THE PHYSICAL GEOGRAPHY OF THE PAST. 
225 
We are thus enabled to form some idea of the immense 
amount of material which has been denuded from the central 
portion of the Pennine area. We have had swept away the 
whole of the Coal Measures, the Millstone Grit, Yoredale 
Shales, and a variable thickness of the Mountain Limestone 
itself, which must represent in the aggregate at the very lowest 
estimate 10,000 to 12,000 feet of rock. If the elevatory forces 
had not been compensated by the sub-aerial waste, we should 
have had not hills in Derbyshire but mountains , raising their 
heads far above the snow line of this latitude. 
Although it is pretty certain that our range of hills at one 
time reached a higher elevation than at present, it is unlikely 
that this ever equalled the total thickness of strata which 
have been removed from its central portions; for we have 
reason to believe that the great upheaval was not the result 
of one sudden earth movement, but was brought about by a 
slow, gradual, and intermittent process, extending over a vast 
period of time. Under these circumstances those never- 
ceasing atmospheric influences, which are constantly at work 
through the agency of rain and river, must have commenced 
their wasting action as soon as the bottom of the Carboniferous 
sea was brought above the level of the water, and the erosion 
of wave and current would begin even before this. In this 
way the planing and sculpturing forces of nature almost kept 
pace with the upheaval, and the great anticlinal ridge was 
scarred, furrowed, and truncated from its earliest childhood. 
We can trace the great north and south Pennine axis 
right through North Derbyshire into the West Riding of 
Yorkshire, a total distance of about 60 miles, but in the 
extreme north of the first mentioned county, the beds, of 
which the hills are composed, begin to bend over a little to 
the north, and this tendency increases rapidly as we travel 
further in the same direction. At the southern extremity, in 
the Weaver Hills, the Limestone is also seen to bend over 
gently, but in this case it is towards the south. It is evident, 
therefore, that we must to some extent correct our notion of 
this great anticlinal, which is not a mere arch of indefinite 
length, but a very long, low, elliptical dome of rock. 
To return once more to the Yorkshire end of this dome, or 
periclinal as it is called, we notice that the north and south 
folding of the rocks gives place to great corrugations in a 
direction at right angles to this, that is east and west. 
The result of this has been to bring up lower beds from 
beneath the Coal Measures, these latter having been entirely 
swept off north of a line drawn due east and west a few miles 
to the north of Leeds, as far as the Tees. These east and 
