1919.] History of the Drainage of Northern India. 89 
ct ee the streams which drained the oad area, according 
o the eatek rig of Medlicott and Middlem 
To complete the explanation of the fasts ‘it. remains 
consider the question as to where the main river flowed, which 
carried all these hill affluents to the sea, why in any part of its 
course it was dammed back on such a huge scale, and how the 
arrage was continued for such a prolonged period as to 
account for the vast thicknesses of boulder conglomerate which 
according to hypothesis were thus formed. 
Each of these will, to my mind, admit of but one answer, 
so far as concerns the main issues involved. uring the 
periods which succeeded the Eocene it is a matter of common 
knowledge that important elevatory movements in regions 
pag adjacent to the Siwalik boulder conglomerate between 
e Chenab and the Ganges are confined to that tract of 
panties which lies to the north and north-west of the outcrops 
in question. We cannot invoke any elevation on such an 
enormous scale and of such duration in any part of the 
country lying to the south and south-east of the es 
area. Bengal, the United Provinces and parts of the Punjab 
formed with the remainder of the Indian peninsula a portion 
of the ancient continent of Gondwanaland. The remnants of 
ancient gneiss, which are exposed ng ‘the course of the 
sidence may have taken place hanes is probable but not the 
’. reverse. Even supposing, for the sake of argument, that a 
movement of elevation in this southern area were at all feasible, 
and that a basin of deposition had been formed by a ridge 
stretching across the present alluvial area of Bengal, one would 
expect that the conglomerate deposited in such a basin would 
thicken as it approached the hypothetical ridge, but as a 
matter of fact we find the reverse of this to be the case It 
follows that the dam must have been formed to the north or 
north-west of the conglomerate outcrop, and that the river 
which was thus dammed back, and to which we owe the whole 
of the Tertiary freshwater etouits of Northern India, flowed 
from pi ee to north-west through a broad valley bounded 
on the south by the ancient, pacbably much denuded and not 
very Se land surface embracing Bengal, the United 
Ovinces and t of the Punjab, and on the north by the 
Soke raleeukad saa probably necdhers slopes of the Hima- 
la 
While the whole of the Himalayan area since the Eocene 
been undergoing elevation, two portions of it mav be 
singled out as presenting special features which distinguish them 
from the rest. One of these is the north-eastern angle, which 
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