290 AMMONIA AND NITRIC ACID. 



proportion of 1 : 2 ; whereas the crops are in the pro- 

 portion of 1 : 14. These facts are fatal to the opinion 

 that there exists any connection between the amount 

 of nitrogen in a soil, and its powers of production ; and 

 in truth no one now entertains this belief. For since 

 Kroker in 1846 determined the nitrogen in 22 kinds of 

 soil from various districts, and discovered that even an 

 unfruitful sand contained more than a hundred times, 

 while in arable soils to a depth of 10 inches there were 

 present from 500 to 1000 times, more nitrogen than is 

 necessary for a good crop, similar investigations have 

 been made in all countries, and Broker's results have 

 been confirmed. 



Since that period the fact has been generally ad- 

 mitted, that the great majority of cultivated soils are 

 far richer in nitrogen than in phosphoric acid ; and 

 that the relative proportion of nitrogen present, which 

 had been adopted as the standard for calculating the 

 value of manure, was quite inapplicable for estimating 

 the productive power of land. 



Hence, between the chemical analysis of manures, 

 and that of the soil, there arose an irreconcilable con- 

 tradiction. In the chemical laboratory the effective 

 value of a manure could be accurately determined ac- 

 cording to the per centage of its nitrogen ; but when 

 the farmer had incorporated his manure with the soil, 

 the determination of the per centage of nitrogen in the 

 ground was no longer of any use in estimating its pro- 

 ductive power. 



This strange circumstance might well have excited 

 suspicion against the theory of the preponderating in- 

 fluence of nitrogen, for which, as already observed, there 

 is not the slightest evidence in point of fact. But in- 

 stead of this, the advocates of the theory maintained it 

 steadfastly, and endeavoured to explain the behaviour 

 of the soil upon new and still more extraordinary 

 grounds. It had been observed that a very small frac- 

 tion of the quantity of nitrogen present in the soil, in 

 the form of guano, farm-yard manure, or nitrate of soda, 

 materially increased the* crops ; whereas, the effect of 



