CHAP, in The Absorption of Nitrogen 325 



new discoveries reopened the whole matter ; somewhat 

 heated controversy set in and was maintained till nearly 

 the end of the century. New aspects of the question 

 attracted new workers and several lines of research yielded 

 very unexpected results, results of far-reaching importance, 

 which the end of the century left still far from complete. 

 Indeed these lines of research are bearing promise of richer 

 results to-day than seemed possible in 1900. 



Of the problems which thus presented themselves, the 

 first we may consider was opened out by Berthelot in 1876 

 and was a subject of examination by him in the midst 

 of his other work till 1892. He objected at the outset to 

 the conclusions arrived at by preceding workers as to the 

 atmosphere as a source of nitrogen to vegetation, on the 

 ground that the experiments on which those conclusions 

 were based were not carried out under natural conditions. 

 He did not, however, confine himself to destructive criticism, 

 but carried out long and careful experiments to show that 

 though atmospheric nitrogen may not be appropriated by 

 the ordinary normal green plant directly, yet there is 

 a continual fixation of it taking place in the soil under 

 the influence of certain organisms, so that it is gradually 

 made available for utilization by vegetation in general. 

 Besides the influence of the organic world in this direction, 

 he claimed that certain physical agencies also are at work 

 causing a similar fixation in the air and the absorption of 

 the resulting compounds by the soil. 



The latter line of research was the earliest he pursued ; 

 in 1876 he showed that free nitrogen can be fixed by various 

 organic compounds in the laboratory under the influence 

 of the silent electric discharge, and suggested that similar 

 reactions probably take place in the air during storms, 

 and at all times when it is charged with electricity. In 

 the statement of his hypothesis he left uncertain what 

 compound of nitrogen may result. In the next year his 



