114 OP FERTILIZERS. 



as common salt, phosphates, sulphates and carbonates of 

 potash, soda, &c., water, and some insoluble salts, namely 

 phosphate of lime and of magnesia. Like flesh, it should 

 be made into a compost with other substances, and it thus 

 becomes a very valuable manure for light soils, while its 

 effect 011 clayey soils is less obvious. 



378. Bones contain more than 53 per cent, of phosphate 

 of lime, a little phosphate of magnesia, some carbonate of 

 soda, c., and more than 7 per cent, of nitrogen. Their 

 principal value is owing to the quantity of the phosphates 

 they contain, as these salts are largely removed from a 

 soil by the feeding of cattle and by successive crops. 

 These salts remain after the bones have been deprived of 

 their fatty substance by the soap-boiler, though most of 

 the nitrogen is lost. Bones should be ground before 

 being used, and may be applied at the rate of ten or 

 twelve hundred weight to the acre. Even when ground, 

 they produce effects which may be seen for several years. 



379. The action of bones may be accelerated by con 

 verting their phosphates into perphosphates or super 

 phosphates, which is done by mixing the ground bones 

 with half their weight of sulphuric acid diluted with three 

 or four times its bulk of water. This is to be thoroughly 

 mixed and left a day or two at rest. One barrel of the 

 pasty mass may then be mixed with one hundred barrels 

 of water and sprinkled upon the field from a water-cart 

 or by scoops. Or the perphosphate may be mixed with a 

 large quantity of earth, or sawdust, soot or powdered char 

 coal, and thus applied to the land. 



380. It is easy to see how it conies that animal manures 

 are so valuable. Animals live almost wholly upon sub 

 stances de-rived from the vegetable kingdom. These sub 

 stances, restored to the earth, from which and from the 



