54 AMERICAN MANURES. 



country indisputably occupies the front rank in 

 regard to agricultural productions. 



" As superphosphate of lime may be viewed as 

 phosphate of lime dissolved in phosphoric acid, 

 the former (phosphate of lime), as soon as the 

 free acid is neutralized, is rendered insoluble or 

 difficultly soluble in water, arid is precipitated. 

 Therefore, one of the objections made, viz., that, 

 when superphosphate of lime is applied to cer- 

 tain soils, the soluble phosphate is lost by rain, 

 is unfounded. From very careful experiments 

 of Dr. Voelcker on the transformation of soluble 

 phosphates in contact with five different soils, 

 which were first carefully analyzed, it is evident, 

 that marly or chalky soils absorb the soluble 

 phosphate more readily, that is, render it more 

 quickly insoluble, than clayey or sandy soils. 

 In the former soils, it appears that lime is the 

 only operating force in this transformation. 

 However quick absorption may take place, it is 

 never instantaneous ; for in soils containing an 

 excess of lime, from 24 to 48 hours are required. 



" As no acid combination can enter the plant 

 without damaging it, and as superphosphates 

 have never proven themselves injurious to plants, 

 it follows herefrom, that phosphoric acid, which 

 cannot exist in soils in a free state, is there 

 neutralized, and that, in consequence, the solu- 

 ble phosphate is converted into insoluble or 



