DISTRIBUTION OF LEAD VEINS. 423 



mena. At Carrigan in the north, in the Hensbarrow granite tin 

 mines occur in the finest mass of greisen in Cornwall. Dr. Foster 

 believes the greisen to be merely altered granite. 1 



Tin in New South Wales, &c. The granite in New South 

 Wales is regarded by Mr. Ulrich as forming a vast stockwork near 

 the township of Inverell, and the quantity of tin lying on the surface 

 in that district is estimated at twenty-five times the annual produce 

 of Cornwall. 



Immense quantities are obtained from Banca and Billiton. 2 



The mines of Chili and Peru also yield a large quantity of 

 tin. 



Lead. Lead occurs in veins chiefly in the newer Primary rocks. 

 Galena is the most abundant ore, but carbonate and phosphate of 

 lead are both met with in some quantity. 



In the Cambrian district of Shelve in Shropshire, towards the 

 borders of Montgomeryshire, the lead mines have been worked at 

 intervals since the time of the Romans. The mineral veins are 

 almost entirely in the Arenig and Llandeilo rocks. In the north- 

 west of Montgomeryshire mines also occur at Llangynog in Arenig 

 and Llandeilo rocks. In the Llanidloes district the veins have a 

 general east-and-west direction. 



When the Carboniferous limestone appears in North Wales, in 

 Flint and Denbigh, ores of lead are found between Flint, Ilolywell, 

 and Llangollen. The general direction of the veins is east and west. 



In Cardiganshire the lodes chiefly occur in anticlinal folds, the 

 corresponding synclinal curves being usually barren. There are 

 many mines on the south side of the estuary of the Dovey along the 

 course of the Rheidol, between Plynlimmon and Lampeter, and on 

 the east side of Plynlimmon. In this district the lodes range from 

 E.N.E. to W.S.W. In Carnarvonshire the lead district lies between 

 Capel Curig, Bettws-y-Coed, and Trefriw. 



In Cornwall the most important are at West Chiverton, near Camel- 

 ford, and near Laureath. Lead is limited to the eastern side of the 

 county ; the direction of the lode is east and west at West Chiverton. 

 Herodsfoot mine, near Laureath, has the lode nearly north and south. 

 The number of lead mines in Devonshire is small. They chiefly occur 

 in the Ilfracombe slates, in the neighbourhood of Combe Martin, and 

 at Frank mills, near Exeter. In the North of England, Cumberland, 

 Northumberland, Durham, and Westmoreland, all yield large quan- 

 tities of lead. The mines at Alston Moor belong to the governors of 

 Greenwich Hospital ; the Weardale mines belong to the Ecclesiastical 

 Commissioners ; but among the more interesting are those of Allen 

 Dale, which belong to the family of Mr. W. B. Beaumont. Nearly 

 all these mines occur along the line of the Carboniferous limestone of 

 the Pennine chain, in the portion which lies above the Great Whin 

 Sill. In Swaledale, in Yorkshire, the ore chiefly occurs in the Main 

 limestone, and extends over an area fifteen miles long by six broad, 



1 Le Neve Foster, "Tin Stockworks in Cornwall," Q. J. G. S., vol. xxxiv., 

 p. 654. 2 Reyer, Banka. 



