C 7 ] 
ful * hue, and, by a dextrous addrefs, may be per- 
fectly unfolded. By this fimpie operation, we find 
that ifinglafs is actually nothing more than certain 
membranous parts of fifhes, diverted of their native 
mucofity, rolled and twifted into the forms above- 
mentioned, and dried in the open air. 
The founds, or air-bladders of frefh-water fifti; in 
general, are preferred for this purpofe, as being the 
moft tranfparent, flexible, delicate fubftances. Tbefe 
conrtitute the flneft forts of ifinglafs ; thofe called 
book and ordinary rtaple, are made of the intertines, 
and probably the peritonaeum, of the fifti. The 
Beluga yields the greateft quantity, as being the largeft 
and moft plentiful fifti in the Mufcovy rivers ; but 
the founds of all frefh-water fifti yield, more or lefs, 
fine ifinglafs, particularly the fmaller forts, found in 
prodigious quantities in the Cafpian fea, and feveral 
hundred miles beyond Aftracan, in the Wolga, 
Yaik, Don, and even as far as Siberia, where it is 
called kle or kla by the natives, which implies a 
glutinous matter ; it is the balls of the Ruffian glue v 
which is preferred to all other kinds for its ftrength. 
The anatomy and -f- ufes of the found in fifti 
feems not yet adjufted by i&hyologifts. I have not 
met with a genuine defcription of its fituation and 
* If the fine tranfparent ifinglafs be held in certain pofitions to 
the light, it frequently exhibits beautiful prifmatic colours. 
+ Kifhermen have a dextrous art in perforating the found of 
frefh-taken cod fifh with a needle, in order to difengage the inclofed 
air. Without this operation, the fifh could not be kept under 
water in the well-boat, confequently could not live; but if by 
accident the operator wounds an artery, the fifh prefently dies, 
through the difcharge of hood, to the lofs of the proprietor, who 
thus can feldom bring it fweet to market. 
figure 
