to deserve 
careful deliberation, and without a knowledge of the powers 
required, and the mode in which they are expressed, the begin- OP THE MICROSCOPE. 
101 
neT will often encounter difficulty. Both these points "being es- 
sential, therefore, before discussing the magnifying powers 
best suited to different purposes, it may be well to say a word in 
regard to the mode in which magnifying power is always ex- 
pressed by scientific men. 
When we look at a small object through a microscope, and 
see it magnified to twice its length, it is evident that its breadth 
is also magnified twice, and consequently its surface, no matter 
what the shape may be, is magnified four times. It might also 
be said that as we only take cognizance of bodies having a sen- 
sible thickness, this thickness must be magnified twice, and 
therefore the obj ect is magnified twice four, or eight times. The 
latter, however, is a view which is never insisted upon, and 
even those who claim the most for their microscopes, never do 
more than express the magnifying power in surfaces. Scien- 
tific men are, however, agreed that to express a magnifying 
power in surfaces is to convey a wrong impression in regard 
to the assistance rendered by the instrument to the natural 
vision, for a careful study of the physiology of vision, teaches us 
that our power to appreciate and distinguish the features of 
any object depends upon the distances to which the characteris- 
tic points of that object are separated, and this can be meas- 
ured only by linear, and not by superficial units. There are 
other considerations which lead to the same conclusion, but 
for the beginner it is sufficient to know that all scientific mi- 
croscopists are agreed that when the magnifying power of a 
microscope is stated, it shall be stated in diameters, and not in 
areas. By common consent, then, ten times means ten diame- 
ters. And yet it is a very common thing for charlatans, and 
those who wish to deceive the public, to say that a microscope 
sold by them magnifies ten thousand times, or one hundred di- 
ameters, and as “ ten thousand times ” is much more readily 
appreciated by the popular mind than “one hundred diame- 
ters,” the majority of those who read such statements suppose 
that they will be enabled to see ten thousand times more than 
they could see with the naked eye, which assuredly is not the 
case. In some instances these advertisers do not even state 
the diameters. We have now before us, clipped from a journal 
of deservedly good reputation, an advertisment which reads as 102 
SELECTION AND USE 
follows, omitting what printers call the “ display ” arrangement 
of the words: “ Microscopes constructed on scientific principles 
magnifying 10,000 times.” The microscope in question, as we 
learned by personal examination, gives a magnifying power of 
about one hundred diameters. Carpenter speaking upon this 
point says: “ The superficial magnifying power is of course es- 
timated by squaring the linear ; but this mode of statement is 
never adopted by scientific observers, although often em- 
ployed to excite popular admiration, or attract customers, by 
those whose interest is concerned in doing so. ” We would, 
therefore, advise our readers to look with suspicion upon any 
concern advertising in this manner. Of course an advertisement 
claiming a magnifying power of “ 10,000 areas or 100 diame- 
ters ” is unobjectionable, because both expressions are placed 
upon an equal footing. It must also be borne in mind that 
great though unintentional mistakes are often made by dealers 
in stating the power of the microscopes they offer for sale. 
Not long ago a friend told us that he had been offered a small 
microscope having a magnifying power of 500 diameters, for 
a moderate sum. We called to see it, taking the precaution to 
put a micrometer and a foot rule in our pocket. By actual 
measurement the highest magnifying power of this microscope 
was 45 diameters ! Another instance occurs in the catalogue 
of a well-known and honorable business house, who offer a 
very neat and well made instrument, whose magnifying power 
is claimed to be 350 diameters. Careful measurement of several 
instruments, however, gave an average power of less than 200 
diameters! Indeed it will in general be found that the magni- 
fying power stated by dealers who do not devote their chief at- 
tention to microscopes, is greatly over estimated. 
So much, then, being clearly understood in each case, the 
question naturally arises, What should be the magnifying powers 
possessed by microscopes intended for certain specified purposes? 
That a certain magnifying power is necessary, no matter what 
the quality of the lenses may be, is true beyond a doubt. 
Thus, for example, suppose we wish to see the lines on the 
Pleurosigma Angulatum, which lines are about the one fifty- 
thousandth of an inch apart; what magnifying power would 
be necessary? OF THE MICROSCOPE. 
103 
With the best illumination, the average human eye can just 
clearly distinguish lines which are the two-hundredth of an inch 
apart. Some eyes, under favorable circumstances, can see 
lines placed as close together as 250 to the inch, but the aver- 
age is as we have stated.* To be visible even to the best eyes, 
therefore, the lines on the Angulatum, must be magnified so 
that they will present the same appearance as lines spaced so as 
to give at the very most, say, 200 to the inch. This requires a 
magnifying power of 250 diameters, and with less than this 
they cannot be seen, no matter how good the objective may be. 
And when Dr. Frey says that they can be seen with a power of 
80 or 100 times, while “weaker objectives, magnifying 40 or 50 
times, should show something of the lines,” he makes a state- 
ment that we cannot accept. 
In order, therefore, that an object may be distinctly seen, it 
must be magnified to a certain extent, but the magnifying 
power absolutely necessary in any given case, will also depend 
upon whether the microscope is to be used for general purposes 
of investigation, or merely for the recognition of known forms. 
For the latter purpose a power of 100 may be sufficient, while 
for the former, on the same class of objects, a power of 500 
would be the least that would be serviceable. The following 
are a few of the cases in which the power required can be stated 
approximately: 
For medical purposes (except for pocket instruments, intended 
merely to enable the observer to recognize known forms) a 
power of 400 is needed, and the objective should be of really 
excellent quality. 
Students of histology require a microscope with a wider 
range of power. Low powers are more useful to them than 
to the medical man, and if they push their researches in cer- 
tain directions, there is no limit to the magnifying power needed. 
*To test the statement in the text, place a glass micrometer, ruled 200 
lines to the inch, on the stage of a microscope, and by means of the 
mirror throw a beam of light upon it, just as if for examination by trans- 
mitted light in the usual way. If we now look at the lines, not through 
the tube, but simply from one side, they will appear distinctly as well-de- 
fined lines. Try the same with a micrometer ruled 250 to the inch; some 
eyes will be able to distinguish the lines, but very many will fail to do so. 104 
A good two-tliird, one-fifth, and one-tenth, giving magnifying 
powers of from 50 to 1000 diameters, will, in general, answer 
most requirements. It must be borne in mind, however, that 
beginners can hardly be expected to use a one-tenth inch objec- 
tive to great advantage, and, therefore, the purchase of this 
item may safely be deferred. 
SELECTION AND USE 
For the study of botany, and the ordinary facts of vegetable 
physiology, a power of 300 is sufficient; but the very minute 
forms of vegetable life require a much higher power, and so 
do certain of the higher points in the physiology of plants. 
For the detection of adulteration, Hassal recommends the 
inch and the quarter-inch objectives, giving a magnifying power 
witli No. 1 and No. 2 eye-pieces, of from 60 to 350 diameters. 
For ordinary purposes of instruction and amusement in the 
household, a microscope magnifying from 30 to 150 diameters 
will be found most satisfactory, and for these reasons: Such an 
instrument is easily managed; if well made it gives a power 
amply sufficient for all ordinary objects, and it need not be ex- 
pensive. Moreover, while it is an easy matter to prepare ob- 
j ects so that they may be seen satisfactorily under low and me- 
dium powers, it requires great skill and long practice to enable 
the student to prepare objects so that they may be examined 
with profit under a high power. And finally, under a high power, 
but a very small portion of any ordinary object can be seen at 
once, and consequently many of those things that are best 
suited for popular examination can only be seen piecemeal— 
a very unsatisfactory mode of proceeding. Thus, under a power 
of 750 diameters, a fly’s foot could not possibly be seen as a whole; 
we might examine a single claw or pad at a time, but not the 
whole foot, and consequently would find great difficulty in ac- 
quiring an idea of what the general structure of the foot is. 
To give the reader clearer ideas upon this point, we have just 
measured the diameters of the fields seen under French and 
American objectives, with the following results; With a magni- 
fying power of 25 diameters, the field is about a quarter of an 
inch; with 50 diameters, it is one-eighth of an inch; with 100 
diameters, one-sixteenth of an inch; with 500 diameters, one- 
eightieth of an inch; and with 1000 diameters, the one-hundred- 
and-fiitieth of an inch, a space which is ordinarily invisible OE THE MICROSCOPE. 
105 
to the naked eye. Consequently, when these high powers are 
used, it becomes very difficult for beginners to place the object 
properly under the microscope, for, as will be readily seen, unless 
it is adjusted with a variation less than the one-hundred-and- 
flftieth of an inch, it cannot be seen at all. 
The lowest powers that will show satisfactorily certain well- 
known objects, are about as follows; The scales, or so-called 
feathers on the wings of most butterflies car very well seen 
with a power of 25 diameters; under the same power, the eye 
of a fly shows very distinctly the several smaller eyes, or ocelli, 
of which it is composed; the individual corpuscles or globules 
of the frog’s blood can be distinguished with a power of about 
35 diameters, human blood requiring 40 to 50; to show dis- 
tinctly the form, etc., of these same corpuscles requires a power 
of 200 and upwards. The same may be said of starch granules. 
Human hair and wool may be seen very satisfactorily under a 
power of 100 diameters, the former appearing like a cord, 
a quarter of an inch thick. In order to show the peculiar char- 
acteristics of these fibres, however, the lenses must be good. 
Cotton and flax can be readily distinguished under a power of 
80 diameters. 
A question very frequently asked in regard to cheap micro- 
scopes is, Will they show the animalcules in water? And in 
almost all the advertisements of cheap microscopes, we are told 
that they will do this. Now, good well water does not contain 
animalcules that can be seen with ordinary microscopes. It 
is only in stagnant water that they are found, and many of 
them can be seen with the naked eye, without the use of any 
microscope whatever. Others require the use of microscopes 
having powers a hundred fold greater than that of the best 
microscopes in ordinary use. It is evident, therefore, that 
such statements are worthless as affording any indication of 
the character of a microscope. A microscope magnifying fif- 
teen to twenty diameters will show objects that are perfectly 
invisible to the naked eye, and with fifty diameters, provided 
the definition is good, we can obtain a very interesting view of 
many of the most beautiful objects described in the books, and 
sometimes called animalcules, such as the Volvox Globator, the 
larger Vorticelli, etc., etc. 106 
SELECTION AND USE 
The Stand —This should be firm and substantial, with the 
centre of gravity very low. Nothing detracts so much from the 
performance of an objective as tremor and vibration, and a large 
majority of the microscopes in market are very shaky, from the 
fact that they are made tall and showy in order to command a 
higher price. It is well, therefore, to bear in mind that size is 
no criterion of the value of a microscope. Instrument makers 
very properly give the size of their instruments, and it generally 
happens that the largest instruments by the same maker bear 
the highest prices. Other things being equal, however, small, 
compact instruments are altogether to be preferred. Some 
years ago the rage was for large, showy microscopes, which 
made a fine appearance in the office of the physician, and the 
study of the naturalist. It was found, however, that in this 
case efficiency was sacrificed to show, and all our best makers 
are now cutting down the sizes of their instruments, and making 
them steady, substantial, durable and easily operated. 
There is, of course, a limit to the extent to which stands may 
be reduced in size without sacrificing their efficiency, and some 
makers seem to forget this. There are stands in market that 
are too small every way for anything but special classes of 
work. The bodies are too small to secure efficiency in the eye- 
pieces and objectives; the stage is too small to allow of the use 
of slides of proper size, and there is no room beneath the stage 
for the attachment of proper illuminating apparatus. All this 
is as inconvenient as the three-feet-high microscopes of the end 
of the last century. 
The weight of the stand is a subject concerning which many 
seem to differ in opinion. One writer goes so far as to say that 
no stand weighing less than fifteen pounds can be steady enough 
for the performance of good work. It will be found, however, 
that a judicious distribution of the material, and a proper con- 
struction of the different parts, will more effectually resist the 
usual sources of unsteadiness than any increase of absolute 
weight. Of course, if it is merely desired to make the micro- 
scope steady, in the sense that an inkstand is steady—that is, 
not liable to be tipped over—weight is everything. But the 
stands that are most difficult to tip over are not those that 
resist vibrations most perfectly. For the latter a tripod with a OE THE MICROSCOPE. 
107 
small area of support is best; for the former a stand with a flat 
base resting over its whole surface on the table should be pre- 
ferred. 
It is obvious that the causes of unsteadiness are either vibra- 
tions transmitted from the floor, or movements caused by the 
hand in performing the necessary manipulations and adjust- 
ments. The first can never be stopped by weight, unless, 
indeed, we make the stand so heavy that its weight will impart 
rigidity to the table and floor, and this would require a good 
deal more than fifteen pounds, or even twice that. For the 
checking of vibrations transmitted from the floor, no device is 
better than the stand or table described in a subsequent sec- 
tion. So far as movements transmitted by the hand are con- 
cerned, if a stand of three or four pounds will not resist them, 
the observer should set himself about learning delicacy of 
movement before he proceeds any further. 
All microscopes made in this country and in England are 
now constructed so that the body may be inclined to any angle, 
thus giving the power of using the microscope in any position 
—vertical, inclined or horizontal. The importance of this is 
easily seen when we consider that on the one hand, when liquids 
are to be examined, it is sometimes necessary, or at least desira- 
ble to use the microscope in a vertical position, though this is 
a very tiresome and inconvenient position, and one that is not 
calculated to enable the observer to obtain the best possible re- 
sults; and on the other, it is equally necessary that the body of 
the microscope should be capable of assuming the horizon- 
tal position when the camera lucida is to be employed for 
making drawings, as will be hereafter explained. And yet 
Frey actually gives the preference to microscopes that do not 
incline, and which must always be used in a vertical position! 
This, of course, necessitates the complicated and expensive ar- 
rangement which he describes for adapting the camera lucida to 
the vertical instrument, a singular instance of prejudice against 
an obvious and successful improvement. 
The Stage . —In every case, a large, roomy stage is of the 
utmost importance. One great objection to most French in- 108 
SELECTION AND USE 
struments is that the stages are too small. It should also be 
firm and substantial, so that its position in regard to the other 
parts of the stand cannot be varied by slight pressure.* The 
most important points connected with the stage are the means 
provided for holding and moving the object, and the facilities 
afforded for attaching accessory apparatus. 
In the most complete stands, the object is held between 
sliding clips, which form a sort of clamp that is capable of 
being moved in two directions, at right angles to each other, 
by mechanical means, which generally consist of a screw for 
one direction and a rack and pinion for the other. This form, 
which is known as the mechanical stage, enables even a com- 
paratively unskilled person to bring any part of the object into 
the desired position in the field of view, and this with the 
utmost precision. These mechanical stages may be said to be 
characteristic of the higher classes of English microscopes, and 
as they are expensive, they are not generally used. Neither 
are they absolutely necessary for ordinary work with low or 
medium powers, for with any objective lower than one-twelfth 
of an inch focus, the object can be moved by hand quite as 
readily as by the screws, and we hold it to be a well established 
rule in all manipulations connected with scientific work, that 
whenever any operation can be performed satisfactorily by 
means of the hands alone, all special contrivances should be 
dispensed with. For low and moderate powers, therefore, we 
prefer the plain stage, on which the object is moved by means 
of the hands alone. But when very high powers are used, and 
especially when delicate micrometrical or goniometrical meas- 
urements are to be made, a well-made mechanical stage becomes 
a necessity. For while it is easy enough to bring an object 
very near to a given point by means of the fingers alone, it is 
almost impossible to secure perfect accuracy. In the effort to 
attain this the mechanical stage is a great assistance, and 
therefore when Frey utters a wholesale condemnation of the 
*At the same time, however, it must be borne in mind that no stage 
ever was made so firm that even a slight pressure would not affect it. If, 
therefore, the reader is determined not to rest content with anything 
short of a perfectly rigid stage, he will reject all the best microscopes in 
market. 109 
OP THE MICROSCOPE. 
English microscopes, and asserts that they are unpleasantly 
loaded with what he is pleased to call “screws and unessential 
appurtenances,” it seems to us that he commits a great error. 
These costly and complex instruments are intended for the 
highest class of work, and the most powerful objectives; per- 
fection of the work to be done, and not simplicity in the means 
by which it is to be done, is the end sought, and this can be 
attained only by the complex means employed. 
We have never found any of the so-called lever stages that 
fulfilled the requirements of the highest class of work, and, 
therefore, if a mechanical stage is to be chosen at all, the best 
form should be procured. 
A microscope fitted with a good mechanical stage leaves 
nothing to be desired, but when other forms are used, it is evi- 
dent that the chief points to be attained are these: 1. The 
object should be held steadily, but at the same time perfect 
freedom of motion should be allowed. 2. It should be possi- 
ble to remove instantly from the surface of the stage, every- 
thing in the shape of clips and holders, so that a clear field 
should be left for the adjustment of very large slides, plates, 
etc., or for the rotation of the object in relation to the light. 
3. Even the simplest forms of the stage should be so constructed 
that it may be possible to pass every part of the object under 
the field of view, and this, without any risk of omitting even 
the smallest portion. This point is of special importance to 
physicians and naturalists. Thus, it not unfrequently happens 
that it is desirable to know whether or not certain forms are 
present in a given drop of liquid; unless we can subject every 
part of that drop to microscopical examination, we cannot be 
sure that the forms we are looking for are absent. There is 
always a risk of omitting some portion of the slide, and conse- 
quently doubt must always hang over the exhaustiveness of all 
our examinations. The only certain means of avoiding all risk 
of missing any portion of a given slide is to pass it across the 
field of view in successive parallel bands, just as a plowman 
plows a field. The process is clearly shown in the diagrams 
on the following page, Fig. 22, showing the mode in which the 
entire surface is completely covered with a series of parallel rib- 
bons, the breadth of each of which is the diameter of the field. no 
SELECTION AND USE 
of view, while Fig. 23 shows the hap-hazard way in which ex- 
aminations are usually made, abundant room being left (as 
shown by the small crosses) for the escape of important fea- 
tures, Now, with ordinary clips, it is difficult to effect this, 
Fig. 22. 
Fig. 23. 
although it may be done by the aid of a plate of metal or vul- 
canite, a little thicker than the glass object-slide, and having a 
straight edge. The forward movement is made by pushing the 
vulcanite plate, while by sliding the object along the edge of 
this plate, we are enabled to examine a narrow strip, the width 
of the field of view, as shown in Fig. 22. A somewhat similar 
device is shown on the stage of Zentmayer’s Histological Micro- 
scope, Plate YI. When slightly modified, this device also 
serves as a guide for the Maltwood finder. 
In the simpler forms of the stage, the object is held in place 
by spring clips, which press it down, and under which it is 
moved. These clips are frequently screwed to the stage, which 
is a great mistake, as we are thus prevented from slipping them 
off, so as to leave the stage entirely clear. They should always 
be held in such a way that they may be instantly removed, and 
they should also be very thin and springy, otherwise it is im- 
possible to move the object with sufficient delicacy. 
The so-called glass stage, or Zentmayer stage, has come into 
extensive use, and is very much liked by some. As made by 
Zentmayer, it consists of a plate of glass, held against a brass 
support by means of a spring, which is pointed with ivory. 
The friction of the glass plate upon its metal support is thus 
easily adjusted, and may be either so reduced that the plate will 
respond to the slightest touch, or it may be so firmly clamped 
as to be practically immovable. Ill 
In some forms tlie glass plate is stationary, and the object- 
carrier moves over it, tlie points of contact being very small. 
Such a stage is seen in the microscope figured in Plate II. 
OF THE MICEOSCOPE. 
Revolving Stage.—It is often desirable to rotate an 
object in the optic axis of the microscope, either for the pur- 
pose of measuring angles or changing the direction of the 
illumination in regard to the object. Means for effecting this 
with perfect accuracy have been applied both to the mechanical 
stage and the glass stage, though the latter is generally so con- 
structed that rotation is impossible. In the large Ross stand (PI. 
I), the stage rotates, and is graduated for measuring angles. 
M. Nachet has devised a special form of the glass stage, in 
which provision is made for rotating it. In this form of the 
stage the object-carrier, F, is 
held to the glass plate, E, by 
means of two springs with ivory 
points, the springs being at- 
tached to the frame in which 
the glass plate, E, is set. Both 
the plate, E, and the object- 
carrier rotate in a light brass 
frame. In all these cases an 
attempt is made to secure coin- 
cidence of the centre of rota- 
tion with the optic axis of the 
instrument. It will, however, be found that it is an impossi- 
bility to attain this object with any great degree of accuracy 
unless provision is made for occasionally adjusting the centre 
of rotation of the stage. No stage that ever was made will re- 
main for any length of time so true that angles can be correctly 
measured by it, and therefore several devices have been sug- 
gested for securing accuracy without adjusting the stage, since 
when well-made an adjustable stage is expensive, and when 
poorly made it is worthless. 
The best known of these devices is what is called the center- 
ing nose-piece. This is a kind of adapter which is screwed on 
the body and receives the objective. It is provided with center- 
ing arrangements, and the objective having been screwed into 
Fig- 24. 112 
SELECTION AND USE 
it, the latter may now be adjusted exactly over the centre of 
rotation. With common objectives this answers very well, but 
first-class objectives are apt to show the effect of being thrown 
out of centre. 
Where rotation in regard to the illumination alone is required, 
several plans may be employed. One of the oldest is that 
found in the large microscopes of Hartnack and others, and 
recently adopted by Mr. Browning. This device consists in 
forming the stage in two pieces, the lower part being connected 
with the foot, and the means of illumination, while the upper 
Fig. 25. 
part, ■which rotates on the lower, is rigidly attached to the arm 
which carries the body. In this way the body, arm, stage and 
object may all be simultaneously rotated in relation to the 
illumination, and for ordinary purposes this answers very well. 
When polarized light is used, however, it is obvious that it 
is impossible to rotate the object in relation to the polarized 
ray, without also rotating the analyzer, and, as every one that 
has worked much in this direction knows, it is often of great OF THE M1CKOSCOPE. 
113 
importance that both polarizer and analyzer should be kept 
stationary, while the object itself rotates between them. 
The stage attached to the New Working Microscope of Mr. 
George Wale, and shown separately in Fig. 25, has a novel 
device for rotating the object. In this case the clips move 
round the stage. As ordinarily constructed they do not carry the 
object with them, but it would be easy to effect this by making 
each clip double, and clasping the object between the two clips. 
The little diatom stage devised by the author, and described 
and figured in a subsequent paragraph, also affords very simple 
and convenient means for rotating many kinds of objects. 
Stages for Special Purposes.—It may be safely asserted 
that there has never yet been constructed a stage which would 
suit the requirements of every worker with the microscope. 
Indeed, each investigator seems to require special modifications 
of his own. Thus, it will be found that the ordinary stage, 
with all its appurtenances, is too thick to admit the use of that 
very oblique illumination which is required by the worker on 
diatoms, while if the stage be made thin enough it loses the 
necessary rigidity. Some makers Lave sought to obviate this 
by supplying two stages—a stout one for common work, and a 
thin one for diatoms. A microscope now in our possession is 
furnished with an extra thin stage, which, by a very simple 
and ingenious device, can be instantly substituted for the heavy 
one. The microscope is said to have been made by Spencer or 
Tolies, and must be over twenty years old. Thin stages, on 
the same principle, called Diatom Stages, have been recently 
introduced by several makers, thus affording another illustra- 
tion of the aphorism that history repeats itself. 
The same object is also attained by means of the secondary 
stage, invented by Mr. Lewis Eutherfurd. This is simply a 
skeleton stage, which is placed on the ordinary stage, and is 
raised so far above it that the illumination may be applied 
between them, Eays of great obliquity may thus be passed 
through the object. Eutherfurd’s skeleton stage forms also an 
admirable safety stage, since the object, being held against the 
under side of the skeleton stage, yields to the slightest pressure 
of the objective. Mr. Spencer has also taken advantage of this 114 
principle, and so formed the under side of the stage in some of 
his stands, that the object may be pressed against it by the 
clips, which for this purpose are pushed through from below 
upwards. In focussing, the objective is passed through the 
stage if necessary. Great obliquity, and perfect safety against 
breakage of the object by the objective, are secured. When the 
microscopist is using valuable slides, costing from ten to one 
hundred dollars, the latter feature is one of great importance. 
In many microscopes, however—notably those of English 
manufacture—the under side of the stage is not flat and even, 
so that a slide cannot be laid against it. The following simple 
device obviates this difficulty : A rectangular plate of metal is 
pierced with a hole of the same size as the interior diameter of 
the sub-stage ring of the micro- 
scope, and in this hole is fastened 
a tube, which just fits this sub- 
stage ring. The plate is provided 
with two light spring clijos, which 
hold the object against its under 
side, and it is easy to see that this 
simple contrivance which is shown 
in Figure 26, serves three very im- 
portant functions : 1. It affords 
means for obtaining light of great 
obliquity, since in reality it forms 
a stage which has no thickness at 
all. 2. It serves as a perfect safety 
stage. 3. It enables us to rotate 
the object very nearly in the optic 
axis of the instrument. 
The rotating clips employed in the New Working Microscope, 
also serve the same end, since they may be applied to the under 
side of the stage quite as well as to the upper one, a groove 
being provided for this purpose. 
SELECTION AND USE 
Fig. 26. 
Sub-Stage.—The sub-stage is used chiefly for holding and 
adjusting illuminating apparatus beneath the stage, and may 
justly be regarded as one of the most important parts of the 
stand. OF THE MICROSCOPE. 
115 
It forms a prominent feature in the New American Model, as 
well as in all first-class microscopes. 
In its simplest form it consists simply of a short tube or ring, 
which is attached to the under side of the stage, and is fitted to 
receive polarizers, paraboloids, condensers, etc. It should be 
made removable, so that it may offer no obstacle to the employ- 
ment of the most oblique illumination. 
In the New American Model it is attached to a swinging arm, 
so that the illuminating apparatus, which it carries, may be 
placed at any angle with the optic axis of the microscope. 
When a mere ring is used for receiving the accessory pieces 
of apparatus, the latter are adjusted by simply pushing them 
up or down, but a much better plan is to have the ring itself 
moveable, as is the case in the instruments shown in Plates III, 
IY, Y, and VI. The accessory is then placed in the ring, and 
the latter may be slid up or down the carrying bar, so as to 
allow of proper adjustment. A still better plan is that shown 
in Plate I, where the distance of the sub-stage from the stage 
may be adjusted by means of a rack and pinion. 
In any case the sub-stage itself, or the apparatus which it 
carries, should have facilities for accurately centering the 
various pieces of illuminating apparatus. 
Tile Mirror.—The mirrors employed for illuminating 
microscopic objects are either plane or concave, and in the 
better class of instruments both kinds are provided, while the 
cheaper forms of the microscope have only the concave mirror. 
The plane mirror reflects the light just as it falls on it—that is 
to say, divergent rays (as from a lamp) remain divergent after 
reflection, and parallel rays (as sunlight or rays from the bull’s- 
eye condenser) remain parallel. The concave mirror, on the 
other hand, causes parallel rays to converge and meet at a point, 
while other rays are rendered either less divergent, parallel or 
convergent, as the case may be. It is very important that the sur- 
face of the mirror should be accurately formed, and therefore in 
all good microscopes they are made of glass, which has been 
accurately ground and polished. Blown or cast glass will not 
answer. And as the quality and quantity of the light is greatly 
affected by the reflecting surface, the best mirrors are silvered 116 
SELECTION AND USE 
■with pure silver, instead of with the amalgam of tin and 
mercury, ordinarily used. The mirror should be so hung that 
it may throw a beam of great obliquity through the object. In 
many cases this is absolutely necessary, and even for ordinary 
work it is of great advantage, since it not only enables us to 
resolve lined objects, but to secure important changes in the 
illumination of common objects. A very fair dark ground 
illumination may be secured if the light is so oblique that none 
of it can enter the object-glass directly. 
The mirror should not only be hung so as to swing to any 
angle, but it should be movable on the mirror-bar so that the 
rays which it reflects may be brought exactly to a focus on the 
object. This is done by sliding the mirror out or in, according 
as the rays are more or less divergent. 
The concave mirror should be large, so that it may collect 
plenty of light. The plane mirror may be small without much 
loss. The concave mirror is frequently used for the illumina- 
tion of opaque objects, as when large it concentrates the light 
very strongly. For this purpose it is either mounted on a 
separate stand, or the mirror-bar is so hung that it may be 
turned Tip over the stage, so as to reflect the light down upon 
the object. 
The Body .—The only points connected with the body of 
the microscope which require consideration are its diameter and 
its length, and these must of necessity vary so much according 
to the purposes to which the microscope is to be applied, that 
no rule can be laid down. Pocket microscopes are of necessity 
small; microscopes intended for use with objectives of low 
power and large angles, must have a large diameter. And since 
the distance of the eye-piece from the objective affects the cor- 
rection of the latter, it has been found necessary to adopt a 
standard length of body. This has been fixed at ten inches in 
this country and in England. On the continent of Europe, 
eight inches is the length that has been adopted, and most of 
the continental objectives are corrected for this length of body. 
Provided it is large enough to take the new broad-gauge screw, 
the diameter is not of very great importance in bodies of 
moderate length, but Beale tells us that in his long tubes, in- 117 
tended to produce great magnifying power, a diameter of two 
to two-and-a-half indies was found to be absolutely necessary 
to prevent the glare arising from internal reflection. An inch 
and a quarter is a good size for ordinary instruments. Since a 
very long body is inconvenient when the microscope is used in 
a vertical position, the best instruments are furnished with a 
OF THE MICROSCOPE. 
Draw-Tube, "whereby the length of the body may be 
varied at pleasure. As explained in a former paragraph (page 
20), when the distance between the eye-piece and the object- 
glass is increased, the magnifying power is increased also. 
The draw-tube, therefore, gives us the means of varying and 
adjusting the magnifying power of the microscope, and this is 
sometimes of great use. Thus, suppose it were required to 
draw an object to a scale magnified exactly one hundred diame- 
ters ; it might be impossible to procure an eye-piece and an 
objective that, with a fixed length of body, would give exactly 
this amplification, but when we are able to vary the magnify- 
ing power by changing the length of the body, it is easy to get 
at it exactly. This, however, is but one of many advantages 
afforded by the draw-tube. If the objective be good, and the 
eye-piece not very high, an easy and very satisfactory way to 
increase the magnifying power of the microscope is to lengthen 
the body by means of an additional tube, which may even be made 
of smooth paper. But it must be borne in mind that any change 
in the distance between the eye-piece and the objective affects 
the corrections of the latter, just as a change in the thickness 
of the covering glass would do. Consequently, unless the ob- 
jective has a considerable range of correction, it may be impos- 
sible to get good results when a very long draw-tube is used. 
On the other hand, the draw-tube may be used to good ad- 
vantage as a means of correcting for covering glass when non- 
adjusting objectives are used. We have a one-fifth objective 
now before us, with which we can see clearly the lines on the 
P. angulatum on the balsam Probe Platte when the draw-tube 
is out, but when the tube is pushed in, the view is foggy and 
indistinct. This is due to a disturbance of the corrections. 
The insides of all draw-tubes and bodies should be well 
blackened. When bright or white the glare greatly injures the 118 
SELECTION AND USE 
defining power. When draw-tubes or long eye-pieces are so 
arranged that they rub against the inside of the tube in which 
they are inserted, they invariably make the latter bright by 
friction. They should, therefore, always slide in a collar. 
It is always well to have the lower end of the draw-tube fur- 
nished with the Society screw, as by this means it is sometimes 
possible to use objectives of greater working distance than 
could otherwise be employed, and this arrangement also affords 
facilities for the use of amplifiers, erectors, etc. 
Adjustments for Focussing.—In the cheaper forms of 
the microscope the adjustment is made directly by hand, one 
tube sliding within another. In a better class of instruments 
the objective is brought nearly into position by sliding the 
body through an outer tube, and then the final adjustment is 
made by means of a screw or other mechanical means. But in 
all the best microscopes, the coarse adjustment, as it is called, 
is made by means of a rack and pinion, while the fine adjust- 
ment is made in the manner just mentioned. Instead of a rack 
and pinion, a chain is sometimes employed, and the coarse 
adjustment is also made in some cases by screws of very wide 
pitch, and similar devices. Nothing, however, can equal a 
smoothly cut and well-fitted rack and pinion. It is sometimes 
alleged that the chain is more delicate, but this is not so. We 
have now in our possession a cheap, but well made microscope, 
the rack and pinion of which is so delicate, that with it we can 
focus an objective of an eighth of an inch focal distance with 
sufficient accuracy for all ordinary purposes. 
For ordinary purposes, especially the work of the physician 
and medical student, the coarse adjustment may be more easily 
dispensed with than the fine one, but at the same time it must 
be remembered that any mode of adjustment in which the body 
is liable to turn round, is incompatible with the use of many 
important pieces of apparatus. Thus, for example, any turn- 
ing of the body interferes with the use of the double nose- 
piece, the polariscope in its higher applications, Prof. Smith’s 
opaque illuminator, etc. A rack and pinion, or its equivalent, 
should, therefore, always be chosen, especially as it does not 
add more than five or six dollars to the cost of the instrument. OF THE MICROSCOPE. 
119 
Of devices for fine movements the name is legion. An old 
plan is to place the object upon a plate attached to the stage, 
and move it towards the objective by means of a fine screw. 
This is a cheap and convenient method. It has been objected 
to it that the object is “tilted,” as it were, but this is imper- 
cejitible in practice, and causes no difficulty. The objection 
is, that when the object moves, many of the finer methods of 
illumination are disturbed. Another common plan is to make 
the nose-piece, which holds the objective, movable. This alters 
the length of the body, and changes the magnifying power 
every time a change is made in the focal adjustment. This 
change is too slight to be observable, but it is sufficient to inter- 
fere with delicate micrometric measurements.* 
To avoid this difficulty, the entire body and its attachments, 
including the coarse movement, are carried by the fine adjust- 
ment. In its general features, this plan is a very old one, and 
at least a dozen modifications of it have been devised by dif- 
ferent makers. As usually constructed, the body is raised by 
means of a lever, the long arm of which is acted upon by a 
delicate screw. A strong spring is arranged to lower the body, 
and as the spring maintains a continuous action, all lost motion 
is prevented. In the fine motion used by the Bausch & Lomb 
Optical Co., and which was invented by Mr. Gundlach, the body 
is suspended on two parallel springs, slides on carefully planed 
ways, and is moved by a fine screw. 
Objectives of large aperture are so sensitive to slight varia- 
tions in focal adjustment, that it is difficult to get a fine adjust- 
ment sufficiently delicate. Mr. Gundlach has recently at- 
tempted to increase this delicacy by using the well-known dif- 
ferential screw, and with very satisfactory results. 
In judging of the quality of either a fine or coarse adjustment, 
the points to be observed are the delicacy and accuracy with 
which the objective may be moved to and from the stage, and 
* It has been alleged that this increase or decrease of magnifying power 
is more apparent with the higher powers than with the lower powers. 
