82 Production of Isinglass on the Coasts of India. 



Isinglass is also employed in making court-plaster, which, in 

 France, is called sparadrap d'Angleterre ; it is a thin coating of Isin- 

 glass with a little tincture of benzoin spread on black sarcenet. It is 

 also employed for giving a lustre to some kinds of woven fabric ; 

 but it is more extensively used for clarifying different liquors, such 

 as wine, beer, and coffee, than for any other purpose. The inferior 

 kind, called cake Isinglass, being brownish coloured, and having an 

 unpleasant odour, is only employed in the arts, and for the purposes 

 of glue. 



The great consumption of Isinglass — necessarily however of the 

 inferior kinds — is chiefly by the brewer, in the process of fining. 

 This he effects by the use of Isinglass, which he dissolves in sour 

 beer to the consistence of thick mucilage. A little of the solution 

 being added to the liquor to be clarified, causes the subsidence of all 

 the suspended matter in the course of a few hours, when the liquor 

 remains perfectly transparent. The sounds of codfish are said to be 

 employed for the same purpose, though I cannot learn that many are 

 imported, except in a salted state, for food. The white of egg, and 

 the serum of blood will also produce the same effect as far as trans- 

 parency is concerned. The mode of action of these substances in 

 this process is usually explained by supposing that the floating par- 

 ticles become entangled within the Isinglass, as in the meshes of a 

 net, and, uniting with it, form insoluble compounds, which precipi- 

 tating, are carried downwards, and thus leave the supernatant liquor 

 free from all impurity. Mr. Donovan explains this process by sup- 

 posing that the substance added, by dissolving in the water, lessens 

 its affinity for the suspended particles, which thus set free, subside 

 by their own specific gravity. 



Such being the uses of Isinglass, and its consumption being no 

 doubt limited by its high price, it is desirable to examine more 

 minutely into the present sources of supply, and to inquire whether 

 efficient substitutes, in the form of new varieties of Isinglass, may not 

 be obtained from other parts of the world. 



It has been mentioned that Isinglass is chiefly obtained from the 

 rivers of Russia, which fall into the Black and Caspian Seas, and that 

 it is principally formed of the swimming bladders of fishes of the 

 genus Acipenser, or Sturgeon. These belong to the great subdivision 



