PART 4 .] 
Medlicoti: Note on the Geology of Nepal. 
99 
that made by the actual course of the streams. Although, wherever a bend of the channel 
touches the edge of the upland, the side-erosion is still in progress, enlarging the area of 
the khola land, the rivers are not now lowering their bed. If any change is in progress, it 
is the reverse; the channels are very wide and shallow, and in some places at or above the 
level of adjoining cultivation. Such at least is the case above the gorge at Choubal; below 
it the channel is more confined, as occurs when a river is deepening its channel: _in this 
position the upper surface of the valley deposits must he 500 feet above the stream, which 
gives a minimum thickness for the formation. 
There are within the valley three remarkable instances of the rivers having cut deep 
narrow clefts through rook-barriers. The one just referred to at Choubal is the largest, 
where the united drainage of the main area crosses the point of the Kirtbipur ridge. There 
is another much higher up on the Baglnnati at Gaokaran, through the point of a ridge 
flanking Sheopuri; and a third at Pashpati, where the Bishenmati passes through a low 
isolated outcrop of rocks on the strike of the Nagarjan ridge. They are mere clefts, narrower 
than are at all usual in the most confined gorges. One must suppose that the bygone con¬ 
ditions which produced them were in some manner special, and connected with the produc¬ 
tion of the alluvial basin ; i. e., they can hardly he accepted as remnants of the primitive 
channel of the Baghmati valley, before that simple feature of denudation had been con¬ 
verted in its upper area into a basin of deposition. 
It may he presumed that the valley of Nepal is a true rock basin—that the rock- 
surface beneath some considerable portion of the covering deposits is below the level of the 
outcrop at the head of the gorge of outlet. It would seem indeed to comprise a series of 
such basins : if the clefts through the several ridges, as described in the last paragraph, were 
filled up, this would certainly be the case now ; and that such has been the case there can he 
no doubt, for the beds now forming the adjoining terrace-land above those gorges could not 
have been formed had these outlets been then available. Thus the excavation of these 
rock-gorges by the existing rivers accounts for the present features of the valley deposits, 
and gives some measure of the antiquity of those features. 
The fact of a rock-basin, even of considerable depth, does not Involve a water-basin. 
This would depend upon the relative activity of the production of the harrier and of the 
accumulation of deposits above it, which cannot be independently determined. The question 
must be settled by observation as to whether the deposits are alluvial or lacustrine, and 
of this the evidence is not very fixed or easy of application. The degree of horizontality 
is one of the best tests, hut needs much caution and accuracy in applying it; the slope at 
which true alluvial deposition may take place being so small, and there being always a chance 
of a very slight movement giving a tilt to originally horizontal layers. There is, indeed, 
sufficient evidence that some such disturbance has affected these deposits in Nepal: at 
several points, south of Ilhatgaon and in the Katwaldar area, along the south side of the 
valley, near the base of the hills, I observed dips as high as 15° in fine deposits, directed 
from the mountain. I could find no such occurrence in exactly similar deposits along the 
north edge of the basin. It would seem as if the action which originally formed the rock 
basin had been again, or still, at work after the formation of some of the highest beds. 
Major Godwin-Austen, records a similar feature in the deposits of the Kashmir valley : 
a dip of 20° and upwards on the south and none on the north (Quarterly Journal, Geological 
Society, London, 1864, p. 383). 
There is, however, one observation showing that at many different levels the surface 
at the time of formation was not a submerged one. Beds of an impure peat are of 
