Clou&*fformation Evaporation. 63 



though the temperature is not above 75 de- 

 grees Fahrenheit, more so even than we are at 

 other times when the temperature is ten or 

 fifteen degrees higher. If the air is saturated 

 with moisture, even though the temperature is 

 not above 70 or 75 degrees, the perspiration is 

 not readily evaporated from the surface of the 

 body. If the air is dry the temperature may 

 be much higher and we be much more com- 

 fortable, because evaporation goes on rapidly, 

 which keeps the body not only dry, but cool. 

 I remember passing through a desert in Ari- 

 zona where there was scarcely a green thing in 

 sight in any direction, and the temperature 

 was said to be 140 degrees. I did not suffer 

 as much as I often have done in the East with 

 the thermometer at 80 or 90 degrees, and 

 there was very little show of sensible perspira- 

 tion ; it was going on rapidly, however, but was 

 being absorbed by the dry air. This goes to 

 show that temperature is not the only factor 

 to be considered when we are making an esti- 

 mate of the good or bad qualities of a climate. 

 Evaporation is carried on much more 

 rapidly when the wind blows than at other 

 times, for the reason that the moisture is 

 carried off laterally as fast as it is formed, 

 all resistance to its escape into the upper air 

 being removed. If the air is charged to satu- 

 ration with moisture at a certain temperature, 

 it will remain so, and evaporation stops so 



