162 BULLETIN OF THE BUSSEY INSTITUTION. 
tive positions of the several classes of fertilizers may be clearly 
exhibited. To this end, I have drawn up the following tables, which 
are analogous to those previously given, and differ from them only 
inasmuch as they include the results obtained from thirty squares 
upon several sections of the field, instead of the results from only 
eighteen squares upon contiguous sections. In the final large table, 
the merit of each fertilizer is given, not in terms of eighteenths, as 
before, but of thirtieths. The thirty experiments compared in 
these tables were selected because of the following considerations : 
During the years 1871 and 1872 there were cultivated, as has been 
seen, 72 squares of barley, 72 squares of beans, and 72 of ruta- 
bagas ; but, as has been explained already, a number of these squares 
(sixteen in all for each kind of crop) were not planted in 1873. The 
two squares treated with green-sand in 1872 and 1873 had no ma- 
nure whatever in 1871. Hence there are left only 54 squares that 
admit of being compared with one another for the three years, and 
from this number we must subtract 18, on account of the squares 
situated upon the fertile soil of Sections A and AA, which cannot 
fairly be put in comparison with the rest. From the 36 squares that 
are left a further deduction of 6 has been made on account of repe- 
titions, such as the five unmanured plots, and the two set's of plots that 
were treated with dungs, the arithmetical means of which are taken in 
each case, whence the final number 30 as the basis of the comparisons. 
It is to be observed that these tables have been drawn up merely 
for the sake of contrasting in a general way the results obtained upon 
different sections of the field. Care must be taken not to lay too 
much stress upon any of the figures, since many of them need to be 
qualified and explained in order that their true significance may be 
comprehended. Many of these explanations and qualifications, such, 
for example, as that the ruta-baga crops are of small significance, and 
that the soil of Section D was charged with elm roots, and is of rather 
inferior quality to that of the other sections, have been made already 
in connection with the tables previously given. It would be unprofit- 
able to repeat them here. It will be enough to say, with regard to 
this general table, that none of the arguments and conclusions here- . 
tofore given have been derived from the consideration of it; they 
depend, in every instance, upon the comparison of results that had 
been tabulated by sections and by divisions. 
