Purchased Food, and of its Residue as Manure. 22,> 
which are specially benefited by nitrogenous food. Applied 
direct to light land, rape-cake thus has a greater practical ma- 
nure-value than on heavy land. Although it may pay a farmer 
to give 6/. a ton for rape-cake on certain descriptions of soils, I 
cannot help thinking that not quite so much would be given for 
it if rape-cake were not held generally in great esteem as a 
remedy against wire-worm. As a direct manure, rape-cake is 
certainly dear at 6/. a ton ; and it would pay better a farmer 
who requires cake as a manure to buy slightly damaged or mouldy 
decorticated cotton-cake, which occasionally is offered in the 
market at 6/. lOs. to 11. per ton. Decorticated cotton-cake con- 
tains nearly one-half more nitrogen, and considerably more 
potash and phosphate of lime, than an equal weight of manuring 
rape-cake ; if a farmer, therefore, finds it answer his purpose to 
pay Ql. per ton for the latter, the fertilising ingredients in a ton 
of decorticated cotton-cake, in comparison with those in manure 
rape-cake selling at 6/. per ton, will be worth to him one-half 
more, or 9/. per ton ; and, consequently, decorticated cotton-cake 
at 6/. 10s. or 11. a ton will be a much cheaper manure than rape- 
cake at 6/. a ton. 
Manure rape-cake presents an example showing that the 
theoretical or estimated manure-value of the cake does not 
necessarily coincide with its practical value or its actual price 
on the market. In the case of rape-cake the estimated manure- 
value amounts only to about 4/. 10s. per ton, whereas 6/. is 
actually paid for it by farmers who are in the habit of using it 
for manuring purposes. 
On the other hand, the practical money-values of the manure 
produced from the consumption of various foods, I am inclined 
to think, are much below the estimated values as given in 
Mr. Lawes's table. In attempting to get some better insight into 
the commercial manure-value of various foods, I believe con- 
siderable deductions will have to be made from their estimated 
money- value. 
My reasons for entertaining this view are the following: — 
In the first place, the nitrogenous constituents of food which pass 
into the manure of fattening-stock occur in it only partially in 
the form of ammonia-salts, by far the greater part existing in a 
variety of organic combinations, yielding their nitrogen in the 
shape of ammonia less rapidly than the salts of ammonia, though 
some more rapidly than others ; whereas the estimated manure- 
value of purchased foods is calculated on the supposition that the 
whole of their nitrogenous constituents which is recovered in 
the manure exist in it in the shape of ammonia. Now the 
practical fertilising effects of nitrogen in the form of ammonia, 
