632 



Mr. Alexander BucJian 



[March 25, 



Period 4. — Dry and warm, third week of April to third week of 

 June. 



Period 5. — Heat, fourth week of June to first week of September. 



Period 6. — Damp and warm, second week of September to third 

 week of October. 



The outstanding features of the death-rate in its relation to the 

 varying types of weather through the year are shown by the top curve 

 of Fig. 4, which represents the total mortality for all ages. This 

 curve shows two maxima in the course of the year : the one, by far the 

 larger of the two, extending over six months from November to April, 

 and the other embracing the period from about the beginning of July to 

 the autumnal equinox. It will be also observed that the comparatively 

 short-continued but strongly-pronounced summer maximum is practi- 

 cally restricted to mere infants, whereas the larger winter maximum 



Fig. 4. 



Weekly Jan. Feb. March. April. INIay. June. July. Aug. Sept. Oct. Nov. Dec. 

 deaths. ^ j i i 



1700 



Age. 



1300 -=^- 



is a feature of the curves for all ages ; and hence of all weather 

 influences the cold element in the climate of London is that which is 

 most destructive to life. 



Figs. 5 to 10 are representative curves of those diseases which go 

 to form the summer maximum when " heat " is the chief characteristic 

 of the weather. The direct relation of the progress of mortality from 

 diarrhoea to temperature is strikingly seen in the startling suddenness 

 with which the curve shoots up during the hottest months of the year, 

 and the suddenness, equally startling, with which it falls on the approach 



