82 COMMON MICA. 
tallized in the cavities of the veins which traverse them. 
In some countries, as in Siberia, it is an article of 
commerce, and is obtained from mines like other mine- 
rals. From these it is extracted by hammers and 
chisels. It is then washed, to free it from the impurities 
which adhere to it ; split into thin leaves or pieces ; 
and assorted into different kinds, according to their 
goodness, purity, and size. We are informed by the 
Abbe Haiiy, that plates of mica a yard or more in width 
have been obtained from the mines in some parts of 
Russia. 
Thin plates of mica are adopted, in many parts of 
Siberia and Muscovy, to supply the place of glass for 
windows. In the shipping of Russia it is considered 
preferable to glass, as the concussion produced by the 
firing of the guns does not shatter it. It is employed 
instead of window glass in Peru and New Spain ; and 
ulso in Pennsylvania. Mica may be advantageously 
substituted for horn in lanterns, as it is not only more 
transparent, but is not susceptible of injury from the 
flame of the candle. It has, however, the inconvenience 
of soon becoming dirty ; and of having its transparency 
destroyed by long exposure to the air. Mica is used 
for enclosing objects that are intended to be viewed by 
microscopes. 
So plentiful is this substance in Bengal, that, for the 
value of five shillings, as much of it may be purchased 
as will yield a dozen panes, each measuring about twelve 
inches in length and nine in breadth, and so clear as to 
allow of ordinary objects being seen through them at 
the distance of twenty or thirty yards. 
Mica, when powdered, is sold by stationers on the 
Continent, in place of sand, for absorbing ink in writ* 
ing, but it does not dry sufficiently quick to be of much 
use in this respect. In Russia it is employed in different 
kinds of inlaid work. It is sometimes powdered, and 
intermixed with the glaze in particular kinds of earthen 
ware. The heat which melts the glaze has no effect on 
