1919.] History of the Drainage of Northern India. 97 
system of which the general direction would be northward. It 
is, therefore, natural to ask how a way may have been opened 
through this obstruction. I am not aware of any facts which 
enable us to determine exactly how this was effected, and it 
must be understood that the explanation that follows is only 
suggested in order to carry the record down to the establish- 
ment of modern conditions 
t the present time in the ‘tract of country embraced by 
between the deposits of the Mahanadi and the Irawaddi in spite 
of the fact that the two rivers rise in what must have been, 
in Miocene and Pliocene times, one continuous watershed, and 
flow into the same ocean. While the Irawaddi furnishes us ‘with 
a continuous series of estuarine and flood-plain deposits extend- 
ing from the Eocene to the present day, the deltaic deposits of 
the Mahanadi are Sub-Recent and correspond in age only to 
those of the lower portion of the modern Irawaddi delta. The 
rise of the Arakan ranges seems hardly sufficient to account 
for the difference in the deposits of the two rivers. It, there- 
fore, seems probable that the Eocene and Miocene fluviatile 
line was not far short of the Andamans, making the continent 
of India much larger than is the case to-day. 
During the Cretaceous transgression the sea a undoubtedly 
flowed in over portions of the ancient Gondwana continent 
and has left marine deposits along the eastern poker of Madras. 
Subsequently, however, it certainly disappeared from within 
It seems, therefore, not unlikely that this area was sub- 
merged later than the Miocene and that in former times the 
Mahanadi drained a much more extensive tract of country 
than it does to-day, which perhaps one would infer both from 
its present width and its complicated system of tributaries, 
which are altogether disproportionate to its length as we see 
it at the present time (see Pls. I and II). 
Similarly it is likely that the Miocene rivers, which may 
which rose originally in the same watershed as the Mahanadi 
(now vanished from that area), were also powerful rivers and 
ssors enter it to-day. A tilting of this region 
sufficient to submerge it during the Pliocene would have 
