The strongest vein in Aldstone mining field is old Carr's cross vein; its direction is north and south, and the sills are from 50 to 100 fathoms higher on the western than on the eastern side of it. Half a mile west of old Carr's, Black-Esk-gill vein is met with. In Nent head and Dowgang mines its course is north and south, and its throw 6 fathoms upon the eastern side.
The vein, called the Devil's-back-bone, is a dyke of considerable magnitude. At Newstones and in many other places on Aldstone moor, it may be traced on the surface by the rider or mass of vein stone protruding above the adjoining strata, the latter seeming to have been decomposed and washed away from each side of it. It ranges from south-east to north-west, and the sills towards the south-west are elevated 20 fathoms.
In Cross-gill burn on Aldstone moor small quantities of copper pyrites mixed with galena and iron pyrites have been obtained; but not in sufficient abundance to induce the miners to prosecute the undertaking.
A few years since a valuable vein was discovered near the top of Cross Fell, bearing ore in the rock immediately below the soil; its throw is about 1 fathom on the north side.
On Muggleswick moors near Hely-field, which is about 27 miles from the eastern coast, and at Blanchland on the Derwent, the mines first become of importance, and continue to be so to the very summit of Cross Fell. The mining field is here about 24 miles in breadth, and its length from the South Tyne to the extremity of Derbyshire may be estimated at 160. Veins containing galena, seem, however, in a certain degree to pervade the whole of this formation in the northern part of Northumberland. Thus one or more veins have been worked for several years near Fallowfield 30 miles west of Tynemouth. A small mine was lately carried on