AGRICULTURE: ALWAY AND McDOLE 
259 
corresponding values of 13.3 and 29.5. In the laboratory experiments 
we employed cylinders 4 to 6 inches in diameter and of various lengths. 
These were filled with soils of known hygroscopic coefficients and mois- 
ture equivalent, and, except where saturation was desired, we deter- 
mined the initial moisture content. 
Five of the loams, placed in capillary connection with the natural 
subsoil mass, saturated with water and allowed to stand protected from 
surface evaporation for several months, lost water until the amount 
retained bore a close relation to the hygroscopic coefficient, being from 
2.1 to 3.1 times this value, according to the particular soil. When a 
layer of coarse sand or gravel separated the column of loam from the 
natural subsoil mass or interrupted it the downward movement of the 
water in the soil above this layer was much delayed. Where the column 
consisted of successive 2 inch layers of loams differing widely in texture 
the order of their arrangement exerted no influence upon their final 
water content. 
Soil columns, 30 to 36 inches long, while protected from all loss of 
moisture at the sides and bottom, were freely exposed to evaporation at 
the surface for periods varying from a few weeks to half a year. The 
moisture content, originally uniform and lying between 2 and 3 times 
the hygroscopic coefficient, fell until it reached, at depths below the 
first foot, an almost constant minimum with the ratio 1.9 to 2.2. 
Employing 2-foot columns of 12 different loams, each with an initial 
moisture content approximately equal to its hygroscopic coefficient, 
enough water was added to raise the average moisture content of the 
column to 1.5 times the hygroscopic coefficient, the water being applied 
in one experiment to the top and in another to the base of the column. 
After the cylinders had stood for three or four months, fully protected 
from evaporation, the distribution of moisture, with regard to the sur- 
face to which it had been applied, was found to be the same in both 
experiments. The maximum distance through which an effect was 
shown was about 2 feet but in most cases the distance was much less. 
The maximum final ratio of moisture content to hygroscopic coefficient 
was found in the section adjacent to the surface of appHcation, where 
it lay between 1.7 and 2.4. The ratio, while falKng within these limits, 
is not a constant, it not being the same for all the soils that have the 
same hygroscopic coefficient. 
The water-retaining capacity of the loams, as determined by labora- 
tory experiments, was found to bear a somewhat closer relation to the 
moisture equivalent than to the hygroscopic coefficient, the ratio vary- 
ing between 0.8 and 1.2. 
