SUPERPHOSPHATE OF LIME 283 



phate are no more than the 1-20,000 of an inch in diameter, 

 as I have just been informed by a friend skilled in the micro- 

 scope, who has measured them at my request. Since the 

 particles of the precipitated phosphate are so very much 

 smaller than those of the finest bone-dust, we can understand 

 that their action as a manure is correspondingly more rapid. 



In fact, the application of superphosphate to the soil is 

 always speedily followed by the formation of precipitated 

 phosphate ; the iron, lime, potash, etc., of the soil, having the 

 same effect as that produced by the saleratus or soda, in the 

 experiment just described. 



The use of dissolving bones in sulphuric acid is, then, not 

 to furnish the plant with a new food, but to present an old 

 dish in a new shape, more readily accessible to the plant. 



In addition to the advantage of subdivision thus presented, 

 Prof. Way, of the Royal Ag. Society of England, insists upon 

 another, viz., distrihution. This may be illustrated as follows : 

 If a quantity of bones be acted upon by sulphuric acid, thus 

 forming superphosphate — and if a part of this have chalk, 

 lime, or ashes mixed with it before use, while the other por- 

 tion is directly applied, in both cases precipitated phosphate 

 will be furnished to the soil. The subdivision will be equal, 

 but the distribution will be unlike. In the first case, the ready 

 formed phosphate is imperfectly mixed with the soil, by the 

 rough mechanical operations of cultivation. In the last in- 

 stance, if the superphosphate is scattered on the surface, it 

 is unaffected until a rain falls upon it. Then the superphos- 

 phate dissolves, and trickles or soaks down into the soil, meet- 

 ing here with a particle of lime or potash, and depositing a 

 particle of phosphate, traveling on a little way and depositing 

 another, and so filling the whole soil with the precious 

 fertilizer. 



It seems then, that it is important not only that the super- 

 phosphate be made, but that it remain as such until strown 

 on the soil. 



The reader's attention is now directed to the analyses of 



