Agriciiltii7-al Chemistry, 
485 
the nitrogen of the manure recovered in the increase of crop ! — 
and certainly the near approximation in the avera^fes of the two 
crops is not a little striking ; especially when we remember, that in 
the case of the barley there were no instances of more than standard 
amomit of nitrogen used, which would obviously have brought 
down its final average nearer to that of the wheat. 
Now, the final average here obtained in the case of reheat, 
would represent exactly 5i lbs. of ammonia for each bushel of 
grain (^with its equivalent of straw), obtained by its use, assuming 
average proportions of corn to straw, and of nitrogen in both : 
and, again, by the same method of calculation, tlie return of rather 
more than 40 per cent, of nitrogen, the result where the standard 
amount of ammonia with minerals was used, would be almost 
identically equivalent to 5 lbs. of ammonia in manure for every 
bushel of corn, and its equivalent of straw, obtained as increase 
of crop I 
So much, then, for the indications of some hundreds of direct 
experiments on this subject. But we further unhesitatingly 
maintain, that tlie general result here arrived at, agrees very closely 
indeed with that of common experience in the use of guano 
and other nitrogenous manures for the increased growth of grain. 
Consistently with tlie object of this paper, which is simply to 
meet the objections of Baron Liebig to our facts and conclusions, 
and to adduce, in the form of condensed summaries of our field 
experiments, such evidence as shall serve to establish the facts 
and conclusions thus disputed, it would be out of place, even did 
our space permit it, to enter into any detailed consideration of 
wliat may be the scientific explanation of the practical loss of 
nitrogen, which we have just illustrated. Hoping, however, 
to recur to this subject before long, we may nevertheless, 
in passing, state, that various experimenters have recorded 
an evolution of nitrogen from the leaves of growing plants^ 
beyond that which they thought they could attribute to the 
atmosphere with which their plants had been supplied ; but as 
observations of this kind have not established a clear distinction 
between the leguminous and the cereal plants of our rotations in 
this respect, further evidence is of course necessary, before we 
should be justified in confidently attributing the phenomenon in 
question, to the functional actions which have been supposed to 
be the source of the evolution of nitrogen from the leaves of 
plants, observed in the experiments alluded to. The only expla- 
nation of this practically observed loss, which has been suggested 
as special to tlie cereals, is that proposed by Mr. Way; namely, 
that the silica required by these plants, is taken up as a silicate, of 
which ammonia is a base ; and that this alkali, or its constituents, 
is evolved upon the fixation of the silica by the plant. Professor 
