Nutritive Values nf different Crops. 
147 
In this table T'rofossor Johnston t;ikes 10 as his standard for 
hay, and sometimes <?ivos a varying- equivalent. In using his 
figures in connexion with Von Thaer's, for the following calcu- 
lation, I liave adoj)ted 100 as the standard in both cases, and have 
taken the mean of his varying equivalents. Thus, in the instance 
of wheat, which he gives as from 5 to 6, I have taken 55 ; but as 
this again differs from Von Thaer, who takes wheat at 27, I have 
again adopted the mean between the two, and call wheat 41. I 
have assumed the relative produce of the crops given in column 2 
chiefly from those in Mr. John Morton's ' Report of Whitfield 
Farm,' and the weights in column 3 from the printed tables in his 
' Farmer's Pocket-book.' It must be admitted that these assump- 
tions are of an arbitrary character, and that calculations based 
upon them are proportionally doubtful ; but it should be observed 
that the figures, both of Von Thaer and Professor Johnston, are 
given as the result of actual experiment in feeding animals by 
practical men. Professor Johnston himself has given a similar 
table to that which follows, but based on the constituents of dif- 
ferent crops, chemically ascertained, as showing, by one set of 
figures, " the nutritive power of these crops" per acre, " in so far 
as they depend upon the starch and sugar they contain ;" and by 
another as it depends on the gluten and albumen. The result 
are very interesting ; but, as Lord Spencer observes, in his paper 
in the second volume of the Journal, ' On the Comparative 
Feeding Properties of Mangold-wurzel and Swedes,' the reason- 
able probability of the relative value of different foods, as deduced 
from chemical analysis, knowing so little as we do of the processes 
of nature in converting food into flesh, seems not quite satis- 
factory ; and he prefers making his comparisons from the actual 
effect of food on animals. So also the equivalents of food, which 
in the two above tables are obtained from practical results in 
feeding, seem to me a preferable basis of calculation ; but at all 
events the comparison of a table showing the nourishment per 
acre, as deduced from the quantities of the different nutritive in- 
gredients, chemically ascertained, with one showing it obtained 
from actual experiment, would be interesting, and perhaps useful. 
In either case the presumed average crop per acre is an arbitrary 
amount, and must be assessed according to the different quality of 
the land to which the formula is to be applied ; and however 
much any of us differ in these assumptions, the use of the calcu- 
lation is still the same. Applying then the equivalent of nourish- 
ment in different crops to the average produce of these crops per 
acre, we get, from the following table, the relative nourishment 
per acre which those crops severally yitld ; — 
L 2 
