THE IRRIGATION AGE. 



li inches deep and having a superficial area of 120 square inches. The 

 evaporator was placed under the covered stand where the meteorolo- 

 gical instruments were located and between the dry and wet bulb 

 thermometers, thus having the same protection from the sun and the 

 same exposure to the wind as those instruments. At 7 o'clock on the 

 morning of the first day 500 grams of water were weighed into the 

 evaporator, and at the end of each twenty- four hours the weight was 

 taken and recorded and the volume made up again to 500 grams. 

 These observations were made daily throughout the year. A second 

 evaporator similar to the first was placed in a barn 30 feet distant 

 from the other. The large doors of the barn were kept open day and 

 night to allow of air circulation, but any violent air movement was 

 rigidly guarded against. The purpose was to secure the same condi- 

 tions of the temperature and humidity of the air as those surround- 

 ing .the evaporator placed outdoors, but to eliminate the factor of 

 wind. The data furnished by the tivo evaporators were taken and re- 

 corded in the same manner and with the corresponding readings of 

 thermometers. The results of these observations covering a period 

 of two hundred and seventy days, reduced to monthly averages, are 

 given in the following table: 



RELATIVE EVAPORATION FROM WATER SURFACE EXPOSED TO THE WIND AND PROTECTED FROM 



THE WIND. 



A relation may be noted between the temperature and humidity 

 of the air and the amounts of water evaporated, but the important 

 fact revealed by the table is the contant and great difference in the 

 amount of water evaporated from two pans. The total amounts of 

 water lost during the eight months by the exposed and protected 

 evaporators were, respectively, 33,480 grams and 14,175 grams. 



The outdoor evaporator lost 136 per cent more water that the in- 

 door evaporator. The vast difference is wholly due to the action of 

 the wind, to which the former was exposed, and it occurred in spite of 

 the fact that the indoor temperature was uniformly 4 degrees higher 

 than the outdoor temperature. 



