528 • Report of Experiments tcith different Manures 
somewhat higher than that represented by the increase in the 
hay crop merely. But were it attempted to make allowance for 
this, the results would not differ very widely from those recorded 
in the Tables. For, not only would by far the larger proportion 
of the nitrogen of the after-grass be returned to the land, but 
it would be only so much of the remainder as was due to 
increase by manure, that would have to be taken into the cal- 
culation. Nor are the data requisite for such a mode of 
estimation sufficiently established to render any such supposed 
correction at all desirable. It is, however, well to make this 
reservation in regard to the figures recorded in the Tables. 
It may be interesting here to observe that, in experiments with 
wheat conducted over six years, 43 per cent., and in others with 
barley, also over six years, 42'5 per cent, of the nitrogen sup- 
plied in the manure was estimated to be recovered as increased 
yield. Against these amounts the average result obtained with 
the meadow-hay over seven years was, in parallel cases, 45"1, 
which, raised by the small amount due to the after-grass, as 
above explained, would show that the mixed herbage of meadow- 
land probably gathers up within the season of application a 
somewhat larger proportion of the nitrogen supplied as manure 
than either wheat or barley. 
In our former report we directed attention to the probable 
explanations of the real or apparent loss of nitrogen here indi- 
cated ; and we would refer the reader to a discussion of the 
subject in a paper " On the Sources of the Nitrogen of Vege- 
tation ; with special reference to the question whether plants 
assimilate free or uncombined nitrogen," in the ' Journal of the 
Chemical Society of London,' Ser. 2, Vol. 1, 1863. 
Upon the whole, the evidence goes to show, that stable or 
farmyard-manure is a much more perfect restorer of tjie con- 
stituents removed in the hay-crop than those purchased or so-called 
artificial manures which, in a practical or economical point of 
view, can be advantageously employed. Farmyard-dung is, 
however, comparatively slow in its action. These characters 
point to the peculiar fitness of such manure for meadow-land 
mown for hay ; and it was shown in our Report in the last 
number of the Journal, that the description of herbage developed 
by it was much more complex, and upon the whole superior 
in quality, to that developed by the more active artificial ma- 
nures. On the other hand, provided the restoration of the potass 
and silica of the hay-crop be duly accomplished by means of 
farmyard-manure occasionally applied, its slowness of action may 
