TIIK WOHUKN EXr'ERlMKXTS : THEIR OIUECT ANT) ^FEIHOI) B3 
dung were used, for when small areas only have to be treated, the great 
variation in the strength of the latter renders the results very uncertain. 
Natural manures we have used in some cases, but for the present our 
manurial experiments are chiefly directed towards ascertaining the more 
elementary facts as to the relative effects of the three main constituents 
of all manures— potash, nitrogen, and phosphorus— and this can only be 
done where we use an artificial manure in which the relative proportion 
of the constituents can be varied at will. Once tlie fundamental facts shall 
have been ascertained, it will be time enough to attack the more compli- 
cated aspects presented by natural and special manures. In the case of 
our plots where the manurial treatment is normal, the manure used 
corresponds in nutritive value to about twelve tons of dung to the acre, 
and the growth obtained so far has been as vigorous as is required. I 
cannot help making mention in passing of the interesting and suggestive 
results, or rather want of results, which we have obtained at present in 
these experiments— manures, whether artificial or natural, having had 
little or no effect on our trees, though on other very different crops in the 
same ground — for instance, wheat and strawberries — their effect has been 
very considerable. 
I have mentioned in outline the general principles on which our 
experiments are inaugurated, but the question arises as to how the results 
are to be ascertained and compared with each other. With any fruit- 
tree or fruit-plant the ultimate standard by which success must be 
measured is the value of the fruit produced from it, not that produced in 
one year only, of course, nor even in several years, but throughout the life 
of the tree, and even this quantity, if ascertained, would have to be 
qualified by considerations based on the length of life and the precocity^ 
of the tree. It is needless to say that we have not yet completed such 
data at the Woburn Fruit Farm, even in the case of the shortest-lived of" 
our fruit-bearing plants — strawberries, and it will be long before we 
can do so with our trees. In the meantime, however, data are being 
accumulated. But a difficulty arises in ascertaining the true value of our 
crops. In the case of every separate experiment the weight and number 
of fruits produced are recorded— in the case of the small berries, currants 
and gooseberries, the weight and volume are taken — and from these 
we can deduce the average size of the fruits ; but how are we to adjudicate 
between two results where in one case we have a larger weight of crop but 
smaller fruits, and in the other a smaller crop but better-sized fruits ? 
The value of a crop depends as much on the size as on the quantity, and 
we want some means of combining these two factors into one expression 
so as to represent its true value. This, I have suggested, might be done 
in the case of apples, and some other fruits as well, by grading them into 
three classes, as would be done for market purposes, and taking the 
relative values of equal measures of these three grades to be in the pro- 
portion of 4, 2, and 1. By counting the number of apples which make 
up a bushel of these different grades, we conclude that the relative values 
of the individual apples of the different sizes are about in the proportion 
of the squares of these numbers, that is, as 16 to 4 to 1 ; and, therefore, 
by dividing the number of apples of each grade by these numbers 
respectively, and adding the results together, we can get numbers repre- 
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