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WORLD-POWER AND EVOLUTION 



days showing the best health and the five showing the worst. 

 Finally we have calculated the average amount by which the tem- 

 perature changed from day to day in the ten days ending with the 

 middle day of each five-day period. This sounds complicated, but 

 all that the reader need do is to notice whether the figures in the 

 table are plus or minus. If they are plus it means that periods 

 of unusually variable temperature preceded those of unusually 

 good health. If they are minus, it means that the variability of 

 the weather was less than usual before the periods of good health. 



Percentages by Which the Variability op the Temperature from 



Day to Day in Ten-Day Periods Preceding the Best 



Health Differs from the Variability in 



Similar Periods Preceding the Worst 



Health. (Smoothed.) 



Grand average 



+3.1 



