24 SKETCH OF THE GEOLOGY OF DERBYSHIRE. 
parts of the new red sandstone. At all events, the existence of the 
mountain limestone at Birchwood Park makes it highly improbable 
that any coal isin the immediate neighbourhood, and almost certain 
that there is none between there and Ashbourne. If we trace the 
E. side of the limestone shale from Turnditch to Breadsall, we shall 
find it spreading out towards the S.E. In this direction, also, the 
millstone grit, which is the base of the coal measures, runs, which 
circumstance, taken in conjunction with the N.E. dip of the coal 
measures about Dale Abbey, renders it probable that the limestone 
shale lies immediately under the new red sandstone for some dis- 
tance to the S. and E. of Derby ; and that, if the coal measures pass 
under the new red sandstone without any sudden downcast to the 
S. but merely by an alteration in their dip and gradual lowering of 
their level, they will still be found to sweep round to the E. and 
that they will be sought with greater chance of success in Notting- 
hamshire rather than in Derbyshire, to the S. of the present boun- 
dary of the coal-field. It is remarkable that the first part of the 
carboniferous system we meet with, when it reappears to the S. 
from beneath the new red sandstone, is the lowest part—the moun- 
tain limestone of Ticknal and Calke.* And this.circumstance seems 
to render it highly probable that by far the greater part of the new 
red sandstone in the S. of Derbyshire conceals only the inferior part 
of the carboniferous system. That mountain limestone and lime- 
stone shale, or millstone grit, but chiefly the two former, compose 
the substratum, and are in similar positions to what we see them 
elsewhere, namely, in alternate elevations and depressions ; and that 
over this uneven surface the new red sandstone has been deposited 
horizontally, leaving one or two of the highest points uncovered by 
its beds. Under this view the northern part of the Leicestershire 
coal-field must be looked on as the connecting link between the 
Derbyshire coal-field on the one hand, and those of N. Staffordshire 
and Cheshire on the other ; this Leicestershire coal-field being only 
apparently divided from the rest by an old valley or depression, 
partly due, perhaps, to ancient denudation, which has since been 
filled up by new red sandstone. 
We have now, then, ascertained the certainty of the supposition 
with which I begged the reader to set out, namely, that the moun- 
tain limestone is continuous over the whole of Derbyshire at the 
* Except a small patch of what appears to be millstone grit at Stanton, by 
the bridge. 
