240 Report of Experiments toith different Manures 
here an average annual increase of ]6'8 lbs. of nitrogen per acre. 
But this increased yield of nitrogen obtained by the use of 
mineral manures, it is to be observed, was not due to an increased 
development of the Graminaceous, but to that of the Leguminous 
portion of the herbage. In fact, the annual yield of nitrogen per 
acre in this case, where the Lefjnminous plants comparatively so 
much predominated, was nearly double that which has been ob- 
tained in the continuously unmanured cereal crops of the arable 
land. 
The next point of consideration in regard to the nitrogen- 
statistics of the hay-crop, is one of great interest, both in a 
practical and scientific point of view ; namely, that of the relation 
of the nitrogen in the increase, to that in the manure employed 
to produce it. Tables VII. and V III. illustrate this part of the 
subject. Table VII. shows the actual increase of nitrogen in the 
produce (in lbs. per acre), where it was supplied in manure. 
Table VIII. shows the proportion of nitrogen recovered in the 
increase, for 100 of it supplied in manure. But in both Tables 
two sets of columns are given. The first of these relates to the 
increase of nitrogen ever that in the unmanured produce, and the 
second to the increase over that in the produce by the ^'^ mixed 
mineral manure.'^ The reader has thus the facts put before him 
in two aspects. It appears to us, however, from a careful con- 
sideration of all the circumstances of the experiments, that the 
only legitimate mode of estimating the. amount, or proportion, of 
nitrogen recovered in the increase of hay, for a given amount of 
it supplied in the manure, will he to assume the nitrogen of the 
unmanured, and not that of tlie 7)iineral manured produce, as the 
standard or normal yield, upon which to calculate the increase 
obtained by the action of nitrogenous manure, whether this be 
used alone, or in addition to mineral manures. 
Thus, it must be remembered, that the increase, both of gross 
produce and of nitrogen, was, when mineral manures alone were 
employed, due to an increased development of Lerjuminous plants. 
On the other hand, when nitrogenous manures were used, either 
alone or in combination with mineral manures, the increase was 
due to the increased development of the Graminaceous herbage 
only. Under these circumstances, it is obvious, that the whole 
increase by the combined action of both nitrogenous and mineral 
manures (it being almost entirely graminaceous), must be supposed 
to be due, so far as the resources of nitrofjen are concerned, to that 
artificially supplied in the manure. That is to say, bearing in 
mind the difference in the description and composition of the 
herbage grown by mineral manures alone, and by mineral ma- 
nures in admixture with nitrogenous ones, the influence of the 
