326 DR R. E. SCORE SB Y- JACKSON 



and this they do whether the results of the highest and lowest ranges only be 

 compared, or a comparison of all the six corresponding months in each case be 

 instituted. 



The Influence of Drought and Humidity. 



We have already seen that, with reference to mean temperature, the relative 

 amount of humidity in the atmosphere is important. We are now briefly to exa- 

 mine into the influence which the various hygrometric conditions of the atmo- 

 sphere exert upon mortality from all causes independent of other meteorological 

 elements. It should always be remembered, however, that the amount of mois- 

 ture necessary to the saturation of a given quantity of air varies with tempera- 

 ture, — the warmer the atmosphere the greater the quantity of moisture requisite 

 to saturate it, and vice versa. We may test the influence of the relative amount of 

 moisture upon mortality from three points : first, with reference to the number 

 of rainy days ; second^ with reference to the quantity of the rainfall in inches ; 

 and, third, with respect to the relative saturation of the atmosphere with mois- 

 ture, as ascertained by means of Mr Glaisher's hygrometric Tables. 



Number of Rainy Days. — A rainy day, it may be premised, does not neces- 

 sarily mean one on which rain continued to fall throughout, nor even during 

 many hours ; a shower of rain is sufficient to constitute a rainy day. Nor has 

 the term any reference to the amount of rain deposited in a given time ; very 

 little or very much rain may fall on a rainy day. Hence, we often find, that 

 with ten rainy days in one month, there is a greater rainfall than in fifteen rainy 

 days of another month. 



In the several sections of Table C, the relative number of rainy days to the 

 mortality from all causes is as follows : — 



Section. Mortality. Number of Rainy Days. 



Maximum Section, 269-49 15-1 



Major Section, 233-25 13-7 



Minor Section, 214-26 15-4 



Minimum Section, 185-85 15-3 



Means, 22571 14-9 



A Table consisting of three factitious years, constituted of months with the 

 greatest number of, and months with the fewest rainy days, together with the 

 means of all the corresponding months, shows the following result. Where two 

 months are alike in the number of rainy days, the one in which most or least 

 rain fell is taken : — 



