416 
Agricultural Chemistry. 
plants upon the atmospJicrc, and not upon the soil, for their 
nitrogen in agriculture as distinguished from normal vegetation — 
and upon the distinctions which he seeks to draw, between fer- 
tility (as implying duration) and immediate production merely. 
But upon the sentence in the altered form, Baron Liebig 
says : — 
"lathe sentences just quoted from my book, the produce of the land is 
compared with the proportion of nitrogenous matter, _ inclusive of mineral 
substances, supplied in the manure, and with the amount of mineral consti- 
tuents, inclusive of nitrogenous substances, supplied in the manure. 
" The words ' by arnmoniacal salts alone ' and ' in the manure ' show that I 
never thought of excluding carbonic acid and ammonia in the manure. Ac- 
cording to Mr Lawes's mistaken notion of my meaning, I ought to have said, 
omitting the word manure, that ' on the contrary the fertility of the land 
rises and fulls with the amount of mineral substances supplied to it.' But this 
I have not said. 
" The meaning of these sentences in my work is this : ' that ammoniacal 
salts alone ' have no effect ; that, in order to be efficacious, they must be accom- 
panied by the mineral constituents, and that the effect is then proportional to the 
supply, not of ammonia, but of the mineral substances." — Frincipiles of Agricul- 
tural Chemistry, p. 54, 55. 
Now, in reference to Baron Liebig's third paragraph of com- 
ment, it may be observed that, inasmuch as in the original he 
speaks of " manures rich in nitrogen," as well as " ammoniacal 
salts alone," the statement that he meant merely " that ammoniacal 
salts alone have no effect," is obviously quite inadmissible ; whilst 
the introduction of the definite article ^^the" is the only founda- 
tion for the meaning claimed by Baron Liebig that he only in- 
cluded manure containing both nitrogenous matter and mineral 
substances — and that he did not speak of the fertility of the land 
rising and falling " with the amount of the mineral substances 
supplied to it." But he himself admits in another page (^Prin- 
ciples, 115) that he did refer to manure generally, whether 
" mineral manure, guano, poudrette, farmyard manure, &c." 
Whatever may have been the meaning of Baron Liebig in the 
sentence we have quoted, or whatever the interpretation which 
he now gives it, we shall presently make such full quotation 
from the same edition of his work, and from other publications, 
and also from other authorities, as will enable the reader to judge 
for himself — not only what was the obvious meaning of the sen- 
tence in question, but what has been the interpretation of that 
sentence, taken in connection with many others in his writings, 
by others of his readers than ourselves. 
Before doing this, however, we will give a single illustration of 
how fundamental was the change made by Baron Liebig from 
the first edition of his work, to the third and fourth and subse- 
quent publications ; as by this means, the reader will not only be 
prepared to form a right judgment of what we shall have after- 
