THE FACTORS WHICH DETERMINE CLIMATE 295 



when living in that region than when living farther south, in Iowa, 

 Illinois, Indiana, or Ohio, " because the atmosphere is so dry." Does 

 the winter relative humidity map confirm this theory? From Table 

 XII, page 220, compute the absolute humidity of these regions. 

 Review Art. 245, page 215, and state whether relative humidity or 

 absolute humidity is the more important factor in this case. Why? 

 Remember that conductivity of heat depends upon absolute humidity. 

 Where is the dryest region of the United States? Explain why this 

 is so. 



FIG. 221. Relative humidity, U. S. 15 years, December, January, February- 



317. Daily Changes in Relative Humidity. 



Exercise 71. Study of the Daily Changes in Relative Humidity, Figs. 



222 and 223 



Study carefully the two maps showing the average relative humid- 

 ity at 8 o'clock in the evening and 8 o'clock in the morning. 



Note the relative humidity of several cities both in the even- 

 ing and in the morning. At which hour, 8 in the evening or 8 in the 

 morning, is the relative humidity higher? What is the approximate 

 difference? 



Recall the fact that the highest temperature of the day is usually 



