ON THE CRYSTALLINE NATURE OF GLASS. [From the American Journal of Science and Arts, Yol. XLI.—Jan., 1866.] 
On the Crystalline Nature of Glass, 
By Charles M. Wetherill, Ph.D., M.D.1 
The usual explanation given for the different appearance of 
etchings by hydrofluoric acid in the gaseous and in the liquid 
state, is that by employing gas, the products of decomposition 
of the glass remain in the corroded cavities communicating a 
ground-glass appearance. This does not obtain by the use of 
the liquid acid, since in this case the said products are removed 
from the cavities. 
An examination of this subject by the aid of the microscope 
at once showed that the ordinary explanation is erroneous. 
Ground glass is seen, under the microscope, to be covered with 
irregular cavities of uniform size, which act by the dispersion of 
light to produce the characteristic appearance of glass in this 
condition. 
When glass is exposed to the vapor of hydrofluoric acid, the 
corrodent is deposited in the condition of minute globules, each 
of which attacks the surface to which it is attached. Articles of 
glass placed near the apparatus in which the gas is generated are 
thus coated with a delicate film of the vapor, and are etched, so 
that the microscope exhibits extremely minute and shallow cav- 
ities in which, after cleansing the surface by water, no trace of 
other substance than glass is perceptible. When the exposure 
to the acid fumes is more prolonged, the cavities are deeper and 
more irregular. A still greater irregularity is effected by a more 
lengthened action of the corrosive vapor; the acid acts more in- 
tensely upon the spots first attacked, and the holes are extended 
with ragged margins and deepened by the action. 
On the other hand, when the glass is immersed in liquid hy- 
drofluoric acid, or if a drop of the same be suffered to fall upon 
the plate, the whole surface is corroded with a certain degree of 
uniformity. There are no minute points of action as in the caso 
of the deposition of spherules of the acid vapor. 
Hydrofluoric acid gas, so called, is thus shown to be a vapor, 
constituted of minute drops, like cloud. It would be interesting 
to test the effect upon glass of the perfectly anhydrous gas ob- 
tained lately. From these considerations, hydrofluoric gas appears 
to possess in an eminent degree the cloud-forming property of 
antozone. An appreciable quantity of this substance exists in 
the Woelsendorf fluor spar, and it may be questioned whether 
all specimens of this mineral do not contain traces of antozone. 
In observing the specimens etched by the liquid acid, the crys- 
talline nature of glass was discovered and witnessed in every 
1 The observations of which an account is here given were made in the labora- 
tory of the Smithsonian Institute, Washington. C. M. Welherill on the Crystalline Nature of Glass. 
3 
case. By an examination of the literature of the subject it was 
ascertained that Leydolt (Wiener Acad. Bericht, viii, 261) had 
made this interesting and important discovery. I have been in- 
clined to publish my results because Leydolt*s observations do 
not appear to have received the attention which they merit; be- 
cause my manner of applying the acid is different; and because 
crystals were observed of form differing from those described in 
Leydolt’s paper. 
In addition to these reasons, his discovery may appear to need 
a certain confirmation, since Daubree has asserted (Comptes 
Bend., xlv, 792) that the crystalline phenomena are due not to 
the glass, but to the deposition of crystals of fluosilicid of potas- 
sium, &c., which retard the corrosive action by protecting the 
glass under them. In the following experiments with as pro- 
longed a microscopic observation as the object-glass could be 
trusted to the corrosive fumes, the result of the reaction of a 
drop of the acid upon the glass appeared to be amorphous. In 
an experiment in which a watch glass was exposed, with the 
convex surface downward, as a cover to a platinum crucible 
containing hydrofluoric acid, a lapse of twelve hours effected a 
deep corrosion. This was most extensive at the lowest point of 
the glass where a large drop of liquid was adhering. The solid 
products of the reaction had settled to the inferior portion of 
the drop, and some of them had fallen with previous drops into 
the crucible. A microscopic examination of the glass demon- 
strated the presence of etched crystals, which could not, under 
the circumstances, have resulted from a protecting effect of crys- 
tals of fluosilicid. 