Indeed, it has been said that with high powers the change of magnifying 
power is quite perceptible. This, of course, is mere imagination, as any 
one of an arithmetical turn of mind can see. Indeed, the facts would 
seem to be rather the other way. 120 
SELECTION AND XTSE 
the freedom from twist or apparent displacement of the object. 
In many microscopes, when a high power is used, and the 
body is moved up or down for the purpose of adjusting the 
focus, the object is actually thrown out of the field of view. 
Such a microscope should be at once condemned. 
Whatever be the nature of the fine or coarse adjustment, see 
that the body has sufficient range of motion to allow of the use 
of objectives of considerable working distance. 
The Diaphragm.—Nothing tends so much to obscure our 
view of the finer points of structure in any object as to have 
them “ drowned ” in a superabundance of light, consequently 
in order to regulate the amount of light which passes through 
the object, a diaphragm is employed. As ordinarily con- 
structed, it is simply a metal plate placed below the stage, and 
pierced with holes of various sizes, which may be brought ex- 
actly under the field of view, the small holes allowing but a 
small amount of light to pass, while the large ones admit a full 
stream. Considerable difference of opinion exists amongst 
microscopisis in regard to the proper position of the dia- 
phragm. Thus Carpenter says (page 133) that unless placed 
half an inch below the object it is comparatively inoperative. 
Continental histologists, on the other hand, allege that it is 
useless unless placed close up under the object. Microscopes 
constructed according to both these plans are to be found in 
market. Where the microscope is furnished with a sub-stage, 
the distance of the diaphragm from the object is variable at will. 
It is obvious that when the diaphragm is placed at a consid- 
erable distance below the object, the illumination is purified, 
as it were, from all cross rays. When the diaphragm is placed 
close to the object-slide, the illuminated field is contracted. 
The action in this case, however, is somewhat complex, 
owing to the influence of the slide in modifying the course of 
the rays. 
Several very ingenious forms of Iris or graduating dia- 
phragms have been devised, by which the size of the hole may 
be changed without interrupting the observation. They are 
exceedingly convenient, and present advantages which more 
than counterbalance the cost. OF THE MICEOSCOPE. 
121 
Objectives.—1These are confessedly the most important 
parts connected with the microscope; they therefore deserve 
the greatest care in their selection. In a former section, we 
fully explained the general characteristics of the different 
kinds of objectives in market, and detailed the best methods of 
of testing them. A careful study of that chapter will, we hope, 
enable the beginner to avoid a glass that is absolutely bad, 
though we must acknowledge that all experienced microscopists 
are agreed that no amount of mere reading will enable a 
novice to pronounce a correct judgment upon the quality of an 
objective, unless its defects should be very glaring indeed. In 
this place we shall confine ourselves to a few hints in re- 
gard to those features which adapt objectives not only to 
special kinds of work, but to the skill of different classes of 
workers. For it is an undoubted fact that objectives which in 
the hands of skillful microscopists, and on certain classes of 
work, would give extraordinary results, would in other hands, 
and for other purposes, prove of far less value than lenses of 
what is commonly considered a greatly inferior grade. 
We do not here propose to take part in what is called the 
“battle of the object-glasses,” such a discussion being out of 
place in an elementary work like the present, but we think few 
will be hardy enough to deny that one who has a taste for such 
things, but has neither the money required to purchase a first 
class glass, nor the time necessary to acquire the requisite skill 
to use it, had better work with a cheap French triplet than not 
work at all. Moreover, it is astonishing how far patience, skill 
and experience will go to make up for a deficient instrument, 
while at the same time, it is unfortunately true that some who 
possess the very best glasses, and have done the most to 
throw ridicule upon all work done with inferior lenses, have 
never made a single contribution of the slightest importance 
to any department of microscopical science. 
In a former chapter we discussed at length the different 
qualities of object-glasses, and showed how these various quali- 
ties might exist in very different degrees in different ob- 
jectives. It is, of course, obvious that the extent to 
which any one quality should be sought in a particular 
glass, must depend altogether upon the kind of work that is 122 
SELECTION AND USE 
to be done. To those who are addicted to what Holmes calls 
“fighting objectives,” resolution will be the quality to be 
desired; others will prefer penetration, flatness of field, etc. 
In our estimation, for the purposes of ordinary scientific work, 
we would assign to these qualities values in the following 
order: 1. Defining power; 2. Freedom from aberration of 
form; 3-4. Resolution or Penetration; 5. Working distance; 
6. Achromatism; 7. Flatness of field. The first quality that should 
be secured in every lens is undoubtedly defining power, and this 
whether its angular aperture be high or low. Achromatism we 
place low in the scale, because unless so marked as to injure 
the definition, a little color does no harm. Flatness of field we 
place last, because it will be found that perfect flatness of field 
is very seldom combined with first rate definition. Indeed, we 
have heard one of the most celebrated makers of objectives 
assert that the two qualities are to a certain extent antagonistic. 
In giving advice in regard to the selection of an objective, 
one of the points concerning which it is most difficult to arrive 
at a decision, is that of angular aperture. Fortunately, however, 
experienced microscopists may safely be left to decide this ques- 
tion for themselves, and since those who have had no experience 
will find it difficult to use objectives of very wide aperture, it will 
certainly be prudent for them to choose those of moderate angle. 
Objectives of very high angle are worthless, unless the illumina- 
tion is Avell managed, and the adjustment for thickness of cover 
properly regulated. On the other hand, a good non-adjusting 
lens will give very fair results, with but a moderate amount of 
skill on the part of the user. Almost all our best makers now 
produce objectives of moderate angle, which do not adjust for 
thickness of cover, but which have considerable resolving 
power. We have now before us a one-fifth which costs but fif- 
teen dollars, and which will easily resolve the Pleurosigma An- 
gulatum by central light. An important point for consideration 
will, of course, be, whether or not the glass is intended for 
original work, or merely for the study or examination of well 
known objects. The work of the physician is chiefly amongst 
well known objects, and may be very satisfactorily accomplished 
by means of good non-adjusting objectives, a great point in 
favor of such glasses being that work may be done with them OF THE MICROSCOPE. 
123 
more rapidly than with glasses that require greater care and 
skill. The same is true of the elementary studies of the bot- 
anist and histologist, carried on under the guidance of a com- 
petent teacher. And as in all such eases it is easy to find out 
the special thickness of glass for which the object-glass has 
been corrected, and to provide a supply of the proper thickness, 
the absence of a means of adjustment for cover thickness is not 
very important. But for all the higher class of studies, good 
glasses, with well-made adjustments for thickness of cover, are 
indispensable.* 
Objectives of very low angular aperture, are, however, to be 
carefully avoided. There is a want of light, and an indistinct- 
ness which renders them worthless. It is generally said that 
the superiority of large angles is most marked in the objectives 
of high power, and that for low powers the common objectives 
do very well. In our judgment, however, the superiority of 
the low powers is quite as marked as that of the higher ones, 
and much more available to the beginner. It is true that the 
superiority of a well made one-sixth of high angle, over any 
triplet of whatever focal length, is immeasurable, but at the 
same time it is equally true that the view of an opaque object 
seen through an inch-and-a-half objective, carefully corrected, is 
as much superior to the same as seen through a common triplet, 
as it is possible to imagine. We have now before us a speci- 
men of bone of very open structure, mounted as an opaque 
object. Seen through a first class inch-and-a-half objective, it 
presents almost a stereoscopic appearance, and the entire struc- 
ture is easily made out. The view afforded by a very fair French 
triplet (No. 0) is so markedly inferior, that any person who 
should see the two would never again use a cheap objective, if 
he could afford to get a good one. Moreover, the objection 
which we have just urged against objectives of high power, and 
*It is not long since a professional maker of microscopes, and one who 
seems to stand high in the favor of the medical profession, tried to per- 
suade the author that the covering-glass exercised no influence on the 
action of the objective, and that a non-adjusting glass could be made 
with as great a resolving power, as one constructed so as to adjust for 
different thicknesses of covering glass! To such men, a famous micro- 
scopist used to apply the term “ shopticians,” and they deserve it. 124 
SELECTION AND USE 
wide angle, viz., that they are difficult to use by novices, does 
not hold in the case of low powers. A good inch, of compara- 
tively high angle, is more easily used than a poor triplet. 
A question which has considerably occupied the attention of 
microscopists, is the value of objectives of high power, and their 
efficiency as compared with those of lower denominations. 
That in many cases considerable amplification or magnifying 
power is absolutely necessary, admits of no doubt; but the ques- 
tion to be settled is: suppose that we wish a power of 2,000 diame- 
ters, would it be better to get this by means of a tenth of an inch 
objective, magnifying 100 times, and a half inch eye-piece mag- 
fying 20 times, or by a twentieth of an inch objective magnify- 
ing 200 times, and an inch eye-piece magnifying ten times ? 
It is not very many years ago since one of our ablest Ameri- 
can objective makers held that a lens of a quarter of an inch 
focus might be made to do anything that a lens of any power 
could be made to do, and the ground of this opinion was that 
the individual lenses of objectives as low as a fourth, could be 
made so much more perfect than the smaller lenses of higher 
powers, that this perfection more than counterbalanced the 
greater magnifying power of the objective of shorter focus. 
The reasoning here seems sound and obvious, but it has been 
found in practice that for everything except resolution, the limit 
to which the power of objectives may be carried, is far beyond 
a fourth. For resolution it has, we believe, been found that a 
well made tenth is capable of doing anything that any lens can 
do; for other kinds of work sixteenths and twenty-fifths, and 
even fiftieths and eightieths have been declared to possess 
advantages that are obvious. This, however, is one of those 
points upon which authorities differ; Beale, for example, favors 
high powers; Carpenter and Frey seem inclined to think that 
very high powers show nothing that cannot be seen by means 
of objectives of greater focal length. 
French, objectives of the numbers 1, 2, 3 and 4, if carefully 
selected, are capable of doing really serviceable work. A few 
years ago, some of the best known makers of American micro- 
scopes used nothing else, even in microscopes costing $150, but 
this course we can scarcely regard as judicious, for whenever 
the microscopist is prepared to expend $75 or more for a micro- OF THE MICKOSCOPE. 
125 
scope, a large part of this sum should be laid out in the pur- 
chase of objectives of the better class, the one-inch and one- 
fourth, or the three-fourths and one-fifth being those that are 
usually selected by beginners. 
French triplets are, however, going rapidly out of use, from 
the fortunate circumstance that objectives of low price and 
excellent quality are now produced by several makers of repute. 
It is well, however, for the reader to be on his guard against 
a fraud which has been but too common of late years. Some 
so-called opticians go so far as to add a little brass-work and 
engraving, and sell these French triplets as objectives of Ameri- 
can make. We do not here refer to the mere operation of attach- 
ing the objective to an adapter, and fitting it in a brass box, for 
this adds greatly to the convenience with which such minute 
objectives may be handled and preserved, but to a sort of 
“making over,” by which they are completely disguised and 
made to resemble the objectives of English and American 
makers. It is hardly necessary to characterize such a pro- 
ceeding. 
Eye-Pieces.—The eye-piece that is at present almost uni- 
versally used is the Huyghenian, which, when well made, gives 
very excellent results. In the use of low powers, wheie a very 
flat and large field is desirable, the Huyghenian eye-piece fails, 
and the same is also true in regard to very high magnifying 
powers, where the enlargement is obtained in a great measure 
by means of the eye-piece. The extent to which the definition 
of really good objectives is deteriorated by the use of eye-pieces 
of great magnifying power, and the loss of light which they 
occasion, render them practically useless. For high powers, 
the solid eye-pieces of Mr. Tolies are vastly superior, while for 
low powers, where a large flat field is desired, Kelner’s ortho- 
scopic eye-piece presents important advantages. 
Mr. Gundlach has recently brought out a new eye-piece, 
which he has named the periscopic, and for which a large field 
and excellent definition are claimed. They are much more ex- 
pensive than the Huyghenian. We have not had an oppor- 
tunity of examining them carefully. 
In determining the quality of an eye-piece, attention is to be 126 
SELECTION AND DSE 
paid not only to its general excellence, but to its adaptability 
to the objectives that are to be used with it. In the higher 
departments of microscopy, the latter is a most important point, 
but one which is too frequently neglected. It does not, how- 
ever, come within the scope assigned to the present work, and 
we, therefore, content ourselves with a few general hints. 
The lenses composing the eye-piece, should be of homogeneous 
glass—that is, free from air-bubbles, specks and striae, and the 
surfaces should be well polished. These points require atten- 
tion, because we have in our possession a microscope in which— 
though it cost enough money to be free from such defects— 
they are glaringly apparent. On looking through the eye- 
piece at a strongly and evenly illuminated surface, the entire 
field of view—that is, the whole of the bright circle that is 
seen, should have the light evenly diffused over its surface, 
and the edges or border of this circle should be sharp and 
black. 
Eye-pieces intended for first-class objectives should give a 
large field of view; but on the other hand, if French objectives 
be used, the field of view should be small, otherwise the defi- 
nition will be poor. This is a point that is frequently over- 
looked, and we have seen very fair object-glasses condemned 
as worthless when used with a stand and eye-piece intended 
for objectives of an entirely different class. It is an easy thing 
to contract the field of view, by means of a round piece of thin 
sheet metal, having a hole of proper size in the centre. As pre- 
viously explained, such a piece of metal is called a diaphragm, 
and should always be well blackened. 
The magnifying power of every microscope depends upon 
three things: The focal length of the objective, the length of 
the body, and the eye-piece. Most microscopes are, therefore, 
furnished with several eye-pieces, whereby the magnifying 
power may be varied. There is, however, a limit to the extent 
to which this may be done. The image obtained by very deep 
eye-pieces, as they are called, is rarely satisfactory. 
The different eye-pieces are generally denoted by letters—A, 
B, C, D, etc. A being the lowest, and B, C, D, etc., successively 
higher’. Some makers use numbers—1, 2, 3, 4, etc. These 
letters and number, are, however, entirely arbitary, in this point OF THE MICROSCOPE. 
127 
resembling the numbers assigned to objectives by continental 
makers. A great improvement upon this arbitrary and uncer- 
tain system would be to assign to each eye-piece its proper 
power expressed in inches. Thus, an eye-piece magnifying the 
same as a simple lens of two inches focus, should be called the 
two-inch eye-piece. 
And here let us call attention to the terms deep and shallow, as 
applied to eye-pieces. By all authors of repute, a deep eye-piece 
is one of great magnifying power, while a shallow eye-piece is the 
reverse. See the Micrographic Dictionary, and the works of Car- 
penter, Beale, Lardner, Frey, etc., etc. It is, therefore, singu- 
lar that Dr. Lankester, in his popular little work, “ Half-Hours 
with the Microscope,” should have committed the mistake of 
giving definitions exactly the opposite, upon the ground 
that eye-pieces of great magnifying power are always short, 
while low eye-pieces are always long. It is evident, however, 
that the terms are liable to give rise to confusion, and we pre- 
fer the words high and low—the meaning of which is so ob- 
vious as to require no explanation, as every body knows what 
high magnifying power is 
While clearness of definition and resolving power are the 
most important qualities of every good microscope, magnifying 
power is also of considerable consequence, as explained in a 
former section. Therefore, every good microscope should be 
provided with at least one eye-piece of considerable power. It 
often happens that with the objectives and eye-pieces at hand, 
the amplification, as it is called, or, in other words, the extent to 
which the object is magnified, is not sufficiently great to enable 
us to make out its structure, while the objective has not by 
any means reached the limit of its defining power. In this 
case a high power eye-piece, which costs comparatively little, 
will greatly extend our power of successful examination. 
ACCESSORY APPARATUS. 
Every microscope should be accompanied with certain pieces 
of accessory apparatus, which are necessary for the convenient 
and thorough examination of objects, but which do not form 
part of the instrument itself. Some of these are intended for 128 
SELECTION AND 
the better illumination of the ob- 
ject, and will be described in the 
section on “Light;” others are used 
for the procuring and preparation 
of objects, and will be described in 
the section devoted to that subject. 
The following are employed chiefly 
for holding and presenting objects 
that have not been “ mounted:” 
Stage Forceps.—This little in- 
strument accompanies the oldest 
microscopes. It consists of a pair 
of very delicate forceps, such as 
those attached to the forceps-car-, 
rier in Fig. 27, which close by the 
spring of the jaws, and hold any ob- 
ject that may be placed in their 
grasp. They are opened by pressing 
on the pins which are seen at the 
sides. They are in general fastened 
to the microscope by being stuck 
into a hole in the stage, and the 
object may not only be moved back- 
ward and forward, but it can be 
turned round. The better class of 
forceps carry a small brass tube 
(shown in Fig. 27) which is filled 
with cork, and which serves to re- 
ceive pins, etc., for holding insects, 
and other objects. 
Fig. 27.—FORCEPS AND FORCEPS CARRIER 
Foi (' e p s-Carrier. — However 
well made the forceps may be, it is 
almost impossible to slide, with suf- 
ficient delicacy, the rod through the 
tube that holds it. Consequently, 
it is exceedingly difficult to bring 
into the field of view, the exact part 
of the object, that we may wish to OP THE MICROSCOPE. 
129 
examine. To avoid this difficulty, the author, instead of insert- 
ing the pin of the forceps in the stage, provides a special for- 
ceps-carrier like that shown in Fig 27. This consists simply of 
a metal plate, the size of an ordinary slide, and having a hole hi 
one end to receive the pin of the forceps. A large hole is 
pierced through the centre, to allow the passage of light from 
the mirror when that is needed. This plate is placed on the 
stage like a common slide, and it can be moved with as great 
delicacy as any ordinary object. The mode of using it is too 
obvious to require further explanation. We have found it ex- 
ceedingly convenient. 
Object-Holder.—The importance of being able to present 
an object to the light in all directions is well-known to every 
microscopist. Many years ago we devised an object-holder for 
effecting this, the construction of which is very simple and in- 
expensive. It consists of a slip of metal, the size of an or 
dinary slide—three inches by one—having a hole in the centre 
Fig. 28.—OBJECT-HOLDER. 
and a short pillar rising from one end, as shown in the en- 
graving, Fig. 28, which gives a sectional elevation of the 
instrument. Through this pillar runs a wire, carrying at one 
end a milled head by which it may be turned, and at the other 
a ring which holds a perforated block. This perforated block 
has a milled collar on the lower end, so that it can be readily 
turned in the ring that carries it. The hole passing through 
the block is just the size of a stout pin, so that a disk of card 
or leather, with a pin through it, will be held steadily when 
the pin is inserted in the hole. The object to be examined is 
attached to the surface of the card, by means of balsam or mu- 
cilage, and it is obvious that by the combined rotations that 
may be produced by the two milled heads mentioned, it may 
be exposed to the action of the light in any desired manner. 130 
SELECTION AND USE 
The changes which are produced in some objects when the 
light is made to fall on then in different directions are very 
marked. Thus, for example, the mineral known as specular 
'iron ore, when illuminated by light falling on it in one direc- 
tion, is brilliant in the extreme, while when the light falls in 
other directions it is dead and lustreless. And as it is not 
always convenient to change the position of the lamp, it is a 
great advantage to be able to turn the object round. The sim- 
ple contrivance just described enables us to do this perfectly. 
A more perfect arrangement, intended for the same purpose, 
has been devised by Mr. Beck, of London. Mr. Beck’s is, 
however, more expensive than ours. 
Plain Slides.—The common plain slides serve very well 
for examining ordinary deposits in liquids. This is particu- 
larly the case where inanimate objects, vegetables and minerals 
are to be examined. Active animals require some contrivance 
for keeping them still. 
The Concave Slide, as it is called, is simply a thick 
slide with a cup-like hollow ground in the centre. Such slides 
are cheap, and very convenient. A drop of water placed in one 
of these concaves, and covered with a thin glass, may be exam- 
ined easily and thoroughly with moderate power. It is 
sometimes desirable to employ a cell with a perfectly flat bot- 
tom of very thin glass. Such cells may be easily and conve- 
niently made out of a slide of metal, or preferably of vulcanite, 
through which a hole the size of the proposed cell has been 
pierced. A piece of thin glass may then be cemented to the 
under side of the slide, so as to form a water-tight cup. The 
hole in our slides is round, and has, on the under side, a seat 
or rebate, a little larger than the hole itself. In this rebate a 
round glass cover fits, so as to leave the under side of the slide 
perfectly smooth. Such cells are very convenient, as they are 
easily cleaned, and are not difficult to repair wrhen the thin 
glass gets broken. The liquid is also easily covered by means 
of a thin glass cover, and when full, considerable inclination 
may be given to the slide before the liquid shows a tendency to 
run out. Various other devices of a simple kind may be con- 
trived by the microscopist for similar purposes. OF THE MICROSCOPE. 
131 
Watch-Glasses.—Dr. Beale recommends small flat watch- 
glasses for holding liquids that are to be examined, and we 
have found them very excellent. The best kind for this pur- 
pose are those known as lunette glasses, which are nearly flat on 
the bottom. They are awkward things to manipulate, how- 
ever, unless some means is provided for holding them steady, 
and moving them about on the stage. We use for this purpose 
a strip of wood, three inches long, and so wide that we can 
easily bore in it a hole, about one-eighth of an inch less in 
diameter than the watch-glass, of which the smallest size should 
be chosen. The thickness of the strip should be such that 
when laid on any flat surface, the watch-glass will not come in 
contact with it. Glasses held in this way are very convenient. 
Fig. 29.—WATCH-GLASS HOLDER. 
Watch-glasses are very convenient for examining a “dip ” from 
a pond or stream, but for this purpose they require a holder. 
The little instrument shown in the cut is formed of three pieces 
of bright tin, which are hinged together. In the upper piece 
is cut a hole just large enough to receive a watch-glass. Aring 132 
SELECTION AND USE 
of metal of proper height surrounds this hole, and forms a 
perfect protection to the glass when the instrument is carried 
in the pocket. The lower slip of tin may be adjusted to any 
angle, and by turning towards the proper direction, the light 
of any bright cloud may be reflected up through the liquid. 
All the joints are made stiff enough to remain in position when 
once adjusted. A watch-glass arranged in this manner holds a 
liberal supply of liquid, so that an entire “ dip ” may be 
readily examined at once. We have found this little contrivance 
far superior to more expensive arrangements. It packs into 
small compass, and is safely carried. 
Animalcule Cage.—This forms a very excellent means 
for holding animalcules that are too active to allow of observa- 
tion on slides, or in watch-glasses. A good idea of its con- 
struction may be ob- 
tained from the en- 
graving, where it will 
be seen to consist of a 
plate of metal, three 
by one inches, to the 
centre of which is 
fixed a short tube. In 
the upper end of this tube is fastened a beveled piece of glass, 
and a second tube fits over the first, and has a thin glass cover 
secured in its upper end. The animalcule is securely held 
between the two pieces of glass, and the lower glass being 
beveled on the edge, a drop of liquid placed on it is held be- 
tween the two glasses by capillary attraction, and cannot spread 
over the inside of the cage. This point is generally neglected 
in the cheaper forms of the cage, in which the lower glass 
is simply a plain disc burnished into the upper end of the 
inner tube. The consequence is that when the two glasses are 
brought together the liquid flows over the entire inside of the 
cage, and the objects are liable to be floated out and lost. As 
it is important that the distance of the two glasses from each 
other should be easily and accurately regulated, the outer tube 
should be slit, so as to make it springy. In this way it may be 
made to move with a soft and equable motion. 
Fig. 30 ANIMALCULE CAGE. OP THE MICROSCOPE. 
133 
The Zoophyte Trough.—This little piece of apparatus 
is almost indispensable to those who desire to watch the growth 
and development of the larger animalcules and small aquatic 
plants. Several forms are in 
common use, the most com- 
plete being that shown in Fig. 
31. The trough itself is sim- 
ply a glass tank, to which is 
fitted a slip of thin plate glass 
that acts as a division, and 
enables the observer to keep 
the objects close up to the 
front plate. The distance of 
the dividing plate from the 
front plate is regulated by an 
ivory wedge, and the dividing 
Fig. 31.—ZOOPHYTE TROUGH. 
plate is kept firmly up to its place by means of a spring. This 
contrivance enables us to regulate the thickness or width of the 
tank, so that the interior of the vessel may be made so large 
that it can be easily cleaned. 
A smaller and simpler form of the Zoophyte trough 
is shown in Fig. 32, It consists of a simple glass box, 
open at the top. The back 
of the box is formed of a 
stoutish piece of plate glass, 
to which is cemented three 
glass strips, forming the 
bottom and ends. The front 
is formed of glass as thin as 
is compatible with durabil- 
ity, and is also cemented to 
the end pieces. The width 
of the trough from front to 
Fig. 32.—ZOOPHYTE THOUGH. 
back is generally from an eighth to a quarter of an inch. When 
the trough is filled with water, and living animals are placed in 
it, their changes and movements may be very readily watched. 
Small troughs, such as that just described, are not difficult 
to make, though the very low price at which they are sold (60 
cents to $1.00) renders it scarcely worth the while of ordinary 134 
SELECTION AND USE 
microscopists to construct tliem for themselves. Where this is 
desirable, however, the best method of making them is as 
follows : Select a piece of plate glass, of the thickness of an 
ordinary slide, and cut it about three inches by one and a quar- 
ter. Then select another piece of glass, as thick as the trough 
is to be deep (from front to back), and cut it to the size of the 
outside of the trough. From the bottom of this piece of glass 
cut a strip a quarter of an inch wide, and from the sides also 
cut strips of the same width. The centre piece may now be 
thrown aside, and the ends of the bottom strip will make a 
tight joint with the side strips. The three strips should then be 
cemented to the large plate, and over them should be cemented 
a piece of the thin glass used for covers. The strongest cement 
is marine glue, but it is somewhat difficult to use by those 
who have had no experience. Prof. Starr, who is well known 
for his success in keeping and exhibiting living microscopic 
objects, uses old Canada balsam, and we have seen a large 
variety of microscopic animals and vegetables which had been 
kept for months in a healthy condition in such troughs or 
cages. 
Walmsley’s Zoophyte Trough.—A serious objection 
to the troughs which we have just described is the difficulty of 
cleaning them, and of repairing them when broken. To avoid 
these difficulties, Mr. Walmsley has devised the little piece of 
Fig. 33.—ZOOPHYTE TROUGH. 
apparatus shown in Fig. 33. This trough consists of two glass 
plates, which are separated by a semi-ring of vulcanized india- 
rubber, against which they are squeezed so firmly as to be 
watertight, by means of two vulcanite plates, held together by 
screws with milled nuts. The front plate may be made of 
thick or thin glass, as desired, while the depth of fluid em- OF THE MICROSCOPE. 
185 
ployed may be regulated by tlie thickness or number of semi- 
rings of rubber placed between the glass plates. 
By means of the three screws with milled nuts, the trough 
may be taken to pieces in a few seconds, and as easily put to- 
gether. In this way it is easy to clean the inside of the glass 
plates, to replace broken ones, etc., etc. 
The Weber Slide.—This ingenious device consists of a 
common slide, rather thicker than usual, m the centre of which 
an annular groove has been ground, as shown in Fig. 34. The 
central part of the cell is left nearly the full original height of 
the glass—just enough being taken off to allow of a thin layer 
of liquid between it and the cover-glass. Any liquid contain- 
ing minute forms of animal or vegetable life having been laid 
on the top of the central elevation, will be held there by capil- 
lary attraction as soon as the cover is laid on, and if the latter 
be cemented round the edges, an air-tight aquarium on a 
minute scale is formed, in which, if the proper balance of 
animal and vegetable life is present, the objects may be kept in 
good condition for a long time. We have kept one of these 
slides for weeks with desmids, diatoms, and minute forms of 
animal life, all in good condition. The proper cement for at- 
taching the cover to these slides is beeswax softened with oil. 
Fig. 34.—THE WEBER SLIDE. 
The Weber slide is a very handy and convenient piece of ap- 
paratus, but it is difficult to obtain. We have, therefore, used 
the following form, which anyone can make for himself. 
The Cell Trough.—The simplest trough in which living 
objects may be kept for some time, is constructed out of an 
ordinary cell and thin cover, as shown in Fig. 35. If we 
have a liquid containing some very minute objects which we 
wish to keep for some time in a condition suitable for examina- 
tion, we place a drop on the centre of a thin cover-glass, which 
must be larger than the cell. A very small cover is then placed 136 
SELECTION AND USE 
over the liquid, for the purpose of forming a layer of equal 
depth throughout, and if there should be any danger of crush- 
ing the objects, a few fibres of hair, silk, cotton, etc., will keep 
the two thin glasses sufficiently apart. The edge of the cell 
having been lightly smeared with a soft mixture of beeswax and 
Fig. 35,—CELL-TROUGH. 
oil, and the interior corner having been moistened with pure 
water by means of a camel-hair pencil, the inverted cell is 
placed on the large cover, which at once adheres, and thus the 
cell is converted into a veritable Wardian case. Owing to the 
moist atmosphere, there is no danger of the liquid under exam- 
ination drying up, and as the apparatus is very cheap, several 
may be fitted up and used for watching the life history of any 
particular subject. 
The Compressorium.—The animalcule cage, shown in 
Figure 30 is open to the objection that it is difficult to 
adjust the pressure with sufficient delicacy, and we are apt 
either to crush the animal or leave it too free in its movements. 
These difficulties may be avoided by the use of a well-made 
Compressorium, of which there are several kinds in use. 
This little instrument also serves another important purpose. 
In the examination of certain objects, it is frequently necessary 
to flatten, and even to crush them, in order to render their 
structure visible, and this the compressorium enables us to ac- 
complish. The most powerful instrument of this kind consists 
of a metal plate, in the centre of which is fixed the disc of glass 
upon which the object is laid. A second disc of glass, fastened 
in a ring which is hung at the end of a lever, by means of two 
pivots, is pressed against the first by means of a screw, which 
tilts the lever. In this way a very strong pressure may be 
exerted, while, owing to the free movement of the ring on the 
pivots, the plates of glass always remain parallel to each other. 
"Where very great pressure is not required, a different form 
of the instrument may be used. Instead of being forced down 
by a screw and lever, the upper glass disc is fastened to a thin OF THE MICROSCOPE. 
137 
plate of metal, which may be raised by a screw, but wlien the 
screw is withdrawn the “spring” of the plate carries it down 
and gives the pressure. 
A compressorium, in which the pressure is caused by the 
weight of the upper plate, is shown in Pig. 36. There are two 
plates of metal, each with a hole in the centre, to receive the glass 
discs. At one end the upper plate has two pins, which fit into 
two holes in the lower plate, and serve to prevent all side 
movements. A screw passes through the other end of the 
upper plate, and serves to separate the two. A drop of water 
containing an animalcule having been placed on the thin glass 
attached to the lower plate, the upper plate, with the screw 
projecting sufficiently from the under side, is laid on it. Then 
by turning the screw, we can bring the two plates together to 
any required degree of nearness, and with the utmost delicacy. 
Fig. 36.—THE GRAVITY COMPRESSORIUM. 
Any minute animal may thus be firmly grasped, without crush- 
ing it, while the compressing power exerted by the mere weight 
of the metal plate is in almost all cases sufficient, even for the 
complete flattening out of small worms, etc. Even such crea- 
tures as the larva of the common gnat or mosquito may be 
completely crushed by the weight of a plate less than the eighth 
of an inch thick; and, where greater force is required, it is of 
course easy to apply the pressure of the finger. In the latter 
case, no danger of exerting too great a pressure need be in- 
curred, as the projecting screw prevents all that. The want of 
parallelism between the plates does not prove a serious objec- 
tion, as it is so very slight that it is hardly perceptible in the 
short distances ordinarily under observation. Where, how- 
ever, it is desirable to avoid this defect, screws may be substi- 
tuted for the pins, and the points may be made to work in 
holes bored half through the lower plate. 138 
SELECTION AND TTSE 
Where animalcule cages are not accessible, a small animal 
may be held between a common slide and a thin cover. To 
prevent crushing it, a hair or even a thread may be placed be- 
tween the cover and the glass. A German author recommends 
the use of fine gauze or netting, in the meshes of which an 
animalcule may be held very conveniently. Acting on this 
idea, we took a thin metal plate, and bored it full of holes of 
various sizes. An animalcule placed in one of these holes may 
be kept in the field of view for any length of time, and exhibited 
to those who desire to see it, but it cannot be kept quiet for 
scientific examination. We like a piece of fine wire-gauze, 
better than cotton or linen netting. 
Growing Slides,-—Where it is desirable to keep the same 
living object for a considerable time, so as to watch its changes, 
it is necessary to use what is called a growing slide, by which it 
may be regularly supplied with air and moisture, A large num- 
Fig. 37.—GROWING SLIDE. 
ber of complicated devices have been described for this pur- 
pose, but the following simple contrivance answers the end 
very well; we have used it for years. To one end of a common 
slide with a concave centre, cement a small bottle, as shown in 
the figure. This is easily done by means of a little marine 
glue. The glue, cut in small pieces, should be laid on 
the slide at the point where the bottle is to be attached; 
the slide is then to be gradually heated until the glue is 
softened, when the bottle is laid on and moved back and 
forth until it has been thoroughly imbedded in the cement. 
The bottle is filled with water and corked, the upper side 
of the cork having two notches cut in it, one for the en- 
trance of air, and the other for the passage of a loose cotton OF THE MIOKOSOOFE. 
139 
thread. The object is placed in tlie concavity, covered with a 
piece of thin glass, and the end of the thread is carried under 
the cover by means of a small notch cut in the slide with a 
file. The bottle must be filled with very pure water, otherwise 
the salts, etc., contained in it, become concentrated under the 
thin cover, owing to the evaporation, and destroy the object. 
Frog Plate.—The circulation of the blood in the capillaries 
of living animals may be observed in the web of the frog’s foot, 
the tail of a small fish or water-lizard, the larvae of many insects, 
the ear of a young mouse and the wing of the bat. The tongue 
of the frog is also a favorite subject with some, and dissections 
of the living animal have also been made, and the circulation ob- 
served in the parts thus displayed. Except, however, for im- 
portant investigations, we have no right thus to inflict torture 
and destroy life, and, moreover, the obvious cruelty of the 
means employed, will to most minds destroy nearly all.the pleas- 
ure arising from the beauty of the exhibition. Fortunately the 
circulation of the blood in the foot of the frog may be witnessed 
without subjecting the animal to any pain. For this purpose 
the web of the hind foot is spread out over a piece of glass, 
which is held in a frog-plate, as it is called, to which the little 
animal is attached. The frog-plates usually sold, however, do 
not lie conveniently on the stage of a small microscope; they 
are apt to tip up, and there is no means of attaching them 
firmly to the stage, so that it is impossible to incline the mi- 
croscope. The annexed engravings represent a frog-plate, in 
which these difficulties are avoided. As seen in the figure, it is 
of the usual form, and has a large opening, into which is 
burnished a piece of thinnish plate glass upon which the web 
of the foot is laid. Around this opening is bored a number of 
small holes, through which threads, tied to the frog’s toes, are 
passed and held firmly by small wooden pins. A series of holes 
are also bored on each side and cut out at the edge, so that it is 
unnecessary to pass the twine through the holes, as it may be 
readily slipped into them. The frog may be enclosed in a bag, 
one foot being left out, but a simpler and better plan is to 
swathe him in a strip of muslin two inches wide and eight to 
twelve inches long. The muslin is dipped in water, and the 140 
SELECTION AND USE 
Fig. 38. 
