fi-20 AMMO^'IA AND NITRIC ACID. 



of plants, cannot be proved by the fact that the crops do 

 not bear any proportion to the amonnt of nitrogen in the 

 soil ; for were this the case, then all soils must be equally 

 abundant in all other conditions for the growth of plants, 

 and everywhere possess the same geological and mechani- 

 cal condition. But this assumption is impossible, for on 

 the whole sm'face of the globe there are not two districts 

 in which the soils are identical in these respects. 



This theory must be strenuously opposed, not only 

 because it is false generally, and that it has never yet been 

 proved to be true even in a single case, but still more on 

 account of the pernicious influence which it exercises 

 upon the practice of the farmer. For since it induces 

 him to suppose that it is impossible to give the necessary 

 efficacy to the store of nitrogen in his land, he will never 

 think even of attempting to do so. Being convinced 

 beforehand that he need not try to raise the treasure 

 buried in liis field, he never even makes the attempt. 



Since the exact observation made in the cultivation of 

 entire countries and divisions of the globe for centuries 

 past, and also well-established facts, make it probable 

 that a source of nitrogenous food exists, which ensures 

 annually to a cultivated field without the husbandman's 

 aid the return of a portion of the nitrogen, and in a ro- 

 tation the whole amount of that substance which has been 

 taken away in the crops ; and fiu-ther, that the field may 

 be exhausted of every other nutritive substance, however 

 great its store in the ground may be, because they are 

 never spontaneously restored to the soil by nature — 

 whereas this can never happen to nitrogen ; then it is 

 contrary to all the rules of logic in any given case, to 

 ascribe without closer examination the exhaustion of 

 a soil above all other things to a loss of nitrogen. 



We might suppose, that apart from the suggestions of 