Frankenheim (Jr. pr. Ch., liv, 480) maintains that solid bodies 
generated from a liquid are always crystalline, although the crys- 
tals may be too minute to be perceptible by our present instru- 
ments. His arguments, in the cases of glass, resins and the like, 
are a priori, being based upon the analogies proceeding from a 
study of the general properties of matter. They render the crys- 
talline character of glass very probable. 
This chemist places the glasses, resins, and fats in the same 
category in their relations to crystallization. In the transition 
of these bodies to liquids by an elevation of temperature, they 
pass through conditions of softness and semi-fluidity before melt- 
ing. This softening does not depend upon a malleability, as in 
the case of metals. Glass, for example, remains perfectly brit- 
tle to a certain temperature, and when fusion begins to take 
place the angles are rounded by the cohesion of the liquid por- 
tions and the adhesion of these to the parts not yet melted, xlt 
a higher temperature, the liquid portion constitutes the mass of 
the body, but in it are suspended innumerable solid particles, 
which communicate to it a sticky or gelatinous character. 
Am. Jour. Sci.—Second Series, Vol. XLI, No. 121.—Jan., 1860. 4 
C. M. Wetherill on the Crystalline Nature of Glass. 
When melted glass cools, its least fusible compounds separate 
at first, and when the refrigeration is gradual a distinct crystal- 
lization takes place. By a rapid cooling the crystals must be 
more numerous and much smaller. If they cannot be detected 
in such glass by the eye or by aid of the microscope, the reason 
may be in their extreme tenuity, so that the light behaves to 
them as to the natural roughness of the polished surface. The 
author observes that silica is often separated in so fine a condi- 
tion that it passes through the small pores of the filter. He 
finds no reason in the phenomena of this class of bodies for an 
actual amorphism; but assumes that they are composed of crys- 
tals, which, although really small, are large in relation to the 
atomic molecules of the bodies. 
He concludes (op. cit., p. 476) that “ amorphous bodies, in the 
ordinary sense of the expression, are unknown among solids, for 
solidity depends upon crystallization.” 
Gaudin, in his brochure (Reforme de la Chemie Minerale et Or- 
ganique, Paris, 1863), endeavors to show what crystalline forms 
are probable for all bodies, deducing his results from the num- 
ber of atoms in their chemical formulae and the simplest man- 
ner in which they may be arranged. Chemists are divided as to 
the reliance to be placed upon Gaudin’s views; but if they are 
tenable, or if in any degree founded upon reasonable grounds, 
the crystalline condition of all solid bodies would seem to be a 
necessary consequence. 
Pelouze (Comptes Rendus, xl, 1321), in an investigation of the 
devitrefication of glass, as in the so-called porcelain of Reaumur, 
exposed a tablet of plate glass to incipient fusion upon the sole 
of a glass furnace for a period of 24-48 hours, and then suffered 
it to cool slowly. The result was a porcelain-like substance con- 
sisting of numerous opaque acicular crystals which were ar- 
ranged in parallel series, the individuals being perpendicular to 
the surface of the plate. It was found that the crystallization 
proceeded from the surface to the interior of the tablet, and that 
when the process was arrested there was a distinct line of de- 
marcation between the crystalline and vitreous portions. In 
rare instances the fibrous structure was wanting, and the crystal- 
lization was of such nature that the fractured glass presented the 
appearance of fine white marble. Occasionally the crystals were 
replaced by an enamel-like material. In repeated experiments 
of this character Pelouze found that the glass experienced no 
chaDge of weight during the devitrefication, and the altered glass 
was restored to its transparency by a simple fusion. The pro- 
cess might be repeated several times without any alteration of 
weight. Devitrefied window glass, and more especially bottle 
glass when in large masses in the melting pots, sometimes exhib- 
ited yellowish-green needles, which were -occasionally small and C. M. Wetherill on the Crystalline Nature of Glass. 
5 
short, but often exceeded a centimeter in length, being closely ad- 
herent one to another and interwoven in all directions. The vacant 
spaces between the crystals recalled the crystallization of sulphur. 
The crystallization of the glass was assisted by the addition of 
infusible or difficultly fusible substances to it when in the pasty 
condition. This is shown by the following experiment per- 
formed upon portions of material weighing one hundred kilo- 
grams. 
