Agricultural Chemistrr/. 
453 
exhaustion, precisely reverse the advocacy reiterated in the fol- 
lowing sentence ? — 
" I had myself, iu the first etlition of my work, attributed to ammonia 
a. prepoti lie rating value and importance ; and I tlmigld I hud sufficiently cor- 
rected this error in the subsequent editions." — Principles, p. 79. 
Surely, if any of the constituents necessary to the production 
of our crops, should have, in the eye of the ac/ricultural chemist^ 
" a preponderating/ value and importance," it should be those whicli 
are the most easily, not those which are the least easily, exhausted 
in the course of practice ! — those by the want of which the limit to 
our production of corn is in practice fixed — not those which, in 
the same course of practice, are ready and Avaiting, but inactive, 
dormant, and unremunerative, because unassociated with others 
which we are told should nevertheless not have attributed to them, 
''^ preponderating value and importance" ! 
But we have not yet done with the limitations to a free and 
unqualified admission of the pre-eminent importance in agri- 
culture, of an accumulation of nitrogen in an available form within 
the soil itself: — 
" The advantage of this artificial supply of ammonia, as a source of nitrogen, 
is limited, like that derived from the presence of humus in the soil, to a gain 
of time" — Ih., p. 74. 
What, we would ask, is gain of time in the growth of plants, 
but the very essence of the distinction between natural growth 
and artificial growth, that is, AGRICULTURE ? In this admission, 
therefore, is involved the fullest and most convincing proof, that 
if any of the constituents of plants should have attributed to them 
" a preponderating value and importance," it should be those 
to which is due a gain of time. 
To resume : The following is a brief summary of the criti- 
cisms to which our experiments on the growth of wheat have been 
submitted by Baron Liebig, with the view of showing that their 
results are at once consistent with his own peculiar doctrines, 
and inconsistent with our own conclusions. 
He maintains alternately, that the supply of ammoniacal salts 
has not, and has, been the source of the increase ! And, when it 
became impossible to avoid the latter conclusion, how does he 
qualify the unpalatable admission ? 
Such a result is precisehj in accordance loith what theory teaches ! 
Salts of ammonia are themselves to he included as mineral 
mayiures ! 
Their action is mainly that of rendering sohthle the minerals of 
the soil, and hence it is the minerals to ichich at last the increase is 
due ! 
