The Ammonia Theory 193 



crops with a short vegetation period had a limited power 

 for accumulating ammonia from the air, and gratefully 

 responded to applications of nitrogenous materials. 



So great was the weight of Liebig's authority that 

 his views were widely accepted in spite of many facts, 

 rapidly growing in number, that seemed to be contrary 

 to these views. Lawes and Gilbert, of England, denied 

 Liebig's claims on the strength of their experiments at 

 Rothamsted. They soon became involved in a contro- 

 versy with the great German chemist. It was not. always 

 free from bitterness. The investigations stimulated by 

 this controversy proved that ammonia does not directly 

 feed the crops, that the amounts brought down in rain 

 or snow are but slight, and that the atmosphere contains 

 but minute quantities of i,t. The adherents of the am- 

 monia theory sought to strengthen their position "by 

 pointing to experiments that, apparently, proved the 

 extensive formation of ammonia in nature. They asserted 

 that either in the burning of organic materials contain- 

 ing no nitrogen, or in the decay of such substances in 

 the soil, ammonia was always formed. 



The German chemist, Schoenbein, thought he had 

 demonstrated that nitrate of ammonia is formed in 

 the simple evaporation of water in shallow vessels. 

 Further investigation, under more rigid experimental 

 conditions, disproved these statements. The experi- 

 ments of Boussingault in France, and of Lawes, Gilbert 

 and Pugh in England, conducted in the fifties of the 

 last century, seemed to have established with certainty 

 that gaseous nitrogen cannot be used by plants. There 

 remained, therefore, but one logical explanation of the 



