364 PHILOSOPHICAL TRANSACTIONS. [anNO 1773. 



have imagined, which bears the least affinity with what frequently occurs in che 

 mical decompositions. 



These phenomena are adduced here as correlative proofs of the impracticability 

 of making isinglass by the previous reduction of the sinewy parts of fish into 

 jelly ; and it seems evident, that the clarifying action of isinglass depends prin- 

 cipally on a crude minute division, not solution of its parts, which is still further 

 confirmed, by diluting a few drops of fining with fair water in a glass; for thus 

 the slender filaments become conspicuous to the eye, especially when assisted 

 with a double convex lens, but these immediately disappear on an addition of hot 

 water. As the general processes for making isinglass appear from hence illusive 

 and erroneous, the long concealed principles of its manufacture, into the various 

 common forms and shapes, become more obvious and comprehensive. If what 

 is commercially termed long or short stapled isinglass be steeped a few hours in 

 fair cold water, the entwisted membranes will expand, and re-assume their ori 

 ginal beautiful hue,* and by a dextrous address may be perfectly unfolded. By 

 this simple operation, we find that isinglass is actually nothing more than certain 

 membranous parts of fishes, divested of their native mucosity, rolled and twisted 

 into the forms above mentioned, and dried in the open air. 



The sounds, or air-bladders of fresh-water fish, in general, are preferred for 

 this purpose, being the most transparent, flexible, delicate substances. These 

 constitute the finest sorts of isinglass } those called book and ordinary staple, are 

 made of the intestines, and probably the peritonaeum, of the fish. The Beluga 

 yields the greatest quantity, being the largest and most plentiful fish in the Mus- 

 covy rivers ; but the sounds of all fresh-water fish yield, more or less, fine isin- 

 glass, particularly the smaller sorts, found in prodigious quantities in the Caspian 

 sea, and several hundred miles beyond Astracan, in the Wolga, Yaik, Don, 

 and even as far as Siberia, where it is called kle or kla by the natives, which im- 

 plies a glutinous matter ; it is the basis of the Russian glue, which is preferred to 

 all other kinds for its strength. 



The anatomy and uses -|- of the sound in fish seems not yet adjusted by ichthyo- 

 logists. Dossie, in his Memoirs of Agriculture, will have it to be the mesentery 

 of the fish ; but the celebrated Gouan, the latest, and perhaps the most accurate 

 author on ichthyology, gives a more satisfactory and comprehensive account of it, 

 under the title of La Vesicule Aerienne. Yet, if the identity of the air-bladder, 



• If the fine transparent isinglass be held in certain positions to the light, it frequentlj' exhibits beau- 

 tiful prismatic colours. — Orig. 



f Fishermen have a dextrous art in perforating the sound of fresh-taken cod fish with a needle, in 

 order to disengage the inclosed air. Without this operation, the fish could not be kept under water in 

 the well-boat, consequently could not live j but if by accident the operator wounds an artery, the fish 

 presently dies, through the discharge of blood, to the loss of the proprietor, who thus can seldom 

 bring it sweet to market. — Orig. 



