The highlands of the peninsula, which are cut off from the encircling ranges by the broad Indo-Gangetic plain, are divided into two unequal parts by an almost continuous chain of hills running across the country from west by south to east by north, just south of the Tropic of Cancer.
The word Bangala was first used by the Mussulmans; and under their rule, like the Banga of old Sanskrit times, it applied specifically to the Gangetic delta, although the later conquests to the east of the Brahmaputra were eventually included within it.
The great thickness of the Gangetic alluvium is shown by a borehole at Calcutta which was carried to a depth of about 460 f t.
The Bengal Central serves the lower Gangetic delta.
The level of the country is low, forming as it does a part of the great Gangetic delta; and the rivers, streams and water-courses are so numerous that it is very difficult to travel except by boat at any season of the year.