Agricultural Chemistry. 
419 
"In conclusion, then: if the theory of Baron Liebig simply implies that 
the growin;^ plant must have within its reach 'a sufficiency of the mineral 
constituents of which it is to be built up, wo fully and entirely assent to so 
evident a truism ; but if, on the other hand, he would have it understood that 
it is of the mineral constituents, as would be cdlhctively found in the ashes of 
the exported produce, that our soils are deficient relatively to other consti- 
tuents, and that, in the present condition of agriculture in Great Britain, ' we 
cannot increase the fertility of our fields by a supply of nitrogenized pro- 
ducts, or by salts of ammonia alone, but rather that their produce increases or 
diminishes, in a direct ratio, with the supply of mineral elements capable of 
assimilation,' we do not hesitate to say that every fact with which we are 
acquainted, in relation to this point, is unfavourable to such a view." — li, 
vol. xii. part i. p. 39. 
The comments Baron Liebig makes on this sentence are as 
follows : — 
" In the first part of this quotation Mr. Lawes admits the tnith of the so- 
called mineral theory ; in the second I find two erroneous statements the con- 
tinued diflusion of which I can no longer tolerate." — Principles, p. 115. 
In the first part, then, of this comment by Baron Liebig, Ave have 
the important admission, that the so-called " Mineral Theory " 
— as he icouhl now have it understood — " simply implies that the 
growing plant must have within its reach a sufficiency of the 
mineral constituents of which it is to be built up." And if it 
should be shown by the copious quotations which we have yet to 
make from Baron Liebig's former writings, that his earlier 
" Mineral Theory," as applied to agriculture, was far more cor- 
rectly indicated by the latter portions of our sentence, which 
Baron Liebig tells us he " can no longer tolerate "■ — if this be 
shown, we may congratulate ourselves on a very material limita- 
tion of his formerly promulgated opinions. We have here also the 
admission, that " we fully and entirely assent " to such a " Mi- 
neral Theory," as " simply implies that the growing plant 
must have within its reach a sufficiency of the mineral consti- 
tuents of which it is to be built up." And in this latter admis- 
sion Baron Liebig must surely be conscious of a rebuke to him- 
self, for the pervading insinuation throughout his criticism of our 
views, that we have ignored the necessity of mineral constituents 
to plants. Thus he says — 
" It is not easy to understand how Mr. Lawes could deduce from his results 
the conclusion ' that nitrogenized manures are jteculiarly adapted for the cidture 
of wheat,' since such manures can onlj^ produce a favourable result if certain 
preliminary conditions, which Mr. Lawes has entirely disregarded, be fulfilled." 
—lb. p. 79. 
And again — 
" Now, every one would suppose from this, that Mr. Lawes thought that 
the use of ammonia enabled us to dispense with that of mineral manure, 
founded on the knowledge of the composition of vegetable ashes, and that 
these, the ashes or mineral constituents, might be replaced by ammonia." . . . 
