C. M. Wetherill on the Crystalline Nature of Glass. 19 
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 
ams, 
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. ; 
elouze found that mirror, plate, lead, bottle, and Bohemian 
lasses were all susceptible of devitrefication, although with dif- 
erent degrees of readiness, the tri-silicate of soda being the most 
ready. A glass of silica, boracic acid, potassa and zine yielded 
mere traces of crystallization; but the combination of silica and 
racic acid with potassa and lime could not be devitrefied by an 
exposure of ninety-six hours to a temperature at which softening 
took place. 
e@ 
States, as the result of many analyses performed by himself, that 
ne pari ee 
~ Damas therefore holds that she ed wets obtained by Pelouze 
are “analogous to mixtures of the fatty acids, which by ‘fasion 
rm a homogeneous liquid, which by cooling gives a fibrous 
Solid, in which although the eye can perceive nothing hetero- 
__ Terreil (Comptes Rendns, xlv, 693) observed in the melting = 
