204 
0)1 the Theoretical and Practical Value of 
Most kinds of cattle-food, such as cereal grains, oilcakes, and 
roots, are compounds containing variable proportions of starch, 
sugar, oil, albuminous substances, woodj-fibre, and mineral 
matters. Their market-value does not simply depend upon the 
proportions of their food-constituents, but also, and to a very 
large extent, upon the economical use which can be made of 
various kinds of food in common life, or in farm-practice ; and 
as we do not know exactly to what extent the starch, or the 
sugar, or the albuminous substances in foods, severally contribute 
to produce the total practical effect which follows from their use, 
it seems to me that the requisite data are wanting from which 
the money-value of various articles of food can be calculated 
with anything approaching precision. 
Attempts have repeatedly been made by agricultural writers 
to place a certain money-value upon the starch, sugar, albu- 
minous substances, and other food-constituents ; but as all such 
attempts have brought to light inconsistencies and discrepancies 
between the calculated and actual price at which various articles 
of cattle-food are sold in the market, I need not dwell further 
upon the practical mistakes of those who have proposed certain 
scales or rates for a given weight of starch, oil, sugar, albumen, 
&c., in estimating the money-value of purchased foods. In the 
earlier periods of the history of the trade in artificial manures, 
valuation scales were used with much benefit in checking un- 
scrupulous dealings ; and even at the present time such scales 
materially assist the agricultural chemist who is neither a mere 
calculating machine nor a purely theoretical man, and who makes 
a discriminate use of them to give a trustworthy opinion of the 
proximate and the comparative money-value of artificial manures 
which may be submitted to him for analysis. In a paper " On 
the Commercial Value of Artificial Manures," published in this 
Journal in 1862, I directed attention to a number of practical 
considerations which have to be taken into account in estimating 
the commercial value of artificial manures, and showed that 
serious mistakes will be made, and possibly undeserved ^injury 
to honest traders may be done, if such estimates are entirely based 
upon the figures given in valuation tables. 
Difficulties, no doubt, occur sometimes when the agricultural 
and commercial value of some kinds of artificial manure is 
sought to be determined with great precision ; but far greater 
and more numerous are the obstacles which present themselves 
in attempts to put a money-value upon articles of food ; and it 
may be as well to state, in plain language, that the money-value 
of cattle-foods cannot be determined simply by analysis. 
Nevertheless, the chemical examination of feeding-stuffs must 
not be regarded as void of all practical interest, for it enables us 
