SCIENTIFIC AGRICULTURE. 193 



animals differ somewhat in composition: phosphate of lime 

 constitutes the largest proportion of the matter of dry bones ; 

 the amount is from forty to sixty per cent of their weight 

 Eight pounds of bone dust are equal in phosphates to 1000 

 pounds of hay or wheat straw. 



The value of bones is not dependent alone on the phos- 

 phates, but partly upon the gelatine and other organic matters 

 which enter into their composition : these latter operate in the 

 same way as the other organic tissues of animals. Bones are 

 prepared for manure by boiling, by maceration in sulphuric 

 acid and water, and by grinding; the last of which methods is 

 thought on all accounts to be preferable. In soils deficient in 

 phosphates, bones are of great value ; and from the compara- 

 tively small quantity of phosphates which most crops require, 

 the effect of a large manuring with bone dust is manifest upon 

 the land for. many years: " 260 pounds of bone dust, (less than 

 six bushels,) are sufficient to supply all the phosphates con- 

 tained in the crops which are reaped from an acre during an 

 entire fourshift rotation of turnips, barley, clover and wheat 

 Some lands remember a single dressing for fifteen or twenty 

 years.'* (Johnston.) 



The prolonged effect of bones is due to the organic as well 

 as mineral matters. Bones should not be ground too fine: 

 they are particularly applicable to turnip crops and pasture 

 lands : the milk of cows contains about half a pound of phos- 

 phates to every ten gallons ; hence the necessity of these salts 

 in the soil of pastures. Animal tissues, when used as manures, 

 ought to be well covered with earth, or ploughed under, in 

 order to facilitate their decomposition, and at the same time 

 prevent the escape of the gases formed during this process. 



Solid excrements of animals, Night soil, or human ordure, 

 is a highly valuable fertilizer. It is best prepared for use by 

 mixture with powdered charcoal, half burnt peat, or scil which 

 is rich in vegetable matter : quick lime has been used for the 



