284 BULLETIN OF THE BUSSEY INSTITUTION. 
conspicuous to the eye while the crops were growing. On the 
26th of January, 1878, three weeks before the plants were har- 
vested, I wrote the following statement in my note-book : — 
‘¢The differences between the high and low numbers in this 
series of experiments is very marked, as it has been all along. 
The jars numbered IV. and V. have large healthy plants bearing 
flowers and seeds, while the plants in Nos. J. and LI. are small 
and well-nigh flowerless. The crops in No. III. are mediocre. 
There are, of course some exceptional jars among the higher num- 
bers, in which the plants have not prospered, doubtless because 
of too wet or too compact soil, or, as one may say, on account of 
‘improper tillage.’ But so far as the general appearance of the 
bench goes, the gradation of crops is really perfect and unbroken 
from Nos. 0 and I. to No. V.” 
For the sake of more convenient comparison I have rearranged 
in the following short table the 
Weicuts or Dry Crop HARVESTED. 
Names and Nos. of the Nos. of the Jars, and weights of real Loam in each; the 
Sets of Experiments. last-named figures in the parentheses. 
0. 1% i BEL: EVs Ve 
(25 grms.) (50 grms.) (100 grms.) (150 grms.) (200 grms.) 
1. Beatley Loam .._ 0.300 0.502 0.610 0,545 2.260 1.010 
2. Saltonstall Loam . — 0.435 0.460 0.565 1.265 1.270 
3. Plain-field Loam . — 0.390 0.445 0.710 1.550 1.750 
4, Bean-Plot Loam. . — 0.310 0.450 1.140 1.150 1.475 
Sum of the weights 
ofthe crops . . == 1.637 1.965 2.960 6.225 5.505 
Average weight of 
the crops. . . 0.300 0.409 0.491 0.740 1.531 1.361 
It should be said that numerous experiments, some of which will 
be published in a subsequent article, had shown that mixtures of 
calcined loams and sand, such as formed the bulk of the soil in 
these trials, are capable of bearing abundant crops of buckwheat 
when supplied with nitrogenized fertilizers such as the nitrates of 
potash and of lime. 
I offer the foregoing experiments merely in confirmation of my 
previous proof that the nitrogen of the soil is of very great value 
as plant food under the ordinary conditions of warmth and moist- 
ure that are proper for the growth of agricultural plants. But I 
may here say that I have not gained from these experiments any 
encouragement to pursue another enquiry which had suggested 
itself to me; namely, whether it might not be possible to test 
(i.e. ‘* assay”) the nitrogen-value of any given soil by mixing 
small quantities of it with a standard calcined earth, and growing 
crops upon the mixtures. In experiments such as the foregoing 
