42 A CHAPTER IN THE PHYSICAL GEOGRAPHY OF THE PAST. 
vertical scale much exaggerated it has been somewhat generalised 
so as to bring into prominence the salient points bearing upon 
the structure of the Range. 
You will observe that the rocks, which, as I have said before, 
were originally laid down in a horizontal position, are now thrown 
into a huge fold or arch, with one or two minor folds or 
corrugations flanking it. 
The direction of the folding is approximately north and south, 
and, looked at in a general way, the strata incline from the centre 
of the arch, both to the east and to the west, just as the slanting 
sides of a roof do from the ridge tile. As we travel from the 
central mass of limestone of North Derbyshire in either of 
these directions, we pass successively, and in ascending order, 
over the edges of all the divisions of the Carboniferous System 
right up to the Coal Measures. A study of the map and 
section would strongly suggest to us that the strata which are 
now thus severed were once continuous right across the arch, 
and this is put beyond doubt, not only by the similarity of the 
sedimentary strata on either side, but also by the proved identity, 
a little further north, of several of the Coal Seams in the 
Lancashire and South Yorkshire Coalfields, which lie on opposite 
sides of the great fold. The crown of the arch or amticlinal has, 
in the district we are considering, been so far destroyed since its 
elevation, by the ceaseless action of rain and river, frost and 
snow, aided to some extent by the sea, that the great mass of 
Coal Measures, Millstone Grit, and Yoredales, which once 
stretched right across from side to side, has been completely 
swept away, exposing to the light of day the Mountain Limestone ; 
so that this, the lowest member of the Carboniferous Series, now 
occupies the most elevated part of the ridge. 
The same graving tools of nature which removed the upper 
measures have also cut deeply into the limestone itself, producing 
those lovely and picturesque dales which render our Derbyshire 
districts so beautiful. 
We are thus enabled to form some idea of the immense amount 
of material which has been denuded from the central portion of 
