CLIMATE AND PLANT GROWTH. 



19 



the mountings were self-contained as devised by Shive. 1 Distilled 

 water was used, but in order further to insure accurate and compar- 

 able readings, the spheres, after a month of exposure, were replaced 

 by restandardized spheres. 



In measuring the evaporation from a free water surface a gal- 

 vanized-iron evaporating pan, 10 by 36 inches, of the Weather Bureau 

 pattern, was used. The evaporation from this free water surface 



/ 1 3 



/ 22 23 Z4 2S Z6 27 20 29 3O 3/ 



AUGUST I9I& 



White sphere 



Free water surface 



-Average daily wind velocity 



FIG. 7. Evaporation from white sphere and from free water surface compared with 

 average daily wind velocity. 



was recorded by means of a hook gauge, reading in hundredth^ of 

 an inch. 



In order that the evaporation records obtained from the two types 

 of instruments 'used might be compared directly, the porous spheres 

 and the free water surface were placed at the same height, namely, 

 2J feet above the ground. 



1 Shive, John W.,. An improved nonabsorbing porous cup atmometer. Plant World, 

 vol. 18, No. 2 : 7-10. 1915. 



