PART I.] 



Influence of Atmospheric Humidity. 



219 



fluctuations most accurately with those of the disease, and there is hardly anything 

 else to which we can ascribe this save the temperature. Taking this into consideration 

 together with the well-established fact of the general tendency to subsidence or even 

 disappearance of the disease during the winter months of periods of its epidemic mani- 

 festation in Europe, there appear to be grounds for ascribing some influence to the 

 atmospheric temperature on the prevalence of cholera in Calcutta. The precise method 

 in which it acts remains, however, undetermined. That it acts directly is extremely 

 improbable, but there are many indirect means by which it may produce an effect. 

 Whatever the latter may be, they must, at all events, be entirely independent of 

 peculiar habits of life of one section of the community as compared with another, for 

 we find as marked a decrease in prevalence among the European troops as among the 

 Native community. 



(c) Atmospheric Humidity. 



TABLE XXI. 



Average Trionthly Attnospheric Humidity (8 years) compared with Cholei'a-prevalence. 



The diagram differs from the previous ones in its method of construction, the line 

 showing the Eelative Humidity representing the reverse and not the direct relation ; 

 in other words, the lower the degree of humidity, the higher the scale on the 

 diagram. This plan has been adopted because there is a certain amount of coin- 

 cidence between diminished humidity and increased cholera-prevalence in Calcutta, 

 and the coincidence being of the reverse nature, the amount of it is rendered more 

 clear by arranging the lines accordingly. 



Average monthly Relative Huniulity 



[8 years]. 

 Saturation = 100. Curve inverted. 



Total monthly Cholera Deaths [38 

 years]. 







-Lov,-cst Humidity = (>7. 



-Highest Humidity = 88. 



Diagram 3. — Atmospheric Humidity and Cholera-prevalence in Calcutta. 



