
472 Journal of the Asiatic Society of Bengal. [September, 1908. 
a its youth, during which it is destructive in its action, 
(the Kosi River in the hills), its middle aye, or constructive stage 
(the Kosi in the plains, as we see it now), and, finally, its old age, 
or perhaps dotage is a better term, in which it again becomes 
ici 
point of view, of elt auarthitaat 
he action of the river in its constructive stage is somewhat 
eased although definite laws are obeyed by every river 
under similar circumstances, there are certain points connected 
with thes e laws which, being often inexplicable to us, aré@ classed 
together as the “character” of a river; for instance, if a river 
invariably carried the same amount of water, if its bed flpwed 
i i c er 
which it passed were homogeneous and of the same material as its 
sree for its whole course, the river might fairl be classed as 
with no individual character. Any va variate however slight 
it. se be, from the perfect river just described, must introduce 
at least one element of characte which moe mene “ any moment, 
the calenlations and plans of the grea river expert living ; 
fortunately for us, theoretosttys the Kosi Doasts vg little rior 
character during the last 80 miles of its cou and, with one 
exception, its feet should be obedient 0 xaieiiod rules. 
The exception is the actual reason for a sudden change of course, 
and it will be dealt with later 
Immediately on the Ieidine side of the falls by which the 
to carry forward and deposit uniformly over the plains, or remove 
to the sea; the loss of energy is due to the sudden change in grad 
which, above the falls, is that of a mountain torrent and below 
them that of a comparatively sedate body of flowing water ; 
through the alluvial cone the river runs in one main channe 1 
which may be considered to be semi-permanent ; its permanency 
depends entirely on no change occurring at its debouching point, 
and, since that point is hedyed in by hard rock, a semi- permanent 
channel at least may be accepted through the débris cone; if a 
very heavy fall of rock occurred on the east or west side of the 
gorge, which now leads the Kosi into its present path, changes of 
e 
‘away so slowly by weathering, and building operations p: 
so comparatively rapidly, that each year renders sudden prasges 
‘at this point more improbable. Sonth of the cone the plains 
oo all sides awaiting the pleasure of the river to elevate 
‘The action of a moving. body of water over a sandy plain .is 
