On the Valuation of Unexhausted Manures. 
9 
the quantity of organic matter it contains, it serves to render 
the soil more open and porous, and so to enable it not only to 
retain more water in a favourable condition, but also to absorb 
and retain more of the valuable constituents of the manure, and 
so to arrest the passage of them in solution into the drains. 
Further, by the gradual decomposition of the organic matter of 
the dung, the pores of the soil become filled with carbonic acid, 
which probably serves to retard the oxidation of the ammonia 
into the more soluble form of nitric acid, in which it would be 
more liable to be washed out and lost by drainage. From these 
facts it will be readily understood how it is that dung is more 
lasting in its effects than the more active artificial manures. 
Still, in the experiments at Rothamsted in which dung has 
been applied year after year for many years in succession, there 
is a large amount of the nitrogen so supplied which is not yet 
accounted for either in the increase of crop or in the soil. 
Whether there is an ultimate loss of a greater or a less pro- 
portion of that supplied than when ammonia-salts or nitrate of 
soda is used ; whether the loss will be proportionally the same 
when dung is used in more moderate quantity ; or whether the 
loss be wholly, or chiefly, by drainage, or in other ways, the 
evidence at present at command is not sufficient to determine 
with certainty. 
From the foregoing observations on the characteristics of 
some of the most important descriptions of manure, it will be 
obvious how essential it is to take in*o careful consideration the 
peculiar properties, and probable duration of effect, of different 
manures, if we would hope to arrive at anything like a fair 
estimate of the money-value of the unexhausted residue they 
leave in the soil under various circumstances. 
Guided by such knowledge as I possess on the various essen- 
tial points of the question, I will now endeavour to estimate the 
value of the unexhausted residue of various manures, under the 
circumstances in which that value is most likely to become 
the subject of claim for compensation. In all cases, the valuation 
is expressed in the number of shillings estimated to be due to 
the outgoing tenant, for twenty shillings original manure-value. 
The valuations given must, however, be taken as only approxi- 
mately correct, as the amounts due might be affected very 
materially — according to the cleanliness or foulness of the land, 
the lightness or heaviness of the soil, the dryness or wetness 
of the locality or of particular seasons, and the difference be- 
tween the purchasing price of the food or manure and its actual 
and relative value. 
