230 THE CULTURE OF FARM CROPS. 



mous shoals, are steamed for the oil they contain; the re- 

 sulting mass of moist flesh and bone is then dried and fine- 

 ly powdered. The substance thus produced is called fish 

 scrap. It is one of the nitrogenous manures, but contains 

 some phosphoric acid and a little potash. It has, as might 

 be expected, somewhat the same character as Peruvian 

 guano, which is derived from the excrement of sea fowl 

 which feed upon fish. An analysis offish scrap gives the 

 following, from a good sample. 



COMPOSITION OF FISH SCRAP DRIED AT 212 



Moisture 9.00 per cent. 



Phosphoric acid 11.72 



Reverted phosphoric acid 4.41 



Insoluble phosphoric acid 7.31 



Potash 89 



Nitrogen 8.16 



Insoluble matter, lime, etc 3.70 



Value per ton, $49.35 



This is seen to be a valuable fertilizer, and by mixture 

 with potash salts would make a most useful manure. Not 

 being immediately soluble, but yet decomposing freely in 

 the soil, it becomes available for the crop gradually; hence 

 it may be applied early in the season, and its effects will 

 continue to be apparent during the whole period of growth. 

 It has been found especially useful for corn; market crops; 

 potatoes ; and for grass and clover. Many farmers have 

 found its useful effects much increased by treatment with 

 sulphuric acid, by which the ammonia contained in it, or 

 evolved during its decomposition, is changed to a sulphate; 

 and its phosphate of lime becomes superphosphate; when its 

 solubility being very much increased, it becomes much more 

 available for the feeding of crops. The coarse fish scrap, 

 unground, sells for a much less price than the kind of which 

 the analysis is given above, and it makes an excellent ma- 

 terial for enriching composts. One ton of it added to 10 

 tons of fresh swamp muck, with a ton of potash salts and a 

 ton of ground gypsum, has been found to make a most use- 

 ful substitute for stable manure, and when used for a crop 

 of mangels gave a very satisfactory yield, equal to that up- 

 on adjoining parts of a field which were manured, one 