Two melting pots were half filled with the same kind of glass, 
which was at first melted and then suffered to cool until it had 
assumed a pasty or tenacious consistence. To one crucible a 
small quantity of vitreous matter was added, and both pots were 
suffered to cool. That to which nothing had been added con- 
tained a transparent glassy mass, while the material in the other 
crucible was nearly opaque from crystal aggregations. One per 
cent of sand added to the pasty glass produced the same effect; 
and when quartz was employed the mineral retained its transpa- 
rency, remaining mingled with the devitrefied mass. 
Pelouze found that mirror, plate, lead, bottle, and Bohemian 
glasses were all susceptible of devitrefication, although with dif- 
ferent degrees of readiness, the tri-silicate of soda being the most 
ready. A glass of silica, boracic acid, potassa and zinc yielded 
mere traces of crystallization; but the combination of silica and 
boracic acid with potassa and lime could not be devitrefied by an 
exposure of ninety-six hours to a temperature at which softening 
took place. 
This chemist infers that the change experienced by glass du- 
ring this process is a physical, and not a chemical one. He 
states, as the result of many analyses performed by himself, that 
the crystals do not differ in composition from the vitreous mass 
in which they are embedded. 
Dumas (op. cit.) takes exceptions to some of Pelouze’s infer- 
ences, having found a difference in the constitution of the glassy 
and crystallized portions of the mass. Thus, in respect to silica ; 
for the vitreous portion 6P7 per cent, and in the crystals 68’2. 
Leblanc found in the two kinds respectively : for mirror glass 
662 and 69*3; for bottle glass 57-9 and 62’95. In the bottle 
glass Leblanc found that the transparent portions contained 1*57 
per cent of protoxyd of iron, although only indistinct traces of 
this base were detected in the opaque part. 
Dumas therefore holds that the products obtained by Pelouze 
are “analogous to mixtures of the fatty acids, which by fusion 
form a homogeneous liquid, which by cooling gives a fibrous 
solid, in which although the eye can perceive nothing hetero- 
geneous, each acid has separated in its own crystal form.” 
Terreil (Comptes Rendns, xlv, 698) observed in the melting 
pots of a glass furnace which had cooled very slowly, a perfectly C. M. Wetherill on the Crystalline Nature of Glass. 
crystalline mass which with small transparent 
crystals. These had a composition similar to that of a transpa- 
rent bottle glass prepared from the same materials in the same 
proportions. Thus: 
Glass crystals. Bottle glass. 
Silica, 55-85 56-84 
Lime, 24*14 21-15 
Magnesia, 7-63 6-37 
Alumina, 2-22 3-64 
Peroxyd iron, 1-06 2-59 
Soda, 8-47 8-69 
Potassa, 0-63 0-40 
Manganese, traces traces 
100-00 99-68 
Spec, gravity, 2-824 2-724 
For the composition of a partially devitrefied glass which was 
formed in the same furnace, under different circumstances, he 
found: 
Vitreous part. Devitrefied part. 
Silica, 62-40 63-67 
Lime, 18-14 18-65 
Magnesia, 4-47 6-12 
Alumina, 7-21 4-98 
Peroxyd iron, 2-66 0-71 
Alkalies, 5‘12 5"87 
Manganese, traces traces 
100-00 100-00 
Spec, gravity, 2-610 2-857 
Leydolt (Wien. Acad. Bericht, viii, 261) introduces his experi- 
ments upon glass etching by observations of himself and others 
upon specimens of glass and slag in which crystals are visible 
without the aid of hydrofluoric acid. 
Thus Prechtl melted a considerable quantity of feldspar with 
one and a half cwt. of glass and cooled the mass in water. In 
the inside of the lump, where the refrigeration had been more 
gradual, were found numerous crystals of feldspar, with well 
defined angles and edges, one of the crystals having the volume 
of a cubic inch. 
Among the specimens of glass with perceptible crystals illus- 
trated by Leydolt are the following: 
1. Green flint glass, perfectly transparent, containing opaque 
grains, which are resolved by the microscope into well defined 
octahedra of one-half a line in diameter. 
