4G2 
Agricultural Chemistry. 
of lime we used is an assumption and erroneoiis ; that his objec- 
tions to admitting an action by an apparent excess of phosphates 
axe captioiis and tinfounded ; that his " incomprehensible " facts 
are coniprehensihie and consistent ; and that his " still more incom- 
prehensible " fact is not even a fact at all, but is founded only 
on an easily discoverable misprint ! 
But after all this strenuous resistance of the notion, that in the 
agricultural — tliat is, in the artificially enhanced — growth of 
plants, there may be required a supply of substances by manure, 
beyond that which can be accounted for by any idea of merely 
supplying what is to become an actual constituent of the removed 
crop — and saying with regard to it, " have we made, after all, 
but a hair-breadth's progress from our old position? " — we find, 
but a page or two further on, the enunciation of a general prin- 
ciple, obviously intended to cover any such instances which it 
may be impossible to deny the existence of as facts. Baron 
Liebig says : — 
" As a general rule, the maniirinp; of a field sJiovId not he calculated from, the 
sum total of the mineral ingredients ivhich the plant takes from the soil, hut 
must he proportional to that maximum of these substances which is required hy 
the p)lant in a certain j'eriod of its yroivth." — Principles, p. ]33 (note). 
We would compliment Baron Liebig on the fact, that we have 
here evidence of more than " a hair-breadth's progress from our 
old position," when we contrast that Avhich is herein involved, 
with liis general conclusions on the subject of manuring, in sum- 
ming up his general retrospect, in the fourth and last edition of 
his main work, where he says: — 
" By an exact estimation of the quantity of ashes in cultivated jolants, 
growing on various kinds of soils, and by their analysis, we will learn those 
constituents of the plants which are variable, and those which remain con- 
stant. Thus also we will attain a knowledge of the quantities of all the con- 
stituents remoued from the soil hy different crops. 
" The farmer will thus be enabled, like a systematic manufacturer, to have 
a book attached to each field, in which he will note the amount of the various 
ingredients removedfrom the land in the form of crops, and therefore how much 
he must restore to bring it to its original state of fertility. He will also be 
able to express in pounds weight, how much of one or of another ingredient of 
soils he must add to his own land, in order to increase its fertility for certain 
kinds of plantsr — \th Edition, p. 212, 213. 
And then again, to cover by general principle, the undoubted 
fact, that the resultant requirements of land under cultivation, are 
certainly not to be ascertained by the consideration of the collec- 
tive mineral composition of the crop to be grown, we are told : — 
" The produce of a field stands related to the amount of that mineral in- 
gredient which its soil contains in smallest quantity.'^ — Principles, p. 133 
(note). 
And this simply common-sense notion (provided that smallest 
quantity be too small for the requirements of a maximum growth). 
