APPENDIX B 253 



diagram with the eight adjacent departures. In every case the de- 

 partures receive a weight in proportion to the number of people 

 they represent. Figure 30 represents the final tabulation of about 

 3,700,000 deaths in France and Italy. For convenience in comparing 

 with the American diagrams the Fahrenheit scale has been used, 

 although the original computations were on the Centigrade scale. 

 K Let us interpret Figure 30. We may begin by inquiring what degree 

 of mortality prevailed during months when the mean temperature for 

 day and night together was 75 °F and the mean humidity 75 to 80 per 

 cent. To find this we note at the top of the diagram the point where 

 the humidity is between 75 and 80 per cent. Then we go downward 

 vertically to a temperature of 75°, as indicated on the left. There we 

 come upon the figure — 1.5. This means- that during the small number 

 of months having this particular temperature and humidity the deaths 

 were 1.5 per cent less than the normal. During the much larger 

 number of months having the same humidity, but somewhat lower 

 temperatures the mortality rate falls to — 7.3, — 11.0, and finally 

 to — 12.2 at a mean temperature of 66°. At lower temperatures the 

 mortality increases once more, for the minus departures become 

 smaller and smaller until at a temperature of about 51° the deathrate 

 at this particular humidity is the same as the normal. Then at still 

 lower temperatures we have plus departures showing that the number 

 of deaths was more than normal when the weather became cool. 

 Finally, when the mean temperature fell below freezing the deaths 

 were more than 20 per cent above the normal. In similar fashion look 

 at the deaths at a temperature of 48°. Beginning on the right of 

 Figure 30 we see that when the mean humidity averaged over 90 per 

 cent, the deaths were 4.1 per cent less than the normal. At slightly 

 lower humidities conditions were still more favorable, for the mor- 

 tality was —4.6 per cent. Farther to the left, however, conditions 

 become less and less favorable. At a humidity of 80 per cent the 

 mortality is normal, and then increases until in very dry months with 

 a humidity of 50 to 55 per cent it is -f-15.8 per cent. 



In order to bring out the salient features of Figure 30 lines have 

 been drawn at intervals of 5 per cent. The heaviest or zero lines 

 indicate the conditions at which the normal number of deaths occur. 



