62 ACTION OF ELEMENTS OF SOIL. 



source be in chloride of silicon ? These are conjectures, but 

 conjectures only, because, refined as modern chemical analy- 

 sis is, it may not be so delicate as to detect the possible 

 combinations, which nature presents in silicates. What is 

 the source of that phosphoric odor, produced by the friction 

 of fragments of pure quartz on each other"? If not due 

 wholly to electrical excitement, may it. not arise from the 

 presence of phosphoric elements'? The elements are Pro- 

 tean, and assume new dresses, by the very processes adopted 

 to unfold them. Whatever may be their origin, their con- 

 stant presence leads to this fifth principle of agricultural 

 chemistry, all soil contains sulphate and phosphate of 



LIME. 



85. This principle is of the highest importance in agricul- 

 ture. The author of these pages stated the fact to the Geo- 

 logical Surveyor of Massachusetts, in 1837, and it was pub- 

 lished in his report. Slowly admitted at first, the fact that 

 phosphates exist in all soil, has been established by the 

 widest observations. Its proofs are both chemical and agri- 

 cultural. The chemical proof is found in the extensive anal- 

 yses of soil contained in various Geological Reports, espe- 

 cially those of Massachusetts, published within a few years. 

 Since the first edition of this work, phosphoric acid has been 

 found in basaltic and hornblende rocks. 



86. The agricultural proof may be stated in a few words. 

 The bones of all graminivorous animals contain about half 

 their weight of phosphate of lime. It can be derived only 

 from their food, and that only from the soil. Hence the 

 soil contains phosphoric acid in some chemical combination. 

 Secondly, the actual result of chemical analysis confirms 

 this statement. Beets, carrots, beans, peas, potatoes, aspara- 

 gus, cabbage, afford phosphates of lime, magnesia, and pot- 

 ash. Indian corn, rice, wheat, barley, oats, all contain nota- 



