Apr. 9, 19x7 
Water-Retaining Capacity of Soil 
4 i 
The ratio of the total water to the hygroscopic coefficient is strikingly 
similar for all the soils where the sand layer did not interrupt their 
connection with the natural subsoil mass, it varying only from 2.1 to 
3.1. For soil J it is similar to that found in section A above. 
From the tables it will be seen that while it apparently makes no 
difference as to the order of the soil layers, with the exception of the 
dune sand Q, the interposition of this has in all cases greatly increased 
the amount of water held by the soils in the layers above it. The ratio 
of the total water to hygroscopic coefficient varies from 4.4 to 5.4 for 
the sand. Soil E shows a ratio of 2.1 in Cylinders I and II when below 
the sand, but of 3.3 to 3.9 in the others, where the sand underlies it. 
The ratios for J are 2.4 to 2.5 against 4.0 to 4.2, for H 2.6 to 3.1 against 
4.5 to 4.7, for D 3.1 against 3.5 to 3.7, and for A 2.2 to 2.4 against 2.9. 
Thus, where the sand layer overlies the finer-textured soil the ratio of 
the retained moisture in the latter to the hygroscopic coefficient varies 
only between 2.1 and 3.1, while where it underlies the latter the ratio is 
from 0.4 to 2.1 higher. 
The concordance of the retained moisture with the moisture equivalent 
(Table IX) where the sand layer does not interrupt is even much closer 
than its relation to the hygroscopic coefficient, the ratio being 1.0 to 1.2. 
The sand layer Q is in all cases low in moisture compared with the 
amount found when water has been added to the surface of a 2-foot 
column of the same soil, it varying from 2.2 to 2.7 per cent; whereas in 
the latter it lies between 3.4 and 6.0 per cent, even 83 days after 1 inch 
of water has been added (p. 54). 
Mitscherlich (20, p. 143) has pointed out that a very thin layer of 
loam in a sandy subsoil may markedly retard the movement of water 
through the latter. It is evident from the above that, conversely, thin 
layers of coarse sand or gravel may retard the movement of water in 
a loam. 
FINAL WATER CONTENT WHEN DIFFERENT AMOUNTS OF WATER 
ARE ADDED TO THE TOP OF A COLUMN OF AIR-DRIED SOIL 
In this experiment we used 8 pairs of cylinders, each 18 inches long, 
6 inches in diameter, closed at the bottom, and provided with a tightly 
fitting cover. Twelve inches of air-dried soil D, containing 3.0 per cent 
of water, was tamped into each of 10, and a volume of water, equivalent 
to 1, 2, 3, 4, and 5 inches of rain, respectively, was added in small por¬ 
tions as rapidly as it was absorbed. The 6 other cylinders were simi¬ 
larly filled with the soil J in an air-dry condition, carrying 2.3 per cent 
of water, and treated with 1,2, and 3 inches of water. Then the surface 
was covered with an inch layer of gravel, the cylinders covered, placed 
in a covered pit, and left undisturbed for 47 days, at the end of which 
they were opened, and the water determined in inch sections. The data 
