The Mineral Theory. 
503 
sequcntly, the action of ammonia is limited to the acceleration of the action of 
the mineral constituents in a given time." — Principles, pp. 86-7 (1855). 
" the other is the action of sulphate of ammonia as a solvent 
for certain important mineral constituents of the soil." — lb., p. 99 (1855). 
" Ammonia, when used as a manure alone, and when there is a want of 
mineral constituents in the soil, is like the spirits which the labourer takes in 
order to increase his available labour, power, or imagination ; and, like that 
stimulant, its action, in this case, is followed by a corresponding exhaustion." 
—lb., p. 106 (1855). 
" A fertile soil must contain in sufficient quantity, and in a form adapted 
for assimilation, all the inorganic materials indispensable for the growth of 
plants. 
" A field artificially prepared for culture contains a certain amount of these 
ingredients, and also of ammoniacal salts and decaying vegetable matter."— 
Fourth edition, p. 169. 
It is scarcely necessary to multiply these citations, as the mean- 
ing of them is nearly the same. 
The conclusion which is drawn by Mr. Lawes from these pas- 
sages is the following : — 
" These sentences will be sufficient to show whether or notLiebig is justified 
in now attempting to fall back, in agricultural discussions, upon the more 
strictly scientific meaning of the terms ' mineral ' and ' inorganic,' so as to 
include within them ' ammonia,' ' ammoniacal salts,' ' atmospheric constitu- 
ents,' &c, and thus to give a new definition to his mineral theory, or rather 
substitute at this date for his own theory, which has proved to be erroneous, 
another not his own." 
It is quite true that I have contrasted ammonia with mineral 
substances ; but the meaning of these passages must be obvious 
to any candid reader of my works. I said (4th edition, p. 59) — 
"No conclusion can have a better foundation than this — that it is the am- 
monia of the atmosphere which furnishes nitrogen to plants." 
In my ' Principles of Agricultural Chemistry,' from which the 
first passages quoted by Lawes are taken, I said : — 
" All these substances (phosphoric, sulphuric, silicic, and the alcalic, lime, 
magnesia, iron, &c), are included in the term mineral food of plants. Carbonic 
arid and ammonia are the atmospheric food of vegetables." (p. 24.) 
In my book I had to explain the relation of the atmosphere to 
the soil in the growth of plants, and to distinguish the elements 
furnished by the air and those by the soil, and to avoid, by con- 
trasting them, a long tedious enumeration of each of these elements, 
which all had been stated as inorganic. I divided them into two 
classes — atmospheric and mineral. 
I must admit that some scientific education is required for a 
man to understand that the word atmospheric, designating gaseous 
compounds, like the word salt (for ammoniacal salts), in whatever 
connection they may be used, entirely exclude the idea of organic. 
We speak frequently of salts of organic acids (acids derived from 
organic compounds), but a salt itself is never called organic, 