FROG PLATE, PLAN AND SECTION. 
Fig. 39. OF THE MICROSCOPE. 
141 
frog rolled up in it and laid on the plate, where he is held by a 
few turns of light packing twine passed into the slits in the side 
of the plate and carried from one to the other and over the 
animal. Small frogs are best for this purpose, but when too 
small they are not easily handled. The position of the animal 
on the plate is so arranged that the foot may be spread over the 
glass plate that fills the large opening. 
The plate is attached to the stage as follows: A cylindrical 
brass block (Fig. 40) is provided—this block having a milled belt, 
which renders it more easily turned. The upper surface of 
this block receives a screw which passes 
through a slot of considerable length, cut in 
the frog plate, thus allowing a wide range of 
motion on the part of the latter; the under 
surface of the block receives a second screw, 
which serves to secure it to the stage of the 
microscope, as shown in Dig. 39. The holes 
for these screws are not in the same line, 
their axes being about a quarter of an inch 
apart, and the consequence is that when the 
brass block is rotated on the stage, the screw 
Fig. 40. 
that passes through the plate acts like a crank in relation to 
the plate, and moves it longitudinally, provided it (the plate) is 
kept from rotating with the block. The upper screw is inserted 
with sufficient tightness to keep the plate from shaking, but is 
left so loose that the plate can be readily moved back and forth. 
Hence, while the plate is attached to the stage in such a way 
that it cannot tip up or fall off, it may readily be moved in two 
directions, one the arc of a comparatively large circle, and the 
other a longitudinal motion at right angles to this. 
This frog plate forms in fact a sort of mechanical stage which 
admits of very delicate movements being very steadily made. 
Where this plate is used, the microscope may be inclined to 
any angle, and no jerking or starting of the animal can displace 
the portion of the foot that is under observation. Different 
parts of the same foot and different corresponding parts of dif- 
ferent feet are more or less suited to purposes of observation, 
according as they are more or less transparent and more 
or less fully supplied with vessels. It is therefore of great ad- 142 
SELECTION AND USE 
vantage to be able to select that part which answers our pur- 
pose most perfectly, and this plate affords peculiar facilities for 
effecting this. 
Table.—The table used for supporting the microscope 
should be firm and substantial, so that all shake and vibration 
may be avoided. Those who use very high powers, and desire 
to avoid vibration as much as possible, will find that a barrel or 
box, filled with sand, and resting on three feet, makes the best 
support. Some years ago, having some rather delicate investi- 
gations to make, we constructed a table in this way, and found 
the results very gratifying. Our table was arranged as follows: 
a common barrel, cut down a little, and filled with sand, was 
supported on three stout blocks nailed to the bottom. The 
table proper was made of plank, nearly square, and it entirely 
covered the top of the barrel. It was supported by a -f- shaped 
piece of wood, which was fastened to the centre of the table, 
and descended into the sand. With such a table, walking on 
the floor, and the passage of heavy teams in the street, produce 
no vibration, though, on an ordinary table, they render work 
with high powers almost impossible. 
Where several persons wish to look through the same micro- 
scope, it is very awkward if each one has to get up and go to 
the instrument. At the same time it is of course impossible to 
move the microscope without moving the arrangement for illu- 
mination also. This difficulty has been avoided by means of 
revolving tables, around which the observers sit, each one in 
turn examining the object, as the microscope is passed round to 
him. This is a very excellent, but a somewhat expensive ar- 
rangement. The same end may be attained by placing the mi- 
croscope, lamp, etc., on a smooth board of suitable size and 
shape, and passing this board to each observer in turn. The 
board, carrying microscope, lamp, etc., may be made to slide 
quite easily, and if placed on three feet, it is tolerably steady. 
Such a support, however, is not to bfe chosen where the micro- 
scope is xxsed for scientific investigations. OF THE MICROSCOPE. 
143 
Double Nose-Piece.—This is one of the most useful 
accessories that the microscopist can possess. The result to be 
obtained, and the method of accomplishing it are obvious. The 
nose-piece screws on to the 
nose, or lower end of the body 
of the microscope, and is 
fitted to receive two objec- 
tives of different powers, 
either one of which may be 
brought into action by simply 
turning the nose-piece. In 
this way a low power may be used for finding objects and ex- 
amining them as a whole, while the details may, without 
trouble, be subjected to an 
object-glass of much higher 
power. Two forms of the 
nose-piece are in use. The 
older form is straight, as in 
Fig, 41; the later form is 
bent, as in Fig. 42. The lat- 
ter form is altogether the most 
convenient. Nose-pieces ca- 
pable of receiving three or 
four objectives have been con- 
structed, and a very old mi- 
croscope, at one time in our 
possession, had a nose-piece 
with eight objectives! The 
modern nose-piece, so ar- 
ranged as to be capable of 
carrying the best objectives, is 
the invention of Mr. Brookes. 
Fig. 41.—STRAIGHT NOSE-PIECE. 
Fig. 42;—BENT NOSE-PIECE. 
ILLUMINATION—SOURCES OF LIGHT, 
Sun L-iglit.—It is generally acknowledged that the best 
light for microscopical purposes is that of the sun; not direct 
sunlight, however, for this is altogether too intense, but sun 144 
SELECTION AND USE 
light reflected from a white wall, or a light fleecy cloud. Sun- 
light is something which we cannot command at will, and, there- 
fore, the microscopist can do nothing more than select the lo- 
cation of the room which he occupies. In general a room with 
a northern aspect is to be preferred; if there should also be 
windows looking towards the east or west, so much the better, 
provided they can be completely darkened when not in use, as 
cross lights produce a bad effect. 
Artificial Light.—While good daylight is the best source 
of illumination, poor daylight is one of the worst, and we have 
frequently, during the day, obtained by the use of lamps and 
candles, results which could not possibly be secured by natural 
daylight. At the present time, gas-light, lamp-light and can- 
dle light are the most available means of artificial illumination. 
Candles are rarely used except when the microscopist is travel- 
ing, or in a peculiar situation, but a good candle gives very fair 
results, especially if the flame be protected from currents 
of air, which may easily be done by extemporizing a 
shade out of a piece of glass tube or small lamp chim- 
ney, Wax, paraffine or sperm candles should be chosen, as 
they give a clear, white flame. Common tallow candles give a 
dull yellow flame of inferior quality. Gas-light, as obtained 
from the ordinary, flat, unprotected burner, is not sufficiently 
steady; it flickers and changes, and for microscopy this is the 
worst fault that an artificial light can have. Where gas is em- 
ployed it is, therefore, necessary to use an argand burner, with 
a glass chimney. Light obtained in this way is in general 
very excellent. But the most convenient, as well as the best 
means of illumination, is a good lamp, of which the ordinary 
student’s lamp is, on the whole, perhaps the best kind. It 
gives a pure, steady and intense light; it is easily regulated, 
both as regards brightness, and also position, and conse- 
quently direction, and it may easily be procured almost any- 
where. In default of a good student’s lamp, any of the ordi- 
nary lamps with circular, or flat wicks, may be made to answer. 
Where a large quantity of light is required, as in the illumina- 
tion of large opaque objects, the circular, hollow wick, from 
the superior brightness and whiteness of the light, is always to OF THE MICKOSCOPE. 
145 
be preferred. But where a small light of great intensity is 
needed, the common flat wick, turned edgewise to the mirror, 
answers very well. It is a curious fact that flame is transparent 
to light, and, therefore, the greater the depth of flame, the 
more intense is the light. This is easily tested by looking at 
the flame of a common hand lamp sidewise and edgewise. In 
the latter case the eye receives the light from the entire flame 
concentrated to a mere band. 
Several varieties of lamps have been devised specially for the 
use of microscopists, and some of them are very excellent, 
the most perfect being that devised by Dr. Drysdale and Rev. 
W. H. Dalliuger, and described in the Monthly Microscopical 
Journal for April, 1876. 
It is hardly necessary to say that all kinds of oil have been 
displaced by the mineral oils ordinarily called kerosene. 
Very intense light, such as that from burning magnesium, 
the calcium light, the Bude light and others, have been tried, 
but without material advantage. Many years ago, we arranged 
a common kerosene lamp, so that the air surrounding the flame 
could be enriched with a supply of pure oxygen when neces- 
sary. Dr. Beale describes the same thing in his work, but does 
not seem to regard it as of any advantage. When used as a 
source of direct light, however, we found that it more nearly 
resembled sunlight than any other artificial source of illumina- 
tion. A large diaphragm or shade, with an aperture of mod- 
erate size, was placed close to the light, which was placed at 
some distance from the microscope, and the rays passed di- 
rectly through the object, not being reflected from a mirror. 
The results in some cases were well worth the trouble incurred. 
It is probable that in some cases very excellent results could be 
obtained from the electric light if properly arranged. This, 
however, is a department of microscopy which is certainly not 
suited to beginners, and we, therefore, dismiss it. 
The rays of light, from whatever source obtained, are either 
parallel, convergent or divergent; and in the illumination of 
transparent objects the character of the light, as depending 
upon these features, is of marked importance. This subject, 
and the action of lenses and mirrors in changing the relative 
direction of the rays, should be carefully studied by the stu- 146 
SELECTION AND USE 
dent, who will find it fully discussed in any work on optica. 
The general principles may be best explained by a few experi- 
mental illustrations. 
Take a piece of cardboard about six inches square, and in it 
punch a hole about half an inch in diameter. If this card be 
held in front of a wall upon which the sun is shining strongly, 
we will see the shadow of the card and a round spot of light 
exactly the size of the hole. If the card be now moved away 
from the wall, the shadow and the bright spot will still remain 
of the same size, showing clearly that the rays proceeding from 
the sun are sensibly parallel. The same holds true of a bright 
cloud or a whitewall placed at a great distance; but when the 
wall or other reflecting object is very near, the rays no longer 
possess this character to the same extent. 
If in the first experiment the wall be illuminated by a candle 
instead of by the sun, it will be found that as the card is moved 
from the wall the shadow and the spot become larger, showing 
that the rays are divergent instead of parallel. The same effect 
is produced by fixing both the lamp and the card on a stand 
and moving them away from the wall. 
Convergent rays, that is rays that tend to meet at a point, 
can be obtained only by passing parallel or divergent rays 
tlxrough a lens, or reflecting them from a concave mirror. By 
carefully arranging a large convex lens in the path of rays that 
are divergent, it is easy to render them parallel. They are 
known to be parallel when the bright spot which they make on 
a fixed surface, after passing through a hole, is not varied in 
size by changing the position of the hole. 
The variations which are produced in the appearances of 
objects when they are viewed by light possessing these different 
characteristics can only be learned by practice, and the young 
microscopist should experiment in every conceivable way. 
Whatever be the source of light employed, most objects may 
be viewed by means of any one of several very different 
methods. Thus, an object, if transparent, may be viewed by 
transmitted light, that is, by light reflected from the mirror, and 
passing through the object. If opaque, it may be viewed by re- 
flected light, in which case the light that passes to the eye through 
the microscope is reflected from the surface of the object. OF THE MICROSCOPE. 
147 
ILLUMINATION OP OPAQUE OBJECTS. 
Diffused Light.—This term is applied to ordinary day- 
light or lamp-light, allowed to fall on the object without the 
intervention of any special means of concentration. That dif- 
fused light may be available for the illumination of objects, it 
is necessary that the objectives be good. Objects which, with 
ordinary triplets of low angular aperture, are entirely invisible, 
become beautifully distinct when a better class of objectives is 
used. Under favorable circumstances the view obtained in this 
way of any well marked object is very pleasant. 
Bulls-Eye Condenser.—This is a large lens of compar- 
atively short focus, which is made to condense the light on the 
object in the same way that the common burning-glass acts, but 
with effects greatly less marked, since the light is so much less 
intense. In some cases the condensing lens is attached to the 
microscope, and in some special cases this is very convenient, 
but where there is only one condenser, it should be mounted on 
a stand, as shown in Fig. 43, so that it may be 
placed at any height and turned in any direc- 
tion. Placed between the object and the 
lamp, it collects the rays of the latter to a 
focus which brightly ilhiminates any object 
upon which it may fall. Opaque objects, 
which by diffused light are barely visible 
under the microscope, become very distinct 
and clearly defined when thus illuminated, 
and many of them, such as the wings of in- 
sects and certain minerals, appear in the most 
gorgeous colors, which, however, are perfectly 
natural, and are not the result of chromatic 
defects in the lenses. 
In viewing an opaque object by reflected 
light, it is evident that we are enabled to 
judge of the irregularities of the surface 
largely by means of the shadows cast by the 
prominences. By raising or lowering the lamp, and also the con- 
Fig. 43.—BULLS-EYE 
CONDENSER. 148 
SELECTION AND USE 
denser, the direction and extent of these shadows may be greatly 
varied. Hence one of the advantages of the students’ lamp. 
An important use of the condensing lens is to change the 
direction or character of the rays employed. Thus, when a 
lamp is in use the rays are divergent, and the easiest way to 
render them parallel is to pass them through a condensing lens. 
To effect this the distance of the lens from the lamp must be 
exactly the same as that at which it brings parallel rays to a 
focus. In other words, the lens must be at a distance from the 
lamp which is exactly equal to its focal distance for parallel rays. 
Condensing lenses are made of all sizes, and some of them 
are quite expensive, but we have frequently obtained wonder- 
fully fine results by means of a cheap lens of small size, but 
good form. A condensing lens is, perhaps, the most important 
accessory that can accompany a microscope. 
Side Reflector.—This is a small silvered concave mirror, 
which is used to throw the light on the object for the same pur- 
pose as the condensing lens. The results which it gives are 
slightly different, and it is a most valuable means of illumina- 
tion. It has not been so generally introduced as it deserves to 
be, and few microscopes are furnished with it unless to special 
order. It should always be used in combination with a bulls-eye 
condenser, as light of much greater intensity is thus obtained. 
Tlie Lielberliiilm.—This was one of the first instruments 
used for illuminating opaque objects. It consists of a small, 
concave, spherical mirror, through the centre of which the ob- 
jective passes, the focus of the mirror and objective coinciding. 
The object must be small, and is generally mounted on a small 
circular disc of leather or card, which stops out the central 
rays, while the light which passes round it strikes against the 
concave mirror, and is reflected back again upon the object. 
The Lieberkuhn gives very brilliant effects with many ob- 
jects, and if Avell managed it enables us to obtain very satisfac- 
tory views, especially with powers which are too high to admit 
the use of the side reflector, the parabola, or the bulls-eye. 
The great objection, however, is the fact that the light falls 
almost vertically, thus obliterating all the shadows pro- OP THE MICROSCOPE. 
149 
duced by elevations on tlie object. For “show” objects the 
Lieberkuhn is unequalled in its effects, and there is no doubt 
that in certain investigations it may be made to do good ser- 
vice. 
The Parabolic Reflector.—This accessory was first 
made by Messrs. Beck for Mr. Sorby, who employed it to ex- 
amine the microscopical structure of iron and steel. As ordin- 
arily constructed, it consists of a parabolic mirror attached to 
the end of a rod furnished with universal joints, so that it may 
be placed in any position as regards the object and the illumin- 
ation. It answers admirably for condensing the light on the 
surface of objects, and by throw- 
ing the rays in any particular di- 
rection across the surface, the 
observer is enabled, by means of 
the shadows, to determine the 
nature of irregularities upon some 
objects in a very satisfactory man- 
ner. In this it resembles the or- 
dinary side reflector, which, how- 
ever, is formed to a spherical in- 
stead of a parabolic curve. Like 
the side reflector, this illuminator 
should always be made to receive 
parallel rays, and condense them 
upon the object. To obtain par- 
allel rays, place the lamp in the 
focus of the bulls-eye condenser. 
The side and the parabolic reflectors cannot be used with ob- 
jectives which have a short working distance, since the rays 
from the lamp must reach the reflector from the opposite side 
of the objective. 
Since many stands have no conveniences for attaching this 
accessory, some opticians furnish it with an adapter, whereby 
it may be fastened between the objective and the nose-piece. 
Such a contrivance, however, must have originated in a want of 
knowledge of the principles which control this method of illum- 
ination. It is evident that the object should always be in the 
Fig. 44.—PARABOLIC REPLECTOR. 150 
SELECTION AND USE 
focus of the reflector; if, in adjusting the focus of the objective, 
we move the reflector, we must, of course, destroy the proper 
relation of the latter to the object. 
Objectives with Tapered Fronts.—When the objec- 
tive has a very broad front and a short working distance, as is 
the case with most objectives of high angles, it is impossible 
to illuminate the object satisfactorily with the bulls-eye con- 
denser. To avoid this difficulty, several makers, notably Mr. 
Swift, of London, have narrowed the brass work of their fronts 
to the last limit, so as not to interfere with the illumination of 
opaque objects. Mr. Tolies has, however, gone a step further, 
and has allowed the glass of his front lenses to project beyond 
the brass work, so that the bull’s-eye may be used with com- 
paratively high powers. We have a one-quarter constructed on 
this principle, which allows of the clearest illumination, and 
shows the P. angulatum as an opaque object so well that the 
markings are sharp) and well defined. These lenses are mode- 
rate in pudce, very easily used, and give very satisfactory 
results. 
Smith’s Vertical Illuminator.—This admirable de- 
vice is due to Prof. Hamilton L. Smith, of Hobart College, Ge- 
neva, X. Y., and is intended for use with objectives of such high 
power, that the Lieberkuhn, condensing lens, side reflector, 
etc., cannot be employed. Several different arrangements have 
been suggested. The first was a small annular silver reflector, 
placed just above the back lenses of the objective, and forming 
an angle of 45° with the optic axis of the microscope. A hole 
in the side of the brass mounting of the objective admitted the 
light, which was thus thrown down through the lenses on to 
the object, and back again to the eye. We have used such an 
arrangement with most satisfactory results. For example, with 
a one-fourth inch objective, thus fitted, it is easy to view the 
P. angulatum as an opaque object, and bring out its markings. 
The illuminator, as thus constructed, may be either a separate 
reflector which may be screwed into the nose-piece of any mi- 
croscope, and which is furnished at its lower end with the So- 
ciety screw, into which the objective is inserted, or it may be OF THE MICKOSCOPE. 
151 
a permanent part of the particular objective employed, and be 
specially adapted thereto. In our oavu experience, the best 
results have been obtained by the latter arrangement. 
Instead of the silver reflector, Mr. E. Beck uses a thin glass 
plate (an ordinary cover-glass), which is inserted into an adapter 
which fits betAveen the nose-piece and the objective. The thin 
glass is supported by a small pin with a milled head, by which 
it may be turned so as to present its surface at the best angle 
for reflecting doAvmA’ard the light admitted through a suitable 
aperture. 
All forms of the vertical illuminator give their best results 
when used with immersion objectives, as has been very fully 
shoAvn by Mr. Geo. W. Morehouse, of Wayland, N. Y., who 
usqs with success as high as the one-tenth. The 
markings on the most difficult tests—even the 19th band of 
Nobert’s plate—are shown clearly and Avell by this arrange- 
ment. 
In using the vertical illuminator, success will depend greatly 
upon the management of the illumination. The size of the 
aperture which admits the light to the reflector should be 
carefully regulated and diaphragmed doAvn, if necessary, and 
the rays should be rendered parallel by means of the bulls-eye 
condenser. 
Tolies5 Vertical Illuminator.—So far as we have been 
able to find, Prof. H. L. Smith was the first to illuminate the 
object by light passed down through the objective, and the 
different forms which have been introduced, such as Beck’s, 
Powell & Lealaud’s, etc., are mere modifications of his original 
plan. To Mr. Tolies, however, is due the invention of a modi- 
fication which exhibits considerable originality. He inserts, 
above the front lens, a small prism, which is so constructed 
that the light passes in freely, and is then totally reflected 
downwards. In this way the rays pass down through only one 
lens of the system, instead of through all of them. Mr. W. A. 
Eogers has used this illuminator with very satisfactory results 
in the examination of fine rulings on metal, incident to his 
investigation of the comparative value of various standard 
linear measures. 152 
SELECTION AND TJSE 
ILLUMINATION OF TRANSPARENT OBJECTS. 
The different methods which have been devised for viewing 
transparent objects are quite as numerous as those available for 
opaque ones, and require quite as much tact and study. A 
skilful worker, who thoroughly understands the points essential 
to good, or rather to appropriate and efficient illumination, will 
attain results wonderfully superior to those achieved by persons 
ignorant of the subject, and this, too, although the latter may 
be working with far superior instruments. This is seen every 
season at our microscopical exhibitions and conversaziones, and 
although the work done on these occasions is chiefly for show, 
the same principle holds good in regard to work done in the 
direction of study and investigation. 
Direct and Reflected Light.—When the microscope 
is so arranged that the light from a lamp or other self-luminous 
body shall pass directly through the object and into the micro- 
scope without being first reflected from the mirror, the illumin- 
ation is said to be direct, in distinction from light which has 
been first reflected from a mirror or other surface. Light from 
a cloud or a white wall can scarcely be regarded as direct. 
Direct light gives results which are appreciably different from 
those produced by reflected light, since light always suffers a 
change in character by reflection. These two kinds of illumin- 
ation may be either axial or oblique, and in the case of both 
reflected and direct light, if the source of light be very distant, 
the rays will be sensibly parallel, but if the source of light be 
very near, the rays will be divergent, and, consequently, under 
such circumstances, the illumination must in part be more or 
less oblique. 
Axial or Central L-iglit.—When the mirror, either 
plane or concave, is placed directly in the axis of the micro- 
scope, and reflects the light through the tube, the illumination 
is said to be axial or central. The same term also applies to 
direct light, when the direction in which the rays pass through 
the object coincides with the optical axis of the instrument. The rays must, of course, be parallel. If either divergent or 
convergent, some of the rays will be oblique. Purely axial or 
central illumination can be obtained only by passing the light 
through a very small hole placed some distance below the stage. 
OP THE MICROSCOPE. 
153 
Oblique Light.—Many objects fail to show their peculi- 
arities when illuminated by parallel rays of light passing 
through them in the direction of the optic axis of the micro- 
scope, but are seen very clearly when the light is sent through 
them obliquely. To secure illumination by oblique light re- 
flected from the mirror, the latter must be so suspended that it 
can be turned to one side, and thus send a beam of light through 
the object at an acute angle. Where direct light is employed, 
the necessary degree of obliquity may be obtained by adjusting 
the position of the lamp—a device to which we have resorted 
when compelled to use a stand in which the mirror did not 
swing to one side. In this way, also, oblique light may be em- 
ployed to illuminate objects viewed through a pocket lens, and 
very interesting effects obtained. For the resolution of fine 
markings upon diatoms, etc., oblique illumination is a neces- 
sity. When the angular aperture of the objective is low, and 
the light is very oblique, the objects appear light on a dark 
ground—in fact a sort of dark ground illumination is obtained. 
Tlie Achromatic Condenser.—The earlier forms of 
the achromatic condenser consisted simply of an achromatic 
lens, similar to an object-glass, so arranged that by means of it 
the light from the mirror could be brought to a focus on the 
object. With some objects, even this simple contrivance gave 
very fine results. It was soon found, however, that great ad- 
vantage was derived from cutting off portions of the pencil of 
rays transmitted by the condenser, and by means of the proper 
diaphragms, central, peripheral and one-sided or oblique illum- 
ination was obtained. First-class achromatic condensers be- 
came, therefore, quite complicated and expensive. Several 
cheaper but very efficient forms are now made by opticians, a 
favorite being the Webster condenser, shown in Fig. 15. 
Of this accessory Carpenter gives the following very practical 
description: “In its present form the arrraugement of the 154 
lenses strongly resembles that used in the Kellner Eye-piece; 
the field-glass of the latter serving as a condenser to receive 
the cone of rays reflected upwards from the mirror, and to 
make it converge upon 
a smaller achromatic 
combination, which 
consists of a double- 
convex lens of crown, 
with a plano-convex 
lens of flint, the plane 
side of the latter be- 
ing next the object. These lenses are of large size and deep 
curvature; so that when their central part is stopped out, the 
rays transmitted from their peripheral portion meet at a wide 
angle of convergence, and have the effect of those transmitted 
through the peripheral portion of the ordinary achromatic 
condenser. When, on the other hand, this combination is used 
with a diaphragm that allows only the central rays to pass, 
these rays meet at a small angle; and the illumination thus given 
is very suitable for objects viewed with low powers. Again, by 
stopping out the central portion of the combination, and re- 
moving the condenser to a short distance beneath the object, 
the effect of a black ground illumination can be very satisfac- 
torily obtained with objectives of moderate angular aperture. 
Further, by stopping out not only the central, but also a great 
part of the peripheral rays, so as only to allow the light to enter 
from a small portion or portions of the margin, oblique illumin- 
ation can be most effectively obtained.” 
SELECTION AND USE 
Fig, 45.—WEBSTER CONDENSER. 
Tine Wcnliam Reflex Iliiiminaior.—This is gener- 
ally conceded to be the most perfect device for illuminating 
balsam-mounted objects when viewed by objectives of very 
high angles. It is shown in section in Figure 46, where a is a 
cylinder of glass half an inch long, and four-tenths in diameter, 
the lower convex surface of which is polished to a radius of 
four-tenths. The top is flat and polished. Starting from the 
bottom edge, the cylinder is worked off to a polished face at an 
angle of 64°. Close beneath the cylinder is set a plano-convex 
lens of inch focus. Parallel rays,/,/,/, sent through the 
lens, after leaving the lower convex surface of the cylinder, OH THE microscope. 
155 
Would be refracted to tlie point, h, if continued in solid glass, 
but by impinging on the inclined polished surface (which is 
far within the angle of total reflection), they are thrown on the 
flat segmental top ; here they would be totally reflected and 
beaten down again to a point outside the cylinder, but if an 
Fig. 46. 
object-slide, c, be laid over the flat top with an intervening 
film of water, the rays will proceed on to the point, g, if the 
glass slide be thick enough. As shown in the engraving, how- 
ever, the slide is of the usual thickness, and the point, g, lies 
above it; therefore, if the upper surface of the slide is clean 156 
SELECTION AND TTSE 
and polished, the rays will he totally reflected therefrom, and 
will be sent to the point, b, outside the cylinder. If, however, 
any insect scales, diatoms, or thin flat objects should be in 
contact with the upper surface of the slide, the rays will be 
enabled to pass through, and the objects will be brilliantly 
lighted up on a dark ground. Objects seen in this way show 
many points of their structure with remarkable clearness. 
Speaking of the Amphipleura pellucida, Mr. Wenham tells us 
that it assumed a substantial appearance not seen in any other 
way, and at once displayed its strife with an £th that had never 
resolved them before. 
It is very evident that the results which we have just de- 
scribed rvill only take place when a stratum of air lies above 
the slide, and the objects which we wish to view must be in 
contact with the slide, and not mounted on the cover, as is 
usually the case. But if the objects be mounted in balsam, 
the light will pass through to the upper surface of the cover, 
whence it will be totally reflected down, and the objects will 
be invisible, or, if sufficiently substantial, will appear on a 
black ground with dry objectives. But if we use an immersion 
objective, the light will no longer be totally reflected at the 
surface of the cover, but will pass through, and will be taken 
up by the objective provided the latter has sufficient angular 
aperture. 
Used under these latter conditions, the reflex illuminator 
constitutes a means of obtaining oblique illumination of great 
purity and force, and the instrument is now a general favorite 
for this purpose, for which it was first used by Mr. Samuel 
Wells, of Boston. 
To use the reflex illuminator successfully demands great care 
and some experience, but those who will carefully study its 
construction and mode of action, will find no difficulty in 
getting good results. First of all, then, we must remember 
that the reflex acts as a condenser, and consequently it is 
necessary to use but a moderate amount of light, which should 
be as intense as possible. This is best obtained from a small 
hand lamp. Secondly, we must use parallel rays, or the points 
to which the light is brought to a focus will not be those which 
accord with the other features of the instrument. Parallel rays OF THE illCKOSCOFE. 
157 
may be either the light from a bright cloud thrown up by the 
plane mirror ; divergent rays from a lamp made parallel with 
the concave mirror; or divergent rays from a lamp made 
parallel with a bulls-eye condenser, and thrown up by the 
plane mirror ; or a combination of these last. Thirdly, we must 
remember that the instrument has two centres, arising from the 
fact that the optic axis is bent by internal reflection from 
the polished facet of the cylinder. Hence, we have the centre of 
the lens below the cylinder, to which the illumination must be 
adjusted, and we have another centre at which the rays are 
brought to a focus, and which must be made to coincide with 
the optic axis of the microscope. This centre is generally 
marked by the maker on the small side piece, e, and it should 
be brought exactly to the centre of the field of view of the ob- 
jective, a low power—say a half inch or two-thirds—being used 
for this purpose, in the first place. 
It is, of course, obvious that by adjusting the other condi- 
tions of the instrument, the points which we have laid down 
may be varied. Thus, for example, divergent rays may be 
used ; but in that case the focus of the rays will not be at the 
point, g, unless the fiat top of the cylinder is depressed a little, 
which may be easily done if a tenacious liquid like glycerine be 
used as the connecting medium. 
We think that if the reader will bear these points in mind, 
and will work over this accessory faithfully for a few hours, he 
will attain results which will abundantly compensate him for 
the labor spent. 
The reader must always bear in mind that where totally re- 
flecting surfaces are used, as in paraboloids, x’eflex illuminators, 
etc., they must be kept scrupulously clean or they lose their 
effect. 
Tlie Wenliam Prism.—This simple and ingenious little 
device was first described by Mr. Wenham in a paper read 
before the Royal Microscopical Society, March 26, 1856. At 
that time immersion objectives were unknown, or at least were 
not in use, and the effect of the prism was to produce a very 
brilliant dark-ground illumination ; but, as with the Reflex 
Illuminator, the introduction of immersion objectives of wide 158 
.SELECTION AND USE 
angle has greatly enlarged the scope of usefulness of this little 
piece of apparatus. 
The Wenham prism consists of a small right-angled prism of 
crown glass, which is “ patched” on to the under side of the 
slide by means of a little glycerine, oil of cloves, or any similar 
fluid. In the figure, b is the slide and 
cover, and a is the prism. Hays of 
light, as shown by the dotted lines, 
if sent through the face of the prism, 
pass straight to the upper surface of 
the cover, and if a dry objective be 
used, they are reflected down again on 
to the underlying objects in balsam, 
Fig. 47 
the wenham prism. 
which appear brilliantly illuminated, as if beneath a speculum. 
An immersion object-glass prevents the covering glass from 
acting as a speculum, and light emerges beyond what would 
otherwise be the critical angle, thus affording very oblique illu- 
mination, which, with suitable objectives, enables us to resolve 
the most difficult tests. 
If the prism is used with dry mounted objects, total reflection, 
instead of occurring from the cover, takes place from the upper 
surface of the slide itself, and all is total obscurity except where 
some object, such as a butterfly’s scale or a diatom, is in inti- 
mate contact with the slide, and then these objects allow the 
transmission of light, and appear curiously distinct in a jet- 
black field. 
This illuminator requires no fitting to adapt it to the micro- 
scope. It is merely stuck on the under surface of the slide 
with a little glycerine; the slide is then placed on the stage, 
the object found, and the position of the prism adjusted by the 
finger. 
It has been objected to this method of attaching it, that when 
the microscope is inclined, the prism is apt to slide down. This 
will not occur if the quantity of liquid used be very small. It 
is not difficult, however, to arrange a very thin plate of metal 
with a square hole in the centre, the metal which originally 
filled the hole being bent down so as to form an ear or clip 
at each side of the opening. These clips grasp the prism, 
which, being cemented into this frame, may be laid on the OP THE MICROSCOPE. 
159 
stage; over it is placed the slide. If the metal plate be 
fastened to the stage by any contrivance, the object-slide 
may be moved about at will without disturbing the prism. 
As we have already stated, the Wenham prism has a right 
angle and two angles of 45° each. Prisms for the same purpose 
have been made with unequal angles at the base, and with other 
than a right angle at the apex, and this is sometimes advan- 
tageous. 
It is, of course, obvious that the Wenham prism transmits 
the rays with their direction unaltered. If we wish to condense 
them, this must be done previously by means of mirrors or 
lenses. Two illuminators, which combine the effects of the 
condenser and the prism, have been devised by Mr. Wenham, 
and we will now describe them. 
Tlie Hemispherical Illuminator.—Instead of a 
prism, Mr. Wenham has used a hemispherical lens, patched on 
to the slide in the same manner as that described for the prism. 
This lens concentrates the rays on the object, and as rays from 
any direction will always enter the lens at right angles to some 
part of its surface, more light and greater obliquity can be ob- 
tained by it than by the prism. This device was described by 
Mr. Wenham in the same paper in which he first described 
the right-angled prism, but we believe it was first applied 
by Mr. Tolies as an oblique illuminator for balsam-mounted 
objects seen with immersion lenses. 
The tC Half-Button.”—A still more efficient illuminator, 
and one winch is complete in itself, is shown in the engravings, 
rig. 48 being a side view, Fig. 49 a section, and Fig. 50 a per- 
spective view of this little contrivance. It consists of a semi- 
circular disc of glass of one-quarter of an inch radius ; the edge 
is rounded and well polished to a transverse radius of one-tenth 
of an inch, for the reason that the focus of a spherical surface 
on crown glass falls within its substance to nearly three times 
the radius, consequently the line of light will be in the most 
concentrated position at one-twentieth of an inch above the 
centre of the semi-disc, which distance is sufficient to reach ob- 
jects mounted on slides of the usual thickness. The “half- 160 
SELECTION AND USE 
button,” as it has been called, is connected to the under side 
of the slide by means of water, glycerine, or oil of cloves, its 
sides being grasped by a simple kind of open clip attached to 
the sub-stage. This illuminator is complete in itself, and re- 
quires no supplementary condensing lens ; the obliquity is 
Figs. 48. 
49. 
50. 
simply obtained by swinging the ordinary mirror sideways, 
and by this means Amphipleura pellucida, mounted in balsam, 
can be at once resolved. 
The Woodward Illuminator.—This method of mount- 
ing and arranging a right-angled prism for the illumination of 
balsam-mounted objects, was described by Col. Dr. Woodward 
in a paper read before the Royal Microscopical Society, June G, 
1877. It consists of a prism of glass, the apex of which has 
been truncated. This prism is cemented to the truncated apex 
of a similar prism of brass, the long side of the glass prism 
being upward, and connected with the under surface of the 
object-slide by suitable liquid (glycerine, oil of cloves, etc.) 
