Relation of Nonavailable Water to Hygroscopic Coefficient 29 
200-gram portions, the contents of each jar being thoroly mixed 
before removing any of the soil. The samples were dried in an 
electric oven, kept at 110° C, thru which a rapid current of air 
was kept passing. In the experiments of 1909 and 1910 all de- 
terminations were made in duplicate, using 100-gram samples, 
but in those of 1911 a single determination of each was made, 
using a 200-gram sample. As in such a study the thoro di ving 
of the samples is extremely important, the following method was 
followed to insure its completeness. In the earlier determina- 
tions, after the samples, 50 to 60 in all, had been in the oven for 
12 hours, five or six from different parts of it were removed and 
allowed to cool in a desiccator. These were weighed, returned to 
Fig. 1. Cylinders used in experiments of 1909 to 1911. a. Lower portion 
with nipple N. b. Manner of opening cylinder in 3-inch sections. At 
x is shown a 3-inch section of soil ready for removal. 
the oven and left there for from 5 to 12 hours longer Avhen they 
were again cooled and weighed. If no appreciable loss in weight 
occurred after the first weighing it was assumed that all the 
other samples were dry, they having been in the hot oven all the 
time. If a loss in weight occurred, however, the drying was con- 
tinued until two successive weighings showed no appreciable 
change of weight. In the later determinations, instead of using 
the above method of control, several 200-gram samples taken 
from a large sample of known moisture content were placed in 
the oven along with the samples from the cylinders. If after 12 
hours in the oven these control samples were found to be fully 
dried the heating was discontinued, but if not they were returned 
and weighed at intervals until thoroly dried, the cylinder samples 
being left in the oven undisturbed until the control samples were 
dry. The former thus had a longer exposure in the oven than the 
latter. This modification of the control greatly shortened the 
time required for the drying, as usually the samples were fully 
