49 
i as foods, it is for the interest of the farmer who uses these feeds 
to see to it that he secures, by careful saving of the manure obtained 
from hisanimals, these valuable fertilizing constituents which these 
and all other foods contain, and thus in large measure making it 
unnecessary for him to purchase commercial fertilizers in order to 
maintain or increase the fertility of his lands. 
- CoMMERCIAL VALUATION OF FERTILIZING CONSTITUENTS oF Foops. 
4 The determination of the commercial value of the potash, phos- 
__ phoric acid and nitrogen in foods, as in commercial fertilizers, is 
comparatively easy and approximately accurate, since, owing to 
the great demand for fertilizers, there has been in every country 
large amounts of capital invested in the several industries which 
have been created to supply this increasing demand, and the 
natural competition of legitimate business enterprise has resulted 
in gradually bringing the prices of the fertilizing constituents to 
as uniform a standard as are the prices of any other product of 
manufacture. 
The rock phosphate of South Carolina, the refuse bone-black of 
the sugar refineries, the phosphatic guanos of the West Indies, 
-and other such natural sources, furnish the raw material upon 
which the value of phosphoric acid mainly depends; while the 
potash salts found in such abundance in the German deposits 
furnish the basis for the estimation of the value of this con- 
_ stituent. Sulphate of ammonia from the gas-works and the 
nitrate of soda of Chili, fix the price for nitrogen in its most avnil- 
able and therefore most valuable form; while the refuse from the 
Slaughter-houses, the pomace left after expressing the oil from 
fish, and such other refuse organic material containing nitrogen, 
furnish the data by which the value of these less valuable forms 
of nitrogen are determined. 
Tt can not be too clearly understood that in the fixing of these 
prices upon these several constituents the agricultural chemist 
has nothing to do. These prices are determined by the same 
laws of trade which regulate the price of nails, sugar, flour and 
other commodities. The agricultural chemist is in a position to 
know from the quotations of the market how much nitrogen is 
worth in Chili niter or in sulphate of ammonia, how much if in 
_ the form of dried blood or fish scrap; how much potash is worth 
in the form of the chloride or muriate, and how much in the form 
