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Imperial Gazetteer of India, v. 1, p. 3.

] P I- PHYSICAL ASPECTS 3 geographical feature than the North-western Himalayas, which were formidable mountains even in Pliocene ages, and were much as they are now in the days when the Siwalik fauna browsed in sub-Himalayan forests. The period of earth- movements appears to have culminated in the Pliocene period, but never to have subsided; for these movements are even now perceptibly re-shaping the ends of Indian physiography. The sea, which once flooded the area of the western frontier hills, Tibet, and Burma, was driven back; and the marine rock deposits of the west were crushed and folded as we see them now, where their serried battalions of ridges, line upon line, present a forbidding front to the Indus valley. The formation of a great depression was more or less coincident with the upheaval of the mountains. At first it was a wide and deep partition between the Himalayas and the Peninsula, which the collected alluvium of ages gradually filled as it was brought by the action of the great river of the west, the Indus, from the whole Himalayan system. A comparatively recent development of these movements between Assam and the Rajmahal hills has formed the eastern or Gangetic depression; and the final dividing of the waters of these two great river-systems (Indus and Ganges) may have occurred almost within historic time. No further change can now take place; for the rivers have marked out their own courses and adjusted their gradients to permanent beds. It is doubtful what happened within the limits of the Peninsula while these great movements and shiftings of level were in progress beyond it. Probably it was then that the connecting link between India and Africa was severed, and that the western continent, indicated by the coral archipelagoes of the Maldive and Laccadive islands, was submerged; but geological science inclines to the opinion that the elevation of the Western Ghats was comparatively recent. The steep- sided, narrow valleys of the Ghats, where the streams are still cutting their way back at their sources and gradually working their beds down to a permanent level, appear to be in the same stage of development as those or the extra- peninsular hills. One result of this process of evolution has been that nearly all the great rivers of Southern India take their rise in the western hills, and flow across the continent to'the Bay of Bengal. The Narbada and the Tapti alone cut their way in deep channels westward; and there are indications farther south of a third great river which may B2