440 
Journal of Agricultural Research 
Vol. VII, No. io 
REVIEW OF THE LITERATURE 
Considerable work has been done on various phases of the evaporation 
problem. One of the important factors influencing water losses is the 
wetness of the soil, or the initial percentage. 
Widtsoe (19, p. 35, Table 20) 1 gives the results of four years’ experi¬ 
mental work, as shown in Table I. 
Tabl3 I .—Total evaporation of water from bare College loam 
Moisture. 
Loss in pounds per square foot. 
1902 
1903 
1904 
1905 
Average. 
► Per cent. 
10 . 
. 9 
23 
51 
32 
9 
10 
38 
16 
30 
69 
16 
21 
60 
I c. 
20. 
80 
Loss increased with the percentage of water up to 20 per cent, which 
was the highest degree of wetness used. He (19) says: “The evaporation 
of water from bare soils increased with the increased saturation of the 
soil. The increase in loss was usually much larger than the increase in 
saturation. In another treatise (20) he found that “the wetter the soil 
at the surface, the more rapid is the evaporation of water from it.” 
This is confirmed by Whitney and Cameron (18) and by Fortier (5). 
In Whitney and Cameron’s work, 26 per cent was the highest humidity, 
that being used in but one set of experiments. Fortier’s highest per¬ 
centage of water was 17.5. In his conclusions he says, “The rate of 
evaporation from soils varies directly with the amount of moisture in the 
top layer.” 
The work of Cameron and Gallagher (3, p. 45-49) indicates that, after a 
certain wetness is reached, there is little if any increase in water loss. In 
their work the soils of different degrees of wetness were placed over sul¬ 
phuric acid of different concentrations in order to control the humidity. 
Over 95 per cent sulphuric acid in desiccators, Podunk fine sandy loam 
gave the most rapid loss by evaporation up to 4 per cent moisture, with a 
very slight increase in loss up to 28 per cent. Miami black clay loam 
lost most rapidly up to 22 per cent, with a small increase to 41 per cent, 
where the loss was highest. 
The color of the soil is claimed by King (10) to affect evaporation 
greatly, since the darker the soil the more heat it absorbs and radiates. 
He found that the rise in temperature, due to the darker color, is the im¬ 
portant factor. 
Concerning winds, King (9, p. 16) shows that up to 300 feet from woods 
the loss gradually increased with the distance. He (11) gives the following 
1 Reference is made by number to "Literature cited,” p. 460-461. 
