MANURES AND FERTILIZERS. 131 



fertilizer manufacturers appreciate its value and take all 

 that is produced. It is sold in the trade by the unit of 

 ammonia. A unit is one per cent. When ammonia is 

 worth $2. 75 per unit, the price of blood analyzing 12 per 

 cent ammonia is 12 times $2. 75, or $33 per ton. 



Dried Fish. The leading animal ammoniate, the 

 one most largely used by both manufacturers and 

 farmers, is dried fish. This is obtained in very large 

 quantities from the menhaden oil factories along the 

 Atlantic coast. The menhaden, or " porgies " are caught 

 for oil. They are steamed in large vats until reduced to 

 a churn, and when this is settled the oil and water is 

 drawn off and the churn is heavily pressed, to express all 

 remaining oil. It is then called wet scrap and contains 

 about 50 per cent of water. This is then dried, gener- 

 ally by the sun, the result being dry scrap. This con- 

 tains about 10 or 12 per cent of water and from 8 to 9 

 per cent of nitrogen, or about 10 per cent of ammonia. 

 It also contains about 8 per cent of phosphoric acid. 

 The percentage of nitrogen varies according to the quan- 

 tity of water contained in the scrap, which is sometimes 

 quite large, even as much as 20 per cent in dry scrap. 

 This variation is caused by defective drying, the effect- 

 iveness of which is largely governed by the weather. In 

 some cases scrap is dried artificially, but this is not very 

 general. 



Dry scrap is sifted to make it uniform, and the 

 result is a light, dry powder, having flaky particles. 

 The finest dust is called fish guano. This runs some- 

 what higher in nitrogen and is more valuable, because 

 its fine mechanical condition renders decomposition in 

 the soil very easy. Fish is classed under four heads, 

 wet scrap, dry scrap, fish guano and ground fish ; the 

 distinction between the last two being slight and diffi- 

 cult to determine. The supply of scrap varies from 

 year to year, according to the quantities caught ; some 