The homologous side of the brass prism is downwards, and 
slides in a holder which is supported by the sub-stage. To 
this brass prism are attached two arms, which serve to support 
a thin screen at some distance below the stage. The screen 
is parallel to that face of the glass prism that receives the light, 
and is pierced with a pin-hole, which permits the passage of a 
minute beam of sunlight. With this apparatus, Col. Dr. 
Woodward secured very fine results. 
Tolies’ Illuminating Traverse .Lens.—TJie most 
perfect arrangement for allowing a beam of liglit to reach, 
without refraction, a suitably immersed object, is the illumina- 
ting traverse lens of Mr. Tolies. The engraving, Fig. 51, and the 
description, wdiich is in Mr. Tolies’ own words, are from the 
Journal of the Royal Microscopical Society. OP THE MICROSCOPE 
161 
The device is represented in the annexed figure, where P is 
the basilar plate of the whole traverse system, having a circular 
groove and track, in which the carriage, C, moves. On a pro- 
jecting arm, A, of the carriage, C, are mounted Avhatever ap- 
pliances are to be used to modify or direct the light upon the 
traverse lens, T, in the direction of the object at the centre of 
the system. 
In the figure the conca\Te lens, N, is shoAvn in position on the 
arm. Thus situated, the interior convex and concave surfaces 
being of no effect, the two exterior plane surfaces of the traverse 
Fig. 51.—tolle’s illuminating traverse lens. 
system constitute it a prism, and every slightest movement of 
this concave facet lens on the traverse lens, T, would would give 
a different prism to infinite variety. In this arrangement, the 
concave mirror can be used in the ordinary manner and con- 
dense light enough upon the object for all ordinary purposes. 
The full interior aperture of a dry objective would be reached 
at the very convenient obliquity of 41°, i.e., at less than the 
critical angle, or angle of total internal reflection between 
crown-glass and air. L is a double-convex condensing lens, 
that may be placed at about its principal focal distance from 
the object. 
For a condenser, Avith the size of apparatus as draAvn in the 
figure, a simple lens of 1|- inch focus, and about ten degrees 
(10°) of aperture is convenient, and if the lens is movable 
along the arm, A, it can be focussed readily on the object, the 
position being fixed by inspection, This Avould be well for 
parallel rays. If diverging rays are used, another lens of two 162 
SELECTION ANT) tTSE 
or three inches focus, mounted on the arm, A, will conveniently 
take up the rays from the radiant at the distance of the focus 
of this supplementary lens. 
The plate, P, is graduated on its circular edge, as in the 
figure, to two degrees, and the arm, A, has a swing of seventy 
degrees of arc each way from the axis of the microscope. An 
index-line is marked on the bevelled edge of the carriage 10° 
from the axis of the condenser, which must be added to or sub- 
tracted from the real obliquity of the illuminating rays. 
It is obvious that any observation made and duly recorded as 
to its conditions, as of obliquity of incidence of illuminating 
pencil or ray, form of the pencil or beam, focal length and dis- 
tance of the condenser, such observation could be successfully 
repeated. The record of the obliquity of the most oblique rays 
reaching the object directly and giving view of it at the eye- 
piece with luminous field, would express the “balsam” aper- 
ture, or more correctly, the half interior aperture of the objec- 
tive when the front lens of the objective and the traverse system 
are of glass of similar refraction. 
Having thus the “balsam” angle, we readily calculate or 
learn the corresponding angle for glycerine or water, or any 
medium of which we have the index of refraction. A corres- 
ponding notation, perhaps for air, might be engraved in juxta- 
position on the basilar plate. 
The Spot Lens.—This is a plano-convex lens of very high 
curvature (it is generally hemispherical), so mounted that its 
distance from the object may be adjusted in such a way that 
the rays which pass through it, may be brought to a focus 
on the object. The central rays are stopped out by means of a 
black spot (hence the name), so that the object is illuminated 
wholly by rays which are of too great obliquity to enter the 
object-glass, except when their direction is changed by the 
object. The latter, therefore, appears brilliantly illuminated 
on a dark ground, and in many cases features which could not 
otherwise be seen are shown very distinctly. 
The larger diatoms, insect scales, and similar objects are 
peculiarly suited to this method of illumination, and some of 
them are very beautiful as “ show ” objects. OF THE MICKOSCOPE. 
163 
The Parabolic Illuminator.—This is an instrument 
intended to accomplish the same end 
as the spot lens, but in a far more 
efficient manner. It consists of a 
block of glass, the outer form of which 
is a parabola with a cup-shaped de- 
pression cut in the upper end. It is 
mounted in a brass fitting, which 
slides up and down in the sub-stage 
of the microscope, and thus may be 
readily adjusted, so as to throw the 
light properly upon the object. The 
results obtained by means of the parabolic illuminator are 
wonderfully beautiful. 
Fig. 52.—THE PABABOLIO 
ILLUMINATOR. 
Polarized JLiglit.—The micro polariscope consists of two 
distinct parts, a polarizer and an analyzer, each of which is 
now generally formed of a Nichol prism properly mounted. A 
Fig. 53.—POLARIZER. 
Fig. 54 —ANALYZER. 
common method of mounting the polarizer is shown in Fig. 53. 
As there shown, the lower ring is intended to slip into the ring 
of the sub-stage, the rack and pinion of which enables us to 
place the end of the prism at a proper distance from the object. 
When the microscope is not provided with a sub-stage, the 
polarizer is turned upside down, and the brass fitting slipped 
into a ring, which is attached to the under side of the stage. 
The milled ring, which is shown uppermost in the figure, 
enables us to rotate the prism in both cases. 
The analyzer may be arranged in either one of two ways. It 
may be slipped over the eye-piece, or it may be mounted in a 164 
SELECTION AND USE 
brass tube, the upper end of which has an external Society 
screw that attaches it to the body, while the lower end of the 
tube has an internal Society screw for receiving the objective. 
Fig. 54 shows the latter arrangement. 
Polarized light, except for the mere beauty of its effects, 
has not received the attention that it deserves. In some de- 
partments of scientific investigation, especially mineralogy and 
geology, its use has afforded very satisfactory and brilliant re- 
sults. As regards its applications to medicine and physiology, 
Dr. Frey says: “ The examination of tissues by polarized 
light has a high scientific value, as, by this means, molecular 
relations become evident, which by investigation with ordinary 
light, remain entirely concealed. The interpretation of what 
is seen, is in many cases difficult, and generally lies within the 
province of optics, with which the medical observer is usually 
but little familiar.” 
To detail the method of using it, and the special features 
which it discloses, would, however, far transcend the limits of 
this work, and we must, therefore, refer the reader to some 
special treatise on the subject. 
HOW TO USE THE MICROSCOPE. 
The remarks which we are now about to offer, are intended 
for the merest beginners—for those, in fact, who have never 
used a microscope at all; and therefore they may, perhaps, to 
some, appear childishly simple. And yet we have seen not 
only teachers, but professors in colleges, who might have de- 
rived some benefit even from these simple hints. We remem- 
ber on one occasion seeing a professor of botany attempt to 
examine a minute plant with a common pocket magnifier with 
three lenses. In the first place he turned the instrument wrong 
side up, so that, although he could see through it, the results 
attained were very inferior to what they would have been if the 
instrument had been properly used; in the second place he 
wore his hat in such a way as to cut off nearly all the light, and 
in the third place he did not know how to hold his hands so as 
to obtain the requisite degree of steadiness. If he had given 
a few minutes thought to the subject, he could no doubt have OF THE MICBOSCOPE. 
165 
corrected liis bad methods, but then he evidently had never 
considered it worthy of earnest thought, although it formed 
the very foundation of his powers of observation. 
Simple Hand Magnifiers.—These are perhaps the most 
important of all optical instruments, and yet we rarely find a 
person who can use them efficiently. There are but three 
points that require attention, viz: The proper position of the 
magnifier itself, the perfection of the illumination, and the 
steadiness with which the instrument is held at the exact focal 
distance from the object. Many magnifiers are so constructed 
that it is impossible to place them in a wrong position; the 
side which should go next the eye, and the side which should 
go next the object are so well marked that no mistake can be 
made. The greatest liability to error exists where two or three 
lenses of different powers are fixed in the same frame and used 
together. This forms one of the most common and useful of 
our magnifiers, and the rule is always to place the lens of great- 
est power nearest to the object. Plano-convex lenses should be 
placed with the plane or flat side next the object. 
Hand magnifiers are, in the majority of cases, used for ex- 
amining opaque objects, and one of the most important con- 
ditions for perfect vision is that the object be veil illuminated. 
First of all, then, see that the light falls full and direct on the 
object; then place the magnifier as nearly in focus as can be 
done without actually looking through the lens, and, after this, 
approach the eye to the magnifier. The errors most commonly 
committed are: Turning the object away from the light; cut- 
ting off the light by the projecting brim of a hat or cap; 
shading the object by the hand or the lens itself; attempting to 
examine an object in a room that is not sufficiently lighted. 
Having secured a proper position for the magnifier and a 
good illumination, the next step is to devise some means for 
holding the lens steadily in focus during the examination. This 
is most readily effected by resting the hand that holds the lens 
upon the hand that holds the object. Lens and object then 
move together, and the focussing remains unchanged. 
Compound Microscopes.—We presume that the instru- 
ment in hand is a very simple one, and that the magnifying 166 
SELECTION AND USE 
power to be used is not very great. No person should attempt 
to use high powers and complicated instruments until he has 
served an apprenticeship by using a microscope of simple con- 
struction, and objectives of considerable length of focus. 
Let the beginner commence by examining some transparent 
object already mounted. To do this, set the microscope 
on a firm table, in front of a window by day, or before 
a lamp at night. Direct sunlight is to be avoided, the light 
from a white cloud being usually preferred to any other 
source of illumination. At night use a gaslight that does 
not flicker, such as an argand burner, or a good kerosene 
lamp, the German student lamp being very well suited to this 
purpose. Good results may, however, be obtained from any of 
the ordinary lamps, especially those with a circular wick, which 
are now so common. Very fair work may also be done by 
means of a good candle. This subject has, however, already 
been discussed at greater length in another section. 
If the microscope be a cheap French one, the objectives will 
be found attached to the body, there seldom being any special 
provision made for holding them. But with all American and 
English microscopes, and the better class of instruments from 
the continent of Europe, special boxes are provided for holding 
the objectives. These boxes are usually made of brass, and 
are indispensable to the microscopist that endeavors to take 
good care of his instrument. Where the objective is kept in a 
separate box, the body of the microscope must be raised to a 
sufficient height, and the objective screwed into its place. In 
doing this be very careful not to let the objective fall and strike 
against the stage. We have seen more than one good lens 
spoiled through such an accident. 
When the objective has been properly secured in its place, 
move the body of the microscope up or down until the front 
lens—that is, the lens which is nearest to the object, is about a 
quarter of an inch above the stage. Then turn the mirror 
until the light from the window or lamp is reflected through 
the microscope, so that when looking through it a bright cir- 
cle of light is seen. 
Place on the stage some mounted object of large size, such 
as a fly’s wing or section of wood. If a low power objective be OF THE MICROSCOPE. 
167 
used, say one magnifying less than 100 diameters, move the 
body of the microscope up, so as to increase the distance be- 
tween the objective and the object. At the same time keep 
your eye at the eye-piece and watch closely. At a certain point 
the object will be seen with great distinctness; it is then in 
focus, and is ready for examination. Always begin with low 
powers. One of the greatest risks that the beginner runs is 
that of breaking the objective by forcing it down on the object. 
To avoid this with high powers, bring the objective down al- 
most into contact with the slide; when doing this do not look 
through the microscope, but watch the objective, and stop 
whenever it is sufficiently near the object. Then apply the eye 
to the eye-piece, slowly raise the body, and watch for the com- 
ing of the object into focus. This is the only safe method with 
high powers. 
Before attempting to place an object on the stage, or to re- 
move one from it, see that tire objective is raised at least half 
an incli above the stage. By attempting to introduce a new 
slide without raising the objective, when using high powers, 
you run great risk of injuring both the object and the objec- 
tive. And in removing objects from the stage, never lift them 
up; always slide them off. In lifting them up, great danger is 
incurred of bringing them into contact with the objective, and 
thus doing irreparable injury. Sliding entirely prevents this. 
Where the microscope is not provided with mechanical 
means for adjusting the focus, such as a screw or rack and 
pinion, a great deal may be accomplished by special methods 
of manipulation. Thus if, instead of pushing the body directly 
through the collar, it be moved with a slightly twisting motion, 
the focus may be adjusted with considerable delicacy, and when 
the microscope is not provided with a fine movement, a great 
deal may be done by means of a slight pressure of the fingers 
on the stage. Bow stages are sufficiently rigid to resist even 
the slightest pressure. 
The chief points which the beginner should endeavor to 
study are the variations which are made in the appearance of 
the object by means of slight changes in the focussing and the 
mode of illumination. Experienced microscopists constantly 
keep their fingers on the fine adjustment of the microscope, 168 
SELECTION AND USE 
and watch the different appearances which are produced by 
a change in the mode of illumination. Swinging the mirror to 
one side, so as to send the light through the object in an 
oblique direction, or, where the mirror cannot be turned to 
one side, merely turning it on the trunnions which support it, 
will often produce most important effects. 
From what has previously been said in regard to the neces- 
sity for clear and brilliant sources of illumination, the young 
microscopist may, perhaps, be led to suppose that the field of 
view cannot be too brilliantly illuminated. Such, however, is 
far from being the case. With ordinary powers (those below 
500 diameters) it is almost always necessary to moderate the 
light, even of a flat-wicked lamp, and still more that of a 
students’ lamp. The finer details of an object cannot possibly 
be made out if the illumination be too strong; they are 
“ drowned out,” and the whole object becomes what artists and 
engravers call flat. The light may be regulated by the dia- 
phragm which has been previously described. Where the mi- 
croscope is not furnished with a diaphragm, increasing the dis- 
tance of the lamp from the instrument is the best mode of 
lessening the intensity of the light. 
Very bright light is exceedingly trying to the eyes, and 
therefore the student will find it advantageous to use lights of 
moderate intensity, and to increase their efficiency in every 
possible way. This may be done to a very great extent by 
judicious management—chiefly by excluding eye all 
unnecessary light. In a room very brilliantly lighted with a 
number of powerful argand burners, it would be impossible to 
secure the proper illumination of a microscopic object by 
means of a candle, for the eye, accustomed to the bright light, 
would fail to be impressed by the weaker one. Extinguish the 
bright lights, give the eye a short time for rest, and the candle 
will answer very well. The principle thus illustrated finds a 
practical application in the use of pasteboard shades surround- 
ing the eye-piece, and excluding from the eye all light except 
that which passes through the microscope. Such a shade is 
easily made and adapted to any microscope, and is of great 
service. We have also in our own practice carried out the 
same principle by means of extra diaphragms to our eye- OF THE MICROSCOPE. 
169 
pieces, thus cutting off all the light -which passes through the 
microscope, except that which actually serves to illuminate the 
object. 
It will also be found of great importance to secure perfect 
purity in the special illumination employed. Thus, if we are 
examining an object by transmitted light, it always detracts 
from the clearness and beauty of the image if light is reflected 
from its surface. It is, therefore, of advantage to shade the 
object by means of a small tin, brass or pasteboard shade, at- 
tached to the stage so as to prevent any light from the lamp 
from falling on the object. 
A difficulty which frequently occurs to young microscopists 
consists in the almost impossibility of securing a field of view 
equally illuminated in all parts. Assuming that the mirror is 
in proper position, and that there is nothing to shade any part, 
it will in general be found that the difficulty arises from the 
fact that the mirror throws images of the lamp, etc., upon the 
object. Sometimes this is very distinctly seen; the shape of 
the flame can be clearly distinguished, and the metal portions 
of the lamp appear as dark shades. The cause is that the lamp 
is at the exact distance at which the mirror forms an image of 
it on the upper surface of the slide, just as a lens, held in 
front of a white wall, will throw an inverted image of a lamp 
or candle on the wall, provided the relative distances of the 
wall, lens and candle are properly adjusted. The remedy is 
very simple; move the lamp either towards the microscope or 
away from it, as may be most convenient. 
As previously stated, the character of the illumination af- 
forded by a mirror, and by a white surface placed at a short 
distance from the object, are appreciably different. A very 
pleasant method of illuminating transparent objects consists in 
the use of a plate of plaster of paris. Its whiteness is probably 
as pure as that of any other substance, and it is easily procured. 
The plate we use was cast in the cover of an old tin box, half an 
inch deep and three inches in diameter, A flat surface was 
secured by casting it upon a board. If cast on glass or metal, 
the surface is glazed and shiny, which is bad. Instead of plas- 
ter, fine white paper or cardboard may be used. Such surfaces 
must not be glazed, and they should be kept scrupulously clean, 170 
SELECTION AND USE 
The light is also sometimes modified by passing it through 
ground or colored glass—blue being a special favorite. Such 
light-modifiers, as they are called, produce a pleasant and 
equable illumination, which is a great relief to the eyes, but, 
except for the resolution of finely lined objects, we have not 
found them otherwise of any special advantage. When it is 
desired to obtain the greatest resolving power that a lens is 
capable of affording, the blue cell, as it is called, is probably the 
most efficient accessory. This is simply a glass tank, somewhat 
like a zoophyte trough, filled with a solution of oxide of copper 
in liquor ammonise. The solution is prepared by adding 
liquor ammonias to a saturated solution of sulphate of cop- 
per, until the precipitate which is first formed is re-dis- 
solved. The intensity of the blue may be regulated, either 
by diluting the solution, or by varying the thickness of the 
layer of liquid. 
When it is desired to examine anything by light reflected from 
it, instead of light transmitted through it, the object should be 
placed before a dead-black surface, such as the dark part of the 
diaphragm, or a blackened card, and at such a distance from it 
that the surface of the background is not in focus. Then, 
place the condensing lens in relation to the lamp, so that a 
bright spot of light will fall on the object, and on bringing it 
into focus it will be clearly seen. Low powers only can be 
satisfactorily used for the examination of opaque objects by 
beginners. 
The beginner should commence with the simplest mounted 
objects, and afterwards, when a little skill in the manipulation 
of the instrument has been acquired, he should proceed to the 
examination of such simple unmounted objects as are easily 
prepared. The latter course will prove altogether the most 
valuable and instructive, for he who confines himself to the ex- 
amination of mounted objects only can never hope to become a 
microscopist. After a time, when a little skill has been 
acquired in the preparation of objects, the student may proceed 
to preserve and mount them. Most young people try to mount 
before they have learned to prepare objects, and the conse- 
quence is that they soon find themselves in possession of a 
large collection of very poor slides. OP THE MICROSCOPE. 
171 
On tlie Use of Objectives of Large Apertures.— 
When the first edition of this book was issued, wide-angled ob- 
jectives were far from common. The “ Battle of the Object- 
Glasses ” was at its height, and objectives capable of resolving 
the Amphipleura pellucida, or Nobert’s nineteenth band, by sim- 
ple lamplight, were comparatively scarce. During the interven- 
ing years the opticians have been hard at work, and have turned 
out objectives of a high class to such an extent that almost 
every microscopical society numbers amongst its members those 
who have glasses of high balsam apertures. It is an unfortu- 
nate fact, however, that thus far the text-books are entirely in- 
nocent of any directions for using these glasses. We have now 
before us a treatise of over 400 pages, which left the author’s 
hands as late as the middle of 1880, and which does not contain 
a single direction for the use of the cover correction ! As a 
justification of such omission, it has been alleged that objec- 
tives of large aperture require no more care and skill than 
others. From this position we most emphatically dissent, and 
if evidence were wanting we could cite the case of a prominent 
officer of one of our microscopical societies, and one who claims 
to be an expert in the use of the microscope, who thought it a 
great feat to show No. 18 of the Probe Platte with a § objective, 
which undoubtedly was capable of resolving No. 20 handsomely 
if properly handled ! The forthcoming work of Prof. J. Ed- 
wards Smith will probably be the first test-book that will have 
treated this department thoroughly, and students are anxiously 
looking forward to its appearance. 
Instruction in the proper methods of handling first-class 
objectives is best obtained from a living teacher. It will be 
found one of the most difficult things to learn from a book. 
One reason for this is that until he has become expert, or has 
seen the objects in the hands of some one who is expert, the 
student does not know what appearance to look for. The con- 
sequence is, that he is all the time working in the dark. But 
after he has seen the Amphipleura or the Saxonica well shown 
by some one who knows how to handle a good objective, he 
has a standard of excellence to go by, and it will be very strange 
if, after a few trials, he does not surpass the work of his teacher. 
Then, as soon as he has learned to bring out what he knows to m 
SELECTION AND USE 
be the best results on difficult diatoms, he knows when his 
lenses are doing good work in his hands, and, so far as his in- 
strument is concerned, he feels confident that lie can apply it to 
any class of objects and get views that are trustworthy. 
To get the best results from modern objectives of wide angle 
of aperture, there are two things that must be carefully at- 
tended to—the illumination of the object, and the adjustment 
of the correction for the thickness of cover-glass. Of delicacy 
in focussing, which, by the way, is a most important point, it 
is unnecessary to speak. 
As regards illumination, the three great points that must be 
secured are purity, intensity, and suitability. By purity we 
mean that the light must be wholly of a certain degree of 
obliquity, for these wide-angle lenses gather in so many rays, 
that a diffused light, which does not affect low-angled objec- 
tives, greatly injures the working qualities of those of high 
angle. Thus, for example, if Ave are working by central light, 
it is necessary to shut out all the direct rays from the lamp, 
which Avould enter at every sort of angle, and produce con- 
fusion. A narrow pencil, produced by sending a beam of 
parallel rays of intense light through a small hole placed some 
distance beloAv the stage, will give central illumination, which 
will give very different results from that obtained by a dull, 
diffused light, such as may be obtained from the flat side of the 
wick of a lamp, falling on a large mirror and reflected upward. 
When oblique illumination is used, great care should be 
taken to prevent rays of different degrees of obliquity from 
falling on the object. A large, concave mirror fills a large 
portion of the arc through Avhich it SAvings, and its upper and 
loAver edges reflect rays Avhich fall upon the object Avith very 
different degrees of obliquity. Where very oblique rays are 
used, but a small proportion of them enter the glass slide, 
unless they are “ guided ” through by some such contrivance 
as the Reflex Illuminator, Tolies’ Traverse Lens, etc. Rays of 
less obliquity enter much more freely, and although less in 
quantity than the others in the first place, they droAvn them 
out. In the exclusion of these rays consists in a great degree 
the value of many of the “illuminators” in common use, and 
the same effect may be secured to a considerable extent by OF THE MICKOSCO- 
173 
means of a simple screen. This fact has been made very ap- 
parent by Prof. J. E. Smith, who, by the use of a simple 
“ oblique diaphragm,” as it is called, has secured results which 
were previously supposed to demand much more complicated 
and expensive arrangements. This oblique diaphragm, or 
screen, consists of a plate of very thin metal secured to the 
under surface of the stage. The stage then forms the upper 
surface of a >, and the metal plate the lower one. The angle 
may be adjusted at will by simply bending the plate, and it is 
evident that all rays from below will be entirely excluded. 
A piece of the thin iron known as ferrotype ptate is the cheap- 
est and best material for this purpose. Its surface should be 
dead black. 
The same result is obtained by the use of a conical dia- 
phragm fitted to the sub-stage. 
When such objects as difficult tests are viewed by oblique 
light, it will be found that there is a certain angle of illumina- 
tion at which the objective will generally perform best, and 
this must be found by careful experiment. The higher the 
angle of aperture of the objective, the greater may be the angle 
at -which the object is illuminated, but it will be found that 
many objectives fail to work up to the full angle claimed for 
them by their makers. 
Such are the general principles to which the student must 
pay attention in regard to the matter of illumination, but in ad- 
dition there are numerous minor details, a knowledge and appre- 
ciation of which can only be acquired by practice. The finer 
objectives are so sensitive to the slightest changes, that the 
least movement of the mirror or lamp influences the result in 
a very marked degree. 
The other important point to be attended to is the cover- 
correction. This will be found to demand great patience and 
attention. The older authorities give fixed rules for regulating 
the cover-adjustment, but as it unfortunately happens that this 
adjustment varies not only with the thickness of the cover- 
glass, but with the depth to which the object is sunk in the 
mounting medium (and this is not always the same), and the 
angle of illumination, it will be seen that each object requires 
special attention in regard to these points. In addition to this, 174 
SELECTION AND USE 
it will be found that each objective has its own special charac- 
teristics, which must be carefully studied by the owner if he 
would command success. 
The difficulty of giving any rules which will enable the 
student to put the “finer touches” on this kind of work, is well 
set forth by Dr. Blackham in a recent article,* from which we 
quote as follows : 
“It will probably be expected that something should be said 
here in reference to the adjustment of the objective for dif- 
ferent cover-glasses, etc., by means of the screw collar, but on 
this point, unfortunately, but little can be said, though, of 
course, it is a most important one, and the better the objective, 
and the wider its angle, the more important is accurate adjust- 
ment. Every wide-angled immersion objective that is worth 
having, is a separate work of art, and, as such, has an individ- 
uality with which the worker must become acquainted, and 
which he must learn to turn to his advantage. 
“ None of these lenses which I have seen are perfectly achro- 
matic, and each has a special wave length at which it does its 
best. In Tolies’, and Bausch & Bomb’s, and I believe in 
Spencer’s lenses, this is between the blue and the green, but 
the exact shade differs with different lenses, and must be found 
by experiment. My plan is to adjust roughly by means of the 
tint of the field, then to bring an object into the field (if we 
are at work on the Probe Platte, one of the easier diatoms, say 
Pleurosigma angulntum), and focus on it and arrange the illu- 
mination as accurately as possible, and then with the finger and 
thumb of the left hand, turn the correction collar of the objec- 
tive backwards and forwards, keeping the object in focus all 
the time by means of the forefinger of the right hand on the 
milled head of the fine adjustment, until the best effect is ob- 
tained. An occasional slight change in the position of the mir- 
ror is often needed. 
“In all these manipulations, deliberation and care are 
needed, and the patience of the beginner will often be sorely 
taxed, but let him remember that nothing worth having, can be 
gotten without trouble.” 
*American Journal of Microscopy for February, 1880. OF THE MIGKOSCOPB, 
175 
Care of tlie Microscope.—A microscope, when not in 
use, should always be kept well covered, either in its case or 
under a suitable cover. There is no more convenient mode of 
keeping a microscope than to stand it upon a cloth mat, and 
cover it with a glass shade. It is thus kept free from dust and 
vapors, and is always ready for use; but when it is kept in its 
case, and especially if it has to be screwed together, interesting, 
valuable, or even important objects, will often fail to be ex- 
amined, simply because too much time and labor are necessary 
to prepare for the operation. 
A good microscope should be so carefully protected, that it 
shall rarely require to be cleaned or dusted, as this wears off 
the lacquer, and exposes the metal, which, when thus uncov- 
ered, soon begins to tarnish. When dusting or cleaning becomes 
absolutely necessary, chamois leather, or a very fine old linen 
or silk handkerchief is most suitable. Never use coarse cloths, 
or those that have been lying about exposed to dust and dirt. 
The lenses should be kept in their boxes when not in use, 
and when they are attached to the microscope, great care 
should be taken to keep them from coming into contact with 
liquids. In order to prevent the latter accident as far as pos- 
sible, never examine liquids unless when they are covered with 
thin glass. In the pursuit of micro-chemical studies, the 
microscopist has frequently to deal with liquids that corrode 
metals, and even glass. In well-appointed laboratories inverted 
microscopes are used in such cases, but with ordinary instru- 
ments, special means must be employed. The object should be 
laid on a large piece of thin plate glass, and the brass work of 
the objective should be coated with oil. The 1’est of the metal 
work may be protected with oiled silk or thin india-rubber. 
When liquids which corrode glass are used, the front of the 
objective should be protected by means of a very thin leaf of the 
best mica, which may be attached either by glycerine or balsam. 
These, however, are exceptional precautions. In ordinary 
work it is sufficient to see that the lenses and metal work are 
kept free from stains and finger marks. 
Never touch with the fingers the surface of any lenses, either 
eye-pieces or objectives, as this will be certain to soil them. Use 
soft camel-hair brushes to remove particles of dust, etc. Where 176 
SELECTION AND USE 
dirt adheres more strongly, use fine linen slightly moistened with 
alcohol, and wipe dry with very fine chamois leather. Semem- 
ber, that alcohol, if used profusely, will attack the lacquer of 
the brass-work, and even dissolve the cement which holds the 
lenses together. When objectives are smeared with balsam, 
the best cleansing agent is said to be kerosene oil. The piece 
of leather used for wiping lenses should be free from dust, and 
is best kept in a small box by itself, and used for nothing else. 
It must be remembered that the glass of which objectives are 
made is easily scratched, being soft when compared with parti- 
cles of sand and grit; consequently, when frequently wiped it 
soon loses that exquisite polish upon which its excellence of 
performance so much depends. What, then, are we to think 
of the directions given by the author of a popular work on 
the microscope, in which we are told to use a piece of leather, 
slightly impregnated with brick dust! ! No better method of 
destroying an objective could possibly be devised. Therefore, 
see that in wiping, the slightest possible pressure is used, lest 
any particle of grit should make a scratch. 
The exposed parts of all microscopes, as well as the objectives 
and their cases, are lacquered, to protect them from being 
soiled by handling, but the interior of the boxes which hold the 
object-glasses are rarely so protected, and the black coating of 
the interior of bodies, draw-tubes, etc., is frequently not very 
firmly attached. Therefore, never touch them with the fingers. 
After taking an objective out of its box, either screw on the 
cover of the box, or place the latter with its open end down. Do 
not stand it mouth up, so that it may catch all the dust. 
When exhibiting the microscope to others, great care is neces- 
sary to keep meddlesome fingers from soiling the glasses. Some 
people are never content when merely allowed to look at things: 
they insist upon handling them, and feeling them. To the 
young microscopist, we would say that if any of your friends in- 
sist upon handling your objectives, eye-pieces, etc., put up the 
instrument and pack it away. A microscope carefully used is 
as good after fifty years as when first made, but we have seen 
an instrument suffer more injury in half an hour at the hands 
of a thoughtless and dirty person, than it would have sus 
tained in twenty years in the hands of a careful microscopist. OF THE MICROSCOPE. 
177 
COLLECTING OBJECTS. 
Those who are engaged in special studies and researches re- 
quire no directions for collecting objects; but to those who use 
the microscope for purposes of general instruction or amuse- 
ment, a few hints may not be out of place. Almost every text- 
book on botany, physiology, mineralogy and kindred subjects, 
will not only indicate a long list of objects, but will give di- 
rections for procuring them. Plants yield a very large variety 
of interesting subjects. Thus the cuticles of the leaves and 
flowers; cellular tissue as shown by dissections, and by cross 
and longitudinal sections; hairs, pollen, seeds, etc., all deserve 
careful microscopical examination. Insects furnish an almost 
unlimited field, and their wings, feet, eyes, mouth, scales, spira- 
cles, hairs, etc., are all worthy of careful preparation and exam- 
ination. 
It is, however, amongst the more minute forms of animal and 
vegetable life, as found in pools and running streams, that the 
most interesting objects are to be found, and the number and var- 
iety of these is so great that several large volumes would be re- 
quired to describe them. Even the ponderous works of Ehren- 
berg and Pritchard do not begin to exhaust the subject, and, 
therefore, it will be obvious, that even if we were to devote the 
whole of the present volume to this department, we could 
but skim the surface. Thus far we have had to depend chiefly 
upon foreign works for descriptions of these organisms, but it is 
fortunate that while the higher classes of plants and animals 
which inhabit Europe, and are described in European works, 
are entirely different from their congeners on this continent, the 
same does not hold true in regard to the lower forms. We have 
found localities which teemed with the Volvox Globator and 
various species of Closterium, Staurastrum, Pediasirum, etc. 
Hydras are to be found in great abundance, and so nearly like 
the described European species that the beginner will find it 
difficult to detect the difference. We have repeatedly found the 
Slephanoceras, Melicerta and other beautiful microscopic objects, 
and as for the more common ones, such as the Vorticelli, or 178 
SELECTION AND USE 
■wheel animalcules and. Entomostraca, or water fleas, they are 
to be found in every pool. 
Every young microscopist that is desirous of pursuing his 
studies in this direction, is met at the outset by two difficulties; 
the first is to obtain the objects, the second is to find out what 
they are after he has got them. The first is by no means a dif- 
ficult task, but the second will often puzzle more experienced 
students than those whom we expect to be readers of this book. 
We know of but two ways to accomplish it; one is the laborious 
plan of searching for them in the “Micrographic Diction- 
ary,” or the books of Carpenter or Pritchard; the other is 
to obtain the desired information from some well-informed 
friend. 
The objects which are of most interest to the microscopist are 
not difficult to obtain, if we know where to look for them, but 
they are not to be found everywhere. Many stagnant pools 
will be found to yield but a scanty supply, while others, which, 
perhaps, to the uninitiated present a less promising appearance, 
will yield a rich harvest. Beginners are very apt to entertain 
the popular notion, that every drop of water teems with animal- 
cules, and that when placed under the microscope, it will appear 
to be literally filled with living things. This idea is fostered 
by popular writers who describe a drop of water as a globe filled 
with life, and by lecturers who exhibit pictures and enlarged im- 
ages of what they call “ a drop of water,” but which is in reality 
a considerable quantity of that liquid which has been artificially 
supplied with inhabitants. Clear well water is almost free from 
microscopic organisms, and the same is true of the water from 
clear brooks, which flow swiftly over a pebbly bottom. Ordin- 
ary rain water, as found in cisterns having free communication 
with the air, usually contains large numbers of the larvae of 
gnats and mosquitoes, and when exposed to the light it is almost 
always rich in wheel animalcules, and some of the lower forms 
of vegetable life. The water supplied to our cities is in gen- 
eral very rich in microscopic vegetables. Thus in the Croton 
water, which is comparatively pure, we have found a large 
number of very beautiful species, amongst them the exquisite 
Monachinus. The best way to secure a supply of the animal 
and vegetable inhabitants of city water, is to pass a considers OF THE MICEOSCOPE. 
179 
ble quantity of it through a filter, the surface of which will 
then furnish a large amount of valuable matter. 
But it is not in such fields that the microscopist will find his 
best hunting grounds. Along the edges of quiet pools of clear 
water is the best place for the finer vegetable forms, such as 
the Volvox Globaior, Closterium, etc. If the water is much con- 
taminated with dead animal matter or with sewage, nothing will 
be found but the coarser organisms and animalcules, such as 
Paramecium. The same is true of small pools found in woods, 
or very much shaded with trees, and filled with dead leaves. 