2. A glass flux, of emerald color, containing many groups of 
four-sided prisms, of white tinge and pearly luster. C. M. Wetherill on the Crystalline Nature of Glass. 
7 
3. A large mass of blackish green glass, with prismatic crys- 
tals singly and in aggregations, also librous crystals in globular 
tufts. The color of the crystals is dirty yellow, passing into 
green; their luster pearly. They had a rhomboidal section, 
and were a line in length by one-eighth of a line in thickness. 
4. A bluish green English glass, containing tufts of needles 
uniting to globules of one and a half lines in diameter. 
5. A glass flux, of red and green color, containing a large 
quantity of small four-sided prisms, solitary, and in tufts. The 
prisms were transparent, and of the same color as the glass, so 
that they could only be distinguished by the different degree of 
their refraction and that of the matrix. 
6. A vitreous iron slag, of bottle-green color, containing per- 
fect cubes of whitish tinge and pearly luster; also feathery 
crystals. 
’ 7. Another specimen of iron ore slag, similar to the last; but 
in which the cubes are larger, of nearly the color of the glass, 
and more equally diffused through the mass. 
In a similar slag the cubes were of olive-green color, and in an- 
other specimen the cubes were sparse and accompanied by feath- 
ery crystals. To these may be added the observations of Split- 
gerber (Pogg. Ann., lxxvi, 566), that in a lead glass slag pre- 
sented to Faraday by H. Rose, he found large and well defined 
six-sided tablets. In a glass prepared with 100 silica, 40 soda, and 
10 carbonate of lime, which were perfectly fused and suffered to 
cool slowly for six hours, he discovered fine acicular crystals 
grouped star-wise, like flakes of snow. These floated in quantity 
in the melted liquid, and disappeared when the temperature of the 
crucible was raised again. 
Ley dolt’s experiments of etching were performed by placing 
slips of glass in a mixture of fluor spar and oil of vitriol; by 
exposing glass plates to an atmosphere of hydrofluoric acid va- 
por ; or finally by employing a very dilute solution of this acid 
contained in leaden vessels. 
The following are his results: 
1. A thick tablet of fine colorless mirror plate glass, after ex- 
posure to the vapor, was covered with colorless rhomboidal crys- 
tals. They projected from the plate, were perceptible to the 
touch, and plainly visible to the naked eye, from the contrast 
between their lustrous surfaces and the rough etched background. 
He obtained similar forms by fluor spar and oil of vitriol, and 
also by the use of the dilute acid. He infers that they are not 
quartz, which does not dissolve in hydrofluoric acid, but that they 
are of similar nature to that of their matrix. 
2. A flint glass of bluish color, passing into violet, transpa- 
rent, and apparently homogeneous, yielded crystals by careful 
etching. Ordinary window glass gave similar crystals which 
were of the form of rectangular tablets. 8 
C. M. Wether ill on the Crystalline Nature of Glass. 
3. A pure transparent English glass (a salt cellar), various 
vessels of French and Bohemian ware, very thick glass stoppers, 
glass of various colors, such as white bluish or green, and differ- 
ently tinted glass fluxes and plates, all yielded similar crystals. 
4. Some of the dilute residue of the reaction of sulphuric 
acid upon fluor spar having been left in a beaker glass, etched 
the same, with beautiful tufts of fibrous crystals, giving the ap- 
pearance of some specimens of agate. 
Leydolt infers from his experiments that all glass consists of 
an amorphous mass containing a variable proportion of crystals, 
and consequently; that not only density , and composition, but 
also the more or less uniform distribution of the crystals, and 
their nature have a marked influence upon the character and op- 
tical behavior of the glass. 
He deems the following questions to be of importance. 
1. Upon what circumstances depends the formation of the 
crystals in relation to quantity? 
2. What influence have the crystals upon optic phenomena ? 
I 3. May not their presence have an influence upon the doubly 
refracting character which glass acquires by heating and sudden 
cooling; or by pressure? 
4. What substances may be dissolved..in melted glass and sep- 
arated therefrom by slow cooling! 
