105 
conditions; so as to permit the absolute volume of soil air per cubic foot to be calcu- 
lated at each date of sampling; so as to give the total pore space, the absolute water 
capacities, and the weights per cubic foot of water-free dry soil. 
The soil temperatures have been determined weekly on the same day in the four 
localities for the eight types of soil at depths of 6 inches, 12 inches, 24 inches, and :!(> 
inches, the records extending through the entire season. A continuous record of the 
soil temperature at 1 foot below the surface under the corn on the eighl types of soil 
has also been obtained. A continuous record of the temperature in a closed shelter 
4 feet above the ground in the field of corn growing on one of the soil types in each 
locality has also been obtained. Likewise a continuous record* of the evaporation 
from 11 square feet of soil kept continuously saturated by capillarity has been kept 
for one of the soil types at each of the four stations. So, too, has the total evapora- 
tion from ten stalks of corn growing on one of the soil types at each station been 
measured. 
The amounts of readily water-soluble salts which could be recovered by a three- 
minute washing in distilled water have been determined for the different soil types 
under the different fertilizations and at different times during the season for depths 
extending to 4 feet by 1-foot sections. Samples of the corn and potatoes growing 
upon the ground were collected at the times the soil samples were taken, under the 
different fertilizations, and these have been examined for the kinds and amounts of 
water-soluble salts they contained, so as to be able to compare these with those found 
in the soil moisture upon which the crops were grown. 
The fallow area was maintained between each crop area on the different soil types 
so as to get a measure of the amounts of water-soluble salts which might be developed 
and retained by the different soils under the different treatments where no crop was 
present to influence in any manner what might form or accumulate through a capillary 
rise of moisture from below. 
Samples of soil have also been taken directly under hills of corn and potatoes and 
at points between rows farthest removed from the hills so as to be able to compare 
the differences in soil moisture and in water-soluble salts with those of the fallow 
ground where no influence of crop has been felt. 
The relative rates of nitrification under like fertilizations and like physical rela- 
tions have been measured for the different soil types. A study has also been made 
of the capillary movement of water-soluble salts as influenced by methods of tillage, 
in order to ascertain in how far the position of water-soluble plant food may be 
influenced or controlled by practical methods. 
We have measured the relative powers of the different soil types to retain water- 
soluble salts contained in a solution passing over or through them, as always happens 
when fertilizers are applied to fields and rains follow which may produce percolation, 
and which takes place in all soils during periods of protracted dry weather when 
large amounts of water are evaporated from the surface and the supply is kept up 
through the capillary rise from below. 
In another series of studies, instead of simply washing the soil sample three 
minutes in distilled water a single time, we have repeated the washing of the same 
sample eleven consecutive times in order to obtain some idea of the amounts of water- 
soluble salts which are recoverable by the use of distilled water only. 
We have studied the textural differences of the soil types, measuring the relative 
permeability of the different types to air, the effective size of the soil granules, and 
their comparative resistance to tendencies to break them down in such a manner as 
to result in imperfect soil ventilation. 
Permit me to present as concisely and briefly as I may some of the results secured 
by these studies, and to point out their practical bearings. 
Beginning with the results which have come from the physical investigations, we 
have found that, generally, the Southern soils are much more compact, especially at 
the surface, having a much higher dry weight per cubic foot, and much smaller pore 
space and absolute water capacity. To illustrate: The two Janesville soils and the 
two Lancaster soils had a combined mean dry weight in the spring of 60 pounds per 
cubic foot, while the two Maryland and Goldsboro soils had a mean weight of 78 
pounds, or 16 pounds more per cubic foot. At the end of August the northern and 
middle-west soils weighed 74 pounds per cubic foot, while the coastal-plain soils 
had an average mean weight of 84 pounds, being 10 pounds higher. The pore space 
of the northern soils is thus much larger than that of the southern soil, the amounts 
being 64 per cent for the former and 54 per cent for the latter. This difference in 
the pore space has a very important influence onthese soils, and I have no doubt 
that it is a very important indirect factor in determining the relative agricultural 
values of the soils in the two regions. 
In the second place it has been shown that the northern and middle-west soils are 
not only better granulated, but the tenacity of granulation is appreciably stronger, 
