IJO 



Journal of Agricultural Research 



fortunately been performed by Buckingham (5) for another purpose. 

 In his studies on the loss of water under arid and humid conditions, 

 Buckingham endeavored to imitate these two conditions in the laboratory. 

 He placed soil in cyUnders 48 inches long and 2^^ inches in diameter and 

 provided each cylinder with side tubes at the bottom for the introduction 

 of water. By means of an electric fan he allowed a current of air to 

 be blown over the top surface of the soils. For the arid conditions this 

 current of air was heated withoiit changing its absolute humidity to a 

 temperature of about 50° to 60° F. above the room temperature. To 

 imitate also the high surface temperature of soils under the strong sun- 

 shine of arid climates, the top i)4 inches of the cylinders under the hot 

 air was heated by coils surrounding the cylinders to about the same 

 temperature as the hot air. The breeze of about 3 miles per hour was 

 kept going all the time. The heating current was turned on for six 



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Fig. II.— Curve showing the evaporation of water from Takoma soil fed with tap water: A, Soil under 

 humid conditions; B, soil under arid conditions; C, water under arid conditions; D, water under humid 

 conditions. 



hours a day, except on Sundays and holidays. For the humid conditions 

 the soils were placed under the current of air at room temperature. 

 Buckingham performed a number of experiments bearing upon this sub- 

 ject and the results he obtained are qualitatively about the same for all 

 of them. Figure 11 shows a typical set of results. 



An examination of figure 11 shows that the loss of water from the 

 soil under arid conditions is much more rapid at first, but after about 4 

 days have elapsed the rate of loss is less under arid than under humid 

 conditions and continues to be so throughout the duration of the experi- 

 ment. The rate of evaporation from the soils for the last 10 days is 11.2 

 inches of rain per year under arid conditions and 51.6 inches of rain per 

 year under humid conditions. 



Buckingham explains these results under the supposition that a mulch 

 was formed on the soil kept under arid conditions more rapidly than on 

 the soil kept under humid conditions, and the mulch prevented rapid loss 



