ELISHA MITCHELL SCIENTIFIC SOCIETY. Ill 



up, under the third supposition, our idea of atoms, for au atom 

 is nothing if not a fixed weight of something. Vogel* 1ms 

 also come to the conclusion that the atomic weights vary 

 because those gotten by the use of certain compounds differ 

 throughout from those derived from other compounds. By this 

 assumption he also explains the cases in which analyses result in 

 a sum total of over 100 per cent. It seems much more plausi- 

 ble to explain these variations on the ground of errors of analysis, 

 constant errors of method, impurities of materials, and the many 

 other difficulties and obstacles which a chemist meets in such 

 work, than by the radical assumption of an inconstancy in the 

 very constants on which the science is founded and built up. 



At any rate until much more proof is forthcoming the matter 

 must rest in abeyance. 



Contribution from N. C. Agricultural Experiment Station. 



No. XVI I. 



OX THE CHANGE IN SUPERPHOSPHATES WHEN 

 THEY ARE APPLIED TO THE SOIL. 



II. B. BATTLE. 



Without discussing at this time the value of the soluble phos- 

 phoric acid of superphosphates over the phosphoric acid of 

 other forms, nor of the exact nature of the so-called reverted 

 phosphoric acid, I have attempted in this article to show the 

 change that takes place in superphosphate- when they are ap- 

 plied to the soil. How the various forms of phosphoric acid, 

 that soluble in water, that insoluble in water, and that insoluble 

 in the standard ammonium citrate solution, all are affected la- 

 this application ; in other words, when agriculturally the acid 



•Nature, Vol. 41, |». 42. 

 8 