Such places are, however, the favorite haunts of the larvae of 
insects, and also of frogs and Tritons. The size of the pools is 
not of much consequence. We remember on one occasion to 
have found by the roadside in Centre County, Pennsylvania, a 
little pool which was almost filled with the larvae of Tritons. 
The gills, which were beautifully developed, would have formed 
a splendid object under the microscope, but when we returned 
next day, for the purpose of securing some, the water had dried 
up, and the larvae were all gone. 
The little pools formed in boggy ground by the footsteps of 
cattle will often be found to contain large quantities of one or 
two species of desmids or diatoms. It will not do to look for 
these objects in similar pools formed in ordinary soft land, and 
temporarily filled with rain water. The ground must be na- 
turally and constantly wet, so that the pools are always kept 
filled by the infiltration of water from the surrounding soil. 
Such pools, however small, usually contain a large number of 
specimens, and it is in such places that one is most likely to 
find a supply of one variety uumixed with any others. 
While many of the most interesting objects will be found 
swimming freely about in the water, others of great beauty are 
always attached to floating weeds, sticks, etc. We have gen- 
erally been most successful in discovering specimens of this 
kind when we have placed the gathering in a large glass jar, and 
allowed it to stand quiet for some time. The water will then 
settle, and the objects of which the microscopist is in search 
will have time to expand, when they may be seen in a form 
resembling light mould, or down, attached to the surfaces of 
the solid matters. 180 
SELECTION AND USE 
The surface of the mud at the bottom of ponds of clear water, 
is frequently very rich in microscopic vegetable organisms. 
These minute plants seem to seek the light, and to rise through 
the mud which would otherwise cover them, so that by care- 
fully scraping the surface of the bottom, we are enabled to 
procure them in large numbers. 
It must, of course, be borne in mind, that while some species 
are found in fresh water, others are marine, that is, they live 
only in sea-water. The best locations for finding marine forms 
are: 1, the pools of c1 ear water, found in salt marshes; 2, 
the surface of the mud at the bottoms of harbors and quiet 
coves; 3, the waters of the ocean itself, as well as that of the 
bays and coves connected with it. 
The apparatus required for capturing these various objects, 
is neither bulky nor expensive. For larvae and the larger ani- 
malcules, the most useful implement is a small net. Ours con- 
sists of a ring of brass wire (iron wire would rust and destroy 
the net) about six inches in diameter, soldered to a tin tube or 
ferrule, which fits tightly on the end of a walking cane. To 
the ring is attached a bag of any light, gauzy material, which 
possesses the two qualities of letting water out rapidly, and 
keeping small objects in. With this net it is easy to capture 
anything from a small fish or a frog to the very smallest larva, 
and it is very portable, since an ordinary walking cane forms a 
sort of universal handle for this and other implements. Next 
to the net, we find the most useful articles to be bottles. They 
should be of clear glass, so that any object contained in them 
may be readily examined by means of a pocket lens. For this 
reason we prefer what are called homoeopathic phials of large size 
(half ounce and quarter ounce), and we generally carry a dozen 
or two when out on a tramp. A fair sample of the contents of 
a small pool is easily obtained by gently lowering the phial, 
mouth downwards, under the water, and bringing it cautiously 
to the place which is supposed to be richest in specimens. The 
phial is then turned mouth upward, the air rushes out and the 
objects are carried into the bottle by the force of the inrushing 
current of water. For small, shallow pools, the phial is most 
conveniently held in the hand, but when the water is deep a 
handle is required, and for this we use the holder shown in OF THE MKJEOSCOFE. 
181 
Fig. 55, which is made to fit on the end of the walking stick. It 
consists of a ferrule having a semi-cylindrical piece soldered at 
right angles to it. The ferrule fits the cane, 
and the bottle is fastened to the cross piece 
by means of a rubber ring—the method of 
arranging the latter being easily understood 
from the engraving. A dozen or more bottles 
of proper size may be taken along, and they 
are so easily attached to the holder that there 
is no necessity for transferring a “dip” to 
another bottle. The contents are most easily carried in the 
bottle in which they were first obtained. 
When the water is too deep for a walking cane, a fishing rod 
or any long pole may be used, and where these prove too short, 
as in harbors, etc., a bottle may be lowered and raised properly 
by means of strings. For this purpose the bottle must be 
heavily loaded with lead round the neck, and two strings must 
be attached to it, one fastened to the neck and the other to the 
bottom. It is by the latter that the bottle must be lowered, 
but it must be raised by the other. If properly managed it 
will descend mouth downwards, but the tension of the string 
attached to the neck will invert it, and when raised by this string 
it will bring up its contents very perfectly. 
Fig. 55. 
For scraping the surface of the mud at the bottom of shallow 
pools, we use the spoon shown in Fig. 56. It is simply a ring of 
tin five inches in diameter and one 
inch deep. The lower edge is 
wired ” as the tinsmiths call it, and 
there is a ferrule soldered to the side 
so that it may be fixed to the same 
cane that is used for the net. Over the 
bottom is stretched a piece of some 
thin fabric, such as thin muslin, gauze or tarletan, which is held in 
place by a rubber band that slips over the wire ring on the lower 
edge It is best to make one side of the ring somewhat flat, so 
as to adapt it better to the flat surface of the mud. When the 
pieces of cloth get soiled, they are easily replaced, and, indeed, 
in some cases it is not a bad plan to carry the mud home in the 
Wet cloths, a dozen or more of which, with their contents, may 
Fig. 56. 182 
SELECTION AND USE 
be easily packed in a tin 
box of small size. One of 
the boxes used by school 
children for lunch boxes 
answers very well, but any 
tin box with a lid or cover 
will answer. As it is im- 
portant that a record should 
be kept of the locality from 
which the dip was taken, 
we carry a few slips of 
parchment paper, one of 
which is pinned to each 
cloth, after the necessary 
memoranda have been 
written upon it with a hard 
pencil. On returning home, 
the contents of each cloth 
may be transferred to a 
separate bottle. This plan 
saves the carrying of nu- 
merous bottles, and the 
water required to fill them. 
An exceedingly coveni- 
ent traveling companion 
for those who are fond of 
collecting, is shown in the 
accompanying engraving, 
Fig. 57. The main part 
forms a very convenient 
walking cane of ordinary 
appearance. Like many 
fishing rods, however, it is 
hollow, and contains a sec- 
ond rod by which it may be 
extended to twice its length. 
This enables the user to 
reach the bottom of any 
ordinary pond, and to reach 
as far as is necessary from 
Fig. 57. OF THE MICROSCOPE. 
183 
the shore. Accompanying the cane, A, are the hooked knife, 
B, and the ring and bottle, O. These are made with a double 
screw, so that they may be attached either to the end of the 
cane itself, or to the inner rod, and in this way we can have 
either a short and stout handle, or a longer and more slender 
one, as circumstances may require. The bottle is made so as 
to screw into the brass ring, and the same screw enables us to 
fit a wooden cap on it, which thus encloses the contents tightly. 
The hook is made of fine steel, and has a sharp cutting edge, as 
seen in the engraving, so that it is easy to cut off a piece of 
weed, drag it out of the water and secure it. 
Those who carry such a 
cane do not attract attention 
by any unusual parapher- 
nalia, and at the same time 
they are at all times ready to 
secure any valuable material 
that may present itself. Sev- 
eral bottles may be carried in 
the pocket, and screwed into 
the ring as required. 
The collector who desires 
to make a thorough examina- 
tion of the microscopic flora 
and fauna of any pool or 
stream, must not rest content 
with infinitesimal quantities 
of material. It is not neces- 
sary, however, to lug home a 
gallon of water for the sake 
of the objects contained in it, 
and so fully have microscop- 
ists been impressed with this 
idea, that the devices which 
have been prepared for strain- 
ing out the valuable portions 
are almost endless. The best 
and simplest that we have 
seen is a modification of an 
Fig. 58.—WATEK-STKAINESc 184 
SELECTION AND TTSE 
arrangement, designed, we believe, by Mr. Higliley, and 
figured in Beale’s work on the microscope. It consists, as 
shown in the engraving (see Fig, 58), of a bag or net of 
some light material, to the bottom of which is attached, by 
means of twine, or a strong rubber ring, a wide-mouthed bottle. 
Any quantity of water may be poured into the bag, and all the 
objects which it contains will roll down the sides of the bag 
and fall into the bottle, while the fluid escapes through the 
sides. Delicate objects are consequently not exposed to 
pressure, rubbing, or any other violence, as they would be in 
an ordinary filter or bag, and the whole affair is so simple that 
any one can make it. 
A slight modification of tins arrangement will be found ad- 
mirably adapted to the microscopic examination of the water 
supplied to cities. The bag may be attached to any faucet, and 
and all the water that is used in the household may be caused 
to pass through it. In this case, if the bag be made of some 
tolerably stout material, it may be firmly fied to the faucet, 
and then all the water that is consumed will be very thor- 
oughly purified. 
Another very excellent device is the bottle invented by 
Mr. Wright, of which a modified form is shown in Fig. 
59. The mouth of the bottle is closed by means of a 
coik in which two funnels are inserted. 
One of these funnels is placed in the bot- 
tle, mouth down; the other projects above 
the cork, as shown in the engraving. The 
mouth of the funnel that is in the bottle 
is covered with muslin or flannel, held in 
place by a rubber band, which is prevented 
by a wire ring from slipping along the con- 
ical surface of the funnel. When water 
is poured into the other funnel, it passes 
into the bottle until the latter is full, and 
then it flows out of the first funnel, and 
is carried off by means of a short piece of 
rubber tubing. Meanwhile, all solid parti- 
cles are held back by the filter, and as the 
latter is horizontal and with the filtering 
Fig. 59. OF THE M1CKOSCOHE. 
185 
Surface downwards, most objects of interest fall away from it, 
and may be found in tlie water. A single bottle of tbis descrip- 
tion is sufficient, as the cork is easily removed, so that the water 
may be poured into other bottles. As ordinarily made and sold, 
Wright’s collecting bottle is an expensive piece of apparatus, 
costing four or five dollars, but as shown in the engraving it 
may be made for a few cents by any tinsmith. 
Where it is desirable to keep the specimens thus obtained so 
that they may be examined, and their life-history studied, 
bottles and jars of almost any kind may be used, but those which 
we have found most convenient are what are known as “quin- 
ine ” bottles, and may be had at most druggists. For ordinary 
objects they are just about the right size, and as they are made 
of tolerably clear glass it is easy to examine the objects through 
the sides of the bottle. A dozen or two of these little aquaria 
occupy very little space, and are easily handled. Great care 
must in general be taken to exclude from the vessels contain- 
ing the finer organisms, such predatory animalcules as devour 
them. Water fleas, the larvae of insects, etc., will soon make 
away with the finer specimens. On this account great diffi- 
culty is found in keeping the Volvox Globator, since it is greedily 
devoured by various rotifers, and these are exceedingly difficult 
to exclude. We have succeeded best in this case by partially 
filling a bottle with well-filtered water taken from the same 
pool as the specimens, and transferring the objects to it singly 
so as to avoid transferring their enemies too. For this purpose 
the dipping tube should be used. Some authors caution us 
against mixing the inhabitants of different pools, on the ground 
that being strangers to each other they will fight. This is more 
fanciful than accurate, though it has a basis of truth. It is not 
the circumstance that they are strangers that causes the diffi- 
culty, but the fact that the one is the natural prey of the other. 
The same thing occurs between inhabitants of the same pool. 
It must be remembered, however, that very slight changes in 
the conditions in which they are placed will often cause the de- 
struction of these .objects. Thus, we have seen some very fine 
gatherings totally destroyed by being removed from soft, boggy 
water to clear, hard well water. Therefore, in transferring 
either animals or vegetables to an aquariun, it is well to supply 186 
SELECTION AND USE 
them with the same water, mud, etc., in which they were origi- 
nally found. It will sometimes, however, be-well to filter the 
water so as to remove all such inhabitants as are apt to eat up 
the others. Water, may be filtered through paper, or where fil- 
tering paper is inaccessible, the neck of a funnel may be loosely 
plugged with cotton. Even this does not quite free it from 
noxious eggs or germs, and we have sometimes boiled it in the 
flask in which the objects were to be kept. The mouth of the 
flask was then plugged with loose cotton, and when the water 
was cold, the objects we wished to jjreserve were introduced. 
When floating freely in these diminutive aquaria, many ob- 
jects are as difficult to find and capture as would be a small fish 
in a large pond. The microscopist, therefore, requires special 
means for capturing them, and placing them on a slide. For 
this purpose nothing serves so well as what are known as dip- 
ping or fishing tubes. These are simply glass tubes of different 
diameters (from one tenth to one quarter of an inch), and of 
any convenient length. They are used by closing the upper 
end with the finger, bringing the lower end near the object (un- 
der the water), and then removing the fingers from the upper 
end. The water, in seeking to find its own level in the tube 
rushes in with great force and carries the object with it. By 
again placing the Auger on the upper end of the tube, the latter 
may be lifted from the bottle, and the water with it, and by a little 
dexterous management it is easy to cause the object to flow out 
on a slide without allowing too much water to go with it. 
These tubes are made straight, curved, and with one end drawn 
to a point, but for most purposes the straight tube answers best 
as it is most easily kept clean. We prefer to grind the ends 
rather than to make them smooth by fusion, as the latter pro- 
cess generally contracts the opening, and renders the tube dif- 
ficult to clean. The best plan, however, is to heat the upper 
end strongly before the blowpipe, and turn the edge outward 
like the mouth of a test-tube. It is then easily closed, and the 
tube is very strong. The lower end should be ground. 187 
OE THE MICBOSOOBE. 
PREPARATION, PRESERVATION AND MOUNTING OF 
OBJECTS. 
These three operations are so frequently applied as a single 
process to objects, that many writers have failed to make a suf- 
ficient distinction between them. By keeping the proper dis- 
tinction clearly in mind, however, the student will not only 
save much valuable time, but he will secure vastly better re- 
sults. Except by those who are more anxious to increase the 
number of objects in their cabinet than the amount of know- 
ledge which they possess, a very large proportion of the ob- 
j ects examined will never be preserved or mounted at all. This 
however, should not prevent the utmost care being given to the 
process of preparing them for thorough examination. On the 
other hand it often happens that objects which have been 
carefully prepared and mounted, spoil because they have not 
been subjected to a proper preserving process. Hence the 
importance of treating these operations separately and fully. 
Tlte Preparation and Examination of Objects.— 
It is a common but very erroneous idea that the only thing 
that is necessary in order to examine any object under the mi- 
croscope, is simply to place it on the stage, and get it into 
focus. With the exception of mounted objects, a very few 
transparent objects—such as the wings of insects—and some 
things that are viewed by reflected light, every substance re- 
quires to undergo careful preparation before it can be fit for 
profitable examination. A good example of the necessity for 
such preparation is seen in the common potato, a piece of which 
when simply placed on the stage of the microscope, and brought 
into focus, appears as a glistening mass, and reveals nothing of 
its true structure. If we now cut from this lump, by means of 
a very sharp knife, an exceedingly thin slice, place it on a 
plate of glass, moisten it with a little spirit and water, or better 
still, glycerine and water, and place over it a thin glass cover, it 
will disclose to us a most wonderful and beautiful structure. The 
entire mass will be seen to be composed of cells, these cells be- 
ing filled with granules of starch of various sizes. 188 
SELECTION AND USE 
The operation which we have thus briefly described as appli- 
cable to the potato, is required for a great many other materials; 
for whenever a substance is to be examined under any except 
the very lowest powers, it is absolutely necessary to obtain it in 
pieces as thin as possible, so that the light may readily pass 
through them, and it is in general requisite to increase their 
transparency either by immersing them in a fluid, or by some 
other means. In preparing objects for the microscope, our 
aim is in general to examine either the ultimate structure ot 
the substance under investigation, or the arrangement of its 
different parts; and the processes which are most available for 
this purpose may be classed under three heads: 1, Mechanical, 
such as section-cutting, dissection and injection; 2, Chemical, 
such as the use of iodine for detecting starch; of alcohol for 
hardening certain structures; of coloring substances for stain- 
ing germinal matter, etc.; 3, Optical, such as the action 
whereby certain liquids change the transparency of some ob- 
jects. Of some of these processes, such as injection, staining 
and the extended use of chemical tests, elaborate descriptions 
would be required in order to enable the student to carry them 
out with success, and we must refer him to the works of Beale 
and Frey, which are very complete on these points. 
Thin sections of any soft substance are easily made with a 
very sharp knife—a good razor being probably the best availa- 
ble instrument. For work in the higher departments of micro- 
scopy, and for the preparation of fine objects for sale, special 
instruments known as section-cutters are employed, but for the 
ordinary work of investigation, they are not absolutely neces- 
sary though very convenient. Using a good sharp razor, it is 
an easy matter to shave off any soft substance a wedge shaped 
piece, the edge of which thins off to nothing, and which pre- 
sents in its different parts all varieties of thickness, so as to afford 
a perfect opportunity to study the object under examination. In 
this way, which is known as the “ free-hand” method, suitable 
sections of most animal and vegetable substances may easily be 
prepared, and the student will be surprised at the dexterity 
which a little care and practice will confer. 
For cutting sections of very soft tissues a special knife, known 
as Valentin’s knife, has been invented. It consists of two OF THE MICKOSCOPE. 
189 
blades so arranged in one handle that their distance from each 
other may be easily regulated. When a cut is made with this 
double-bladed knife, a thin slice of the tissue passes between 
the blades, and constitutes the section. It is an instrument, 
however, which will hardly be used by beginners. Sections 
of substances of greater consistence, such as wood and soft 
bones, are most easily made in a regular section cutter. The 
patterns according to which these instruments are constructed 
are very various, but they all act on the principle of raising 
above the surface of a brass table, by means of a fine screw, the 
substance to be cut, and then passing a very sharp razor or 
knife over the table so as to shave off the projecting part of the 
object. The table is usually of brass, ground and polished. 
This gives rise to two serious defects. The metal is too soft in 
the first place, so that it is impossible to press with sufficient 
force on the razor without cutting into the table, and secondly, 
when any soft metal has been ground on a grindstone or emery 
wheel, the surface becomes so impregnated with gritty matter, 
that it very rapidly destroys the edge of the cutting tool. We 
avoid these difficulties by fitting to our section cutter a stout 
plate of hardened steel, the surface of which has been highly 
polished by means of buff leather, Quekett describes a cut- 
ting machine in which the difficulties we have mentioned are 
obviated by fixing the knife in a frame so that it is raised above 
the table, and does not touch the metal. Its edge is thus pre- 
served from injury, and the blade itself cannot be affected by 
variations in the pressure exerted. Dr. Curtis, of this city, has 
adopted the same principle in his section cutter, the details of 
which are admirably carried out. 
In making sections of wood and similar substances, the speci- 
men is first well soaked in dilute alcohol, and is then fastened 
securely into the tube of the section cutter, either by wedges or 
by casting wax or paraffin around it. The process of raising it 
by means of the screw and passing the knife over it, is simple 
enough, and can easily be learned. 
With the ordinary cutting machine, success in making thin 
sections seems to depend upon the perfect sharpness of the 
cutting edge, the thorough moistening of the knife and section, 
and the rigidity of the blade. The latter point frequently fails 190 
SELECTION AND USE 
to receive the attention that it deserves. Where a thin, flexi- 
ble blade is used, a moderate change in the amount of pressure 
employed will make a great difference in the thickness of the 
section, even so far as to double it. When the blade is stiff, a 
change in the degree of pressure has but little effect. 
Soft substances must first be hardened either by immersion 
in alcohol or other means, and in general must be supported by 
being surrounded with melted wax or paraffin. Where the 
specimen is very slender (such as a hair) it must be carefully 
supported between firm and rigid clamps. Corks and similar 
yielding substances, which are recommended in most books, 
never give a cross section accurately taken at right angles. The 
same is true of the plan so much recommended for obtaining 
sections of hair, viz.; to pass the razor over the face shortly 
after shaving. We get sections it is true, but they are all 
oblique. The best way to get true sections is to imbed the sub- 
stances in glue, gum, paraffin, wax or some such material. 
Sections of bone are prepared by sawing off a thin slice in the 
first place, and cementing it to a slide by means of thick or old 
balsam; one side is then filed or ground flat, and polished on 
buff leather, after which the section is transferred to another 
slide so as to expose the other side, which is then filed down 
and polished as before. Great care must be taken so as to hit 
just the right thickness, and the operation of cementing to the 
slide must be performed expeditiously, so that the balsam may 
not saturate the section, and render it too transparent, as when 
this occurs certain very important features become invisible. 
Yery hard substances require special apparatus, and consid- 
erable skill. Still it is astonishing what may be accomplished 
by means of good files, whetstones and grindstones in the way 
of preparing thin and transparent sections even of such sub- 
stances as rocks and stones. 
In order to acquire correct ideas in regard to the structure of 
objects, of which sections are examined, the student should fa- 
miliarize himself with the geometrical forms produced by cut- 
ting cylinders, cones, spheroids, etc., in various directions. 
Thus a cylindrical vessel, cut square across, shows a circle; when 
cut obliquely it shows an oval (ellipse) of greater or less length5 
and when cut longitudinally it shows two lines which have no or THE MICROSCOPE. 
191 
apparent connection with each other. The truth is, however, 
that we should never deduce the form of vessels from sections 
alone. In every case it is necessary to examine carefully dis- 
sected preparations as well as section?. 
The soft parts of animals and vegetables are frequently pre- 
pared for examination by careful dissection, that is to say the 
different parts are separated from each other, and freed from ex- 
traneous matter by means of knives, scissors, forceps, needles, 
camel hair pencils, etc. The knives used by the microscopist are 
similar to the scalpels ordinarily employed by anatomists, but 
smaller, and unless very finely tempered and well-sharpened, 
they are worthless. The knives sent out with low priced micro- 
scopes are in general the veriest trash, and the same is true of the 
needles. There are three kinds of scissors which the microscop- 
ist will find useful—plain, straight scissors, elbow scissors, and 
curved scissors. They must be small, sharp and well made. But 
the most useful, as well as the simplest instruments for dissecting 
are a pair of needles, or, rather, a needle and a very fine 
spatula. The needles used are those ordinarily employed by 
seamstresses-, they should be fixed in a light wooden handle and 
carefully polished. The latter is a most important point, for 
it will be found that ordinary needles are too rough for deli- 
cate work, as may be easily seen by examining them under the 
microscope. For microscopical purposes needles are made 
both straight and curved—the latter being a very useful form. 
In order to bend a needle, it must first be heated in the flame 
of a candle, then bent by proper pliers, after which it must be 
carefully re-tempered. There is little danger of getting it too 
hard, provided it is not burned. After being hardened it must 
be carefully re-polished. The handles should be light and 
smooth. Ordinary penholders make good handles and cost but 
a trifle, but in case of need any piece of straight-grained, light 
wood will answer. Universal handles, handles with ferrules, 
handles wound with thread, etc,, look as if they were not com- 
mon articles, and are purchased by many, but no working mi- 
croscopist would give them table-room. All the so-called uni- 
versal handles in market are too clumsy and heavy. 
In using needles or knives for dissection, they are generally 
used in pairs, that in the right hand being used for teasing or 192 
SELECTION AND USE 
cutting, while the one in the left hand is used for holding the 
object firmly in its place. Tor the latter purpose, however, we 
prefer a very narrow spatula, curved and highly polished. 
Curved needles, with the curve placed flat, answer very well, 
however. 
For the removal of loose matter, and for arranging parts 
which have been dissected out, there is nothing more useful 
than good camel hair pencils. Indeed, they are indispensable, 
and with needles and pencils—two of the simplest and cheapest 
articles—it is possible to do almost everything. 
During the process of dissection the object must be supported 
upon a glass plate or a dissecting pan, according to its size. Some 
of the finest preparations have been worked up on ordinary slides 
three inches long by one wide, and as it is almost always neces- 
sary to have the object covered with liquid, a single drop suf- 
fices in this case. But where larger objects are to be dissected, 
ordinary slides are not large enough, and besides there is no 
provision made for holding a sufficient quantity of liquid. 
Various kinds of dissecting dishes or pans have therefore been 
devised. Those used by the author are exceedingly simple 
and cheap, and are shown in Fig. 60. We use three kinds, 
two with opaque bottoms, and one 
in which the bottom is transparent. 
The latter is used for objects which 
are transparent, and is precisely like 
the others, except that a portion 
of the metal bottom is cut away and 
a piece of plate glass cemented over 
the aperture. Those used for opaque objects are simply 
oblong tin dishes, each two inches long, one and a quarter 
wide and half an inch deep. The bottom plate extends on each 
side, so as to form rests for the fingers, by which the pan may 
be kept steady. Into this pan is poured a mixture of equal 
parts of resin and beeswax, softened if necessary with a little 
lard. It should be just so soft that a pin may be easily stuck 
into it, and this affords us the means of pinning out the different 
parts of a dissection as we progress. In one dish the wax is 
colored black with lampblack, and this forms a wonderfully 
effective back ground for most objects; the wax in the other 
Fig. 60. OF THE MICROSCOPE. 
193 
pan is white,. clialk or sulphate of baryta being substituted for 
lampblack. The pan with a transparent bottom is of precisely 
the same size, except that the depth is but half as much—the 
extra depth in the other pan being filled with wax. A quarter 
of an inch is a sufficient depth of liquid for most objects, and 
when the sides of the pan are higher than necessary they inter- 
fere with the use of knives and needles. 
Dissections may also be carried on in watch-glasses, though they 
are not quite as convenient as pans with perfectly flat bottoms. 
The kind known as lunette glasses should be chosen, as they 
are fiat in the centre. When a watch-glass is used for this pur- 
pose, it is necessary to cement it into a hole cut in a thin piece 
of wood about four inches long, and of a width which is rather 
greater than the diameter of the glass. 
Most of this work is, of course, done under a simple micro- 
scope. The Excelsior, when screwed to a larger base, as de- 
scribed on page 42, answers very well. Larger and more ex- 
pensive dissecting microscopes are supplied by most opticians. 
In addition to these general methods, which are applicable 
to a great variety of subjects, there are a few special processes 
which must be adopted in particular cases. In some instances, 
as when the line of investigation is a new one, the microscop- 
ist must work out his own processes, but the following special 
cases will probably prove interesting to beginners. 
It frequently happens that the objects for which the micro- 
scopist is searching are found mixed with coarser materials, 
and in this case it will be found possible to effect a separation 
by the process known as elutriation or washing. Mix the mat- 
ter thoroughly with water in a tall jar and allow it to settle. 
In a short time—say one minute—the very coarse particles will 
have fallen to the bottom, and if the liquid be now poured off 
and allowed to settle, the finer portion will be found in the 
second vessel. By graduating the time and carrying the pro- 
cess out to its full extent, a wonderfully perfect separation may 
be effected. Diatomaceous earth may frequently be treated in 
this way to advantage. 
In some cases separation must be effected by burning, or the 
action of chemical agents. Guano and various organic matters 
yield interesting residues after everything soluble has been 194 
SELECTION AND USE 
washed away and everything combustible has been burnt either 
with fire or nitric acid. So too the siliceous cuticles of plants 
may be procured by destroying all the other parts by chemical 
means. The best way is to heat them in nitric acid, and add 
to the hot liquid a small quantity of powdered chlorate of pot- 
ash. The quantities used must be very small, and great care 
must be exercised. 
It is frequently necessary to separate a small quantity of 
deposit from a large amount of liquid, filtering being inadmis- 
sible. For this purpose use a conical glass or a large test tube, 
allow plenty of time for the deposit to settle, and give occa- 
sionally a slight stir, so as to detach the particles from the 
sides of the vessel. Then pass a large dipping tube (one quar- 
ter of an inch in diameter) to the bottom, the upper end of the 
tube being closed with the finger. On withdrawing the finger 
the liquid and deposit rush in. Have ready a small ball of 
soft cement (resin and beeswax equal parts, softened with oil) 
and with it close the upper end of the tube, which may now be 
withdrawn, carrying the liquid with it. Place the tube in a 
vertical position, with its lower end on a slide or in a watch- 
glass, and support it either by means of the ring of a small 
retort stand or by a simple wire having a ring (horizontal) at 
the upper end, and a small piece of board for a foot. Beale 
directs us to cork the tube, but this is difficult unless the tube 
is made specially for the purpose with a mouth like that of a 
test tube. Tubes made in this way are, however, the most con- 
venient, and a good velvet cork closes them perfectly. 
There is a class of insect preparations, which are quite inter- 
esting, though they are not as instructive as inferior prepara- 
tions made by the process of dissection. We refer to the whole 
insects found in most collections. They are prepared by soak- 
ing the insect in liquor potassse, which may be had from any 
druggist; this renders the internal organs soluble and the outer 
horny skeleton transparent. The viscera are then expelled by 
pressure with a camel hair pencil, the insect well washed in pure 
water, soaked first in alcohol, and then in turpentine, and 
finally mounted in balsam. The points requiring attention are 
these: Soaking just the right length of time in the potash, for if 
the insect remains too long in this liquid it will be destroyed; OF THE MICROSCOPE. 
195 
allowing plenty of time for the alcohol to displace the water, 
and for the turpentine to displace the alcohol; and manipula- 
ting the insect with great care, so as not to break any of the parts. 
The eyes of insects are prepared by macerating them in very weak 
potash, and, while still soft, pressing them between two slips of 
glass. If allowed to harden before being pressed they will 
split at the edges. The handsomest preparations of eyes are 
obtained by taking a thin slice from a large eye, such as that 
of a dragon fly, and treating it as directed. 
The feet of insects are in general easily prepared. Moderate 
soaking in potash, careful washing in water, thorough soaking 
in alcohol and turpentine, and careful management in properly 
displaying them on. the slide, are the secrets of success. The 
student who wishes to make a careful study of these objects, 
however, should place them in glycerine, after soaking them in 
potash and thoroughly washing them. They should of course 
be deposited in a cell filled with liquid, and then covered with 
thin glass, and examined. The so-called tongues, etc., of in- 
sects require no potash, being sufficiently transparent without 
it, and after being soaked successively in alcohol and turpen- 
tine, they may be mounted in balsam. When wanted for exam- 
ination merely, immerse them in dilute glycerine, and if the 
student can succeed in mounting them in cells, in glycerine or 
some of the gelatinous media hereafter described, they will show 
their structure to far better advantage than in balsam. 
In determining the character of what is brought into view by 
the processes detailed, great aid will be derived from the use 
of chemical tests. Thus, in the case of the potato, previously 
described, most persons who had read anything at all upon such 
subjects, would recognize the starch granules. All starch granules, 
however, are not of the same form as those found in the potato; 
indeed, some would hardly be recognized at all, except by those 
having considerable experience. But if a little of the tincture 
of iodine be brought into contact with them, they at once be- 
come deeply blue. This subject is too extensive to be dis- 
cussed here, but those who desire to become proficient in the 
use of the microscope cannot safely neglect it. 
In most cases after an object has been carefully brought into 
proper mechanical condition, in one of the ways we have de- 196 
SELECTION AND USE 
scribed, it is necessary to immerse it in some suitable medium, 
so as to render it clear and transparent. The action of such 
media may be very well illustrated by the following experiment: 
Take a short piece of black human hair, place it on a slide,, 
bring it into focus and examine it. It will appear as a dark 
cord with a light line running down the centre, and from this 
circumstance has arisen the erroneous popular idea in regard to 
the tubular structure of hair. Apply a drop of glycerine di- 
luted with an equal bulk of water, and again examine it. The 
appearance will have entirely changed, having become clearer 
and more definite, so that the structure of the hair is more 
easily made out. This effect depends upon the refracting power 
of the liquid used. The following liquids are usually employed 
for this purpose, their efficiency being in direct ratio to their 
index of refraction, which we append to each. Water, 1.336; 
glacial acetic acid, 1.38; alcohol, 1.372; vitreous humour, 1,340; 
sea-water, 1.343; equal parts of glycerine and water, 1.40; pure 
glycerine, 1.475; oil of turpentine, 1.478; Canada balsam, 
1.532—1.549; bisulphide of carbon, 1.678; oil of annis, 1.811. 
Alcohol and water, and solutions of various salts in water are 
also very useful. When a pure article of glycerine is not avail- 
able, a solution of white sugar may be used with good results. 
Great care must be exercised lest the fluid that is added 
should change the form or structure of the object. Upon this 
subj ect the remarks of Frey are very j udicious. He says: ‘ ‘ Theory 
requires that each constituent of the body should be examined 
in a fluid medium which resembles in respect to quality and 
quantity, the fluid which saturates the living tissue. Naturally 
this requirement cannot be completely fulfilled in practice; oui 
aim should be to approach it as nearly as possible. Saliva, 
vitreous humour, amniotic liquor, serum and diluted albumen 
are generally recommended as suitable media for the investiga- 
tion of delicate changeable tissues, and, in certain cases, they 
accomplish their object in a satisfactory manner. But do not 
expect them to suffice for every case. Not unfrequently one 
and the same tissue of different species of animals reacts differ- 
ently with the same fluid medium, as may be seen with the 
blood corpuscles. M. Schultze has communicated to us an im- 
portant and readily proved observation of Landolt’s, that ani' OR THE MICROSCOPE 
197 
mal fluids may be preserved from decomposition for a long time 
by the addition of a small piece of camphor.” 
Schultze recommends as a neutral fluid, suitable for most 
tissues, a liquid which he calls “lod-serum.” It consists of the 
amniotic fluid of the calf, to which has been added a concen- 
trated tincture of iodine or a strong solution of iodine in the 
proportion of six drops to the ounce. The color of the solution 
is at first wine yellow, but after a few hours it becomes paler; 
this paleness afterwards increases, and the subsequent addition 
of a few drops of the iodine solution becomes necessary. As 
the amniotic fluid is not always attainable, a good substitute 
may be prepared by mixing 1 ounce white of egg, 9 ounces 
water, and 40 grains chloride of sodium, with the proper pro- 
portion of tincture of iodine. 
During the entire process of preparation, the greatest atten- 
tion must be paid to cleanliness. Particles of dust, which to the 
unassisted vision are invisible, become offensively prominent 
under the microscope. To exclude these, and to protect the 
objects, it is important that the latter should be kept carefully 
covered when not actually undergoing some operation. Small 
bell glasses are recommended for this purpose by Dr. Carpenter, 
and they answer admirably. We prefer, however, as being 
cheaper and less bulky, watch glasses to which a handle has 
been cemented as shown in Fig. 61. The 
handle may be a little knob, turned out of 
a piece of wood, or where this is not conveni- 
ent a small cork will answer. A little sealing 
wax serves for a cement, the watch glass be- 
ing heated before the wax is applied. Flat 
plates of glass answer well to cover the dissecting pans previ- 
ously described. 
When a number of objects are to be protected for some time, 
we place them on a piece of plate glass eight inches square, 
cover each with a watch-glass cover, and protect the whole by 
means of a bell jar with ground edges. The latter fits closely 
to the plate glass and excludes everything, while the small covers 
protect the individual specimens when the large cover is raised 
for the purpose of getting at them. 