Daubrde (C. R, xlv, 792) obtained various crystals by expos- 
ing glass for weeks to the-action of water and steam in sealed 
iron vessels, at a temperature of 400° C. The glass was con- 
verted into a white, swollen, kaolin-like substance, composed al- 
most entirely of crystalline particles. He found many crystals 
of quartz, and also acicular forms of nearly the same composi- 
tion as Wollastonite (53 p. c. silica, 46 lime ; with traces of mag- 
nesia). The quantity of water equalled half the weight of the 
glass, and the action of the water was the same as that of the 
steam. 
Daubree does not believe that the crystals preexisted in the 
glass; but were formed by the action of the water. Although 
this is probable, it may be questioned whether some of the crys- 
tals were not ready formed in the glass. 
My own experiments were performed by dropping strong 
liquid hydrofluoric acid upon plates of glass, using one or suc- 
cessive drops, according to the degree of etching desired. By 
this means the energy of the acid is expended upon one particu- 
lar spot of the glass, and by taking more or less of the solvent, 
or by employing it of greater or less strength, the reaction is 
completely under control. 
The acid was generated in the usual manner in a leaden retort 
with a condensing tube of the same metal, cooled with a mix- 
ture of salt and ice; the liquid acid was received in a platinum 
crucible, also refrigerated. C. M. Wetherill on the Crystalline Nature of Glass. 
The following are the results of the experiments: 
When the vapor escaping from the crucible was condensed 
upon plates of glass, a “ground glass’’ etching, with in some in- 
stances distinct traces of crystallization, resulted. 
The following is the action of the liquid acid upon different 
kinds of glass. 
1. Greenish window glass, free from lead. One drop of the 
acid acted energetically, ' coating the glass with a white sediment. 
When washed, the spot was found to be deeply etched, and pre- 
sented a roughened although transparent appearance. Under 
the microscope, with oblique, transmitted light, the surface was 
found to be covered with a web of acicular crystalsncrossing at 
alb angles, and presenting exactly the appearance of sublimed 
caffeine. The average length of the needlesjwas 0'08 of a 
millimeter; their thickness somewhat less than 0’006 mm. 
It was difficult at first to determine whether the crystals were 
elevated, or depressed below the surface of the plate, in which 
case they would have represented casts of crystals dissolved out 
by the acid; but by,careful management of the light, studying 
the shadows and comparing them with caffeine crystals, they 
were judged to be in relief. Polarized lignjt had no effect upon 
them. Beside these crystals, there were observed scattered over 
tlie field of view a few irregular etchings, in intaglio, which 
seemed to be casts of crystalline scales dissolved out by the hy- 
drofluoric acid, 
2. A piece of the same plate m glass was treated with succes- 
sive drops of the acid upon the same spot, waiting to add a drop 
until the reaction of the former one had ceased. 
A deep etching was the result, and the extensivel}'' corroded 
surface presented here and there a ground glass appearance. 
Acicular crystals were apparent, although not as well defined as 
in the former example. 
Nos. 3, 4 and 5 were slips of the same glass etched by vapor. 
Of these No. 3 was very slightly corroded ; upon No. 4 and still 
more upon No. 5, the action was of greater duration. In these 
examples the evidence of acicular crystallization was apparent, 
as a shading upon the ground glass surface. Toward the edges of 
the etched spot the needles were as distinct as in example No. 1. 
Here a few well defined prisms with oblique extremities and one 
or two very small rhombic tablets were observed. 
No. 6. Mirror plate glass. This specimen was corroded by a 
drop of the acid with greater uniformity than the window glass, 
although the etching was not so deep. It required careful man- 
agement of the light to detect the crystals which were observed 
here and there in the form of scales or tablets, apparently bro- 
ken and very small. A few acicular crystals were also detected. 10 C. M. Wether ill on the Crystalline Nature of Glass. 
No. 7. Plate glass (microscope slide). This specimen, when 
etched, presented the same appearance as No. 6. Yery small 
acicular crystals distributed sparsely over the field of view could 
be„seen. 
No. 8. Three specimens of thin glass 'covers for microscopic 
objects. The etching of these was very uniform. Numerous 
and extremely minute needle-shaped crystals, requiring a high 
power for their definition, were observed. 
