2l6 



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



CHAPTER II. 



A COMPARISON OF THE SEASONAL FLUCTUATIONS IN INDIVIDUAL PHYSICAL CONDITIONS WITH 

 THOSE IN PREVALENCE OF CHOLERA IN CALCUTTA, 



Having acquired this information regarding the seasonal fluctuations in the 

 prevalence of cholera, we have now to enquire into the meteorological and other 

 physical conditions coincident with them, in order, if possible, to determine whether 

 any connection be traceable between the two series of phenomena; whether, in fact, 

 there be any series of meteorological and physical constants characterising the 

 various seasons of prevalence when compared with one another. 



The conditions which have been selected for consideration are, (1) atmospheric 

 pressure, (2) air-temperature, (3) atmospheric humidity, (4) rain-fall, (5) water-level, 

 (6) soil-temperature, and (7) amount of carbonic acid in the soil-air — mainly 

 regarded as an index of soil-ventilation. 



The sources from which our data regarding these conditions are derived are the 

 following : — (1) the Report on the Meteorology of India in 1875, by Mr. H. F. 

 Blanford, Meteorological Reporter to the Government of India ; (2) the Report of the 

 Meteorological Reporter to the GTovernment of Bengal for 1874; (3) the Abstracts of 

 the Meteorological Observations taken at the Surveyor General's Office from the year 

 1856 ; (4) the register of water-level kept at the Alipore Jail by Dr. S. Lynch since 

 1870 ; (5) our own observations regarding the temperature and carbonic acid of the 

 soil-air. 



(a) Atmospheric Pressure. 

 The accompanying diagram and table show the phenomena of atmospheric 

 pressure compared with cholera prevalence. In the diagram the line of atmospheric 

 pressure is drawn to the second decimal place of the 9 years' averages given in 

 Mr, Blanford's report and reproduced in the table. The cholera line was originally 

 constructed on a scale allowing one graduation to every thousand, and the figures 

 employed are those of the total obtained on adding Drs. Macpherson's and Payne's 

 statistics together. The figures in the table explain themselves. 



TABLE XVIII. 



Average Monthly Atmo8'pheric Pressure (9 years) compared with Cholera-prevalence. 



