306 C. E. De Ranee — Mineral Veins in the North-ivest Country. 



travels through a subterranean channel, the limestone dipping 5° to 

 N.W. ; two small lead lodes cross the beck, in which no iron was 

 observable. Below the junction of John's with Crookburn, the 

 bar of limestone is seen, resting on sandstone ; the former is overlaid, 

 a little lower down, by 30 feet of Boulder-clay, at a height of 1770 

 feet above the sea. Beaching and ascending the Tees, the Tees 

 Metal Band Mine is passed, where the surface of the limestone is 

 covered with a curious enamel of brown oxide of iron and man- 

 ganese. The lode stuff in the adjacent Providence Mine is very 

 beautiful, consisting of crystals of galena, blende, and galena, with a 

 breccia of broken banded chert pebbles set in quartz ; no iron occurs 

 here, but the lode was rich in lead, much of which probably still 

 remains in the mine, the miners not having been able, with the exist- 

 ing machinery, to contend with the water — which drains in from 

 the Tees. 



A good exposure of the Whin Sill is seen in the South Tyne, 

 around the Tyne Head Smelting Mill, at an elevation of from 1500 

 to 1560 feet on both sides of the river, which has cut a narrow 

 gorge. On the west side of the South Tyne the basalt is capped by 

 a cliff of stiff bluish-coloured Boulder-clay about 40 feet in height, 

 containing a great number of scratched stones and boulders, but few 

 of great size, and, as far as I saw, none of erratic origin. 



Above the basaltic section, but below Calvert Fold, Black Shale 

 and plates below the Scar Limestone is well seen, dipping N.E. at 

 12°, and then N.N.W. at 5°. Shale and plate are seen in the road 

 near Tyne Green Mines (5° to N.W.), and at Ladies Vein the Four 

 Fathom Limestone rests on a grit, from which a large specimen of 

 Sigillaria was procured. On the slope of the Fell above, below 

 Bel Beaver Eigg, occur thick Black Shales over the Scar Limestones, 

 dipping S.E. at 5°, with numerous ironstone Septaria, with 38 per 

 cent, of metallic iron. 



The nodules of carbonate of iron occurring in the shales of these 

 limestones, like the nodules of earthy iron ore in the Yoredale Shales 

 of Lancashire, appear to have a similar origin to that adduced by 

 Sir H. de la Beche, from the experiments of Mr. Hunt, F.E.S.,^ to 

 account for those in the Coal-measures, viz. that the decomposition of 

 vegetable matter prevents the further oxidation of the proto-salts of 

 iron, and converts the per-oxide into the proto-oxide " by taking a 

 portion of its oxygen to form carbonic acid." The presence of 

 Sigillaria in the shales of Ladies Vein, Tynehead, and the occasional 

 fragments of ferns, prove that decomposition of vegetable matter 

 must have gone on forming carbonic acid, which, mixing with the 

 water, would spread over local areas, which " meeting with the 

 proto-oxide of iron in solution," would unite with it and form a car- 

 bonate, mingling with the mud ; and that impure beds either of 

 carbonate of iron or lime would be thrown down, " according as the 

 matter deposited from solution exceeded that thrown down from me- 

 chanical suspension," and both would form nodules when supplies 

 of carbonates were short. 



1 Mem. Geol. Surv.,vol. i.p. 186, London, 1846. 



