Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/91

 at Thockrington, and at Welphington in the same neighbourhood, 90 miles west of the sea at Camboes. Strings of ore have also been discovered on the coast of Northumberland at Ellwick nearly opposite to Holy Island, and on the eastern side of the island itself: but all undertakings begun in a flat country must be insignificant when compared with those in a mountainous district, where the mines are won by levels or drifts, which not only free the works from water, but are the means of discovering numerous rich veins by passing through them in their course.

The veins bearing lead-ore on the hills near Shieldon and Blanchland, are reported to have attracted the notice of miners at a remote period, and that part of their wealth, which lay near the surface, has been long since removed. Within these few years an attempt has been made on a great scale to win the ore supposed to lie below the level of the Derwent, by drawing the water from a considerable depth by powerful steam engines; but it is said that as yet the metal obtained repays but a small part of the annual cost of the undertaking.

In this dale the veins appear wide and open upwards, allowing water to percolate through them from the surface. In Allenheads mine, though the shaft is about 100 fathoms deep, the quantity of water is so inconsiderable, that a set of water wheels, three in number, are sufficient to raise it from the greatest depth of the workings, and to discharge it at a drift.