VOL. LXIII.] PHILOSOPHICAL TRANSACTIONS. 367 



book, but those of ling both shapes. The thicker the sounds are, the better 

 the isinglass, colour excepted; but that is immaterial to the brewer, who is its 

 chief consumer. 



This isinglass resolves into fining, like the other sorts, in subacid liquors, as 

 stale beer, cyder, old hock, &c. and in equal quantities produces similar effects 

 on turbid liquors, except that it falls speedier and closer to the bottom of the 

 vessel, as may be demonstrated in tall cylindrical glasses; but foreign isinglass 

 retains the consistency of fining preferably in warm weather, owing to the greater 

 tenacity of its native mucilage. Vegetable acids are, in every respect, best 

 adapted to fining : the mineral acids are too corrosive, and even insalubrious in 

 common beverage. 



It is remarkable that, during the conversion of isinglass into fining, the aci- 

 dity of the menstruum seems greatly diminished, at least to taste, probably not 

 on account of any alkaline property in the isinglass, but by its inveloping the 

 acid particles. It is likewise reducible into jelly with alkaline liquors, which in- 

 deed are solvents of all animal matters; even cold lime-water dissolves it into a 

 pulpous magma. Notwithstanding this is inadmissible as fining, on account of 

 the menstruum, it produces an admirable effect in other respects : for, on com- 

 mixture with compositions of plaster, lime, &c. for ornamenting walls exposed 

 to vicissitudes of weather, it adds firmness and permanency to the cement; and 

 if common brick mortar be worked up with this jelly, it soon becomes almost as 

 hard as the brick itself: but for this purpose, it is more commodiously prepared, 

 by dissolving it in cold water, acidulated with vitriolic acid; in which case, the 

 acid quits the jelly, and forms with the lime a selenitic mass, while, at the same 

 time, the jelly being deprived, in some measure, of its moisture, through the 

 formation of an indissoluble concrete among its parts, soon dries, and hardens 

 into a firm body ; whence its superior strength and durability are easily compre- 

 hended. 



It has long been a prevalent opinion, that sturgeon, on account of its cartila- 

 ginous nature, would yield great quantities of isinglass; but on examination, no 

 part of this fish, except the inner coat of the sound, promised the least success. 

 This being full of rugae, adheres so firmly to the external membrane, which is 

 useless, that the labour of separating them supersedes the advantage. The in- 

 testines, however, which in the larger fish extend several yards in length, beine 

 cleansed from their mucus, and dried, were found surprizingly strong and elastic, 

 resembling cords made with the intestines of other animals, commonly called 

 cat-gut, and from some trials, promised superior advantages, when applied to 

 mechanic operations. 