Singular mistakes have arisen from the fact that foreign 
Fig. 61 198 
SELECTION AND USE 
bodies which have accidentally found their way into a prepara- 
tion have been mistaken for part of the specimen. The only 
way to avoid similar errors is to exclude all such intruders by 
means of proper covers, and to become familiar with them so 
that they may be instantly recognized when present. Dr. Beale 
gives the following list as those that are most apt to find their 
way into the preparations of the microscopist: Oil globules; 
milk; starch from the potato, wheat and rice; bread crumbs; 
feathers; worsted; fibres of flax, cotton and silk of different 
colors; human hair, cat’s hair and hair from blankets; the scales 
of butterflies and moths, particularly those from the common 
clothes moth; fibres of wood, fragments of tea leaves, hairs 
from plants, vegetable cellular tissue and spiral vessels; particles 
of sand. The curious circumstances under which such bodies 
will find their way into a specimen was recently illustrated in the 
author’s experience. In a liquid submitted for examination, 
and said to be pure, he found foreign matter. It proved to be 
brick dust, used to clean the tin funnel with which the vessel 
was filled, and which had been washed in by the passage of 
the fluid. The student can have no better exercise than to 
examine these intruders and familiarize himself with their ap- 
pearance. 
Preservative Processes.—The object of all preserva- 
tive processes is to prevent any change either in the structure 
or composition of the object. An object may be most perfectly 
prepared and beautifully mounted, but if it be not so treated 
as to preserve it from change, the labor thus expended is wasted, 
as regards the preservation of a permanent record. And yet 
how many objects there are that we would like to keep for 
future examination and comparison, or to show to friends. 
This department of the treatment of objects is, therefore, of 
great importance, and success in it can only be obtained 
through a thorough understanding of the principles involved. 
There are four methods in common use for the preservation 
of perishable animal and vegetable substances; 1, Constant ex- 
posure to temperature considerably below the freezing point of 
water; 2, the perfect exclusion of air; 3, reduction to a state of 
complete dryness; and i, the employment of certain anti-septic Oi’ THE MIOBOSCOPE. 
199 
Compound. The third and fourth are the methods usually em- 
ployed in microscopy, but the same principles which render the 
second method so successful in the preservation of canned fruits 
and meats, deserve the attention of the microscopist. 
Drying, as a preservative process, can be applied to but few 
specimens, chiefly transparent insect preparations, and opaque 
objects. Blood and similar matters are also sometimes pre- 
served by drying. Such preparations are so easily dried that 
no special directions are needed. Warming them over a lamp, 
or preferably on a water-bath, before applying the thin glass 
cover (as directed in the section on mounting objects) is al- 
most always sufficient. Where the specimen is liable to be in- 
jured by heat it may be dried by placing it over sulphuric acid, 
and covering both acid and preparation with a bell jar having 
ground edges and resting on a perfectly flat plate of glass. The 
acid soon absorbs all the moisture and renders the object perfectly 
dry. Where a cell is used for an opaque object, and dryness is 
essential, great care must be taken to make the cell impervious 
to air, otherwise dampness will be sure to penetrate, and if the 
object be of animal or vegetable origin, fungi will be very apt to 
grow on it. We have found cells of cardboard peculiarly 
liable to this defect, and such cells should always be thoroughly 
saturated, and coated with varnish, such as gold size or Canada 
balsam. 
The great dependence of the microscopist, however, is in the 
employment of certain preservative media, of the most impor- 
tant of which, the following is a list: 
Canada Balsam.—Of all the media employed for the mount- 
ing and preservation of objects, Canada balsam is undoubtedly 
the most generally useful, and it is probable that more objects are 
mounted in this material than in all the other media put together. 
As a 'preservative it is perfect, and its action in rendering many 
objects transparent and clear is often of great value. Frey tells 
us that “ several sorts of Canada balsam occur in commerce. 
To be good it should be of thick consistence, nearly colorless, 
and thoroughly transparent.” One difficulty, however, is that 
much of the Canada balsam that is sold is factitious, being 
made of cheap resins dissolved in impure turpentine. Such 200 
SELECTION AND USE 
balsam soon becomes cloudy, and is very apt to crack. Balsam 
that is too highly colored may be bleached by exposure to sun- 
light—a process applied by most opticians to the balsam used 
by them for cementing the lenses of achromatic combinations. 
Balsam when new is quite fluid, too much so, indeed, for the 
mounting of most objects. On*the other hand, old balsam is 
thick, and is apt to crack. Microscopists generally keep balsam 
in wide-mouthed bottles, and take out what is wanted by means 
of a glass rod. As the process of evaporation, which makes 
balsam thick and viscid, goes on more slowly in narrow-mouthed 
bottles, we prefer the latter, and transfer the balsam to the glass 
slide by means of a fine wire with a small loop at the end. The 
wire is passed through a cork, or preferably a wooden stopper, 
and descends to such a depth as to be just below the surface of 
the balsam. As the latter is used up, the wire is pushed down, 
and if cemented in its place by the balsam, a little heat soon frees 
it. The latter remark applies also to the wooden stopper, which 
is very apt to stick in the neck of the bottle. A very slight ex- 
posure to the flame of a spirit lamp is sufficient to loosen it. 
Solution or Balsam.—When the objects that are to be pre- 
served in balsam would be injured by the heat necessary to 
melt it, it is advisable to use a solution of balsam in ether or 
chloroform. The balsam used for making the solution should be 
old and thick. This solution is frequently sold with the label, 
“ Balsam for use without heat.” 
Colophony.—Thiersch recommends a solution of resin or 
colophony in absolute alcohol. The advantage which this ma- 
terial presents is that the preparation may be placed in it di- 
rectly from the absolute alcohol, without becoming cloudy, 
and without prejudice to the durability of the specimen. He 
advises the microscopist to prepare the colophony himself from 
Venice turpentine, which is done by dissolving it in an equal 
volume of ether, filtering it through paper, and evaporating, 
until, when cold, it breaks with a conchoidal fracture. The 
material that remains is then to be dissolved in absolute alco- 
hol until it is of a syrupy consistence. OF THE MICEOSCOm 
201 
Damab Medium.—Gum damar has been recently introduced 
amongst the materials used by microscopists, and with some it 
has found great favor. Carpenter speaks highly of it. Dia- 
toms are said to show better in it than in balsam, and for 
delicate physiological preparations, especially transparent in- 
jections, it is very excellent. It is thus prepared: Half an 
ounce of gum damar is dissolved in one ounce of oil of turpen- 
tine, and half an ounce of gum mastic in two ounces of chloro- 
form. The solutions are filtered and mixed. 
Ordinary damar varnish, such as is used by painters, is some- 
times sold for microscopical purposes, but it does not give 
satisfactory results. 
Preparations which have been preserved and mounted in 
balsam or damar are very durable, while those that are 
mounted in fluids are a source of continual annoyance and loss. 
Many microscopists, therefore, exclude from their cabinets 
all preparations mounted in liquid on the ground that sooner 
or later they will become worthless. And many of our best 
dealers refuse to have anything to do with them. Neverthe- 
less, as Frey well says, “ the natural condition of the tissues is 
completely represented only wnen mounted in a moist condi- 
tion. This method permits of the most accurate recognition of 
delicate textural relations, pale cells and fibres, etc., and should 
not be omitted with any tissue in the production of histologi- 
cal collections.” 
Glyceeine.—At the head of the list of preservative media 
for moist preparations stands glycerine. “Its strong refrac- 
tive power, its property of combining with water, and of at- 
tracting the same from the atmosphere, render it an invalua- 
ble medium for mounting animal tissues containing water. 
It may be truly said, that what Canada balsam is to dry tissues, 
glycerine is to moist ones.”—(Frey.) Much of the glycerine in 
market is very impure, and although the impurities do not 
show themselves very strongly at first, they soon become mani- 
fest by the darkening of the liquid, (owing probably to the 
presence of lead), and the formation of a cloudy precipitate. 
Dr. Beale strongly recommends Price’s glycerine, and we have 
found it very excellent. 202 
When employed as a preservative, glycerine is used either 
pure or diluted, according to circumstances. Equal parts of 
glycerine and water form a very excellent medium for most 
objects. It is alleged, however, that fungi are very apt to grow 
in glycerine and its solutions. We are inclined to believe 
that this may be avoided by adopting the precaution detailed 
at the end of this section. We have now before us specimens 
that were mounted in pure glycerine and water, eighteen years 
ago, and they are still quite perfect. If, however, there should 
be any danger in this direction, the addition of a little camphor 
will prevent the evil. Glycerine exerts a powerfully solvent 
action on many salts, particularly salts of lime, such as the car- 
bonate, and hence it is employed for preventing scale in the 
boilers of steam-engines. This property renders it dangerous 
to use it for the preservation of structures containing com- 
pounds of lime. 
SELECTION AND ESE 
Glyoekine Jelly.—The original directions given by Law- 
rance are as follows: “ Take any quantity of Nelson’s gelatine, 
(any good gelatine will answer, however,) and let it soak for 
two or three hours in cold water; pour off the superfluous 
water, and heat the soaked gelatine until melted. To each 
fluid ounce of the gelatine add one drachm of alcohol, and mix 
well; then add a fluid drachm of the white of an egg. Mix 
well while the gelatine is fluid but cool. Now boil until the 
albumen coagulates, and the gelatine is quite clear. Filter 
through fine flannel, and to each fluid ounce of the clarified 
gelatine add six fluid drachms of Price’s pure glycerine, and 
mix well. For the six fluid drachms of glycerine a mixture of 
two parts of glycerine to four of camphor water may be sub- 
stituted.” 
Glycerine jelly is a very excellent medium, and is easily used. 
At ordinary temperatures it is quite solid, but when slightly 
heated it melts, and may be used like balsam, directions for 
mounting in which will be found in the next section. Objects 
that are to be mounted in glycerine jelly should be soaked 
until thoroughly saturated with a mixture of 7 parts glycerine, 
G parts water, and 1 part alcohol. It is also well, after immers- 
ing them in the melted jelly, to place the slide for a short time OF THE MICROSCOPE. 
203 
on a water bath heated to about 125° Fall. The jelly then pen- 
etrates every part of the preparation. 
When intended for use in very warm climates the proportion 
of the gelatine to the other ingredients should be increased. 
Hantzsch’s Fluid.—Very beautiful preparations of delicate 
vegetable forms have been prepared with this liquid, even the 
coloring matter being left unaltered. It consists of 3 parts of 
pure alcohol, 2 parts of distilled water and one part of glycer- 
ine. The object, placed in a cell, is covered with a drop of 
this liquid, and then set aside under a bell-glass. The alcohol 
and water soon evaporate, so that the glycerine alone is left, 
and another drop of the liquid is then to be added, and a 
second evaporation permitted; the process being repeated if 
necessary, until enough glycerine is left to fill the cell, 
which is then to be covered and closed in the usual manner. 
We have used this liquid with gratifying success. It is easily 
prepared, is not difficult to use, and it gives very excellent re- 
sults. 
Glycerine and Gum.—Of this medium Carpenter says; “ For 
many objects that would be injured by the small amount of heat 
required to melt Deane’s gelatine or glycerine jelly, the gly- 
cerine and gum medium of Mr. Farrants will be found very 
useful. This is made by dissolving 4 parts by weight of picked 
gum arabic in 4 parts of cold distilled water, and adding 2 parts 
of glycerine. The solution must be made without the aid of 
heat, the mixture being occasionally stirred, but not shaken, 
whilst it is proceeding: after it has been completed, the liquid 
should be strained (if not perfectly free from impurity) through 
fine cambric previously well washed out by a current of clear 
cold water; and it should be kept in a bottle closed with a glass 
stopper or cap (not with cork), containing a small piece of 
camphor. The great advantage of this medium is that it can 
be used cold, and yet soon viscifles without cracking; it is well 
suited to preserve delicate animal as well as vegetable tissues, 
and in most cases it increases their transparency. 
Deane’s Gelatine.—Before the introduction of glycerine 
jelly, Deane’s gelatine was a favorite medium, and we still use 204 
SELECTION AND USl! 
it with success. Take gelatine, L ounce; honey, 5 ounces; 
water, 5 ounces; rectified spirit, £ ounce; creosote, 6 drops. 
Soak the gelatine in water until soft, and then add it to the 
honey, which has been previously raised to a boiling heat in 
another vessel. Then boil the mixture, and when it has cooled 
somewhat add the creosote mixed with the spirit. Lastly, fil- 
ter through fine flannel. When required for use, the bottle 
containing the mixture must be slightly warmed, and a drop 
placed on the preparation upon the glass slide, which should 
also be warmed a little. Next, the glass cover, after having 
been breathed upon, is to be laid on with the usual precau- 
tions. The edges may be covered with a coating of Bruns- 
wick black. Care must be taken that the surface of the 
drop does not become dry before the application of the 
glass cover; and the inclusion of air-bubbles must be carefully 
avoided. 
Alcohol.—Mixed with water in various proportions, alcohol 
forms one of our best preservative liquids, for both animal and 
vegetable substances. The chief objection to it is the difficulty 
with which it is retained in the cell. 
Thwaite’s Fluid.—Take water, 16 ounces; alcohol, 1 ounce; 
creosote, sufficient to saturate the spirit; chalk, as much as may 
be necessary. Mix the creosote and spirit, stir in the chalk 
with the aid of a pestle and'mortar, and let the water be added 
gradually. Next add an equal quantity of water saturated with 
camphor. Allow the mixture to stand for a few days and filter. 
Used for preserving desmidise, and also animal substances. 
Beale’s Liquid.—Creosote, 3 drachms; wood naphtha, 6 
ounces; distilled water, 64 ounces; chalk, as much as necessary. 
Mix the naphtha and creosote, then add as much prepared 
chalk as may be sufficient to form a thick, smooth paste; after- 
wards add, very gradually, a small quantity of the water, which 
must be well mixed with the other ingredients in a mortar. 
Add two or three small lumps of camphor, and allow the mix- 
ture to stand in a lightly covered vessel for a fortnight or three 
weeks with occasional stirring. The almost clear supernatant 
fluid may then be poured off and filtered if necessary. It should 
be kept in well-corked or stoppered bottles. 205 
Goadby’s Fluids.—Goadby used two distinct fluids, desig- 
nated by letters A and B, the difference being tliat alum was a 
constituent of one and not of the other. Of both fluids there 
were several degrees of strength, which were designated by 
numbers. A fluid, as usually employed (A2), consisted of rock 
salt, 4 ounces; alum, 2 ounces; corrosive sublimate, 4 grains; 
boiling water, 2 qu irts. To make the B fluid take rock salt, 8 
ounces; corrosive sublimate, 2 grains; boiling water, 1 quart. 
03? THE MICROSCOPE. 
Pacini’s Fluid.—Take corrosive sublimate, 1 part; pure 
chloride of sodium (common salt), 2 parts; glycerine, 13 parts; 
distilled water, 113 parts. This mixture is allowed to stand for 
at least two months. After that time it is prepared for use by 
mixing one part of it with three parts of distilled water, and 
filtering it through filtering paper. This fluid is very strongly 
recommended by Frey. It is used for blood globules, nerves 
and ganglia, the retina, cancer cells, and especially delicate pro- 
teinous tissues. 
Castor Oil.—This is used for preserving certain crystals. 
The best cold-drawn castor oil answers the purpose. 
There are a few general rules which we have found essential 
to the successful use of these media, but which are often 
neglected, the result being the ultimate destruction of the 
specimens. One of the most important points is the use of an 
abundance of the medium (we are now talking of preserving, 
not mounting) and the gradual saturation of the object with it. 
A piece of fresh muscle, simply mounted in a shallow cell with 
a drop or two of Goadby’s fluid, will spoil in a very short time. 
The same object, properly treated, may be preserved indefin- 
itely. The proper course is to completely immerse the object 
in a considerable quantity of the liquid, and if necessary 
change the liquid several times until the substance to be pre- 
served has been thoroughly subjected to the action of the 
medium. For this purpose the quantity contained in ordinary 
cells is altogether too little; small cups, basins, large watch- 
glasses, etc., are needed. It must be remembered that the sub- 
stance acted upon generally absorbs certain constituents of the 
preserving fluid, and hence the latter is left either very weak 20C 
SELECTION AND USE 
or there is an unequal distribution of the constituents as re- 
gards the substance itself and the surrounding fluid. Moreover 
the fluids contained in many objects are displaced by the pre- 
serving medium, and tend to dilute the latter. In most cases, 
therefore, where the preserving medium is a liquid, the desired 
result is best attained by soaking the substance in the fluid for 
several days before mounting, changing the liquid two or three 
times, and finally mounting in fresh fluid of regular strength. 
We would lay great stress upon this point, having seen many 
fine preparations spoiled by pursuing a different course. The 
late Dr, Goadby, whose skill in this department was well 
known, always insisted upon this course, and during a some- 
what extended intercourse with him, and observation of his 
methods and processes, we became fully convinced of its im- 
portance. 
With many preservative liquids, it is well to begin with a 
diluted article, and gradually increase the strength at each 
change of fluid until the proper strength has been reached. 
This course is specially recommended with glycerine and saline 
solutions. 
Another point which demands attention is the entire exclu- 
sion of air, especially of oxygen. Now air adheres with great 
tenacity to most surfaces, such as those of glass or metal, and it 
dissolves to a considerable extent in all watery solutions. To 
get rid of it, the surface of the cell and cover should be either 
well warmed, and then allowed to cool just before being filled, 
or washed with alcohol (after which it may be dried). To ex- 
pel the air from the liquids, they should be boiled, and to pre- 
vent the absorbtion of a fresh dose of air, they should be kept 
well stoppered. But as air will find access to the liquids so as 
ultimately to saturate them, it,is necessary to boil the fluids at 
frequent intervals, so as to get rid of this element. Without 
strict attention to these points it is almost impossible to pre- 
serve animal substances for any length of time in saline fluids. 
Mounting Objects.—For the purpose of conveniently 
exhibiting and comparing objects, and arranging them in cab- 
inets where they can be at all times accessible, it is necessary to 
mount them securely in such a manner that they may be easily OP THE MICROSCOPE. 
207 
handled. For purposes of mere examination and study, 
mounting is unnecessary, but when the objects are to be kept 
for future reference it is indispensable. It is true that where 
the specimens are large they might be kept in bottles in a pre- 
servative fluid, and taken out when wanted. This would be 
very inconvenient, however, and with very minute or delicate 
objects it would be almost impracticable. 
There are three modes in which objects are mounted: 1. Dry, 
the object being simply attached to the slide and suitably pro- 
tected. 2. In balsam, the object being immersed in Canada 
balsam, damar medium, copal varnish, or some similar mate- 
rial. 3. In fluid, the object being mounted in some of the pre- 
servative liquids previously described. Specimens may be 
mounted in any of these ways, so as to be viewed either as 
transparent or opaque objects, and the instruments and mate- 
rials required are neither numerous nor expensive. "With those 
named in the following list almost any ordinary object may be 
neatly put up, though it is of course to be expected that occa- 
sions will frequently arise when special instruments and 
methods, which are not described by any author, will be 
needed. Experience alone can enable the microscopist to treat 
such cases successfully. 
Slides.—Most objects are mounted between two pieces of 
glass, one of which is called the slide and the other the cover. 
As it is convenient to have these slides all the same size, so that 
they may be easily arranged in cabinets, the Microscopical 
Society of London has adopted a slide three inches long by one 
inch wide as the standard size for use amongst their members, 
and this size has been generally adopted by microscopists 
throughout the world. All the best slides that are found in 
market are of this size, and the microscopist who fails to adopt 
it will be subject to great inconvenience when he desires to ex- 
change objects with others who are pursuing similar studies. 
Several other sizes are employed by the French, most of them 
being quite small (2f by f and 2| by f), but as these small slides 
are the only ones that can be used with some French micro- 
scopes—the stages of which are too small to take a slide 3 by 1— 
they are usually kept in stock by dealers in microscopic appar- 208 
SELECTION AND USE 
atus. Small slides have this advantage, that they cost less, and 
take up less room in a cabinet. Large slides look best, and af- 
ford more room for descriptive labels, which is an important 
point. But since slides 3 by 1 have been adopted by common 
consent, the microscopist who mounts specimens, or who buys 
objects mounted on slides of a different size, commits a mis- 
take for which the advantages offered by the small slides are 
but a slight compensation. The only exceptions to this rule 
are where the objects are too large to be mounted securely on a 
slide of standard size, or where a large number are to be pre- 
pared for the purpose of illustrating some special series of in- 
vestigations. It is to be presumed that such a series will never 
be broken up and separated, and as it will in all probability be 
assigned to its own cabinet, it is sometimes of advantage to 
have it upon slides of a size other than that in common use. 
As the objects composing such a series will probably be num- 
bered and catalogued, there is no necessity for extended de- 
scriptions on the labels, and therefore slides of half the usual 
size (lj by 1) will serve very well. The cabinet may thus be 
reduced in bulk by one-half. We have a special cabinet, illus- 
trative of textile fibres, mounted upon slides of small size, and 
find it quite convenient. 
The glass from which slides are cut should be free from air- 
bubbles, scratches and that wavy appearance which is due 
either to inequalities in the surface or to irregularities in the 
composition of the glass itself. Ordinary window glass is en- 
tirely unfit for the purpose. The most suitable kind is plate 
glass, the surface of which has been ground and polished, so as 
to be perfectly even and smooth. Glass of this kind is used for 
looking-glasses and by photographers, and when other material 
could not be had, we have made very excellent slides out of 
broken looking-glasses and photographer’s plates, though it is 
difficult to get the latter thin enough. Slides of good glass 
are, however, manufactured in quantity and sold at a reason- 
able price, so that under ordinary circumstances it will hardly 
pay the microscopist to cut out his own slides. Moreover the 
slides sold by the dealers have the edges neatly ground, an 
operation which the microscopist will find tedious and trouble- 
some. OF THE MICROSCOPE. 
209 
As procured from the manufacturers, the slides are always 
dirty, never having been washed after the process of grinding 
and polishing the edges. If this dirt were soft it would not 
matter so much, but it is in general hard and gritty—being in 
fact the grinding sand—and the consequence is that the surfaces 
of the slides are very apt to be scratched and injured. There 
is but one firm that exports slides to this country, and they are 
very careless in this respect. Out of a gross of slides it is often 
difficult to find two dozen that are not so scratched as to be 
worthless for the finest class of work. Having procured the 
slides, however, the first thing to do is to clean and assort 
them. They should be cleaned by being rinsed in water con- 
taining a little washing soda; the dirt being removed if neces- 
sary by the use of an old nail brush or tooth brush. Until 
this has been done they should not be wiped with cloth or 
leather, for by so doing the particles of sand are dragged along 
the surface, making a deep mark. They should then be washed 
in pure water, carefully wiped with a soft cloth, and assorted 
for thickness and quality. It is in general best to sort them 
into three classes—thick, medium and thin—the latter being 
used for test and other very delicate objects. Elaborate instru- 
ments have been devised for measuring the thickness of the 
slides, so as to assort them accurately, but they are entirely un- 
necessary; the eye is a sufficiently accurate guide. To deter- 
mine their quality, they must be examined under the micro- 
scope, and as it is only the central portion that is of any con- 
sequence in this case, we place them on a brass plate, 3 by 1, 
with the edges slightly turned up, and having a hole five- 
eighths of an inch in diameter in the centre. That part which 
lies over the hole is the only part which it is necessary to ex- 
amine. Slides which contain air-bubbles, strite or scratches, 
are at once laid aside to be used either for opaque objects or 
those of a very coarse kind. Those that are perfect are care- 
fully stored away where they will not be subject to injury. 
Covers.—After being properly arranged on the slide with a 
suitable preservative medium, the objects must be covered with 
a small piece of thin glass. Glass intended specially for this 
purpose is made in England, and imported either in sheets or 210 
SELECTION AND USE 
cut into squares and circles of suitable sizes. Directions for 
cutting these covers would be out of place here. The beginner 
will always find it most economical to buy them ready cut. Of 
the two kinds—round and square—the former are, for all ordi- 
nary purposes, the most convenient, as covers of this shape are 
best suited to cells made with the turn-table, and they may also 
be finished more easily and neatly than the square ones. 
Covers should be carefully assorted for thickness, since the 
thickness of the cover exerts a material influence on the per- 
formance of all lenses except those of the lowest power or 
quality. Where objectives which do not adjust for thickness of 
cover are employed, the microscopist should find out the exact 
thickness to which they have been corrected by the maker, and 
use glass of this thickness in covering all objects that are to be 
examined by means of these lenses. 
The inexperienced student will be apt to find some difficulty 
in cleaning these covers. They are so fragile that it is difficult 
to rub them, so as to remove dirt, without breaking them. 
The best method is to soak them in a weak solution of potash, 
rinse them off carefully several times with clean water, and after 
pouring the last wrater off, give them a final rinsing by taking 
them up in a pair of forceps and moving them about in a tum- 
bler of clean water. They should then be laid (singly, of 
course) on a wiping block and wiped. Wiping blocks are made 
by covering a flat block of wood with chamois leather or linen, 
drawn tightly so as to present a flat but somewhat soft surface. 
These blocks are generally made round and with handles, but we 
prefer them oblong (4 by inches) and without handles. One 
of them is laid on the table face up; upon this face the thin 
glass is laid and wiped with the other block. In this way the 
thinnest glass can be cleaned without risk of fracture. 
Cells -Turn-Table.—All objects that are mounted dry or in 
fluid should be placed in cells, as unless this is done it is dif- 
ficult to arrange the object properly or to secure the thin cover 
permanently. In the majority of cases these cells consist of 
little more than a ring of cement laid on the glass slide and 
allowed to harden, and their depth does not exceed the thick- 
ness of a sheet of paper. Such cells are in constant demand. OB’ THE MICKOSCOPE, 
211 
and are almost always made by the microseopist himself by 
means of a little instrument known as a turn-table or whirling 
table, of wbicb there are several different forms in market. A 
cheap and efficient form is shown in Fig. 62. The table is sup- 
ported by a spindle upon which it turns, motion being com- 
municated by means of a milled ring. The slide is held in its 
place by two spring clips, and it is brought to the centre by 
means of a guide or bar, c, with a square projection. This is 
carefully arranged, so that a slide 3 by 1 shall be accurately 
centered. Hence it follows that the rings and cells on all the 
slides put up by the owner may be instantly and accurately 
Fig. 62. —TUEN-TABLE. 
centered by simply placing them on the table and bringing 
them up to a firm bearing against the guide. This bar or 
guide may, however, be instantly removed when desired, and 
when this is done, any cell may be truly centered by the usual 
methods. This turn-table, therefore, enables us always to bring 
cells of our own make instantly to a perfectly accurate centre, 
while other cells can be centered at any time with very little 
trouble. 
To most turn-tables there lies the objection that the devices 
for centering and holding the slide make one side heavier than 
the other, and consequently, as every mechanic knows, irregu- 
lar and eccentric motion is the result. On many otherwise 
well-made instruments it is, from this cause, impossible to make 
a true cell, particularly if we attempt to work at a high speed, 212 
SELECTION AND USE 
In the turn-table just described, provision is made to obviate 
this difficulty. A heavy-headed screw, of the precise weight 
necessary, is screwed into the under surface of the table, and 
gives a perfect balance to the wheel. It then runs smoothly 
and truly. 
Numerous attempts have been made to produce a self-center- 
ing table, i. e., one in which the 
slides would be truly centered 
without requiring care and skill 
on the part of the operator. One 
of the earliest forms was that of 
Dr. Matthews, the centering part 
of which is shown in Fig. 63, 
Upon the surface of the table he 
arranges two triangular plates 
of brass, which rotate upon pins 
placed at equal distances on each 
side of the centre, and as the 
plates are of the same size, when- 
ever their inner faces are par- 
allel, these faces must be equi- 
distant from the centre. Hence, when a slide with parallel 
sides is placed between them, and the plates turned so as to 
press upon the sides of the slide, the slide will be truly cen- 
tered so far as its width is concerned. It is centered for length 
by a stationary pin, against which the end is always brought. 
Slides of irregular size are therefore centered only one way. 
There are at present, however, before the public, two tables 
which centre slides accurately in both directions. One was in- 
vented by C. Mason Kinne, of San Francisco, who describes it 
as follows: “AS will be seen from the engravings, Figs. 64 and 
65, which are reduced one-half, t*he slide will be grasped autom- 
atically, upon removing the finger from the lever, the spiral 
spring causing the clutches to instantly clasp the slide, and 
retain it in a central position. One corner of either end of the 
slide projects sufficiently for the purpose of taking hold with 
one hand, while the other is pressing the lever, and can be 
fixed or removed without pushing along a circular disc to its 
edge. The slots are made to allow movement enough, so that 
Fig. 63.—Matthew’s then-table. OF THE MICROSCOPE, 
213 
the clutches can grasp 
any piece of glass from 
Ij to 3J inches in diag- 
onal length, and the 
table is made of brass 
about a quarter of an 
inch thick, which gives 
weight sufficient to se- 
cure stability of move- 
ment. The whole rests 
on a small spindle 4 or 
5 inches long, screwed 
into the centre of the 
brass stud, which is the 
fulcrum of the lever, 
and can be removed at 
pleasure to pack away. 
The pointed lower end 
of the spindle is stepped 
into a counter-sunk 
metal rest, and with a collar placed at a suitable distance above 
to allow of free movement of the hand, I find that a steady 
motion can be obtained with the thumb and finger, of any re- 
quired velocity, and is under greater control than with any 
milled-head device.” 
Fig. 64.—kinne’s turn-table. 
(Upper side.) 
Fig. 65.—kinne’s turn-table. 
(Under side.) 
Mr. Kinne suggests a very simple method of constructing a 
home-made table on this plan: “ The spindle can be fitted into 
any appliance, primitive or expensive, at the option of the 
worker, and I find that an old cigar box, with a portion of one 
end removed, is just as useful as anything else, though if made 
for sale, a cheap varnished box cotild be furnished, and in 
which the table and spindle could be packed when desired. If 
fitted up with the cast iron stand, the whole might present a 
neater appearance, but the additional expense would not add to 
its utility.” 
Slides which have been imperfectly centered on other tables, 
are recentered for varnishing by the use of two rectangular tri- 
angles and a little wedge. The inventor uses the corners of a 
broken slide and a piece of match. 214 
SELECTION AND USE 
The other self-centering turn-table was invented by Mr. C. 
F. Cox, of New York, and is shown in Fig. 66. The slide is 
Fig. 66.—COX TUEN-TABLE. 
grasped by two angle-pieces, which are simultaneously moved 
to and from the centre by means of a right and left hand 
screw. When it is desired to re-varnish slides which have 
not been accurately centered in the first place, a pair of spring 
clips, attached to a stout bar, are fastened on. This can be 
effected in an instant. The arrangement is shown in Fig. 67. 
Fig. 67.—COX TUEN-TAELE. 
There is also a very ingenious device for placing a row of 
small cells along the jniddle of a slide. This consists of two 
equal right-angled triangles, the square corners of which fit into OF THE MICROSCOPE. 
215 
the clutches, thus allowing the long sides to lie parallel to each 
other, and at equal distances from the centre. A slide may 
thus be grasped between them, and pushed along longitudin- 
ally, as may be desired. 
Those who once see a turn-table, will find no difficulty either 
in understanding the method of using it, or in putting this 
knowledge into practice. The slide, being held on the table 
either by springs or clutches, is made to revolve rapidly, and a 
brush, charged cement or varnish, is held against its sur- 
face so as to leave a ring. There is a slight knack about making 
good cells, which it requires a little practice to acquire. The 
brush must be held in the direction of a tangent to the ring— 
that is, it must not point to the centre of the circle, but must 
lie so that the ring, as it revolves, will draw the cement away 
from the brush. Practice alone can give expertness in doing 
this, and we would advise the beginner to work steadily for a 
few hours at making cells on pieces of common window glass, 
strips of which can be had for nothing from any glazier. The 
chief points to be attended to are the position of the brush and 
the consistence of the cement. If the latter be too fluid, it 
spreads and does not form a well-defined circle. If too thick 
it does not leave the brush as freely as is necessary. The 
method of preparing the cement will be explained under the 
proper head 
Fig. 68. 
Where a turn-table is not at hand, very good cells may be 
made as follows: On a card draw the outlines of a slide with a 
series of circles in the centre, as shown in Pig. 68; lay the 
slide on the card so that the centre of the circles will be at the 
centre of the slide, and then paint a circle of cement on the 216 
SELECTION AND USE 
slide by nand, the rings beneath serving as a guide. Very good 
cells may be thus made, but the process is of course more 
tedious than that with the turn-table, and does not give as neat 
results. 
A few precautions are necessary in order to insure the per- 
manent adhesion of the cells to the glass. In addition to pro- 
viding cement of good quality, we must see that the slide is 
dry and recently heated. It is difficult, with most cements, to 
use hot slides, as the cement is apt to flow; but the slide should 
have been recently heated, and after the cement has partially 
hardened, the cells should be baked by exposure to a temper- 
ature as high as they will stand. This is easily done by placing 
them on a board or plate, and leaving the latter for a short 
time in an oven. 
Where cells of greater depth are required, rings of various 
materials are cemented to the slide. For objects mounted dry, 
rings of leather or cardboard answer well, provided they are 
carefully varnished so as to be impervious to air and moisture. 
For liquids, rings of glass, tin, ebonite, etc., are used. Rings 
of rubber and gutta-percha have been suggested, but they do 
not answer, as they soon become rotten. Full directions for 
making and using deep cells may be found in the works of 
Quekett, Carpenter, Beale, Frey, etc. 
Hot-Plate.—This is simply a stout plate of brass or iron, 
which is supported over a lamp by suitable means. The com- 
mon plan is to insert four stout wires to serve as legs, but a 
better mode is to support the plate on the ring of a retort 
stand, as its distance from the lamp can thus be readily ad- 
j usted and the temperature regulated. The hot-plate serves to 
distribute the heat, and thus to prevent the slides from becom- 
ing suddenly and unequally heated. Moreover, by means of 
it several slides can be heated at once, and thus much time 
may be saved. It should be tolerably heavy. The one we use 
is of cast iron, six inches long and three inches wide. The 
upper surface has been ground so as to be tolerably smooth, 
When a hot-plate is not at hand, a good substitute may be 
found in a smooth brick, or, better still, a plate of soapstone. 
These may be heated in the fire and will retain their heat for a 
long time. 217 
Lamp.—Any lamp, or even candle, will answer, but we prefer 
a spirit lamp, the flame being free from smoke and easily man- 
aged. At night the kerosene lamp used for giving light will 
answer. Where gas is used, the Bunsen burner is a great con- 
venience. Whatever lamp or burner be used, it should be sur- 
rounded with a chimney or shade, so as to prevent the flicker- 
ing of the flame by currents of air. The best shade is a tin 
cylinder, with rows of holes at top and bottom for the admis- 
sion and exit of air. 