No. 9. Green bottle-glass (two specimens). In these crys- 
tallization was different from that of the former examples. In 
some places-die etching was-granular, as if small and short crys- 
tals had beyh removed’ by the acid. In other places blade-shaped 
jrystals were apparent; thesgjhad a tendency to unite in star- 
's i.£e groups,fas-an snow. C|bua one portion of the plate affew 
rlall squares Md triangles ru-iolubje in water) were seen. 
No. 'VO.' mens of Bohemian glass combustion-tube 
etch&d upon the'"inside. These yielded a granular, very regular 
dug. and pres-mt-ed a.-.tte ground glass appearance, 
which was resolved % tbern-'’r'ggo]'e into, small crystalline ta- 
. : fttai -. 
Go. 11. Boi ' . . ■ • m ■ •: v '■ 
non the ktner sur- 
■f’ae$iof the vessel. Jpnufit ..vwuular .cryltars, resembling those of 
, ♦ r-ii, ,.A. ,e.; a -•* and trape- 
zoids Verf-wletected. f f 
No. 12. Lead glass t&lfing; twp specimens, etched upon the 
inside. The action ofgW:f solvent was energetic. The etching 
was granular, with numerous snort and minute needles, requir- 
ing a high power of the microscope for their definition. 
No. 13. A portion of a soda glass flask etched upon the in- 
side. This was corroded very readily and yielded plenty of 
needles resembling in appearance those of No. 1. 
No. 14. Lead glass; inside surface of a matrass. The action 
of the hydrofluoric acid upon this specimen was energetic. The 
crystals presented the appearance of confused broken tablets, 
with here and there a needle-shaped crystal. 
The acid employed in the experiments gave no etching when 
dropped upon the different surfaces of a clear transparent quartz 
crystal. 
No. 15. After having completed the preceding series of obser- 
vations the object-glass of the microscope was protected from 
the action of the hydrofluoric acid by cementing upon it a plate 
of thin glass with Canada balsam. A large number of experi- 
ments were then made with slips cut from the same piece of 
window glass, similar to No. 1, with the object of ascertaining 
by the microscope whether the residue of the reaction was crys- 
talline, and whether, if so, it could have any influence upon the C. M. Wetherill on the Crystalline Nature of Glass. 
11 
etching to give an appearance of crystals having in reality no ex- 
istence. 
The acid employed was strong enough to hiss when water was 
added, and emitted Dropped upon the glass it 
spread, or jfilm of solid substance 
By a blqjse inspection small prism* were visible here 
an.i there in this residue. They were not as numerous as the 
etched crystals perceptible when the was and it 
"was not certain that they were nob shadows of the glass crystals. 
In.some cases larger prisms- could be roe a the edge yf the 
IdiSc: these might, be re:imumd by the • •-Om point'.i out under 
them was found no eonvyo.idiug et< AOpearm’Ob ot&ery;-fal 
Sn one instance the dy of glass was boy-, i with vw.:<: 
purpose of confining the acid to. a small disc- where the glass was 
laid bare. This g:i.ve t> ."mb.' oryeieK um.i'm- to ' other 
specimens. When the pl.u.r ■ vaa covered aith a thin mm of ofi| 
the crystalline etc! hug res a lie ; e • ig jho kn mm instances. When 1 
the acid was constantly stirred upon %<♦. xr!:,t / wit:. the platinum 
spoon employed for dropping it, ilm erysi uh.m Etching resulted^ 
Nc§ Id. At length an etching was found which served as an 
•• '■/ ■ ,• ■;nentu,.\ cruris to dm ywm;c\i'oi: the protect-iny action, of 
' u r n — J ' dps q:> t.lfl am 1 . : ■ 'sii >htly ddme-o. Ira. .-till 
famed in •.b-h-. . .Wr-VsavJhr! beta acted -a •:on- 
■ v,! ■ mevv’rdo s atchcs oh a gro'oysid glassapfiea, .nee. By' 
t;.1 - mi;;,, -.rope th-wr v .• >j‘* g ' groups o( siar-sl 
crystal-. which* in sem i lcffrom eorroaio 
oiltiny were < stalk Their dppearacho-wad eKtihd v 
similar to that of the s new-flake,coebroSrd of heedles 
which were combined with' smaller meedles forming 'feathery rays. 
