permanent Flint Glass is that which by the greatest caloric can be
made to contain the largest proportion of silex; but it is not so well
calculated for chandeliers, (which should be more highly refractive,)
nor for optical purposes, as for ordinary use.
Flint Glass is remarkably elastic: it may
be spun so thin as to bend nearly double without fracture; by the aid
of slight heat, it may be curled into ringlets to represent human hair,
or it may be blown so thin as nearly to float in the atmosphere; and it
has been woven with silk and other substances by Messrs. Williams and
Sowerby's Patent Process, so beautifully as to give the brilliant
effects of silver and gold, in colours superior to the precious metals
themselves.* Hollow Glass balls are so elastic than if dropped from
a height of ten or twelve feet upon a solid polished anvil, they will
rebound from half to three-fourths of that height, and generally without
fracture, until after the second rebound.
Flint Glass, of not less than the usual
density of 3.200, well polished by the lapidary, is considered the
nearest approach to the diamond.
Glass is admitted to be one of the most
useful and beautiful of materials in ornamental and industrial art.
Chemistry and astronomy could scarcely exist without it. The delicacy
and accuracy of the chronometer require its aid; while the common green
bottle Glass can be manufactured cheap enough for casting conduit pipes,
for chemical uses, or the supply of the metropolis with pure water.
No chemical test is so delicate
* It is not within our province
to describe the constituents of arsenic, exide of tin, or the
colouring oxides, which will be found detailed in treatises on