184 OF MANURE. 



ashes of wheat straw contain 11*5 per cent, of the 

 same salts; hence with every 100 Ibs. of the ashes of 

 the beech, we supply a field with phosphoric acid suf- 

 ficient for the production of 3820 Ibs. of straw (its 

 ashes being calculated at 4*3 per cent. De Saussure), 

 or for 15-18000 Ibs. of corn, the ashes of which 

 amount, according to De Saussure, to 1*3 per cent. 

 Bone manure possesses a still greater importance 

 in this respect. The primary sources from which 

 the bones of animals are derived are the hay, 

 straw, or other substances which they take as food. 

 Now if we admit that bones contain 55 per cent, 

 of the phosphates of lime and magnesia (Berzelius), 

 and that hay contains as much of them as wheat- 

 straw, it will follow that 8 Ibs. of bones contain as 

 much phosphate of lime as 1000 Ibs. of hay or 

 wheat-straw, and 2 Ibs. of it as much as 1000 Ibs. 

 of the grain of wheat or oats. These numbers ex- 

 press pretty exactly the quantity of phosphates 

 which a soil yields annually on the growth of hay 

 and corn. Now the manure of an acre of land 

 with 40 Ibs. of bone dust is sufficient to supply 

 three crops of wheat, clover, potatoes, turnips, &c., 

 with phosphates. But the form in which they are 

 restored to a soil does not appear to be a matter of 

 indifference. For the more finely the bones are 

 reduced to powder, and the more intimately they 

 are mixed with the soil, the more easily are they 

 assimilated. The most easy and practical mode of 

 effecting their division is to pour over the bones, 

 in a state of fine powder, half of their weight of 



