ARTIFICIAL MANURE. 177 



CHAPTER VII. 



ARTIFICIAL MANURES, AND IRRIGA- 

 TION. 



253. The class of salts as manure, is to be dis- 

 tinguished from the salts, called mineral manures, 

 by this circumstance, that they contain large por- 

 tions of peculiar animal products, called urea, and 

 uric acid. These afford ammonia, in large quantity, 

 by their decomposition. Having considered the rel- 

 ative value of the two classes of manure, those com- 

 posed of salts, and of salts and geine, that consist- 

 ing chiefly of geine, is now to be explained. 



254. First and foremost in this class, is swamp 

 muck, mud, or peat. This class includes also, dry 

 leaves, dry vegetables of all sorts ; ploughing in of 

 green or dry crops, irrigation. These are fruitful 

 topics. The principles only of their action, can be 

 pointed out. The application of the principle, must 

 be left to the farmer. The why, of things has been 

 shown ; the how, must be deduced from the why, by 

 practical men. 



255. Peat is too well known, to render it neces- 



