

1 64 EVOLUTION OF THE EARTH 



the weather conditions are like those included within this area, 

 the number of deaths averages at least 10 per cent less than the 

 normal. In Figures 31 to 33 and in others of similar char- 

 acter not here reproduced the favorable conditions when 

 deaths are more than 5 per cent below normal range as follows : 



Mean Temperature at Which Deaths Are More than $ Per 

 Cent Below Normal 



1. The northeastern quarter of the United States 51 to 71 



2. France and Italy 51 to 74 



3. California 55 to 75 



4. The southeastern United States 60 to 63 



5. The dry interior of the United States 57 to 73 



6. Colored people in the United States 53 to 78 



In each of these cases the central part of the area of high 

 vitality lies not far from a mean temperature of 64 and a mean 

 relative humidity of 80 per cent or JSj per cent. In each case 

 there is a tendency for the lines to converge toward the right 

 at high temperatures, which means that hot and very damp 

 weather is not favorable, as everyone knows. To the left 

 is also a similar tendency toward convergence which indicates 

 that although a certain degree of dryness may be favorable 

 in hot weather, too much is bad. Another notable feature is 

 that toward the top of the diagrams above the area indicating 

 most favorable conditions the lines are closer together than 

 they are toward the bottom. In other words, temperatures 

 that are too high have a worse effect than those that are too 

 low. Again it is noticeable that at lower temperatures the lines 

 tend to swing from a horizontal position on the left to a 

 vertical position on the right. This means that in cool weather 

 moist conditions are decidedly better than dry. In this respect 

 the diagrams are surprising, for it is rarely realized that there 

 is any such pronounced difference between cold damp weather 

 and cold dry weather. In fact, the vast majority of persons, 



