18 



BULLETIlSr 700^ U. S. DEPARTMENT OF AGRICULTUEE. 



mercury thermometers and exposed in shelters of the Weather 

 Bureau pattern 4c^ feet from the gi-ound. 



PRECIPITATION. 



The precipitation record was obtained by means of automatic 

 tipping bucket rain gauges, the data from which were liarmonized 



2 3 ■^ S 6 789 



'2 /3 /^ jS /& /7 /8 /9 20 2/ 22 23 2-* ZS 26 27 -ZS 29 30 3/ 



AUGUST JSI6 



White sph ere 



Free water- surface 



— '—Daily mean temperature 



Fig. 6. — Evaporation from white sphere and from free water surface compared with daily 



mean temperature. 



with standard rain gauges. In this way reliable data were obtained 

 as to the amount and rapidit}^ of the rainfall. 



EVAPORATION. 



The evaporation was recorded in two waj^s: (1) By means of the 

 standardized porous cylindrical and spherical atmometers, and (2) 

 by means of a free water surface. 



In the case of the porous spheres, both the black or radio cup and 

 the white cup were used at each station. The spherical, as well as the 

 white cylinder cups, were fitted with rain-correcting apparatus and 



