198 
Journal of Agricultural Research 
Vol. VIII, No. 6 
all discarded, and the one shown in figure 1 was finally adopted and em¬ 
ployed throughout this investigation. It consists of a glass bulb, A, 
in which the soil is placed, the glass stem, B, on 
which the expansion is read, and the thermom¬ 
eter, C, which serves to indicate the tempera¬ 
ture of the soil or mass and also acts as a stop¬ 
cock to the bulb A. The bulb has a capacity of 
50 c. c.; the stem is a 1 c. c. pipette and is cali¬ 
brated to 0.1 c. c.; and the thermometer reads 
from — 5 0 C. to +30°, and is calibrated to i°. 
That portion of the thermometer which is in¬ 
serted into the mouth of the bulb is suitably 
ground down so that it forms water-tight connec¬ 
tions with the latter. 
It was found absolutely necessary to have a 
thermometer in the dilatometer, in order to in¬ 
dicate the degree of supercooling, because the 
amount of water that freezes in the soil is in¬ 
fluenced to a considerable extent by the de¬ 
gree of supercooling. If the magnitude of super¬ 
cooling was not the same, no concordant results 
could be obtained in the different samples of the 
same kind of soil. 
For completely filling the bulb of the dilatom¬ 
eter after the soil was added and for measuring 
the volume of expansion of the soil water upon 
freezing, ligroin was used. Ligroin, of course, 
is a derivative of petroleum and is sometimes 
called “ light petroleum.” It proved to be a 
very satisfactory material for completely filling 
the bulb and for measuring expansion. 
For determining the amount of water that 
soils cause to become inactive or unfree, the fol¬ 
lowing procedure was adopted: To 25 gm. of 
air-dry soil were added 5 c. c. of distilled water. 
These were thoroughly mixed. In those soils 
which possessed a high water-holding capacity 
the mixing was done in an evaporating dish be¬ 
fore the soil sample was placed in the dilatom¬ 
eter, while in those soils which possessed a low 
water-holding capacity the soil sample was first 
placed in the dilatometer and then the water 
added to it. In both of these processes precau¬ 
tion was taken to guard against the loss of water through evaporation 
and thus to avoid inequalities. 
