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L. A. GIDDJNGS 



second evaporimeter was suspended at a height of 114 cm. from 

 the ground; and the third evaporimeter at a height of 237 cm. 

 from the ground. Wind velocity and psychrometric readings 

 were taken beside each evaporimeter. The experiment was run 

 ten hours, beginning at 7.30 a.m. The data for the experiment 

 are given in table 2. 



TABLE 2 



Rates of loss from Piche evaporimeters (in cubic inches) at different heights, loith the 

 concurrent wind velocity/ {in miles per hour) relative humidity, and temperature 

 (Fahr.). September 8, 1912 



From the data for this experiment it seems very evident that 

 elevation played a very important part in the rate of evaporation. 

 The variation in the amount of evaporation during the day was 

 very much the same at the three heights, but the total amount 

 of loss increased regularly with an increase in height. Wind 

 velocity also increased with height, but the increase was greater 

 between the two lower positions than between the two higher 

 ones. This was probably due to the fact that the lower position 

 was somewhat protected by vegetation while the two upper ones 

 were not thus protected. Relative humidity was highest at the 

 lowest position and decreased with increasing height, while 



