
474 Journal of the Asiatic Society of Bengal. {September, 1908. 
Geological Society, considered that bank elevation, so far as the 
was concerned, was often due to the running water of the 
water at its sides, 
mes little still water on sat a side (for tlie ras of the 
country is too great to admit of water standing as freely as it 
does near the Ganges ), steadil y for the whole of their dongles sacs 
their banks. Other writers give other reasons for this phenomenon, 
but none, I venture to think, meets the case of the Kosi so a 
as the ploughing theory given above. When once the bank i 
formed there are other agencies which tend to raise it still farther, 
or one of these is particularly significant in the case of the Kos 
ver. 
At about Longitude 87° East the force of the west west winds 
which sweep Bihar from March until the monsoon bursts, s, begin s 
to feel, in a very marked manner, the effect of the damp climate 
of Eastern Bengal; these winds, heavily laden with dust and sand, 
on meeting the first sign of a damp atmosphere begin to lose their 
strength, and, as in the case of a silt-laden river, the decreasd 
velocity causes the dropping of, at any rate, a part of the burden 
is 
banks are actually raised by this ei cannot be said, althongh 
it would not be difficult to obtain a tolerably accurate idea if a 
few simple field experiments were pone out. 1t must be remem- 
the banks of the river, since it must give ‘hens ciimatel width. 
There remain two other points which throw a considerable 
light on the building operations of the river; they are the effect of 
spill ern aes on undulating country, and the reasons for, 
We will first examine the effect of spill water deposits on undu- 
dating tracts. 
‘spill waters cover an undulating country en a 
deposit will be greatest where the water is deepest ; it is ther 
easy to see how low lands grow more rapidly than those situated 
at a greater elevation ; a series of floods, consequently, may be looked 
on as capable of levelling altogether a slightly undulating area. 
