1 66 EVOLUTION OF THE EARTH 



uniformity prevails. The effect is like that of exercise. The 

 people whose bodies are exercised by frequent transitions from 

 one set of weather conditions to another are more healthy and 

 energetic than those who live where there are no changes. 

 infT like that of southern California comes 

 not from staying therePyear after ^year/but from going there. 

 Since the temperature never departs far frorrT the optimum, 

 people who come from other regions usually experience a help- 

 ful change. It is like what they experience in their own homes 

 during the favorable months of spring and fall, but it has the 

 added advantage of rest, novelty, interesting scenery, and 

 out-of-door life. 



Since storms are the chief cause of variations of weather 

 ifrom day to day, they appear to be a most valuable stimulant. 

 \Hence they have much to do not only with human energy but 

 with civilization. In the trying winters of the northeastern 

 United States, to be sure, the most stormy months have about 

 6 per cent more deaths than do those with only a moderate 

 number of storms. Months with almost no storms, however, 

 are not so good as those with a moderate number. Even in the 

 mild winters of California the same is true. There at tem- 

 peratures below 56 the following conditions prevailed from 

 1900 to 1912 : 



1. In months of practically no storminess, the deaths, 

 which numbered 27,700, were 6.1 per cent more than the 

 normal. 



2. In months with a medium number of storms, the deaths 

 (11,920) were 5.3 per cent more than normal. 



3. In months of great storminess, the deaths (13,200) 

 were 7.3 more than normal. 



In warm weather, on the other hand, the most stormy 

 months are the most favorable. In the northeastern quarter 

 of the United States the deaths are about 5 per cent less in 

 such months than in those with least storms. In California 

 for mean temperatures above 65 the figures are as follows: 



