THE SOURCES OF THE NITROGEN OF VEGETATION, ETC. 507 
It is quite evident that, whilst in some instances there has been no evolution of Ni- 
trogen, in.others the amount of decomposition involving such evolution has been very 
great. Indeed, in some cases, the indication of the loss of Nitrogen in this way is so 
great that we could not have believed such a result possible had it not been attested by 
repeated analysis. But we have not been able to trace these differences to their ulti- 
mate causes. 
The amount of decomposition, as indicated by the physical condition of the several 
substances at the termination of the experiment, as also by the proportion of carbon 
given off as shown in Table VIII., might lead to the conclusion that the process had 
gone about equally far, and attained about an equal completeness, in all the cases to 
which Tables VIII. and IX. refer. But here the equality of effect ceases. Thus, from 
60 to 70 per cent. of the total carbon in the original organic matter has passed off; but 
the proportion of the original Nitrogen that is not recovered in the products varies, 
under the same circumstances, from 0 to 40 percent. of it. The proportion of the Nitrogen 
of the original substance which was retained in the mass, or absorbed in the oxalic acid 
in the bulb-apparatus (C) in such form as to be given off as ammonia on distillation 
from a weak alkaline solution, and which probably existed, therefore, in the products as 
ammonia, ranged from 12 to 58 per cent. of the total quantity involved in the experi- 
ment. And, again, the proportion of the Nitrogen evolved from the mass as ammonia 
during the decomposition, and which was retained in the oxalic acid solution (C), varied 
from 0 to about 1°5 per cent. of the original or total Nitrogen. 
If we attempt to trace a relation between the loss of carbon, the loss of nitrogen, the 
formation of ammonia, and the evolution of the small amounts of it during. the decom- 
position, on the one hand, and the circumstances of matrix, moisture, growth, decay, 
&c., pointed out in the notes preceding the Tables, we fail to discover any connexion 
which we may with safety regard as exhibiting cause and consequence. 
The most that we can venture to say is that, under a wide range of circumstances, 
a considerable loss of Nitrogen occurs in the decomposition of nitrogenous organic 
matter; that under particular, and apparently rather rare circumstances, this loss of 
Nitrogen does not occur; that the proportion of the Nitrogen taking, under the same 
circumstances, such form that it may be driven off as ammonia on the distillation of the 
. products with a weak solution of alkali, varied from one-eighth to more than one-half 
of the total present; and that the amount of the Nitrogen evolved from the mass as 
ammonia during the process was quite inconsiderable. 
These conclusions, though necessarily expressed in very general terms, have never- 
theless a very important bearing on certain questions in practical agriculture. Whilst 
it would appear that there may be a very great loss of Nitrogen—a very important 
element in manure—under circumstances of decomposition of organic matter, closely 
allied to those to which, in practice, nitrogenous organic manures are subject, it is at 
the same time indicated that it is possible for such matters to pass through the process 
of decomposition without such loss. The importance of further investigation is hence 