OF THE MIOEOSOOPE. 
Eetoet Stand.—n. suitable retort stand is a very simple 
affair, and is best made at home. Ours consists of a board of 
hard wood, 5 inches by 4, into which is screwed a rod fourteen 
inches long, and a quarter of an inch in diameter. The rings 
have no screws, but are simply pieces of wire, one end of which 
is twisted round the rod, while the other is formed into a ring 
of the required size. Eings formed in this way are easily 
moved on the upright rod, but no weight placed on them in 
the usual manner can cause them to slip down. 
Cards for Centering the Objects.—Unless the objects 
are placed on the centres of the slides, the latter have a very 
awkward look. By drawing the outlines of a slide on a card, 
and marking out the centre, this difficulty is easily overcome. 
A card marked off in this way is shown in Fig. 69. 
Fig. 69, 
It is well to have two cards, one black with a white centre, 
and the other white with a black centre, as some objects, when 
immersed in the medium in which they are to be mounted. 218 
SELECTION AND USE 
show best against a dark ground, while others are most easily 
seen against a light one. Those who use the self-centering 
turn-tables may readily centre their slides by painting on them 
a ring of some water-color, which is easily washed off. The 
ring is, of course, laid on the side opposite to that which 
receives the object. 
Mounting Needles.—These are similar to dissecting needles, 
but being used in balsam, varnish and similar substances, they 
cannot be used for dissection, and should be kept by them- 
selves. They are most easily cleaned by being warmed over the 
lamp, and wiped with a piece of soft leather. When the balsam 
is burned on them, as recommended by some, it leaves a crust 
which is not easily removed. 
Coyer Forceps.—In placing the cover on the object, the 
I ordinary forceps are very inconvenient. We 
have long used a pair of forceps bent as in 
Fig. 70, and with the points carefully 
adjusted. The mode of using the instrument 
will be obvious from the engraving. A very 
ingenious device intended to answer the same 
purpose has been invented by Dr. Fletcher. 
These forceps are self-closing, so that the 
thin glass cover is held without any effort. 
After the cover is in position on the slide, 
by pressing on the blades they open and allow it to slip out. 
If the cover should 
stick to the forceps 
in the slightest de- 
gree, it may be pre- 
vented from moving 
when the forceps 
are removed by in- 
serting a common 
pin in the slit seen in Fig. 71. When using the forceps 
shown in Fig. 70, the same end may be attained by means of a 
wire fork (a hair-pin is as good as anything), which may be 
made to straddle the nose of the instrument. 
Fig. 70. 
Fig. 71. OF THE MICROSCOPE. 
219 
Slide Holder.—The hot slides cannot be comfortably held 
in the fingers, and therefore a pair of wooden forceps become 
a necessity. Those usually sold are made by screwing together 
two thin slips of wood with a piece of brass or lead inserted be- 
tween them at one end. To admit the slide, the slips are forced 
apart by pressing on pins arranged as in the stage forceps. 
When placed on a table the 
metal counter-balances the slide, 
and keeps it from touching the 
surface on which it is laid—a 
very important point. The Eng- 
lish forceps, being all wood, fre- 
quently tip with a heavy slide. 
A common spring clothes-pin 
is frequently used, but when we 
come to lay the slide down, the 
clothes-pin holds it in an awk- 
ward manner. The end of the 
hot slide is sure to lie on the table, 
and if fluid balsam or other me- 
dium should be present, the fact 
that the slide is not level produces 
bad results. By cutting off about 
half an inch from one of the 
limbs of the forceps part of the 
pin, however, this difficulty is 
avoided. The slide may then be 
grasped in such a way that when 
the clothes-pin is placed on the 
table, the glass will be held in a 
perfectly level position. A glance 
at Fig. 72 will show what we 
mean. A great advantage of this 
form of holder is that it costs but a trifle, so that the micro- 
scopist can supply himself with an abundance of them, and 
thus several slides may be cooling, while work on others is 
going on. When very heavy slides are used, it may become 
necessary to screw a plate of sheet lead to the under side of the 
clothes-pin, so as to prevent tipping 220 
SELECTION AND USE 
Water Bath.—A water bath is indispensable in those eases 
where a certain very moderate degree of heat is not to be ex- 
ceeded. Few persons fully appreciate the difficulty of regu- 
lating or even estimating the temperature of an object held over 
a naked flame, and mischief is often done before the operator 
is aware of it. A serviceable water bath is easily extemporized 
out of an old fruit can and a small beaker glass. This serves 
for exposing material and preparations to a temperature lower 
than that of boiling water. Where slides are to be so heated, 
the simplest contrivance is a flat tin box, with all the joints 
(cover and all, of course,) tightly soldered. A small tube, 
closed with a cork, serves to admit the water. 
Spring Clips.—One of the first of the needs which impress 
themselves upon the mind of the beginner, is the necessity foi 
something to retain the thin cover in its place, until the ce- 
ment, which is intended to hold it permanently, dries. An end- 
less variety of spring clips have been invented for this purpose, 
but we have never seen anything that we liked better than the 
simple article shown in Fig. 73, and which we have used for 
Fig, 73. 
over fifteen years. It consists simply of a piece of brass wire 
bent as in the engraving. The slide being held in the left 
hand, the clip, held by the upper wire, is brought so that the 
projecting part of the ring is placed under the edge of the 
slide. The upper part is then lifted up so as to open the clip, 
which is then slid on to the slide until the vertical point is in 
the right position. When a broader surface than the point of 
the wire is needed, a piece of cork may be stuck on it, and if OF THE MIOEOSCOPE. 
221 
there should be need for greater pressure than that which the 
spring of the wire affords, this can be obtained by sliding a 
small brass ring on to the clip. 
Various other forms of spring clip have been invented, but 
none that we consider more simple, or that we like better than 
the above, which has this great merit, that any one can make it 
for himself out of materials that may be obtained at any hard- 
ware store. It must be borne in mind, however, that all clips 
constructed upon this plan are apt to cause a slight displace- 
ment of the object, from the fact that the movement of the 
point is not quite perpendicular. With delicate objects this is 
a matter of importance. The only remedy is to use the end 
pressure of a rod moving in fixed guides. 
CEMENTS AND YAENISHES. 
A supply of carefully selected cements and varnishes is indis- 
pensable to the microscopist, and it is also well that he should 
understand the nature and properties of the materials used, 
otherwise he will be liable to make gross blunders. Thus, of 
the different articles in use, some are easily mixed with each 
other, while others separate as soon as left to themselves; some 
dry in one way and some in another. It would require a vol- 
ume to detail the properties of the different substances which 
enter into the composition of the cements used by the micro- 
scopist. We have space for only the following hints, which, 
however, we hope will prove useful. 
Cements become hard in three different ways—cooling, evap- 
oration and oxidation. Shellac, sealing wax, electrical cement, 
etc., when melted by heat, furnish examples of the first pro- 
cess. Shellac and sealing-wax dissolved in alcohol, and asphalt 
and damar dissolved in turpentine, dry by the second process— 
the solvents evaporating and leaving behind the material which 
they had dissolved. Drying oil in all its forms, such as gold 
size, paint, etc., becomes hard by oxidation—not, as is gener- 
ally supposed, by evaporation. 
In the case of varnishes which dry by the evaporation of 
some of their constituents, it is obvious that if a fresh layer 222 
SELECTION AND USE 
be laid oyer an old one, the old layer will be softened, and 
if there should be any tendency to a vacuum in the cell, 
jUo softened cement will be unable to resist the outside 
v»essure, and will creep in and spoil the object. So, too, 
with varnishes or cements formed chiefly of drying oil or gold 
size. If the different coats be laid on too thickly or too 
rapidly, the part that is beneath cannot easily harden, but will 
remain for a very long time in a semi-liquid condition. We 
have just removed some brass rings from slides to which they 
were attached four months ago by means of gold size, and 
although the outer surface of the cement was hard and dry,, the 
interior was quite liquid, freely soiling the fingers. 
Gold Size.—The most extraordinary recipes have been given 
for the preparation of this cement, which is in reality nothing 
but good linseed oil rendered very drying by the usual 
methods. Gilders frequently make it into a semi-paint by 
adding coloring matter, thus forming a ground of a shade 
similar to the gold they use, and this seems to have misled some 
of our best writers. There is no ochre, litharge, or anything 
of the kind present in good gold size. It does not pay to pre- 
pare gold size in small quantities, and it may be obtained from 
any color dealer. The older it is the better, and it is well, 
therefore, to lay in a good stock, which must be kept carefully 
corked. The working supply should be kept in a small bottle. 
This is the favorite cell making material employed by Dr. Car- 
penter, and it is certainly the most reliable cement we have. 
It adheres firmly to glass, and if laid on in very thin successive 
layers, tolerably deep and very durable cells may be built 
up, but the process requires considerable time, otherwise the 
under layers will remain soft. It has this .great advantage over 
asphalt, damar, and other cements composed of solid materials 
dissolved in some menstruum, that fresh coats have but very 
slight action on the old layers on which they may be laid. It 
mixes with turpentine, and consequently with most materials 
soluble in turpentine, but when once dry and hard, turpentine, 
alcohol, ether, etc., have little or no action on it. It does not 
mix with alcohol, and therefore cannot be mixed with the 
solution of shellac in alcohol in any of its forms. 223 
Black Japan.—When this can be procured of good quality, 
it makes a very excellent cell. It adheres very firmly to the 
glass provided the latter be exposed to a moderate heat after 
the cement has become dry. Black Japan dries up and thick- 
ens when kept, but may be thinned with turpentine. 
OB' THE MICROSCOPE. 
Brunswick Black.—This is simply a solution of asphaltum 
in turpentine. Occasionally it is rendered very black by the 
addition of a little lampblack. When good, it makes a very 
excellent cement. Its quality depends chiefly upon the char- 
acter of the asphaltum that is used in its preparation. Now 
there are several varieties of asphaltum in market, the most 
common kind at the present day being that obtained from coal 
tar. This seems to be entirely unfit for the purpose. The 
proper kind is that which is found native in several parts of the 
world. The two kinds are easily distinguished by their odors. 
Shellac.—This well known substance, when dissolved in 
alcohol, forms a varnish or cement of great value to the micro- 
scopist, and is the proper one to be used when glycerine is em- 
ployed. Much of the shellac in market is artificially made 
from resin and wax, and makes a poor varnish. Beal shellac 
must be employed if failure would be avoided. 
Bell’s Cement.—Carpenter states that this cement is merely 
shellac dissolved in alcohol. With us it has presented no ad- 
vantage over other cements. 
Sealing Wax Yarnish.—This is prepared by dissolving the 
best sealing wax in alcohol. It unfortunately happens that all 
the fancy colored sealing wax in market is of inferior quality. 
Yery excellent red wax may be obtained, but we have never 
been able to obtain good blue, black, green or other colored 
wax. We therefore make varnish of these colors by dissolv- 
ing in alcohol the materials used for making the best red wax, 
substituting some other color, however, for the Vermillion. 
Colored Shellac.—Bleached shellac, dissolved in alcohol, 
and colored with aniline blue, red, etc., makes a very fine trans- 
parent varnish. 224 
SELECTION AND USE 
Damae Cement.—This is a mixture of equal parts of damar 
famish and gold size, mixed together. It should stand for 
some time before being used. It is said to be very excellent. 
It is very tough, and serves well as an outer coating over such 
brittle cements as shellac and sealing wax varnish. 
Marine Glue.—This is undoubtedly the strongest cement 
in use for joining pieces of glass or glass and metal together. 
Skilful microscopists make great use of it; beginners do not 
find it so easy to manage as some others. In using it, the 
simplest method is to cut it in small pieces, lay it on one of the 
surfaces that are to be joined, melt it by heat, and apply the 
other surface, making sure of perfect contact by rubbing the 
two pieces upon each other, if they will allow of it. Marine 
glue may be obtained from most dealers in microscopes. 
The cement known as liquid glue, is simply a solution of 
shellac in alcohol. 
For attaching labels, paper covers, etc., to the slides, nothing 
is better than good dextrine. After having mixed the dextrine 
with water to the proper consistence, add six drops of glycer- 
ine to the fluid ounce of dextrine. This will prevent the labels 
or covers from cracking off. 
Having provided himself with the necessary tools and mater- 
ials, the next step is to learn how to use and apply them, and this 
will probably be most easily taught by describing a few char- 
acteristic examples. And first of all, selecting the most easily 
mounted of all objects, we commence with the scales on the 
butterfly’s wings. Having prepared a cell of proper size, and 
allowed it to dry, the first step is to select a cover to suit it, 
and give a final cleaning to both slide and cover. When every 
particle of dust has been removed, breathe gently on the slide, 
and press the wing lightly against it, and within the cell. A 
large number of scales will at once adhere to the slide, and 
the next step is to attach the cover. Place the slide on the hot- 
plate, (which must not be too hot, however,) and when it is 
thoroughly dry, and the cement somewhat soft, lay the cover 
on by means of the cover forceps. Press it into contact with 
the cement, and the operation is completed. It is not difficult 
to see when the cover and the cement are in perfect contact. OF THE MICEOSCOPE. 
225 
and great care must be taken to close the cell all round in this 
way. It is true, this point is not of so much consequence with 
the particular object under consideration, but with some ob- 
j ects it would be quite important. The scales are now mounted 
dry, and may be kept for any length of time; no dust can soil 
them, and they are not liable to be injured by contact with 
other bodies. It only remains to label and “ finish ” the slide 
as hereafter directed. 
Next to the above in simplicity is the mounting of such ob- 
j ects as the wings of insects in balsam. Suppose we wish to 
mount one of the smaller wings of a bee or wasp, so as to show 
the curious hooks with which it is armed: Place the warm slide 
on the centering card, drop a little balsam on the centre, and 
again warm the slide, so that any air that may be present may 
collect in fine bubbles which can be removed by means of a 
cold mounting needle. When the air-bubbles have been re- 
moved, seize the wing (previously well cleaned with a camel 
hair brush) with a pair of fine forceps, and lower the tip of it 
i nto the warm balsam. Then slowly lower the wing until it is en- 
tirely immersed. Drop, very little more balsam on it, warm 
the slide again (slightly this time), and remove air bubbles if 
there should be any. Then take a clean cover in the cover for- 
ceps, make it quite warm, and place it over the object by allow- 
ing it to first touch one edge of the balsam, and then to grad- 
ually fall down so as to exclude all air bubbles. In the case 
of the bee’s wing it does not answer to apply much pressure as 
this would tend to distort the hooks. Press the cover into 
place as much it will bear and no more, lay the slide in a 
warm place for some time until the balsam hardens, and then 
clean and finish the slide. 
In mounting objects in balsam and fluids, the great difficulty 
to be encountered is the presence of air bubbles. Careful and 
j udicious management, however, readily enables us to avoid 
them. In the first place see that they are entirely removed 
from the balsam on the slide. This is much more easily done 
before immersing the object in the balsam then afterwards. 
Next see that the air is expelled from the object. In the case 
of the wing, this is effected by slowly immersing the object in 
the balsam. Lastly see that no air enters with the cover. To 226 
SELECTION AND USE 
do this see that the cover is hot, and that it is lowered on the 
balsam slowly, and from one side. If in any case there should 
be a vacant space under the cover as at a Fig. 74, and it should 
be desired to fill it, do not apply the fresh balsam directly at a. 
To do so would certainly be to inclose a large air bubble. Drop 
the balsam at h, warm the slide, and the balsam will creep in by 
capillary attraction, and expel the air. 
Fig. 74. 
Let us now suppose that we have some small insect which 
we have prepared by soaking in potash, and which we desire 
to mount in balsam. Such a preparation if immersed directly 
in balsam, would be spoilt, since the balsam and watery solu- 
tion would not mix. Therefore, proceed as follows: Wash the 
insect in pure water, and drain off the water; wash with strong 
alcohol, drain off the alcohol, and soak for twenty-four hours 
in the strongest alcohol you can get. Pour off the alcohol and 
soak for twenty-four hours in turpentine. The object may 
now be immersed in balsam without difficulty. 
Air pumps and similar contrivances are generally recom- 
mended as the best means for removing air bubbles, but we 
never use them. If the object be dry, we soak it in alcohol 
until all the air has been expelled, then transfer to turpentine, 
and finally to balsam. This requires time, it is true but it does not 
occupy the time of the microscopist. The soaking process 
goes on without any attention from him, and while it involves 
far less labor, with us it has always given far better results, 
though we have used very fine air pumps, and followed the 
best published directions. Take the case of a dry shaving of 
wood, many of which are well worth mounting. It would be OF THE MICROSCOPE. 
227 
very laborious to get the air out of this by means of the air 
pump, while by soaking successively in water, alcohol, and tur- 
pentine, it can be mounted with great ease without a bubble. 
Let us now take the case of an object mounted in fluid in a 
cell. Suppose it is the so-called tongue of a fly, which of course 
has been soaked for some time in the liquid in which it is to be 
finally mounted, viz., dilute glycerine. We make a cell of suita- 
ble thickness, which in this case may be made with shellac 
dissolved in alcohol. Several coats will be required, and as 
shellac alone does not adhere well to glass, we prefer to lay on 
first a coat of gold size or Japan, and when this is thoroughly 
dry, to lay the shellac on it. No difficulty will be found in 
making a cell of sufficient depth. The cell is now to be filled 
with the liquid, the object placed in it, and the whole carefully 
examined for air bubbles, which must be removed if they exist. 
The cover is now applied, all superfluous fluid removed by 
means of a camel hair pencil, which has been moistened and 
then squeezed dry, and finally the edge of the cover is to be 
coated with a thin layer of cement. After a day or so another 
layer of cement should be laid on, and this process repeated 
until at least three layers have been applied. 
We give no directions for the construction and use of very 
deep cells as this is work that will hardly be attempted by be- 
ginners. 
When opaque objects are to be mounted either in balsam, or 
in fluid, the process required is the same as that employed for 
transparent objects. Yery many opaque objects are, however, 
mounted dry, and in this case all that is needed is to attach 
them to a slide, and see that they are properly protected. 
When thin they may be readily mounted in cement cells, and 
this is altogether the neatest and most secure plan where it can 
be used. Thicker objects require deeper cells, which may be 
made of card, ebonite or electrical cement. (3 parts resin, and 
1 of wax, colored with ochre or any similar matter). Cells of 
card are made by first punching out a disc like a gun wad, 
and then punching a hole in this so as to leave a ring. The 
ring is to be cemented to the glass slide and carefully var- 
nished. 
Wooden slides with a cell bored in the centre, are recom- 228 
SELECTION AND USE 
mended very highly, and seem to answer a very good purpose. 
The cells are not bored quite through the wooden slip, and as 
they are blackened on the inside, any small object that may be 
cemented to the bottom of them shows very well. For seeds, 
small shells, and similar objects, they answer admirably. In 
most cases it will be found unnecessary to cover the cells with 
thin glass. Several slides may be packed together face to face, 
and if held in firm contact by means of a rubber ring, dust will 
be entirely excluded. Or they may be arranged in the drawers 
of an ordinary cabinet, face down, the labels being placed on 
the backs. This will effectually exclude the dust. 
Some years ago we mounted a large number of specimens of 
minerals on leather discs, which were cemented to glass slides. 
These leather discs were three-quarters of an inch in diameter, 
and we had a lot of pill-box covers which exactly fitted them. 
These covers, when slipped on to the discs, protected the ob- 
jects perfectly, and the whole formed a very cheap, convenient 
and excellent mode of mounting. 
A very ingenious cell for opaque objects, the invention of 
Prof Pierce, of Provi- 
dence, E. I., is shown in 
Pig. 75. It consists of a 
metallic cell, having a 
broad flange like the 
rim of a hat, which is 
cemented to an ordinary 
glass slide, as shown in 
section in the lower figure. To this cell is fitted a metal cap, 
which covers and protects the object. The object may be placed 
directly on the glass, or raised by means of a disc of any re- 
quired thickness, so as to be more easily illuminated. The 
slide, with cell uncovered and containing an object, is shown 
in the upper figure. Uncovered objects may in this way be 
very perfectly protected from dust and mechanical violence. 
Some persons object to any slide that is mounted without a 
glass cover. It must be acknowledged, however, that while 
glass covers add to the appearance of the object and serve to 
protect it, they interfere somewhat with its examination, as it 
cannot be so brilliantly illuminated, and the rays in their passage 
Fig. 75. 229 
to the objective are interfered with to a considerable extent. 
The objections to mounting opaque objects in cells with mov- 
able covers are that even during the short period in which they 
are exposed for examination they are liable to be contaminated 
with dust, the cover is liable to be lost, and the object when 
exposed is liable to mechanical injury. Therefore, while a few 
brilliant and striking objects, such as minerals, seeds, etc., may 
well be mounted in open cells, all delicate and valuable objects 
should be permanently .covered. 
Of late years the most popular cell for opaque objects is un- 
doubtedly that devised by Prof. Hamilton L. Smith, and known 
as the wax cell. Various methods of making it are in use, the 
following being that originally published by the inventor: 
Take a circular disc of thin sheet wax, which is easily cut with 
a common gun punch from the sheet wax ordinarily used for 
making flowers', and attach it by means of heat to the cen- 
tre of a glass slide. A brass curtain ring, of which the inte- 
rior is the same size as the disc, is then slightly warmed and 
laid on the wax, to which it, of course, adheres. The object is 
fixed to the wax by slightly moistening the surface of the latter 
by a minute drop of turpentine. When dry, a cover, which 
exactly fits into the bevel of the ring is attached thereto with a 
little cement, and the whole may then be finished off on the 
turn-table. 
OF THE MICROSCOPE. 
The appearance of objects mounted in this way is very ele- 
gant, and consequently it has become a general favorite. It 
has, however, recently been condemned in most unsparing 
terms by the inventor, who has found that the under surface 
of the cover becomes in time coated with a deposit which 
causes a glare that entirely prevents clear vision. As soon as 
this difficulty was announced, an animated correspondence 
took place in the scientific journals, and it was found that 
while some microscopists had experienced this difficulty, it 
had never occurred to others. The final conclusion seems to 
be that the difficulty arises from the kind of wax used, and the 
method of attaching the object to it. The wax should have 
been thoroughly melted at a temperature as high as it will 
bear, so as to drive off all volatile matter, and instead of using 
discs punched from sheets, the wax should be applied in a 230 
SELECTION AND USE 
melted condition, by means of a brush, to the warm glass slide. 
The object should not be stuck on with turpentine or similar 
cement, but should be attached to the wax after a small spot 
on the latter has been softened by bringing near it a hot wire. 
Objects mounted in this way, in cells so prepared, seem to re- 
main in good condition for years. 
A very ingenious cell has been devised by Mr. D. B. Scott. 
This cell is punched out of thin sheet metal, as shown in plan 
and section in figures 76 and 77. The cell is formed by the 
Fig. 76. 
Fig. 77. 
central depression, and there is a turned-down edge all round 
the slide which gives it strength, and causes it to lie steadily 
on any flat surface. The cell has a ledge, or rebate, as seen in 
figure 77, for the purpose of supporting the thin glass cover. 
When made of tin the whole slide is japanned; those made of 
brass are lacquered, and the interior of the cell is covered with 
black asphalt, or some similar dark varnish. The objects are 
attached to the surface of the varnish by means of gum water, 
to which a very little glycerine has been added, and the thin 
glass cover may be cemented down and varnished on the turn- 
table in the usual manner. 
METAL SLIDE AND CELL EOR OPAQUE OBJECTS. 
Fig. 78.—CELL FOR OPAQUE OBJECTS. 
The alleged failure of the wax cell gave rise to a great many 
devices, one of which, proposed by Mr. Atwood, consists of a 
vulcanite or hard rubber cell, of which a sectional view is 
given in figure 78, the dotted lines showing the thin glass OF THE MICROSCOPE. 
231 
cover. The base is solid, thus giving a black back-ground of 
rubber; around the top is a ledge fitted to receive a one-half 
inch cover glass; this being secured by a trifle of shellac or 
any similar cement, completes the mounting. The cell may 
be attached to a glass slip by any cement, before or after 
preparation. For exchanges it offers superior advantages, in- 
asmuch as the cell, with objects enclosed, may be sent through 
the mails independent of the glass slips, the recipient attach- 
ing them. 
Cells similar in construction to the hard rubber cell may be 
moulded out of melted shellac by any one who is possessed of 
a proper die or mould. The die is easily turned out of a piece 
of brass, and with two or three moulds of different sizes, and a 
little shellac colored black, the microscopist may easily and 
cheaply provide himself with a supply of cells suitable for 
almost any object. The idea is due to Dr. Dayton, of Cleve- 
land, and the details of the process may be found in the Ameri- 
can Journal of Microscopy for June, 1881. 
A cell which we have found very durable, easily and quickly 
made, and very neat, is constructed as follows: Having pro- 
cured some good gold size and pure litharge, grind the latter 
to a very fine powder. Mix the litharge and gold size to the 
thickness of cream, and color either black or dark olive by 
adding lamp-black. With this cement it is easy to make as 
many cells as may be wanted, by laying on a ring with a brush 
while the glass slide revolves on the turn-table. As soon as 
the rings or cells are made, dust finely-powdered litharge over 
them until they are covered a sixteenth of an inch deep; allow 
them to stand a few minutes, and then shake off all the loose 
litharge by means of a few smart taps. The surface of the cell 
will now be quite rough. Allow it to stand a few hours, and 
then press it against a p’ate of glass. If this be done carefully, 
a smooth, level, solid ring will be left on the slide. If the 
edges should not be as smooth as they ought to be, it is easy 
to trim them off on the turn-table by means of a small chisel. 
Any turn-table with stout spring clips will hold a slide with 
sufficient firmness to allow of such soft material being turned 
quite true and smooth. Of course the tables which grasp the 
slides by the corner are best for this purpose. Such cells, after 232 
SELECTION AND USE 
a few weeks, become very hard, and may be finished so as to 
be very neat. When covered with a few coats of shellac var- 
nish or pure gold size, and completely dried, they hold liquids 
very well. They adhere so firmly to the slide that on several 
occasions when the slide has been broken by a fall, the cell has 
not parted from the glass. The only objection which we find 
to them is the length of time which it takes them to harden. 
Tin foil, which may be had of various thicknesses from that 
of thin paper to a sixteenth of an inch, makes a capital mate- 
rial for cells. It is difficult to get the inner and outer circles 
which form the ring, concentric, except by the use of special 
tools. Prof. Chester avoids this difficulty by placing a large 
number of rings on a rod or mandril which just fits the open- 
ing, and after screwing the rings tightly endwise, he turns off 
the outside so as to leave it perfectly true and even. Mr. A. Y. 
Moore cements the sheet of tin foil to the slide by means of 
shellac, and cuts out the ring on the turn-table by means of a 
sharp knife or chisel. 
Finislsing the Slides.—The appearance of a collection 
of slides depends very much upon the style in 'which they are 
finished, and although in some instances it may be said that 
the finish does not affect the intrinsic value of the object, it 
is generally the case that a well-finished slide is more durable 
than one that has not been properly completed. The old sys- 
tem of covering the slides with paper is now entirely obsolete, 
and properly so. It was troublesome, unsightly, unless in pro- 
fessional hands, and not very durable. Fortunately slides 
with ground and polished edges are now so cheap that there is 
no occasion to resort to the paper cover. Objects mounted on 
these slides, whether in cells or otherwise, are in general cov- 
ered with round covers, which are adjusted on the turn-table 
so as to be perfectly central. After the mount has been com- 
pleted so far as fastening down the cover is concerned, the 
edge of the latter is finished with a neat coat of varnish. This 
varnish serves to do something more than merely ornament the 
slide; it secures the cover in its place, and prevents the drying 
up of the medium used for mounting. Even in the case of 
Canada balsam it is of use, for if gold size be used as the var- OF THE MICROSCOPE. 
233 
nish, ifc prevents the evaporation of the turpentine, anil the 
ultimate drying and cracking of the balsam. Where glycerine 
jelly, glycerine, or glycerine and gum are used, it becomes 
indispensable. i 
The process employed for finishing slides in this way is as 
follows: The objects having,been mounted, the slides are laid 
away until the balsam, cement, etc., have been hardened, when 
all superfluous matters of this kind are easily removed with a 
small chisel made out of a brad-awl ground thin and sharp. A 
small chisel-pointed piece of hard wood, and a little water, will 
remove the last traces of balsam or varnish, and if necessary a 
final cleaning may be given with a rag moistened with alcohol. 
The slide is then placed on the turn-table, and a neat ring of 
varnish, either plain or colored, is run around the edge. The 
varnish used for this purpose should be selected according to 
the material in which the object is mounted. Thus, for ob- 
jects in glycerine, glycerine jelly, or gum, the best coating is 
shellac varnish, which may be left quite transparent and 
colored with some of the aniline colors. Shellac also answers 
on Canada balsam, when the latter has become hard, but gold 
size is better, and the gold size may either be colored with 
the ordinary artists’ colors, which are sold in tubes, and 
which give an opaque-colored ring, or transparent colors may 
be used. 
Labeling the Slides.—The proper labeling of slides and 
material is a most important matter. All bottles should be 
labeled, not only on the bottles themselves, but on the corks 
or stoppers, and the slides should be kept labeled or numbered 
during every stage of their progress. Our system is as follows: 
Before the object is mounted the slide is labeled on the under 
side with a very thin gummed label. Numbering with the 
writing diamond is deferred until the mount is completed, be- 
cause, if spoilt, the whole may be thrown into a jar to be soaked 
off, and this cannot be done with figures written or scratched 
in with a diamond. As soon as the slide is finished the regular 
label is attached, and the slide numbered with a writing dia- 
mond. Of this number a record is kept, so that even if the label 
should fall off or get soaked off, a new label may be provided; 234 
SELECTION AND USE 
and unfortunately it sometimes happens that labels drop off 
either from exposure to moisture or excessive dryness. 
As regards designs, etc., for labels, the variety is endless. 
Each microscopist will probably select the one that accords 
most nearly with his own taste. The only suggestion that we 
■would make is that severe simplicity be adopted as the rule. 
Complicated and fancy labels look well at first, but they soon 
pall, and we get tired of them. It is well to have a large blank 
label at one end, on which memoranda may be written, such as 
the power best adapted to show the object; whether it is best 
seen by reflected, transmitted, or polarized light; the location 
of interesting points as determined by the Maltwood Finder, 
etc., etc. An important point also is the direction in which the 
reading should run—whether across or lengthwise of the slide. 
There seems to be no rule on this point, and it wrould be well 
for our societies to discuss this subject, and establish a rule for 
the benefit of exchangers. Nothing is more aggravating than a 
lot of slides labeled in different ways. The direction will de- 
pend, of course, upon the kind of cabinet used. For cabinets 
with racks, either way will answer, though the lengthwise direc- 
tion is somewhat the most convenient. For the old style Eng- 
lish cabinet, in which the objects lie flat and endwise to the front 
of the drawers, the writing should run across the slide. For our 
American cabinets with drawers having spaces divided off for 
each slide, the writing should be lengthwise of the slide. In 
short, when the slide lies in its proper position in the drawer, the 
lines of writing should run parallel with the front edge of the 
drawer. 
Cabinets.—The value, either for work or for exhibition, of 
a collection of microscopic objects, is greatly enhanced when 
they are properly arranged and easily accessible. Conse- 
quently every microscop ist who possesses even a small number 
of slides, should provide some kind of a case or cabinet for 
keeping them. 
The simplest form of case is one with racks, and these are 
made in a great variety of styles, forms, and sizes, from the 
simple mailing box, holding two or three slides, to large and 
expensive cabinets. The common box, with a hinged lid, and OF THE MICROSCOPE. 
235 
holding twenty-five objects, answers well for carrying a few 
objects to exhibitions and the like. The chief objections to 
this style of cabinet consist in the difficulty of lifting out any 
particular slide and of reading the names. The latter difficulty 
may be obviated by writing the names on the bottom of the 
box on a line with the slide; the first objection may be miti- 
gated by placing the spaces in the rack as far apart as possible. 
These rack boxes make altogether the cheapest cases, and when 
placed in cabinets holding, say, a dozen boxes, or three hun- 
dred slides, they form a very economical and convenient ar- 
rangement. The cabinet, or outer case, should, of course, be so 
made that the boxes will stand on end, as in this way the slides 
lie flat—a most important point. 
Cases or cabinets of shallow drawers in which the slides lie 
flat, with the labels fully exposed to view, are, however, alto- 
gether the best. They have been made of various forms. A 
cheap, simple case, holding about six dozen slides, may be had, 
in which the drawers do not slide in grooves, but lie one above 
the other. The only objection to this plan lies in the fact that 
all the drawers must be taken out if we wish to get at the lowest 
one; but where there are not more than a dozen drawers this is 
not a very serious difficulty, and the compactness, lightness and 
cheapness of the arrangement make it quite a favorite. 
In the English cabinets the slides lie with their ends towards 
the front of the drawer, so that the motion of pulling the drawer 
out or pushing it in, does not cause the slides to slip over each 
other. This is a very excellent arrangement, and one which 
we like better than any other. In the American cabinets as 
hitherto made, the slides lie with the long edges towards the 
front of the drawers, and are prevented from slipping over 
each other by small partitions which divide the rows into 
spaces one inch each in width. This is, theoretically, the most 
perfect arrangement, but it requires a little more room than 
the other. . The American cabinets have, however, one feature 
which is a most important one: The spaces in which the slides 
rest have a depression under the ends of the slides, and by 
pressing on the end, the slide is lifted so that it is very easily 
grasped. In the English cabinets this feature is wanting, and 
it is only with great trouble that a tightly-fitting slide can be 236 
taken from its place. Fortunately, any drawer which is deep 
enough, may have this device applied to it by simply glueing a 
thin strip of wood or pasteboard on the bottom of the drawer 
so as to raise up the part on which the slides rest, but leaving 
a space of about three-quarters of an inch under the end of the 
slide, into which the latter may be tipjied. 
SELECTION AND USE 
Tlie Maltwood Finder.—This is a most important ac- 
cessory to every microscope, as it not only facilitates inter- 
change of notes between 
microscopists living at a 
distance from each other, 
but it enables observers to 
make an accurate record of 
the position of any object, 
and thus make sure of its 
identity when under ex- 
amination at different times. It consists of a glass slip, a lit- 
tle wider than an ordinary slide, upon which is a photograph 
occupying a space 1 by 1 inch, as shown in figure 79. This 
space is divided into 2,500 squares (50 divisions on each side) 
and each of these small squares contains two numbers, one of 
which indicates its position from bottom to top, while the 
other marks its position from right to left. Thus the square 
which lies on the tenth line from the bottom, and the fifteenth 
from the right-hand side, would be 
MALTWOQD'S 
FINDER 
STOP, 
Fig. 79. 
