Bengal District Gazetteers. Darjeeling

The ridge continues southward to the level of the plains first as the boundary and then as the top of slopes on the left bank of the Mechi river. [...] The colour and the coldness of the latter are no doubt due to the number of glaciers drained by it : while the Rangit is chiefly supplied by the rainfall of the outer ranges of the Senchal and Singalila hills and hence its water is warmer and clearer except in the height of the rains. [...] The rivers to the west of the Tista the Mahanadi the Balasan and the Mechi all flow into the Ganges. [...] the dolomite of the Baxa series the limestone bands in the Tertiary rocks and the calcareous tufa deposited by springs at numerous localities chiefly at the junction of the Gondwana and the Tertiary rocks. [...] The magnitude of a. landslip depends on the thickness of the soil-cap the amount of saturation of the soil the steepness of the hillslope the nature of the underlying rocks and the erosive power of the streams and waterfalls in the area.