CAUSE OF INACTIVITY OF NITROGEN IN SOILS. 301 



explain them. When practice tells us that farm-yard 

 manure, guano, and bone earth have restored or in- 

 creased the crops in certain cases, no one can maintain 

 that these are not real facts, or are not trustworthy. 

 ,But the observations of the practical man extend no 

 further than these facts ; he has not actually remarked 

 that the increased crops were produced by the ammonia 

 in the farm-yard manure, or by that in the guano, or by 

 the nitrogen in the nitrate of soda ; all this he is led to 

 believe by persons who themselves know nothing about 

 the matter. 



It is certainly a most remarkable circumstance, oc- 

 curring in no other trade or industry, that in most cases 

 the farmer cherishes representations or theories, for the 

 truth of which he has no evidence ; nay, he seems even 

 to give up completely the very idea of inquiring into 

 their correctness. It is quite incomprehensible that he 

 should allow himself to be guided and convinced by 

 facts which have not been remarked by himself upon 

 his own ground, but have been observed in altogether 

 different districts, and which must at least remain 

 doubtful as far as their application to his own land is 

 concerned. 



If, during the last ten years, only one farmer in a 

 thousand had resolved to institute experiments upon his 

 own land with ammonia or salts of ammonia to test the 

 theory, whether in fact this manure is useful beyond all 

 others in increasing the corn crops, how soon and how 

 easily would an accurate estimate have been formed of 

 its true value by other farmers ! 



The simple reflection that not one of the substances 

 nutritive to plants does of itself exert any influence 

 upon their growth, and that several other substances 

 must be present, if the first is to prove useful, should 

 have brought him to the conclusion that the case cannot 

 be otherwise with nitrogen ; and that the value of a 

 manure cannot be measured by the amount of nitrogen 

 which it contains ; for this presupposes that the nitro- 

 gen possesses an operative power, which must manifest 

 ^tself under all circumstances, and that the money 



