part 3.] Medlicoil: Ossiferous deposits of the Narbada valley. 
53 
while largely affecting the result, can only be indirectly conjectured. For instance, a change 
of levels would greatly affect the eroding and depositing power of rivers; or a change 
of climate and of rainfall, with perhaps the addition of severe frost, would have a like dis¬ 
turbing effect upon the work done, without our being able to assign the amount of those 
by-gone conditions. But taken all in all, reliable indications, and comparative, if not actual, 
measurement can bo made. 
The Narbada valley, meaning that broad area of the river’s course from where it 
leaves its gorge in the trappean plateau of Mandla near Jabalpur, to where it enters its 
narrow gorge through the Vindhvan quartzites below Hosungabad, is about as unfavorable 
a case as one could select to exhibit symptoms of change. It is a rock-basin, a valley 
excavated chiefly, if not entirely, in crystalline and slaty metamorpbic rocks, between two 
plateaus of little-disturbed sandstone-formations, the Vindhyan on the noi'tb and the 
Mahadeva on the south, and converted into a rock-basin by some oscillation of level. It 
would seem that the change was not rapid enough to produce a lake, for in all the sections 
now exposed coarse gravels occur. As soon as this basin bad received the charge of deposits 
due to this change of level, and supposing no further earth-movement to occur, the change 
of features to what we now find would depend upon the eroding power of the river to 
lower the rim of the rock-basin, and thus gradually to bring under denudation the deposits 
it had so lately laid down. If then we could fix the maximum thickness attained by the 
deposits, and also the rate at which the river can lower its gorge of discharge, we could 
assign something like actual dates for the successive phases both of denudation and of 
deposition, on this supposition of normal conditions, without interference of crust move¬ 
ments or other occasional forces. The process is now going on. The river at least cuts faster 
than pluvial denudation can work in lowering the general surface, for its bed is now 
some 80 to 100 feet below the level of the adjoining plains. There is nothing' to suggest 
that the depth of the valley-deposits ever much exceeded what we now find. The plains 
deposits never extended into the valleys of the Satpura, some of the minor streams from 
which are still accumulating materials upon the deposits of the main valley. There ai - o 
nowhere any signs of high-level deposits, along the borders of the basin, whether remnants 
of a former phase of denudation of the actual valley-formation, or (like the ossiferous gra¬ 
vels of Northern Europe) remnants of deposits formed in a more ancient shallower rock- 
valley. The ossiferous beds of the Narbada seem to be simply a member of the last and 
only valley-deposits, which have now for a long period been undergoing denudation. But 
I know of nothing to suggest that the change from deposition to erosion supervened at a 
time much prior to the ‘recent’ of the geological scale. 
The only debateable stratigraphical point upon which a stand might be made, is 
whether unconformity occurs, indicating a general and possibly a great interruption of 
deposition between the ossiferous beds exposed at or near the present level of the river 
channels and those above them. I have examined many sections with a view to testing this 
supposition, but I have failed to confirm it. One often finds local unconformity—coarse 
gravel upon a weathered surface of stiff clay; but these are no more than must occur in 
the normal process of formation of river deposits; and most frequently it is impossible to 
detect any break in the section. The fossils, moreover, occur largely in the gravels above this 
supposed unconformity, without any sufficient grounds for supposing them to have been 
washed out of the clays. Thus, then, there is nothing like a corresponding amount of 
evidence foi; work dono here since the age of these hones, as there is in Europe for work 
dono since the formation of the ossiferous gravels and cave-deposits ; although the permanent 
staff of operatives is much more powerful in the former case. Every season there occurs in 
the Narbada a rise of from 40 to 70 feet, with a stream of great force. It is, as I have 
said, impossible to make an exact comparison, on account of the undetected influences that 