In two places long neecrfes of oigpreighth tof; ahyneh in length 
were visible. Beside these, the acicular web of the former spe- 
cimens covered the glass. These starry crystals were undoubt- 
edly in intaglio. The depression could be distinctly felt with a 
needle when observing under the microscope, and fine powder 
of vermilion filled the rays. When first viewed, before the glass 
was cleansed perfectly, the corroded remains of the crystals 
could be removed from the depressions with a needle point. 
Now while we can conceive that a crystal formed by the 
action of an acid, might adhere so closely to the glass as to 
retard the corrosive effect of the acid under it, it is impossible to 
see how such a crystal could eat away the glass beneath it and 
thus sink itself under the surface. 
In some of the other specimens these starry groups were per- 
ceived ; but in no case as distinctly as in this one. There hap- 
pened here to be groups of crystals which were large and very 
Am. Jour. Sci.—Second Series, Yol. XLI, No. 121.—Jan., 1866. 12 
C. M. XVelherill on the Crystalline Nature of Glass. 
favorablyjdisposecTfor process. The result of this 
series of experiments seemed to throw some doubt upon the 
“ elevated ” character of the acicular web of crystals; at least 
as much doubt as may arise from of judging the 
question from the shadows. The fqriueqjjoacinaioi: reached 
by a compare ' .> - • ",hi V < -■ T a. 7.r,. \ 
of sublimed wh|oh - were known to be in relief i|Jm 
intaglio, d core hi An, to too slight to be able to form a jSclg- 
■ ■■X with vermilion powder. B§H8 
s af< km.-wtrryto - anions, it may bo ihat Uv: scat- 
tereo hc-odles character, 
h- ?oi c -vo; ■ ; • [ crystal were seer?; 
v i ; fiiku in other eases was transformed 
■jtose. 'r:to-- •; -cfYsjtob to: • ! ■ 1 former page may* 
were to*rmined. 
It sidi »o d 0 <yJi\s? exat;:;,icd contains crystals 
Already forntoff ■ are-more soluble in hydrofluoric 
• i timn ibeo v.-a to,:. »i id e-ta;- oihers b. -;s ncluble in the 
,: >; to vto, ■. ■ • si vtombtod to the action of'hydro- 
hfe 
the 
pressing, rolling &c^r to'whicl^he matbria! had been subjected. 
Doubtless aoSitidnM interesting phenomena might be observed 
by a more extendccritudy of different varieties of glass under 
different conditions by the use of this method. 
An analogous action of certain solvents upon other supposed 
amorphous bodies, as the resins, &c. may demonstrate a crystal- 
line character in them. 
From a more extended study of this interesting subject, results 
the most important respecting the true nature of glass may be 
expected. 
The effect of annealing may here find its true explanation. 
If we were able to produce at will an interlacement of long 
fibrous transparent crystals, a glass of superior flexibility and 
strength might be obtained. It would also be interesting to 
ascertain what kind of crystals of different substances might be 
introduced into glass without destroying its valuable properties. C. M. Wetherill on the Crystalline Nature of Glass. 
13 
If such, having the crystalline character of mica or asbestus, 
could be added a valuable product might result. 
Ley dolt observed 41 a slagjsge his No. 7) cubic crystals of 
nearly same ’ ' -y y ’ ~ •?.- and visible to the eye. If we 
tals as well as that of 
bie matrix (which may Ms* be or .•sf-allme) . .. ’’"W we might, 
by the laws of isomorphism, Ho aKyto coir e cryiii.&L at will, 
thus pro-ano/ng new and beautifid daL;-. _r> artiei ur-ware. 
Xy. this connection Lm .- >t m vatic of proto,< d oi * in 
ransparent portion aw' but trace? .. v 5 
talline part of a specimen . f glass, may he noted.': 
The .detection of the crystalline nature o' gii$f 
that we .are as yet unacquainted with the true of this 
complex substance ; but at the same 'date it ]:y> to 
be pursued for acquiring this desirable kuovvled&Tb