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oxygen, hydrogen and the carbon requisite for 

 their existence. 



CHAPTER II. 



NITROGEN. 



The preceding table shows that the amount 

 of nitrogen in the crops is also greater than 

 that of the manure, but the difference is less 

 remarkable. The role of this element in agri- 

 culture is most important; and as every thing 

 relating to its mode of action is of great inte- 

 rest, we quote here the opinions of that learned 

 and skilful chemist, Boussingault. 



"I have, I believe, established by my nume- 

 rous analyses, that in extensive cultures, the 

 nitrogen comprised in a succession of crops 

 always exceeds, and frequently in a large pro- 

 portion, that originally existing in the manures 

 consumed in their production. This excess is 

 evidently derived from the atmosphere, and in 

 that case it is more than probable that a portion 

 of it enters the plants in the form of nitrate of 

 ammonia, a nitrate, which according to Lie- 

 big's analyses, is frequently found in rain wa- 

 ter falling during a storm. In that event it 

 must be an electrical phenomenon, that dis- 

 2* 



