A(j> icultura I Cliem istry. 
451 
be considered as an increase of fertility ; and the farmer is 
therefore* to be cautious how he adopts any such ruinous means of 
raising the produce of his land. Baron Liebig says : — 
" In that work of mine I have fully explained that the idea of fertility in a 
soil, essentially comprises that of the continuance and duration of the crops, 
ivo one regards as fertile land such as, without manure, hears good crojjs for a 
year or two, and no more. In this point of view, the fertility of a soil is in 
direct proportion to the conditions of fertility present in it ; that is, to the 
mineral substances which are necessary for the nutrition of plants." — Prin- 
ciples, p. 75-6. 
" If we manure the same land with 3 cwt. of ammoniacal salts, we shall 
have, in one year, a crop one half heavier than on the inimanured land ; we 
shall obtain annually onc-and-half crops, or, in eight years, the produce of 
twelve average crops. That is to say, the soil will have lost, in eight years, as 
much mineral matter as it would have lost in twelve years without ammoniacal 
salts ; it will therefore he exhausted, or become unfruitful for wheat, four 
years sooner than if no ammoniacal salts had been used. 
" I hold, therefore, that which in my work I have endeavoured so fully 
and minutely to explain, that, in reference to the exhaustion of the soil, 
ammonia or ammoniacal salts, used alone, are the kinds of manure which 
impoverish a soil, or in other words, consume the capital of the land, the most 
rapidly. 
"In one case only does the fertility of the soil manured with ammonia, or 
its salts, maintain itself, namely, when these are accompanied by the mineral 
substances which are annually removed in the crops. These may be restored 
either by annually adding as much as is removed, or by adding after the fifth 
crop a tive-fold quantity of them. If this be once omitted, the eftect must 
become perceptible in a series of years. 
" The rational agriculturist must not believe, that he can remove from a rich 
fertile soil, without any compensation whatever, a part of its constituents, and. 
not, by so doing, sooner or later impair its fertility ; for this fertility, or the 
produce in a given time, is the effect of the whole sum of the actions of all its 
constitaents ; not only of that portion of them, which has entered the plants, 
but also of the rest of the available supjjly, which is left in the soil. The 
entire supply, or sum, has produced this result, namely, that the roots found 
everywhere their necessary food ; and if we remove a part of the whole supjjly 
of these constituents, then the roots will no longer find their proper food in 
that part of the soil where they are wanting. 
" Let us only suppose that during the last few centuries our ancestors had 
acted on the principles here laid down, in their full extent and strictness ; 
what a paradise of fertility would England be at this day ! " — Jh., p. 81-3. 
We must here first notice the running insinuation in these 
passages, that we would recommend as a practice for adoption in 
agriculture generally, the continuous growth of corn by means of 
nitrogenous manures, without any other return to the land. It 
is only to those who have never read our Papers, that it is 
necessary to say, that a more incorrect impression of our views 
could not possibly be given than that which is herein implied ; 
and Avhich is more plainly, if not more courteously, expressed 
in the following sentence : — 
" It is not easy to understand how Mr. Lawes could deduce from his results 
the conclusion '■that nitrogenised manures are peculiarly adapted fm- thecal- 
