Introduction

In common with the Ganges Valley the Ganges Delta falls within an intermediate zone lying between regions characterized by extremes of rainfall. In a deltaic region when the main river reaches the delta, the force of the current is checked, and owing to the slight slope of the country it cannot carry away its heavy burden of silt which is deposited in the river-bed and on the banks. The deltaic soil varies from the hard clay of the old alluvial formations to soft clay of the new alluvial formations rich in mineral and vegetable substances. The whole of Western and Central Bengal with the exception of the littoral tracts lies in a moribund delta, in which the activity of the rivers has almost ceased, and decadent conditions of health and subsistence have checked the growth of population through successive decades.