220 



Cholera in Relation to Certain Physical Phenomena. [part i- 



Starting as usual from November, we find a considerable decrease of humidity in 

 December, continuing until February, and followed by a slight fall to the minimum 

 in March. A considerable increase occurs in April, followed by a smaller one in May 

 next follows a rapid increase through June and July to the maximum in August. This 

 is followed by a slight fall in September, succeeded by a considerable fall in October, 

 and an even greater one in November. The above data refer to the facts of 8 years, 

 but very much the same results are shown in the following table of monthly averages 

 from November 1864 to October 1876, which was specially compiled from the meteoro- 

 logical abstracts of the observations taken at the Surveyor Greneral's Office for com- 

 parison with the figures of cholera-prevalence of the same period. 



TABLE XXII. 



Average monthly Humidity {Novemher 1864 to October 1876) and average 

 monthly Prevalence {January 1865 to October 1876). 



In this table the humidity of November is slightly lower than in the previous 

 table. That of December is the same as in it, but January shows a slight increase, 

 and February a decrease as compared with December. March again gives the minimum 

 humidity, but the rise between March and April is less than that between April and 

 May. August again gives the maximum, and July and September are equal as before. 

 We again encounter a rapid fall in October and November, but the fall between 

 September and October is greater in place of less than that between October and 

 November. Taken generally, however, the results of the two tables agree closely, the 

 periods of maximum and minimum being identical in both. 



On comparing these data with the figures of cholera, some very striking coin- 

 cidences present themselves. We find the periods of maximum prevalence and of 

 minimum humidity, and of minimum prevalence and maximum humidity, coinciding 

 very closely. Taking Dr. Payne's figures alone, we have maximum prevalence and 

 minimum humidity in March, and taking Dr. Macpherson's figures, or the total of both 

 sets, we find minimum prevalence and maximum humidity in August. Not to lay 

 much weight on such details, there can be no doubt of the general coincidence of 

 the phenomena of seasonal prevalence in Calcutta with those of the seasonal fluctua- 

 tions in atmospheric humidity. The maximum and minimum periods hold a reverse 

 relation ; there is a rapid rise in cholera coincident with an equally rapid fall in 

 humidity during October and November, and a similar phenomenon of coincident fall 



