WINDBREAKS AND TENTS TO SAVE WATER 215 



relative efficiency with increased velocity of the wind. 

 (2) The relative humidity under the tent was higher 

 than outside, and during a good part of the time 

 attained a difference of 10 per cent. The effect of this 

 was to reduce evaporation, by from 53 to 63 per cent 

 on different days in July, in spite of a higher tempera- 

 ture inside the tent. (3) The direct effect of these was 

 to increase the moisture content in the soil in spite of a 

 larger crop growth under the tent. These differences 

 are shown by the following curves, which represent the 

 per cent of water in the soil to a depth of nine inches 

 from June 13 to August 1. 



20 



IB 



10 



JUNE 13th 



65.U0 .10-1.54-.17 



DATE 



.22-.03 .17 .44 



INCHES RAIN 



AUGUST 1ST 

 .24 .2-.16-.10 



Fig. 68. Curves representing the per cent of moisture in a sandy soil to a 

 d^pth of nine inches inside and outside of a loosely woven cloth tent, July 13 

 to August 1, Western Connecticut. 



Not only was the effect of the tent to prevent evapo- 

 ration and thereby increase the average moisture con- 

 tent of the soil, but the soil was able to maintain a more 

 uniform content, due to the more free movement and 

 adjustment of the capillary water under the tent con- 

 ditions most conducive to rapid crop growth. (See 

 page 172.) 