The method of using the Finder is as follows: Placing on the 
stage an object mounted on an ordinary slide, with its lower 
edge against a ledge of some kind, and its left-hand edge against 
a stop (the stop and ledge both being movable as regards the 
stage), we bring some particular spot into view. Removing 
the slide, we now place the finder in its place, and read off the 
two numbers. It is now evident that if at any future time we 
should place the finder against the movable ledge and stop, and 
bring the same numbers into view, then on removing the finder 
and placing the slide on the stage and against the ledge and 
stop, which, of course, must occupy the same position that 
they did when the finder was in place, the precise spot origin- 
ally under examination will be in view. TVe can therefore OF THE MICROSCOPE. 
237 
easily register the location of any object of interest, and so be 
certain of finding it at any future time. 
The mechanical stage, or the ordinary movable glass stage, 
described at page 110, or that shown in Fig. 24 (page 111) af- 
fords special facilities for using the Maltwood Finder. But un- 
less fitted Avith some special contrivance, microscopes Avhich 
have only the ordinary 
clips, are unsuitable for 
this purpose. A movable 
ledge and stop, which 
may be used with the 
common spring clips, is, 
however, easily devised 
and made. We often use 
a simple Avooclen slide 
with a little projection on the edge near one end. The wooden 
slide must be thicker than the glass slide Avhich carries the 
object to be registered, as it is necessary that the springs should 
hold the wooden slide firmly in place, while the object-slide 
mo\Tes freely below the springs. A piece of vulcanite or hard 
rubber about the eighth of an inch thick and the size of the 
usual 3x1 glass slide answers admirably. It should have a 
stop fastened to one end, as shown in figure 80, Avhere a is the 
hard rubber slide, and b is a small piece of brass, let into the 
end and screwed fast. 
Fig. 80.—STOP FOR MALTWOOD FINDER. 
Microscopical Misinterpretations.—The observer 
Avho uses the compound microscope labors under certain dis- 
advantages Avhich do not affect those Avho examine large ob- 
jects Avhich can be handled, and thus subjected to the scrutiny 
of several senses. The fallacies to Avhich the microscopist is 
liable in this Avay deserve special attention and special precau- 
tions. We have already (page 198) alluded to certain fallacies 
of another kind, which must be avoided by such careful and 
extensive study as Avill enable us to recognize foreign matter 
Avhen Ave see it; the fallacies now under consideration can only 
be avoided by careful study of the laAvs of optics, and by intro- 
ducing considerable ATariety of methods into our examinations. 
One of these sources of fallacy arises from the liability Avhich 
most persons have to see objects pseudoscop ically, as it is called 
—that is to say, hollows appear to be elevations, and elevations 
appear to be IioHoavs. The extent to Avhich this tendency ex- 
ists is not generally recognized. Taking a gold coin, on Avhich 
the letters, etc., were knoAvn to be raised, Ave placed it under 
the microscope, and submitted it to seven intelligent persons. 
Out of these, five declared that they saw the letters sunk into 238 
SELECTION AND USE OF THE MICKOSCOPE. 
the metal; two said they were raised. In objects too small to 
be felt, and where sections cannot be made, the truth may be 
ascertained by watching the effect of raising or lowering the 
object glass in focussing. 
Another fallacy of this kind has led to the belief that hairs 
and many similar bodies are hollow. Seen under the micro- 
scope, a hair looks just as if it were a tube—but then, so does 
a wire, which is known to be solid. The test in this case is to 
make a cross section of the object. 
The true form of objects may frequently be determined by 
studying the effect of light and shade produced by sending 
the light across them in different directions. This is most 
readily effected by means of the revolving stage, which, for this 
purpose, should have very accurate rotation in the optic axis. 
The most singular fallacies, however, are those arising from 
certain illusions of vision, which affect every one, and which in 
ordinary practice, are easily corrected. For a full account of 
these, the reader is referred to the works of Helmholtz; a brief 
account of the most common cases is given in the Young Scientist 
for 1881. The one which is of most interest to microscopists is 
the famous optical illusion of Nachet, of which a figure is given 
below. In the course of his examination of the markings on the 
Fig. 81.—hatchet's optical illusion. 
P. Angulatum, M. Nachet found that if a series of round black 
dots be arranged on a white ground, as in Fig. 81, the dots, 
when viewed from a distance of twelve to twenty inches, will 
appear to be hexagonal, though we know that they are round. 
FINIS. Plate I. 
ROSS MODEL. 
As made by Ross & Co. As made by Bausch & Lomb Optical Company. 
JACKSON MODEL. NEW BIOLOGICAL STAND. 
As made by W, H. Bulloch, Plate IV. 
THE HISTOLOGICAL MICROSCOPE 
As made by Joseph Zervtmayer, Plate V, 
vAs made by Bausch Sc Lomb Optica! Company. 
the investigator microscope. THE ACME BINOCULAR MICROSCOPE. 
As made by J. W, Sidle & Co. CATALOGUE 
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Rhymes of Science: Wise and Otherwise. 
This consists of a series of short poems, chiefly hu- 
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By John Phin, Editor of the “ American Journal of 
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12 mo., Cloth, .... 75 cents. 
In this volume an attempt is made to trace the evolution of our 
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“ Practical Hints on the Selection and Use of the Micro- 
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Hand-Book of Urinary Analysis. 
For the Use of Physicians Medical Students, and Clinical Assistants. 
By FRANK HI. DEEMS, HI.B., Ph. !>., 
CHEMICAL AJN13 MICROSCOPICAL. 
Formerly Laboratory Instructor in the Medical Department of the University of New 
York; Member of the N. Y. County Medical Society; Member of the New 
York Microscopical Society,, etc. 
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LIST OF ILLUSTRATIONS. 
Frontispiece, Urinary Analysis Set (after Prof. Draper). i. Urinometer and 
Cylinder. 2. Separate Crystals of Diabetic Sugar. 3. Normal Deposit from Ammo- 
niacal Urine. 4. Extraneous Substances found in Urine, 5. Nitrate of Urea. 
6. Oxalate of Urea. 7. Apparatus for the Quantitative Estimation of Urea. 8. Com- 
mon Forms of Uric Acid. 10. “Hedge-hog” Crystals of Urate of Sodium. 
11. Crystals and Amorphous Deposit of Urate of Sodium, and Spherules of Urate 
of Ammonium. 12. Spherules of Ammonium Urate. 13. Hippuric Acid from Human 
Urine. 14. Oxalate of Lime. 15. Dumb-bells and Ovoids of Oxalate of Lime. 
16. Crystals of (‘ Stellar”) Phosphate of Lime. 17. Different Forms of Ammonio- 
magnesian (“triple”) Phosphate. 18. Crystals (“fern-leaf”) of Triple Phosphate. 
19. Leucin Spheres and Tyrosin Needles. 20. Cystin, Hexagonal Tablets and 
Prisms. 21. Xanthin from Human Urine. 22. Mucus Cloud. 23. Renal, Vesical, 
Urethral and Vaginal Epithelium. 24. Mode of Formation of Tube-casts. 26. Fatty 
and Blood Casts, Free Fatty Molecules. 27. Waxy Casts. 28. Mucus Casts. 
29. Blood Corpuscles in the Urine. 30. Pus Corpuscles. 31. Human Spermatozoids. 
32. Body and Upper Part of the Tail of a Spermatozoon. 33. Bacteria and Vibriones. 
14. Penicilium Glaucum, Aerial Fructification. 35. Torula Cerevisiae, Aerial Fructi- 
fication. 36. Sarcina in the Urine. 37. Apparatus for Collecting Urinary Sediments. 
38. The New Working Microscope. 
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HOW TO SEE WITH THE MICROSCOPE. 
JUST PUBLISHED. 
Being Useful Hints Connected with the Selection and Use of the Instrument: also 
Some Discussion of the Claims and Capacity of Modern High-Angled Objectives, 
as Compared with those of Medium Aperture. With Instructions as to the 
Selection and Use of American Object-Glasses of Wide Apertures. 
By J. EDWARDS SMITH, M. D. 
Professor of Histology and Microscopy; Corresponding Member San Francisco, 
Dunkirk, and other Microscopical Societies, etc., etc. 
Handsomely Illustrated. 
Prof. Smith is well known as the most expert manipulator in this country, as regards 
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A Manual of the Infusoria, 
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By W. SAVILLE KENT, F.L.S., F.Z.S , F.R M.S. 
This important work, the result of many years’ careful labor and investigation on the 
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HOW TO USE THE MICROSCOPE 
A SIMPLE AND PRACTICAL BOOK, INTENDED FOR BEGINNERS. 
JOHN PHIN, 
Editor of “ The American Journal of Microscopy." 
The Microscope.—What it Is; What it Does; Different Kinds of Microscopes; 
Principles of its Construction; Names of the Different Parts. 
Simple Microscopes.—Hand Magnifiers; Doublets; Power of Two or More 
Lenses When Used Together; Stanhope Lens; Coddington Lens; Achromatic 
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Stands; The Binocular Microscope; The Binocular Eye-piece; The Inverted Micro- 
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SpecialPurpo.es: “Class” Microscopes. 
Objectives.—Defects of Common Lenses; Spherical Aberration; Chromatic do.; 
Corrected Objectives; Defining Power; Achromatism; Aberration of Form; Flatness 
of Field; Angular Aperture: Penetrating Power ‘ Working Distance; Immersion and 
“Homogeneous” Lenses; Duplex Fronts; French Triplets, etc., etc. 
Testing Objectives.—General Rules; Accepted Standards—Diatoms, Ruled 
Lines, Artificial Star; Podura; Nobert’s Lines; Moiler’s Probe Platte, etc., etc. 
Selection of a Microscope —Must be Adapted to Requirements and Skill of 
User; Microscopes for Botany; For Physicians; For Students. 
Accessory Apparatus.—Stage Forceps; Forceps Carrier; Plain Slides; Concave 
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The Cell-Trough; The Compressorium ; Gravity Compressonum; Growing Slides; 
Frog Plate; Table; Double Nose-piece, 
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Illumination of Opaque Objects.—Bulls-Eye Condenser; Side Reflector; The 
Lieberkuhn; The Parabolic Reflector; Vertical Illuminators. 
Illumination of Transparent Objects.—Direct and Reflected Light; Axial or 
Central Ligh ; Oblique Light; The Achromatic Condenser; The Webster Condenser, 
and How to Useit; Wenham’s Reflex Illuminator, and How to Use it; The Wenham 
Prism; The “Half-Button;” The Woodward Illuminator; Tolies’ Illuminating 
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How to Use the Microscope.—General Rules; Hints to Beginners. 
How to Use Objectives of Large Aperture.—Collar-Correction, etc. 
Care of the Microscope.—Should be Kept Covered: Care of Objectives; Pre- 
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thr Objectives from Vapors which Corrode Glass; Cleaning the Objectives; Cleaning 
th Brass Work, 
Collecting Objects.—Where to Find Objects; What to Look for; How to Capture 
Them. 
The Preparation and Examination of Objects.—-Cutting Thin Sections of 
Sofi Substances: Valentine’s Knife; Sections of Wood and Bone; Improved Section 
Cutter; Sections of Rock; Knives; Scissors; Needles; Dissecting Pans and Dishes; 
Dissecting Microscopes; Separation of Deposits from Liquids; Preparing Whole 
Insects: Feet, Eyes, Tongues, Wings, etc , of Insects; Use of Chemical Tests; Liquids 
for Moistening Objects; Refractive Powers of Different Liquids; lod-Serum ; Artificial 
-od-Serum; Covers for Keeping Out Dust; Errors in Microscopic Observations. 
Preservative Processes.—General Principles; Preservative Media. 
Apparatus for Mounting Objects.—Slides: Covers; Cells; Turn-Tables,e'te. 
Cements and Varnishes.—General Rules for Using. 
Mounting Objects.—Mounting Transparent Objects Dry; in Balsam; in Liquids; 
Whole Insects: How to Get Rid of Air-Bubbles; Mounting Opaque Objects. 
Finishing the Slides.—Cabinets; Maltwood Finder; Microscopical Fallacies. 
CONDENSED TABLE OF CONTENTS. SUBSCRIPTION REDUCED TO $4.00. 
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London Lancet for 1882. 
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gently than they could without a knowledge of its contents. 
Many difficult and troublesome mathematical problems can be 
solved by the use of this tool, and the methods of solving them are 
shown in the work. It describes how Painting, Plastering, and Brick 
Work can be measured, and how many mechanical difficulties can be 
overcome with great ease. It explains how Ellipses, Parabolas, 
Octagons, Circles, and many other figures may be described bv the 
Steel Square. 
This is the “ book of the period ” for all who work in wood, and its 
low price places it within the reach of every journeyman and appren- 
tice in the land. The engravings are of a high order, and the whole 
is printed on heavy calendered paper. 
INDUSTRIAL PUBLICATION COMPANY, 
14 I>ey Street, New York. 
£ENT BY MAIL. TO AN V ABDRESs ON RECEIPT OF PRICE. THE WORKSHOP COMPANION. 
A Collection of Useful and Reliable Recipes, 
Rules, Processes, Methods, Wrinkles, 
and Practical Hints, 
FOR THE HOUSEHOEIfi THE SHOE. 
Abyssinian Gold:—Accidents, General Rules;-—Alabaster, how to work, polish and 
clean;—Alcohol:—Alloys, rules for making, and 26 recipes;—Amber, how to work, 
polish and mend;—Annealing and Hardening glass, copper, steel, etc.;—Arsenical 
Soap;—Arsenical Powder;—Beeswax, how to bleach;—Blackboards, how to make;— 
Brass, how to work, polish, color, varnish, whiten, deposit by electricity, clean, etc., 
etc.;—Brazing and Soldering;—Bronzing brass, wood, leather, etc.;—Burns, how to 
cure:—Case-hardening;—Catgut, how prepared;—Cements, general rules for using, and 
56 recipes for preparing;—Copper, working, welding, depositing;—Coral, artificial;— 
Cork, working;—Crayons for Blackboards;—Curling brass, iron, etc,;—Liquid Cu- 
ticle;—Etching copper, steel, glass;—Eye, accidents to;--Fires, to prevent;—Clothes on 
Fire;—Fireproof Dresses;—FlyPapers;—Freezing Mixtures, 6 recipes;—Fumigating 
Pastils;—Gilding metal, leather, wood, etc.;—Glass, cutting, drilling, turning in the 
lathe, fitting stoppers, removing tight stoppers, powdering, packing, imitating ground 
glass, washing glass vessels, etc.;—Grass, Dry, to stain; —Guns, to make shoot close, 
to keep from rusting, to brown the barrels of, etc., etc.;—Handles, to fasten ;—Inks, 
rules for selecting and preserving, and 34 recipes for;—Ink Eraser;—Inlaying;—Iron, 
forging, welding, case-hardening, zincing, tinning, do. in the cold, brightening, etc., 
etc.;—Ivory, to work, polish, bleach, etc.;—Javelle Water ;■ —Jewelry and Gilded Ware, 
care of, cleaning, coloring, etc.;—Lacquer, how to make and apply;—Laundry Gloss;— 
Skeleton Leaves;—Lights, signal and colored, also for tableaux, photography, etc., 25 
recipes:—Lubricators, selection of, 4 recipes for;—Marble, working, polishing, clean- 
ing;—Metals, polishing:—Mirrors, care of, to make, pure silver, etc., etc.;—Nickel, 
to plate with without a battery;—Noise, prevention of;—Pairting Bright Metals;— 
Paper, adhesive, barometer, glass, tracing, transfer, waxed, etc. Paper, to clean, take 
creases out of, remove water stains, mount drawing paper, to prepare for varnishing, 
etc., etc.;—Patina:—Patterns, to trace;—Pencils, indelible;—Pencil Marks, to fix;— 
Pewter;—Pillows for Sick Room, cheap and good;—Plaster-of-Paris, how to work;— 
Poisons, antidotes for, 12 recipes;—Polishing Powders, preparation and use ol (six 
pages);—Resins, their properties, etc.;—Saws, how to sharpen;--Sieves;—Shellac, 
properties and uses of;—Silver, properties of, oxidized, old, cleaning, to remove ink 
stains from, to dissolve from plated goods, etc., etc.;—Silvering metals, leather, iron, 
etc. ;—Size, preparation of various kinds of;—Skins, tanning and curing, do with haii 
on;—Stains, to remove from all kinds of goods;—Steel, tempering and working (six 
pages);—Tin, properties, methods of working;—Varnish, 21 recipes for; —Varnishing, 
directions for;—Voltaic Batteries:—Watch, care of;—Waterproofing, 7 recipes for;— 
Whitewash:—Wood Floors, waxing, staining, and polishing;—Wood, pol.'shii.g —• 
Wood, staining, 17 recipes;—Zinc, to pulverize, black varnish for. 
CONTENTS. 
164 closely-printed pages, neatly bound. Sent bv mail for 36 cent* 
(postage stamps received). Specimen pages free. 
INDUSTRIAL PUBLICATION COMPANY, 
14 Dey Street, New York. A NEW SERIES OF PRACTICAL ROOKS. 
WORK MANUALS 
The intention of the publishers is to give in this Series a number of small books which 
will give Thorough and Reliable Information in the plainest possible language, upon the 
./V 11 T S OF K VEBYB JL Y LIF EL 
Each volume will be by some one who is not only practically familiar with his 
subject, but who has the ability to make it clear to others. The volumes will each con- 
tain from 50 to 75 pages; will be neatly and clearly printed on good paper, and bound 
in tough and durable binding. The price will be 25 cents each. 
The following are the titles of the volumes, and the order in which they will be 
issued. No. I. is ready for delivery, No. II. is in press, and the others will follow 
at short intervals. 
I. Cements and. Glue. 
A Practical Treatise on the Preparation and Use of All Kinds of Cements, Glue 
and Paste. By John Phin, Editor of the Young Scientist and the American 
Journal of Microscopy. 
Every mechanic and householder will find this volume of almost everyday use. It 
contains nearly 200 recipes for the preparation of Cements for almost every conceivable 
purpose. 
II. The Slide Rule, and How to Use It. 
This is a compilation of Explanations, Rules and Instructions suitable for mechanics 
and others interested in the industrial arts. Rules are given for the measurement of 
all kinds of boards and planks, timber in the round or square, glaziers’ work and 
painting, brickwork, paviors’ work, tiling and slating, the measurement of vessels of 
various shapes, the wedge, inclined planes, wheels and axles, levers, the weighing and 
measurement of metals and all solid bodies, cylinders, cones, globes, octagon rules and 
formula, the measurement of circles, and a comparison of French and English measures, 
with much other information, useful to builders, carpenters, bricklayers, glaziers, 
paviors, slaters, machinists and other mechanics. 
Possessed of this little Book and a good Slide Rule, mechanics might carry in their 
pockets some hundreds of times the power of calculation that they now have in their 
heads, and the use of the instrument is very easily acquired. 
III. Construction, Use and Care of Drawing Instruments. 
Being a Treatise on Draughting Instruments, with Rules for their Use and 
Care, Explanations of Scales, Sectors and Protractors. Together with Memor- 
anda for Draughtsmen, Hints on Purchasing Paper, Ink, Instruments, Pencil--, 
etc. Also a Price List of all materials required by Draughtsmen. Illustrated 
with twenty-four Explanatory Illustrations. By Fred. T. Hodgson. 
IV. Plaster: How to Make aiicl How to Use It. 
V. Hints for Painters and Paper-hangers. 
VI. Rules, Tables, Data and Memoranda for Mechanics and 
Others. (Parti.) 
VII. The Construction and Use of Saws. 
With Directions for Filing, Setting, etc. 
VIII. Rules, Tables, Data and Memoranda for Mechanics and 
Others. (Part II.) 
INDUSTRIAL PUBLICATION CO., 
P. O. Box 3853. 
14 Bey Street, New York- GENESIS AND GEOLOGY 
The only really scientific and logical system of harmony betwee* 
Genesis and Geology is to be found in a little work, just published, 
and entitled 
THE CHEMICAL HISTORY 
OF 
The Sis Days of Creation. 
BY JOHN PHIN, C. E., 
EDITOR OF “HANDICRAFT.” 
1 vol., 12tno., cloth. 75 cents. 
In this work an attempt is made to show that the account given of the 
Creation, in the first chapter of Genesis, agrees literally with the record 
developed by the investigations of modern science. 
May be ordered through any bookseller. Single copies sent by mail, 
on receipt of price, 
The following are a few of the Opinions of the Press: 
This is a small book, but full of matter. The author believes in the book of Genesis 
as the 'work of Moses, and believes in the entire correctness of the statements made 
by Moses .in regard to the work of creation. He defends the accuracy of the first 
chapter of Genesis, and defends it from a scientific standpoint. We think this book 
is full of interest and value; and as the discussions concerning the harmony of science 
and ‘faith are rife at the present day, we commend the reasonings of Mr. Phin to the 
great number of readers and students who are investigating these subjects.—The 
Presbyterian (Philadelphia). 
The author gives a new solution of this difficult question, and certainly presents 
many very plausible arguments in support of his theory.—Sunday-School Workman. 
A very candid and ingenious essay.—Christian Union (H. W. Beecher’s paper). 
It is a topic which needs a calm and well-directed intellect to approach, and Mr. Phin 
has surrounded its discussion with thoughts of the deepest interest to all minds seek- 
ing rest on this much perplexing question.—Journal of the Telegraph. 
The reasons and conclusions are clear, distinct, and natural. The book will interest 
and instruct, and is intended to lead the reasoning mind to firmer faith in the light oi 
revelation.—New York Globe. 
No one can read this book without compensation, without becoming more thoughtful 
concerning the phenomena of creation; and he need lose none of his reverence for the 
supremacy of the Divine Law.—Rural New-Yorker. 
We could say much in commendation of Prof. Phin’s little book. An intelligent 
reader can hardly fail to be interested in it, and many might be benefited.—Country 
Gentleman. 
The book can not fell to interest even those who do not fully accept the theory it 
advocates.—Boston Journal of Chemistry. 
It is a new scientific view of the matter.—Phrenological Journal. 
The book, although not large, will prove exceedingly interesting to all who have 
ever directed attention to this matter, and contains more solid and suggestive thought 
than many voluminous treatises on the subject.—Insurance Monitor. 
The work is ingenious and original, and presents many striking suggestions.—Ameri- 
can Baptist. 
We believe Prof. Phin has started upon the correct basis, and his theory is mainly 
tenable. His views are presented in a manner which, though terse, is easily compre- 
hended.—Paterson Daily Guardian. A New and Live Book on the Gun• 
Just Published. Price 75 cents, in cloth. 
PLAIN DIRECTIONS 
SHOOTING ON THE WING. 
FOR ACQUIRING THE ART OF 
With Useful Hints concerning all that relates to Guns and Shoot' 
ing, and particularly in regard to the art of Loading so as 
to Kill. To which has been added several Valuable 
and hitherto Secret Recipes, of Great Practical 
Importance to the Sportsman. 
AN OLD GAMEKEEPER 
Sent free by mail on receipt of price. 
Opinions of the JFreiS. 
The directions are so plain that they cannot well be mistaken, 
and they are expressed in the fewest possible words.—Turf, Field 
and Farm. 
Facing the title-page is one of the handsomest, best-executed 
woodcuts, we have ever seen. It is entitled “The Wounded 
Snipe,” and almost equals a steel engraving.—Baptist Union. 
From its pages we should think even the most experienced 
sportsman might derive some new ideas, while the beginner will 
And it an invaluable assistant.—Country Gentleman. 
For concise instructions as to how to shoot, to select, load, 
jarry, and keep a gun in order, etc., it cannot be surpassed.— 
Western Rural. 
1 pleasantly written, and, it seems, to us, correct and practical 
treatise on the sportsman’s art; a modest little book, but one from 
the reading of which a good deal ot the right kind of knowledge 
is to be gained.—Appleton's Journal 
>A practical and well-written handbook, especially adapted for 
one use of young sportsmen, as it gives sensible advice on the 
manipulation of firearms, and the rules and etiquette of the field. 
Scientific American, THE YOUNG SCIENTIST, 
A Practical Journal for Amateurs. 
ISSUED MONTHLY. Price 50 Cents per year. 
Tt is characteristic of young Americans that they want to be doing something. 
They are not content with merely knowing how things are done, or even with 
seting them done; they want to do them themselves. In other words, they want 
to experiment. Hence the wonder*’! demand that has sprung up for small tool 
cnests, turning lathes, scroll saws, wood carving tools, telegraphs, model steam 
engines, microscopes and all kinds of apparatus. In nine cases out of ten, how- 
ever, the young workman finds it difficult to learn how to use his tools or ap- 
paratus after he has got them. It is true that we have a large number of very 
excellent text-books, but these are not just the thing. What is wanted is a liv- 
ing teacher. Where a living teacher cannot be louud, the next best thing is a 
live journal, and this we propose to furnish. Audio attempting this it is not 
our intention to confine ourselves to mere practical directions. In these days 
of knowledge and scientific culture, the “ Why ” becomes as necessary as the 
"How.” Theobjectof theYouNG Scientist is to give clear and easily followed 
directions for performing chemical, mechanical and other operations, as well as 
simple and accurate explanations of the principles involved in the various 
mechanical asd chemical processes which we shall undertake to describe. 
The scope and character of the journal will be better understood from an in- 
spection of a few numbers, or from the list of contents found on a subsequent 
page, than from any labored description, There are, however, three features to 
which we would call special attention: 
Correspondence.—In this department we intend to place our readers in com- 
munication with each other, and in this way we hope to secure for every one 
just such aid as may be required for any special work on hsnd. 
Exchanges.—An exchange column, like that which has been such a marked 
success in the Journal of Microscopy, will be opened in the Young Scientist. 
Yearly subscribers who may wish to exchange tools, apparatus, boobs, or the 
products of their skill, can slate what they have to offer and what they want, 
without charge. Buying and se ling must, of course, be carried on In the adver- 
tising columns. 
Illustrations.—The journal will make no claims to the character of a "pic- 
ture book,” but wherever engravings are needed to make the descriptions clear 
they will be furnished. Some of the engravings which have already appeared in 
our pages are as fine as anything to be found in the most expensive journals. 
Special Notice. 
As our journal is too small and too low-priced to claim the attention of news 
dealers, we are compelled to rely almost wholly upon subscriptions sentdirectly 
to this office. As many persons would no doubt like to examine a few numbers 
before becoming regular subsorib rs, we will send four current numbers as a 
trial trip f. r 
FIFTEEN CENTS. 
Where three or more subscribe together for the journal, we offer the following 
liberal terms: 
3 copies for , $1.26 
6 “ “ 2.00 
7 “ “ 2.75 
10 “ “ 3.50 
Advertisements, 30 cents per line. 
As postal currency has nearly disappeared from circulation, we receive post 
age stamps of the lower denominations (ones, twos and threes) attheirfull value. 
Postal orders are, however, much safer and more convenient. To avoid delay 
and mistakes address all communications to “ The Young Scientist, Box 2852 
New York,” and make all checks and orders payable to John Phin. 
CLUBS. WHAT PEOPLE SAY OF US. 
In a letter to the Editor, Oliver Wendel Holmes, the genial “Autocrat 
of the Breakfast Table,” says: “I am much pleased with the Young 
Scientist. It makes me want to be a boy again.” 
“It is a little publication, calculated to call out and educate all the 
latent ingenuity and thirst for knowledge which the youthful mind pos- 
sesses, and we hope it will win its way into every household in the laud.”— 
[Scientific Press. 
“We have never seen a periodical, designed for youth, which came 
nearer to our ideal of what such a journal should be.”—[Canadian Phar- 
maceutical Journal. 
“The Young Scientist is one of the choicest publications for juvenile 
minds in this country. Every page treats on subjects of importance to 
young and old, portrayed in a clearly comprehensive manner, which at 
once interests the young idea in its careful perusal.”—[Lapeer Clarion. 
“It seems to fill the bill.”—[Newport Daily News. 
“It is pleasing to note that its youthful subscribers will not be misled 
by clap-trap advertisements or advertisements of patent medicines, which 
will not be received at any price. The Young Scientist is doing good 
work ih setting its face against this class of humbugs.”—[Manufacturing 
and Trade Beview. 
“The work is a copiously illustrated monthly, and is full of practical 
hints that will instruct and amuse the young folks.”—[Industrial ScHfcol 
Advocate. 
“A small but elegant and very instructive monthly.”—[Pittsburg 
Chronicle. 
“ Contains the best possible reading for the young of both sexes.”— 
[Ottawa Journal. 
“ We can safely recommend this magazine as one of the very best 
publications for the young folks.”—[The Independent, Fenton, Mich. 
* This journal occupies a new field, and is needed to put the minds of 
our youth on the right track to secure a correct understanding of the 
nature of things.”—[Wayland Press. 
“It is ably edited by John Phin, who will make a large -uace in the 
heart of the rising generation, if he persists in his venture. We hope his 
success in the field will be equal to the article furnished—first best.”— 
[Sunset Chimes. 
“ The articles are written in a popular, readable style, and profusely 
illustrated.”—Akron City Times. 
“The Young Scientist is excellent in conception, and well designed to 
amuse and instruct young people.”—[Chicago Evening Journal. 
“ The Young Scientist is a handsome monthly magazine, each number 
containing about 16 pages, handsomely illustrated. It will supply a 
place which baa been heretofore unoccupied. The copy before us eomes 
fully up to the promise of the prospectus.”—[The Times, Iroquois, Mich. 
“It is a journal which should be in the hands of both young and old, 
and is a great benefit to the young scientist as well as the advanced pro- 
fessor. It is a thousand times more valuable than the dime novel series, 
so much read by boys. Parents would do well to have it in their house- 
holds.”—[The Iron Home. 
“This publication is a new launch, and it i- very gratifying to witness 
the ableness which pervades its pages.”—Amherst Free Press. THE AMERICAN 
Journal of Microscopy. 
The object of the Journal of Microscopy is to diffuse a knowledge of the best 
methods of using the Microscope; of all valuable improvements in the instrument and 
its accessories: of all new methods of microscopical investigation, and of the most 
recent results of microscopical research. The Journal does not address itself to those 
who have long pursued certain special lines of research, and whose wants can be 
supplied only by elaborate papers, which, from their thoroughness, are entitled to be 
called monographs rather than mere articles. It is intended rather to meet the wants 
of those who use the microscope for purposes of general study, medical work, class 
Instruction, and even amusement, and who desire, in addition to the information afforded 
by text-books, such a knowledge of what others are doing as can be derived only from 
a periodical. With this object in view, therefore, the publishers propose to make the 
Journal so simple, practical and trustworthy, that it will prove to the advantage 
of every one who uses the microscope at all to take it. 
PROSPECTUS-SIXTH YEAR—1881 
ILLUSTRATIONS.—The Journal will be freely illustrated by engravings 
representing either objects of natural history or apparatus connected with the 
microscope. 
TRANSACTIONS OF SOCIETIES.—The American Journal of Micro- 
scopy is not the organ of any Society, but it gives the proceedings of all Societies 
whose officers send us a report. As the Journal is devoted w}wlly to Microscopy, and 
is in §ood form and size for binding, no better medium can be had for preserving the 
scientific records of any Society. Matters of mere business routine we are frequently 
obliged to omit for want of room. 
EXCHANGES.—An important feature of the Journal is the exchange column, by 
means of which workers in different parts of the country are enabled, without expense, 
except for postage, to exchange slides and materials with each other. 
Published Monthly at $1.00 a year. 
SPECIMENS FREE. 
Four copies for three dollars. Those who wish to economize in the direction of 
periodicals, would do well to examine our clubbing list. 
Foreign Subscribers.—The Journal will be sent, postage paid, to any country in 
the Postal Union for $1.24, or 5 shillings sterling per year. English postage stamps, 
American currency or American postage stamps taken in payment. In return for a 
postal order or draft for £1 ss., five copies of the Journal will be furnished and mailed 
to different addresses. Make all drafts and postal orders payable to John Phin. 
BacK Volumes. 
Yol. I is out of print. We are occasionally able to complete volumes which, when 
bound, we offer for $1.50. Of Vols. II, III and IV we have a few copies on hand. 
Price each. 
A.dLvertisem cuts. 
The Journal of Microscopy, from its very nature, is a visitor to the very best 
families, and its value as an advertising medium has therefore proved to be much 
above that of average periodicals. A few select advertisements will be inserted at the 
rate of 30 cents per line, nonpariel measure, of which twelve lines make an inch. 
Address 
AMERICAN JOURNAL OF MICROSCOPY, 
P. O. Box 2852, New York. NEW DESIGNS 
FOK 
Eret or Scroll Sawyers. 
MR. F. T. HODGSON, whose admirable series of articles on the USE OF THE 
SCROLL SAW are now in course of publication in the Young Scientist, has pre- 
pared for us a series of 
of which the following is a list: 
No. i.—This shows one side, back, and bottom, of a pen rack. It may be made 
of ebony, walnut, or other dark wood. 
No. 2.—Design for inlaying drawer fronts, table tops, box lids, and many other 
things. It is a sumach leaf pattern. 
No. 3.—Design for a thermometer stand. It may be made of any hard wood or 
alabaster. The method of putting together is obvious. 
No. 4.—This shows a design for a lamp screen. The open part may be covered 
with tinted silk, or other suitable material, with some appropriate device worked on 
with the needle, or, if preferred, ornaments may be painted on the silk, etc. 
No. 5.—A case for containing visiting cards. Will look best made of white holly. 
No. 6.—A placque stand, it may be made of any kind of dark or medium wood. 
No. 7.—A design for ornaments suitable for a window cornice. It should be 
made of black walnut, and overlaid on some light colored hard wood. 
No. 8—A design for a jewel casket. This will be very pretty made of white holly 
and lined with blue velvet. It also looks well made of ebony lined with crimson. 
No. 9.—Frame. Will look well made of any dark wood. 
No. 10.—Frame. Intended to be made in pairs. Looks well made of white holly, 
with leaves and flowers painted on wide stile. 
No. 11.—Horseshoe. Can be made of any kind of wood and used for a pen rack. 
When decorated with gold and colors, looks very handsome. 
No. 12.—Design for a hinge strap. If made of black walnut, and planted on a 
white or oaken door, will look well. 
No. 13.—Design for a napkin ring. May be made of any kind of hard wood. 
No. 14.—Hinge strap for doors with narrow stiles. 
No. 15.—Centre ornament for panel. 
No. 16.—Corner ornament for panel. 
No. 17.—Key-hole escutcheon. 
These designs we have had photo-lithographed and printed on good paper, so that 
the outlines are sharp, and the opposite sides of each design symmetrical. Common 
designs are printed from coarse wooden blocks, and are rough and unequal, so that 
it is often impossible to make good work from them. 
The series embraces over forty different pieces, and designs of equal quality cannot 
be had for less than five, ten or fifteen cents each. We offer them for twenty-five 
Cents for the set, which is an average price of only one cent and a half each. 
SEVENTEEN DESIGNS, 
Mailed to any address on receipt of price. 
INDUSTRIAL PUBLICATION CO., 
14 Dej Street, New York.