258 



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



As in Calcutta, the relative humidity of the air at Dinapore bears to a certain 

 extent an inverse relation to the degree of cholera-prevalence ; this is brought out 

 very clearly in the diagram (No. 14), where the curve, as in the case of the rainfall and 

 water-level curves, is shown inverted so as to convey a clearer impression of the relation 

 to the cholera and temperature curves forming the lower section of the chart, but 

 which are not reversed. 



Hmmffliiil 



Mean monthly Rainfall (in inches). ) 



Degrees of monthly Humidity (dotted <, 



curve). I 



^\ 



~'EI^BB^^EEIBlS3HSBIBaiB^Hil 



Water-level (in feet) 



Total Cholera [51 years] 



Mean monthly Temperature [7-8 years] 



^FiHHCSKKiaaaiBDBBKV^HiHK 



= Rainfall. 

 = Humidity. 



Water-level farthest from 

 the surface. 



-Water-level nearest to the 

 surface. 



-licast Cholera-prevalence. 



-Lowest Temperature. 



DlAGBAM 14. — niustrative of average monthly Relative Humidity, Rainfall, Water-level, 

 Temperature, and total Cholera at Dinapore. 



The mean monthly temperature at Dinapore differs somewhat from that of the 

 stations which are situated further down along the Ganges and its various branches. 

 Taking Calcutta, again, as a standard for comparison, we find that, although the mean 

 temperature of the year does not materially differ, being 79°*3 at Calcutta and 77°'6 

 at Dinapore, still its distribution over the year presents a marked difference. From 

 April to August the average heat at the latter is greater than at the former by from 

 one to three degrees, but in October the condition becomes reversed, the temperature 

 being from five to six degrees cooler at Dinapore than at Calcutta during the cold 

 season. On comparing the curves in the above diagram, it will be observed that the 

 temperature-curve follows that of the cholera-prevalence curve much more closely than 

 it was observed to do in Calcutta, the minima and maxima of both at Dinapore 

 corresponding with considerable accuracy. The Calcutta temperature diagram (No. 2) 

 is reproduced here (Diagram 14 a), for convenience of comparison. 



No closer relation can be traced between the fluctuation of barometric pressure 

 and the cholera-prevalence at Dinapore than could be done with regard to Calcutta- 

 What correspondence there is, however, is of an inverse kind ; for, whereas the period s 



