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336 mollusca might in this way accumulate to any extent, so that the waters might overflow some of the heights originally bounding the valley, and deposits of 'platform mud,' as it has been termed in France, might be extensively formed. At length, whenever a re-elevation of the Alps at the time of the second extension of the glaciers took place, there would be renewed denudation and removal of such loess; and if, as some geologists believe, there has been more than one oscillation of level in the Alps since the commencement of the glacial period, the changes would be proportionally more complicated, and terraces of gravel covered with loess might be formed at different heights, and at different periods.

Some of the revolutions in physical geography above suggested for the continent of Europe during the post-pliocene epoch, may have had their counterparts in India in the recent period. The vast plains of Bengal are overspread with Himalayan mud, which, as we ascend the Ganges, extends inland for 1,200 miles from the sea, continuing very homogeneous on the whole, though becoming more sandy as it nears the hills. They who sail down the river during a season of inundation see nothing but a sheet of water in every direction, except here and there where the tops of trees emerge above its level. To what depth the mud extends is not known, but it resembles the loess in being generally devoid of stratification, and of shells, though containing occasionally land shells in abundance, as well as calcareous concretions, called kunkur, which may be compared to the nodules of carbonate of lime sometimes observed to form layers in the Rhenish loess. I am told by Colonel Strachey and Dr. Hooker, that below Calcutta, when the flood subsides, the Gangetic mud may be seen