T. H. D. La Touche—Relics of Ice Age in India. 197 
a recent elevation of the mountains or a depression of the plains, 
causing an increased fall, and consequently higher velocity and 
greater erosive power in the rivers, have been evoked in order to 
account for the facts; but a visit to any of the valleys will show that 
the loose material of the terrace cliffs extends in most cases down to the 
present water-level, and it is evident therefore that the existing valleys 
must have been excavated to their present depth before the terraces 
were deposited in them. In other words, that the configuration of 
mountain and valley was much the same before the terrace-forming 
period as it is now, and that since that period the rivers have been 
able to do little more than clear out their old channels. There may 
have been some elevation of the inner Himalaya during the course of 
these events, but the diminution of the burden thrown into the 
rivers, due, as we have seen, to the reclothing of the hills with 
vegetation on the retreat of the ice, is quite sufficient, I think, to 
account by itself for the change from deposition to erosion. 
A depression in the Indo-Gangetic Valley, which by increasing 
the gradient would also increase the erosive power of the rivers, 
seems equally out of the question; for, as we have seen, the 
excavation of the river-valleys took place before the terrace-building 
period, and the material removed from them must have filled up the 
depression as quickly as it was formed, even if the addition. of this 
weight on the rocky floor below the plains did not actually cause the 
depression, as some have supposed. In any case, there is nothing to 
show that during the terrace-building period the hills and plains did 
not stand in much the same relation to each other as they do now. 
Even at the present day it is sometimes possible to find the 
conditions of the terrace-building reproduced at quite low levels 
among the hills. Owing to the recent immigration of Nepalese 
cultivators into Sikkim, the forests that once clothed the hill-sides in 
that very jungly country have to a great extent been cut down, and 
the natural consequence is that landslips are very common. One 
striking instance of this I came across in the valley of the Rangpo, 
a large tributary of the Teesta north of Kalimpong. The forest on 
the north bank of this river has been almost entirely cleared off, and 
owing to the steepness of the hill-slopes and to some peculiarity in 
the le of the rocks, an almost continuous line of landslips, extending 
for several miles, has taken place. These have thrown an enormous 
quantity of debris into the river, which is unable to carry it away at 
once, and the bed of the river is thus being rapidly raised, the water 
flowing in numerous channels over the surface of the deposits. If 
now the forest were to grow up again and the landslips cease, the 
supply of material would come to an end, and the river would at 
once begin to cut for itself a defined channel through the accumulation 
of loose stuff in its bed, and as it wound from side to side would 
leave terraces on either bank, and this without our having to imagine 
any increased velocity in the stream due to increase of gradient. 
The terraces I have described are not confined to the valleys of the 
Himalaya, but are to be found all round the northern limits of the 
Peninsula, from Assam on the east to Baluchistan on the west. 
Even in this latter country, now so extremely arid, they attain to 
