4 SOUECES OF THE NITROGEN OF VEGETATION 



the importance of any supply of combined nitrogen to the 

 plant ; provided that the soil were supplied with the mineral 

 constituents removed by the crop, he argued that it would be 

 able to grow luxuriantly and obtain for itself all the nitrogen 

 necessary. It is difficult now to estimate exactly the positions 

 held by controversialists of more than half a century ago, 

 but there can be little doubt that Liebig overestimated 

 the amount of ammonia which could be obtained from the 

 atmosphere, and that he and his followers, arguing from 

 general grounds as to the origin of the original stock of 

 combined nitrogen in the world, were disposed to believe 

 that some, if not all, leafy plants could assimilate and fix 

 free atmospheric nitrogen. 



Some little time before the publication of Liebig's re- 

 port, Lawes had begun his experiments on a small scale ; 

 as early as 1835 he was making trials in pots at Roth- 

 amsted, and these were year by year extended to the fields 

 on the home farm, until in 1843 the scale had so far in- 

 creased that he secured the co-operation of Gilbert and 

 the Rothamsted Experiments as we now know them 

 began. 



Curiously enough, at this very time (1842) Dr Daubeny, 

 some of whose lectures Lawes had attended at Oxford, was 

 writing in the new Journal of the Royal Agricultural Society 

 about the necessity of systematic experiments to ascertain the 

 value of manures : "I know not how such experiments can 

 well be instituted, except it be on an experimental farm, 

 established for the purpose, and placed under scientific hands. 

 Productive of no immediate advantage to the land on which 

 they are tried beyond what could be equally well attained by 

 a much inferior expenditure of labour, they are not likely to be 

 taken up by any private individual who combines practical 

 experience and pecuniary resources with the requisite scientific 

 skill ; and even if such a person were to present himself, what 

 guarantee can we offer to the world that he possesses the 

 requisite qualifications ? " For it should be remembered that 



