a 

q 
Vol. IV, No. 9.] The Kosi River. 473 
[N. sith 
bed ; ’ these, in their turn, help to in rease the size of the bar; if 
we apply the action of this batons river to that of the Kosi 
in the seaaite, on which eres is no sea to neutralize the flow, it is 
stones which it is propelling, , and with t 
material as can be conveniently Pema the at, is a nase. 
what steep bed until, with a decreased current, the power to roll 
material falls to a minimum; the river has then reached what we 
may look on as a normal of gradient; even then it will continue to 
roll matter along its bottom, but the further we get from the cone 
the smaller in bulk will be the matter rolled. All this time two 
other phases of actions are in progress; as the feicmeac dl = ao 
current decreases, its suspension-carrying capacity | 
and matter is steadily deposited in the bed, so that the “ed 
aan gradually raised. The other phase is one which I believe 
has not been sufficiently noticed by writers on the subject; it is a 
eee of ploughing action which tends to push to one side, and 
deposit there, a considerable amount of material which helps very - 
greatly to form the unstable banks which all such rivers as the 
Kosi have. Were we see the parallel between water running into 
the sea and into aplain sand. In the former a bar was formed, 
in the latter the water continues to push forward, and meidedtally 
to one side, all the material that it can, this material being that 
which, under different conditions, would have made up a bar. 
te processes described above are permitted to. continue 
undisturbed for some years, the river, its bed and its will, 
except at high flood, be entoud well above the country on either 
side ; at flood times the banks will, however, be overtopped by 
water, and a spill, great or small, according to circa prorat will 
inundate the surrounding country. These spill waters, coming 
-rest, deposit tically all the sedi t they held in cuaponaiot, 
thus spreading a layer of sand or mud over the areas in which 
they operate ; a gradual building-up of the low lands is thus 
effec 


question of h 
stesso. in a masterly note! read by him in — before the 
| Geological Society of London—Journal, 1863, p,. 321—354. 



