PART I.] Geological Features of Transition Area of Cholera. 259 



of low pressure in Calcutta corresponded generally with those of minimum cholera- 

 prevalence, we find that in the neighbourhood of Dinapore the minimam of pressure 

 corresponds more closely with the maximum of cholera. 



Atmospheric Temperature [mean of 28 

 years]. 



Total monthly Cholera (Deaths) [38 



years]. 



Bgg 



DiAGEAM 14 a.— Atmospheric Temperature and Cholera- Pre valencejjin Calcutta. 



III.— CHOLERA IN THE NON-ENDEMIC AREA OF BENGAL. 



CHAPTER I. 



THE SEASONAL PREVALENCE OF CHOLERA IN NON-ENDEMIC AREAS OF THE BENGAL 

 I 



PRESIDENCY. 



(a) The leading Geological features of the "transition" area, and of the Gangetic 



plain eastward of 84° East Longitude, 



In the introductory chapter to his work — Cholera Epidemics of Recent Years — 

 Dr. Bryden starts with the proposition that the cholera of the Bengal Presidency has 

 a geography which can be demonstrated, that in Upper India the disease has not a 

 permanent habitation, but that in certain areas of the Lower Provinces cholera has a 

 permanent and perennial abode. Other writers also have directed attention to this 

 fact, and it has seemed expedient to epidemiologists to divide the Presidency into two 

 areas — the endemic and the non-endemic. 



In the preceding chapters we have endeavoured to point out the leading physical 

 phenomena which are associated with the maximum and minimum prevalence of the 

 disease in the former of the two areas, and we now come to inquire whether a like 

 combination of physical conditions is associated with the maximum and minimum 

 cholera periods in the latter. 



The data at our disposal for the study of this matter are derived from similar 



