for Twenty Years in succession on the same Land. 333 
was found to be, in some cases, very considerable ; but even with 
equal amounts supplied, it varied, both in total amount and in 
distribution, according to circumstances, the depth to which the 
unused supply had penetrated being apparently influenced by the 
character and amount of the associated manurial constituents. 
The general result was, that, although a considerable amount of 
the nitrogen supplied in manure which had not been recovered 
as increase of crop was shown to remain in the soil, still a larger 
amount was as yet unaccounted for. Initiative results indicated 
that some existed as nitric acid in the soil, but it was believed 
that the amount so existing would prove to be but small. In 
fact, it was concluded that a considerably larger proportion would 
remain entirely unaccounted for within the soil to the depth under 
examination than was there traceable, and the probability was, 
that at any rate some of this had passed off into the drains, and 
some into the lower strata of the soil." 
It was at the same time shown, by reference to field results, how 
very small was the increase of subsequent wheat crops due to the 
large residue of nitrogen accumulated in the soil, notwithstanding 
its amount was many times greater than that which would yield 
an increase of 20 bushels or more, if applied afresh to soil other- 
wise in the same condition. 
Thus, then, it was established, that there was a considerable 
accumulation within, the soil, of nitrogen supplied in manure 
and not recovered in the increase of the crop, but that there 
remained a considerable quantity not so accounted for ; and it 
was concluded that some of this had passed off into the drains, 
and some into the lower strata of the subsoil. 
Being fully occupied at the time with other subjects, and 
finding that Dr. Voelcker was desirous to investigate the ques- 
tion of land drainage, we gladly provided him with samples of 
the drainage-water from the differently-manured plots in the 
experimental wheat-field, and also with full particulars of their 
history for the purposes of inquiry. In the ' Journal of the 
Chemical Society of London' (vol. ix. s.s. p. 291, 1871), Dr. 
Voelcker has published the results of the complete analysis of 
seventy samples of drainage-water of accurately known history so 
collected. Those results are a most valuable contribution to our 
knowledge of the subject, not only in its agricultural bearings, but 
also in relation to the question of the influence of the sources of 
potable and other waters upon their composition and quality. 
For the details we must refer the reader to Dr. Voelcker's own 
paper ; but the following table gives a summary of the results 
so far as they relate to the loss by drainage of the nitrogen supplied 
to the soil by manure. 
