The west and south-west boundary of this plain are the slaty mountains of Cumberland winding from Ravenstone dale to near Hesket, Newmarket, Ireby and Cockermouth; a belt of entrochal or mountain limestone covered by a concentric belt of coal measures separates the red sandstone from the slaty rocks just mentioned.
The same plain is bounded on the east by an almost precipitous escarpment, extending north and south from near Brough by Dufton Fell and Cross Fell to Croglin, Castle Carrick, and the hills south-east of Brampton. The elevation of great part of this escarpment is considerable, varying from 1000 to 2000 feet; Cross Fell, its highest point, is 2901 feet. It displays the outcrop, and is chiefly composed of the lower members of the great series of strata described by Mr. Winch as occurring between Newcastle and the base of Cross Fell.
The regular structure of the plain of sandstone at the base of this escarpment is interrupted near Appleby by projecting masses of slate and greenstone, attended by some broken strata of lime and coal measures, which it will be the object of this paper to describe.
These rocks (as may be seen by reference to the annexed map)[1] form an insulated group extending nearly north and south along the base of the escarpment of the great limestone series of Cross Fell, and of which the lowest stratum is stated by Mr. Winch to be incumbent on the old red sandstone (Geol. Trans. vol. iv.) This old red sandstone, which it is of the highest importance to distinguish from that more recent red sandstone which forms the plain of Appleby and Carlisle, appears here in its common form of a coarse pudding stone, and may be traced along the scar in the place thus assigned to it from Melmerby to a spot called Highcup near Murton.
Coextensive with this conglomerate is a subjacent mass of slate which forms a kind of broken under-terrace at the base of the great
- ↑ Plate 5.
