Dec, 4, 1916 
Evaporation of Moisture from the Soil 
455 
Fig. 12.—Evaporation of water in 115 days from quartz and river 
sand of different sizes with a water table maintained 3 cm. below 
the surface. 
A study of two sand mulches inch and i inch deep, respectively, 
when placed where the sun would shine on them for half the day for 32 
days shows a loss of 57 gm. for a mulch 1 inch deep, 60 gm. for a mulch 
% inch deep, and 155 gm. for the cheesecloth with no dry soil over it. 
Thus the shallower mulch lost but little more than 5 per cent more than 
the deeper. The check 
in which the water 
evaporated through 
the cloth and gauze 
lost nearly three times 
as much water as that 
from the mulches. 
This bears out For¬ 
tier’s findings in regard 
to the effectiveness of 
mulches, but not in 
regard to the relative 
value of deep and 
shallow mulches. 
Figure 13 gives the 
results of the evapo¬ 
ration from 1-cm. mulches of river sands varying in size from 0.1 mm. 
to 7 mm. for 40 days. The loss is somewhat greater through the 
smaller sands. When, however, the sizes are larger than 1 mm., the 
variations in loss are irregular and inconclusive. The mulches pre¬ 
vented over half the 
evaporation that oc¬ 
curred from free water. 
* With perforated 
aluminum lids <> cm. 
in diameter and with a 
mulch nearly 2 cm. 
thick, a more exhaust¬ 
ive experiment was 
conducted. It was simi¬ 
lar to the above, except 
that quartz sands were 
used for the smaller 
sizes and that tests with 
Fig. 13.—Loss of water from glasses having dry mulches of sand of niUCk, day, loam, and 
various sizes suspended above free water. i 
straw were also run. 
This experiment continued for a period equivalent to 180 days, the weigh¬ 
ings being made at about 10-day intervals. Results of this experiment 
are shown in figure 14. Of the mulches the greatest loss was through the 
muck, followed by loam, clay, and straw in order, with the sand mulches 
