Dec. 4,1916 
Evaporation of Moisture from the Soil 
449 
Since the latter ran 20 days, the total losses have been divided by 2 in 
order to get the total loss for 10 days to make the figures comparable. 
r There is a decided difference in the results of the two experiments. 
The losses in the cloth boxes were nearly 20 times as great as those in the 
germinator, showing the enormous retarding effect of high humidity. 
Moreover, the open laboratory was somewhat dri$r and about one degree 
warmer than the air in the cloth boxes. No test was made in the open 
laboratory, but the losses would have been somewhat higher, since both 
a drier air and a higher temperature prevailed. This would, of course, 
further accentuate the already enormous differences. 
WIND VELOCITY 
As was suggested in the literature on wind velocity, King (9) has shown 
that vessels 20 feet from a windbreak lost 30 per cent less moisture by 
evaporation than ves¬ 
sels 30 feet distant. 
This was because the 
outer vessels were 
more exposed to air 
movement. Payne 
(13) shows nearly 
similar results, while 
Bowie (1) reports 
that with light winds 
and normal temper¬ 
ature there is an 
evaporation loss of 
0.5 per cent for each 
mile of wind. 
In order to deter¬ 
mine the effect of wind velocity on the rate of evaporation, a series of 
alleys 8 % inches wide and 70 inches long were arranged in such a way 
that the air could be made to pass through them at different velocities. 
The alleys were separated by oilcloth partitions 2 feet high; the air 
currents were made by electric fans placed in such positions that the 
desired velocities could be obtained. The velocity of air in each alley ■ 
was measured with an anemometer placed at the end of the alley away 
from the fans. 
The soils were contained in copper evaporimeters 6 inches in diameter. 
The loss each day was made up by adding water through a tube entering 
the evaporimeter at one side of the soil. In each alley there were five 
evaporimeters—one containing distilled water, one Greenville loam, and 
one each of quartz sand 0.25 mm., 0.5 tnm., and 0.8 mm. in diameter. 
Two tests were made in the experiment, one running continuously for 
16 days with three wind velocities and another running continuously for 
66846 °— 16 -- 3 
Fig. 5.—Loss of moisture from Petri dishes containing different per¬ 
centages of soil moisture and kept in a saturated and unsaturated 
atmosphere. 
