58 THE CHEMISTEY OF THE FARM 



Hoofs and Horns are extremely rich in Ditrogen, the 

 proportion being usually 15 per cent. Shoddy, and 

 other forms of wool waste, are very variable in com- 

 position, owing to the different proportions of water, 

 cotton, dirt, and grease which they contain ; the nitro- 

 gen will generally range from 5 — 8 per cent. 



The nitrogen of blood, horn, wool, and hair is not 

 in a form suitable as plant food. Blood readily de- 

 composes in the soil, yielding first ammonia and 

 then nitric acid. Horn, wool, and hair decompose 

 much more slowly, and their effect is spread over 

 many years. 



Soot is generally employed as a top dressing for 

 spring corn. Dried blood is an excellent manure for 

 wheat. Wool and hair are chiefly used for hops. 



Meat Meal, Meat Guano.— This is the residue from 

 the manufacture of meat extract. It varies in com- 

 position according to the amount of bone ground up 

 with the meat fibre. The nitrogenous kinds contain 

 11 — 13 per cent, of nitrogen, and 06 — 3"0 per cent, of 

 phosphoric acid. The phosphatic kinds contain 6 — 7 

 per cent, of nitrogen, and 14 — 17 per cent, of phos- 

 phoric acid. 



Bones. — These are largely employed as manure ; 

 the fat is usually first extracted by steaming. Com- 

 mercial bones contain about 3"6 per cent, of nitrogen, 

 and 23 per cent, of phosphoric acid, existing as phos- 

 phate of calcium. Bones that have been boiled to 

 extract the gelatin contain about 1*4 per cent, of 

 nitrogen, and 29 per cent, of phosphoric acid. 



JJones decompose but slowly in the soil, especially 



