464 
Agricultural Chemistry. 
" It is obvious that, if we could double or treble the proportion of carbonic 
acid and ammonia in the air, the plants would, in the same circumstances, 
take up twice or thrice as much carbonic acid ami ammonia in the same time, 
or as much as they could do in the normal condition in twice or thrice the 
time."— 76. 77. 
Here, then, we are told, that the supplies of carbonic acid and 
ammonia in the atmosphere, though enough for normal vegeta- 
tion, are " very limited." Surely, however, they still remain as 
before, " quite suffieient for the purposes of agriculture " ? Baron 
Liebig answers this question thus : — 
" But the wcic;ht or amount of the crops is in proportion to the quantity of 
food of both kinds, atmospheric and mineral, which is present in the soil, or 
conveyed to it in the same time. By mamcring ivith ammoniacul salts a- 
soil rich in available miveral constituents, the crops are augmented in the same 
')vny as they would have been if we had increased the proportion of ammmiia in 
the air.'" — Ih. 11, 78. 
How neatly, then, has Baron Liebig here begged the whole 
question of the necessity in agriculture as distinguished from 
natural vegetation, of an accumulation of available nitrogen 
xcitJdn the soil itself ! How curiously, too, are the very circum- 
stances, under which we have previously been told that our crops 
are the most capable of relying upon the atmosphere for their 
nitrogen — namely, those of mineral ricliness — iioic made the very 
conditions under which the supply of ammonia to the soil is 
most necessary ! Thus, speaking of the supply of ammonia, he 
says — 
" that it may be even superfluous, if only the soil contain a sufficient 
supply of the mineral food of plants, when the ammonia required for their 
development will be furnished by the atmosphere." — ith edition, p. 212. 
And again : — 
" If the soil be suitable, if it contains a sufficient qvantify of alhalies, 
'jjiosphates, and sulphates, nothing will be wanting ; the ]ilants will derive 
their ammonia from the atmosphere as they do carbonic acid." ( ! ) — Trans- 
lation of Letter, Farmer's Magazine, vol. xvi. p. 511. 
But not only does Baron Liebig do this, but he claims it as 
the established principle of his previous writings, that it is for 
" wheat " distinctively, that ammonia must be added in the 
manure. Thus he goes on to say : — 
" This is the meaning of the passages above quoted from my work, which 
tell Ihe agriculturist that, in order to raise the produce of his land above a 
certain point, in the case of such plants as have not many leaves— /or 
example, of ivhcat — he must add ammonia in the manure." — Princijtles, p. 78. 
Here, then, the importance of nitrogen in the soil for ivhcat, as 
distinguished from other crops, is claimed as a conclusion estab- 
lished by " the passages above quoted." But strange to say, 
after thus attempting to claim that which is now so far an 
established fact, that it would be only ridiculous to deny it, 
