CONDITIONS INFLUENCING PREVALENCE 175 



This process has been going on ever since, and is still in 

 progress ; till to-day, this enormous area of alluvium forms 

 an apparently level plain, stretching from sea to sea, and in 

 most places some hundred miles wide. Though apparently 

 as level as the ocean the imperceptible v^atershed between 

 the Ganges and Jumna flowing east and the westward 

 bound rivers of the Punjab is really some 700 to 800 feet 

 above the sea, and the depth of the alluvium is in some situa- 

 tions enormous. The whole of this area consists of sand 

 and silt of various degrees of fineness, modified at the 

 surface with a variable amount of decomposed organic 

 matter. Saving where waters, rich with lime in solution, 

 have matted together vegetable fibre and sand into " kun- 

 kar," nothing of the nature of a stone is to be found. 



At both the eastern and western limits of this wide 

 alluvial area, the ground water is necessarily close to the 

 surface, as hundreds of square miles of country are but a 

 few feet above the level of the sea ; but speaking generally, 

 as one travels further inland the level of the subsoil water 

 gets deeper and deeper, and on the watersheds between the 

 rivers may at times be as much as a hundred feet from the 

 surface. 



The eastern or Gangetic half of this area is for the most 

 part naturally fertile, the natural rainfall being, in normal 

 years, sufficient to water a sufficient crop to support a large 

 population. In the easternmost portion indeed the normal 

 rainfall may be said to be excessive, and malaria is neces- 

 sarily rife and long continued. 



On the other hand, once the country drained by the 

 Indus is reached the rainfall becomes scanty and precarious. 

 Whether, however, we start from the Gangetic or Indus 

 delta, the subsoil water becomes deeper and deeper as 

 we travel inland so that in Oudh and the North-west 

 Provinces, forty or fifty feet is no uncommon depth for a 

 well, and in parts of the Punjab, the water may not be 

 reached for twice that depth. On the western side the 

 rainfall progressively diminishes, so that the country, even 

 where the ground water is at no great depth, is a water- 

 less desert ; and cultivation, apart from irrigation, an 

 impossibility. 



