Field Experiments on the Fixation of Free Nitrogen. 655 
of straw. On No. 24 the produce was, per acre, 55 bushels of 
grain and 24 cwt. of straw. 
Whether the superiority of crop on No. 24, as compared with 
that on No. 23, was owing to the loss of some plants on the latter 
by wireworm, or whether it was owing to the more perfect 
mixing and turning over of the soil and subsoil in No. 24, I am 
unable to say. Taken together, they gave a general average crop 
of 46 bushels of grain and over 23 cwt. of straw per acre, and 
this without the addition of any nitrogenous or organic manure 
whatever, but with a full complement of ash constituents. 
At this stage it is necessary to explain that when I planted 
the beans I was not doing it with a view to the special study of 
the problem of the fixation of free nitrogen. The first very 
clear ideas I acquired on this subject came in conversation with 
my friend Dr. Gilbert. It is quite true that nitrogen was “in 
the air,” so to speak, short notices of the experiments of Hell- 
riegel and Willfarth, Berthelot, Schloesing, and others having 
attracted attention, so that it was felt by many besides myself that, 
as regards agricultm’e, the nitrogen question was the question. 
The bean experiment, which, made under the circumstances 
I have described, was very striking, did not, however, prove 
anything as to the source of the nitrogen. Orthodoxy suggested 
the explanation that the nitrogen was derived from the soil and 
the subsoil, and that to the bean plant belonged a power of 
assimilating soil nitrogen not possessed by the cereals. But, 
in view of the conclusions established by Hellriegel and Will- 
farth, there could be no difficulty in understanding where the 
nitrogen of the bean crop came from. 
From this period onward I looked at the experiment on the 
two plots. Nos. 23 and 24, as bearing directly on the nitrogen- 
fixation question, and in that sense continued it. With a view 
to accumulate in the soil an increased quantity of nitrogenous 
residue I seeded both plots, on March 3, 1890, Avith a mixture of 
the following leguminous plants : cowgrass, white clover, alsike, 
yellow trefoil, and a little lucerne. Mown on August 18, the 
crop gave 1 ton 8 cwt. of hay per acre. 
The next year (1891), with two cuttings, it gave a mean 
produce of nearly 3 tons per acre, no manure of any kind having 
been applied. 
In the autumn of 1891 the clover and bean ley of the two 
plots. Nos. 23 and 24, was trenched to sixteen inches, and thrown 
up in ridges to undergo weathering action during the winter. 
I had thus accumulated in the soil the root-residues of the bean 
and clover crops, and, in addition, the supposed accumulated 
