1881.] 



on the Weather and Health of London. 



G31 



corresponding to the minimum period of the other, and viC4i versa. It 

 is also seen that the mortality curve for small-ixjx (Fig. 3) is quito 

 distinct from the other two curves. 



In order to ascertain the dcgi'eo of steadiness of these curves, a 

 curve was calculated and drawn for each of the seven opidcmics of 

 scarlatina and for each of the eight epidemics of whooping-cough 

 during the thirty years, with the instructive result that the curve for 



Fig. 2. 



Jan. Feb. March, April. May. Juno. July. Au?. Sept. Oct. Nov. Dec. ' 

 50 n I I III I LUJ Al I III MM Ml III I I I I III III I II n 



Moan 



50 LI I I 111 I I I I 111 III I I I I III III 

 Whooping Cough. 



Moan 



soDlliiil Ml! Ml Ml nil III III I 11 mil 111 JiiC 



Small -pox. 



each of the separate epidemics was substantially identical with the 

 general curve for the whole thirty years' period, each of the four 

 prominent phases of each curve occurring all within a week of each 

 other. As regards the small-pox curve, if the deaths during the 

 epidemic of 1870-72, by far the most fatal of all the ejudemics during 

 the thirty years, be deducted from the general result, we obtain a curve 

 which is substantially the same curve as that for the whole thirty 

 years, but only less pronounced. From these results it follows, and 

 the remark is of general application to all the curves, that the mortality 

 curves fur the diflcrent diseases arrived at in this inquiry may be 

 regarded as true constants of these diseases for London. 



The climate of London, looked at as influencing the health of the 

 people, may be divided into six types of weather according to the 

 season of the year. These are respectively — 



Period 1. — Damp and cold, fourth week of October to third week 

 of December. 



Period 2. — Cold, fourth week of December to third week of 

 February. 



Period 3. — Dry and cold, fourth week of February to second week 

 of April. 



