130 THE FISHING INDUSTRY 



The glue is sometimes made more flexible by the 

 addition of glycerine and glucose. The flexibility of 

 fish glue makes it useful for the manufacture of court 

 plaster, labels, stamps, and in book-binding. 



The residue from the press is dried and sold as chicken 

 feed or fertilizer. For the latter purpose it is frequently 

 mixed with Carnallite. 



Fish Gelatine. Fish gelatine or isinglass is obtained 

 from the swimming bladder of the sturgeon and also 

 of the cod. The bladders are exported, either opened 

 (pipe isinglass) or washed, split open and dried (purse, 

 lump or leaf isinglass). 



Isinglass is the purified and dried inner skin of the 

 bladder. It has but feeble adhesive power. It is used 

 for clarifying wines, ciders and beers, and for making 

 jellies and plasters. 



Fertilizers. In many places near the sea, fish are 

 employed whole as manure. Sprats particularly are 

 caught in large numbers and distributed over the fields, 

 and left to decompose. Fresh sprats contain 63'7 per 

 cent of water, T94 per cent nitrogen, 2'1 per cent ash 

 (0-43 potash and 0-90 phosphoric acid). 



Fish guano or fish manure is generally prepared from 

 the fish waste discarded by the curer. An average 

 sample of this manufactured fish manure will contain 

 12 per cent water, 60 per cent organic matter, yielding 

 10 per cent ammonia, 16 per cent of calcium phosphate, 

 and a residue of salt, sand, magnesia and potash, the 

 amount of potash being inconsiderable. Fish guano is 

 mainly valuable as a source of ammonia, the ammonia 

 content ranging from 6 to 11 per cent, according to the 

 kind of fish used and its previous history, e.g. whether 

 fresh or salted. 



In many places, such as London, the fish offal from the 

 shops and restaurants is collected, dried and ground up 



