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THE POPULAR SCIENCE MONTHLY. 



In order to inquire into the accuracy of these views, another ob- 

 servation, taken from India, may be cited. Places which are outside 

 the region of endemic cholera, and which have a rainy season at the 

 same time and of about the same amount as Calcutta, have the same 

 amount and periodicity of cholera. Such an instance is afforded in 

 Bombay, which is a city as large as Calcutta, and the rainy season of 

 which depends on the southT^est monsoons. In a table which shows 

 the frequency of cholera, the rainfall, and the temperature on the aver- 

 age for a period of fifteen years, it is evident that in all three particu- 

 lars there is a remarkable correspondence between Calcutta and Bom- 

 bay, (See Table III.) 



Table III. 



Average Frequency of Cholera^ Average Rainfall, and Average Temperature (in 



Degrees Centigrade), at Bomhay. 



The temperature has been given for the reason that it brings out 

 the fact that temperature has not much influence on the progress of 

 cholera. That Bombay is not within the endemic area of cholera is 

 sufficiently testified by the results of the statistics for fifteen years. 

 During this period there were three years in which no epidemic oc- 

 curred. That a whole year should pass without the occurrence of a 

 single case of cholera in Bombay is not to be expected, when the active 

 intercourse between it and the endemic areas is borne in mind. If the 

 table of averages relating to Bombay be compared with that of Cal- 

 cutta, the resemblance is seen to be striking. The maximum incidence 

 of cholera is seen to occur in both in April, and the minimum is found 

 in Calcutta in August and in Bombay in September. After this mini- 

 mum the increase takes place equally in both cities. The years during 

 which no epidemic occurred in Bombay were characterized either by 

 too much wet or too great dryness. Thus, in the years 1852-'53, the 

 diminished frequency of cholera followed on a period of great wetness, 

 and that of 1860-'61 came on after a very dry season. That this de- 

 pendence on the weather is really sound is shown by a study of the 

 years immediately following the lessened intensity of cholera. The 

 years 1853-'54 and 1861-'62 in Bombay showed the same rhythm for 

 cholera as Calcutta ; whereas, on the contrary, the year 1858-'59 in 

 Bombay had the same abnormal rhythm as Lahore. The average 

 number of deaths from cholera in Bombay in March was 253, in April 

 295, and in May 294. In June, when the monsoons begin, the number 

 further diminishes. The number of deaths in March, 1859, was 9, in 

 April 7, in May 69, and, when in June the monsoons set in and 26*8 

 inches of rain fell, the number rose to 843, while the mean for June 



