440 
Agricultural Chemistry. 
Thus, comparing the produce of 1844 with that of 1845, the 
latter being twice as great as the former, he says : — 
" If in the year 1844 a certain amount of rain fell on the land, and thus a 
certain amount of mineral constituents was rendered available for the plant ; 
and if, in 1845, there fell, at the favourable season, one half more rain, tins 
obviously dissolved one half more of mineral constituents. Had these not 
been dissolved they could not have entered the plant and been there employed 
— that is to say, without their aid the crop of 1845 could not have increased 
by one-half. 
" That to which, in these remarks, I wish particularly to direct the attention 
of farmers, is the fact that, in this striking case, the produce of the land in 
grain and straw, and therefore in uitrogenised matters, was much increased 
without the smallest addition of nitrogenous manure, for the land received 
no manure whatever ; and solelj' from the increase in the amount of the mineral 
constituents, present in the soil, dissolved in the same time." — Frinciples, pp. 
G9, 70. 
Here Baron Liebig maintains that the large amount of mine- 
rals dissolved by the increased fall of rain enabled the plant to 
appropriate the additional supply of nitrogen from atmospheric 
sources. We hold, on the contrary, that, owing to climatic 
variations, the atmosplieric supply, either through the medium 
of the soil, or directly to the plants themselves, or both, was 
greater ; tkerefore the plants were enabled to take up a larger 
amount of minerals from the soil. And that this was so, is, we 
think, susceptible of proof far more logical than the contrary 
supposition. Thus our experiments show, — 
1st. That the varying produce of the unmanured plot by no 
means bore any constant and direct relation to the varying amount 
of rain-fall of the different seasons ; that is to say, to the amount 
of viineral solvent ; but that, on the contrary, it depended much 
more on the coincidence with a certain amount of rain-fall, of 
those conditions of atmosphere as to temperature and moisture, 
which Baron Liebig himself admits must influence the amount 
of fluid passing through the plant, and which are also known to 
imply a greater power in growing plants to assimilate atmos- 
pheric food ; — even though it cannot be supposed that they effect 
a greater solubility of the minerals. Whilst, without this greater 
available supply of atmospheric nutriment, either to the roots or 
to the leaves, the necessary and abundant mineral constituents in 
the soil would have been utterly unavailing. 
2ndly. That a direct supply of soluble mineral constituents 
yielded scarcely any increase over the unmanured plot ; whilst 
the supply of available nitrogen — eve7i with one and the same 
set of conditions as to mineral supply, rainfall, and tempera- 
ture, nearly doubled the amount of produce. That is to say, 
an increased supply of the normally atmospheric food of plants 
had a far greater effect in enabling the plants to take up 
