318 AMMONIA AND NITRIC ACID. 



influence of superpliospliate upon Field 2 was exhibited ; 

 for the crop of this plot, when unmanured, did not 

 correspond to the amount of active nitrogen which it 

 contained ; but by the addition of superphosphate the 

 crop rose to more than double. And when to the super- 

 phosphate upon Field 1, 137 kilogrammes of common 

 salt, and 755 kilogrammes sulphate of soda were added, 

 there was a still greater increase, i. e. there were now 700 

 Idlogrammes of corn, and 1550 kilogrammes of straw, 

 a still greater quantity of apparently inactive nitrogen 

 having been rendered efiective. 



The intelhgent farmer who reflects upon questions of 

 this kind, will be led to the conclusion, that an essential 

 diflerence may exist between his own practical experience 

 and the theories of the school which seeks to explain 

 them. When practice tells us that farm-yard manure, 

 guano, and bone earth have restored or increased 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 

 beheve by persons who themselves know nothing about 

 the matter. 



It is certainly a most remarkable circumstance, occur- 

 ring in no other trade or hidustry, 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 gromid, 



