PART I.] Comparison of MediuTn, Maximum, and Minimum Prevalence, 239 



The ventilation of the soil and the depression of the water-level are, as before 

 shown to be, greatest during the season of maximum prevalence, but the latter is now 

 also characterised by the minimum humidity, rainfall and soil-temperature. 



Such are the results arrived at on comparing the entire seasons of cholera-prevalence ; 

 it remains to be seen how far these are confirmed by the comparison of typical months 

 selected from the individual seasons. November, April and August are the months 

 indicated by the statistics as those of actual medium, maximum and minimum pre- 

 valence during the course of the entire year, and are therefore those selected for 

 comparison. 



TABLE XL. 



Ccmiparisoa of the characters of the months of actual Medium, Maximum and 



Minimum Cholera-prevalence. 



Meteobological conditions. 



Atraospheric Pressure ... 



„ Temperature 



,, Humidity . . . 



Kainfall 



Water-level 



Soil- temper ature 



Relative amount of carbonic acid in the soil-air 



November 

 (medium). 



29-980 

 74°-9F. 

 71 



0"'66 

 ll'-5 

 78°-lF. 



5 



April 

 (maximum) . 



29-757 

 84°-7 

 73 

 2"-49 

 14'-6 



August 

 (minimum). 



29-608 

 83°- 1 

 88 



13"-7 

 9'-5 



8r-7 



5 



Here, again, the period of maximum prevalence is characterised by excessive soil- 

 ventilation and depression of the water-level. The other results agree with those of 

 the Table (XXXVIII) in which June and October are omitted, except that here the 

 atmospheric temperature is higher in the maximum than in the minimum period, and 

 that the amount of carbonic acid in the soil of the minimum period is now equal to, 

 in place of slightly less than, that of the medium period. 



In all the previous comparisons the maximum period has been uniformly dis- 

 tinguished from the others by two characters only — by depressed water-level and excessive 

 soil-ventilation. On leaving the medium period of prevalence out of consideration, and 

 comparing the maximum and minimum periods, it appears that the former is characterised 

 by its higher atmospheric pressure, its lower atmospheric and soil-temperature, humidity 

 and rainfall, and by its greater soil-ventilation and depression of the water-level. When 

 the medium and maximum periods are combined and the year regarded as divided into 

 two seasons, one of major and one of minor prevalence, the characters of these are as 

 shown in the following table : — 



