PART I.] Cholera and Rainfall at Twenty -five Selected Stations. 261 



the territories over which it is spread are alluvial, nevertheless, as Dr. Oldham says, the 

 essential character of the deposit and the physical conditions of the surface vary very 

 materially. 



As we have just seen, there is a marked difference between the alluvium found 

 below and above Benares. Speaking generally, the prevailing character of the deposits 

 constituting the plains of Behar and the North- West Provinces consists, not, as below 

 Dinapore, of incoherent sand and silt, but of " layers of older and very kunkury clay." 

 This, says Dr. Oldham, is not universal, but it is general, whereas its absence is the 

 general character below Benares. Moreover, the more superficial deposits present every 

 possible variety, from the barren white saline soil on the one hand to the fertile black 

 cotton soil,* which covers such large tracts, especially of the more southerly portion of 

 the area under review, on the other. It is therefore incorrect to suppose that, taken 

 generally, no material difference exists both as to physical and chemical properties 

 between the soil of the endemic and non-endemic areas. 



(b) Prevalence of Cholera according to Monthly periods in the Non-endemic area in 

 Bengal and the mean Monthly Rainfall. 



Before proceeding further at present with this subject, it will perhaps be well to 

 adopt the plan followed in Part II., and to take a general inventory of the statistical 

 data at our disposal regarding the particular group of stations now under consideration, 

 previous to entering into details concerning individual stations. In a former chapter, 

 a monthly tabular statement was given of the cholera-prevalence in a dozen stations 

 of the endemic area, together with the average monthly rainfall. We have compiled 

 a similar table (L next page), regarding the cholera and rainfall of 25 selected stations in 

 the non-endemic area of the Bengal Presidency, such stations being selected, as far as 

 possible, which, in addition to furnishing correct returns regarding their military and jail 

 population, were also capable of furnishing meteorological and other collateral data. 



* Regw or cotton soil has long been a puzzle to Geological and Medical writers. It is generally seen 

 surface-soil covering kunkur and gravelly beds; Captain Newbold (Journal of the Royal Asiatic Society, 

 Vol. VIII., p. 254) referring to it writes, — " The best kinds of this extraordinary soil are rarely suffered to lie fallow 

 and never receive manure. It has yielded annually crop after crop for upwards of 2,000 years without receiving 

 any aid from the hand of man except an annual scratching with a small plough. It is irrigated solely by the 

 dews and rains of heaven. It is remarkably retentive of moisture, and it has been ascertained that if 

 exposed to moist air it will absorb 8 per cent, of its own'weight. Contracting by the powerful heat of the sun, 

 it is divided like the surface of dried starch by countless and deep fissures, and while the surface for a few 

 inches in depth is dried to an impalpable powder raised in clouds by the wdnd, darkening the air, the lower poi-tion 

 of the deposit still retains the character of hard black clay. In wet weather the surface is converted into a deep 

 tenacious mud." 



Mr. W. T. Blanford says that it is extremely adhesive when wetted, and expands and contracts to an 

 unusual extent under the respective influences of moisture and dryness, hence the great cracks by which it is 

 fissured in hot weather. Like all argillaceous soils it retains water, and hence requires less irrigation than more 

 sandy ground. — Memoirs of the Geological Survey of India, Vol. VI., p. 235. 



