THE CARBONIFEROUS AREA lies in the south of Wales, and covers part of the counties of Pembroke and Carmarthen, nearly the whole of Glamorgan and Monmouth, and part of Brecon. The Coal Measures come to the surface over the greater part of this region, while the productive coalfield has an area of about 1,000 square miles. The land, which has a plateau-like formation, and slopes from north to south, is cut up by a number of deep trans verse valleys, including those of the Nedd, Afon, Rhymney, Taff, and Ebbw. These valleys, by exposing many of the coal seams, facilitated in the past the economical working of the coal, which could be obtained by driving adits and galleries from the outcrops along the hillsides ; and, as a result, deep mining was rare in this region until within comparatively recent years. At the same time, the eastern part of the coalfield is traversed for many miles by an important anticlinal fold, which converts it into two troughs, and in this way brings within reach of the miner much coal which would otherwise have lain at too great a depth to be worked. The char acter of the coal varies from bituminous in the east, to pure anthracite in the west, the steam coal used in the Navy and on all fast boats occurring chiefly in the central part of the field between Llanelly and Neath. The whole coalfield is estimated to have a net available content of 26,470,000,000 tons, of which about 14 per cent. is classed as first-class steam, 22 per cent. as anthracite,
30 per cent. as bituminous, and 33 per cent. as second-class steam. The annual output of the field is now about 50,000,000 tons, of which more than one-half, consisting largely of steam coal, is sent abroad. The export of coal from South Wales, like the mining of it, is greatly aided by the transverse valleys, which open up easy railway routes across the field, and which have at their mouths the chief exporting towns : Llanelly, Swansea, Cardiff, and Newport. Barry Dock, situated a few miles west of Cardiff, though not at a river mouth, is also engaged in the coal trade.
In addition to the mining and exportation of coal, metallurgical industries of considerable importance are established on the coal field. These industries, although they owe their origin to the proximity of raw materials, are now mainly dependent on ores imported from abroad. Iron is brought from Spain for the iron and steel works at Dowlais, Merthyr-Tydfil, Cardiff, Port Talbot, and Swansea. For the tin-plate industry which has grown up in the west of Glamorgan, raw material was formerly obtained from Corn wall, but is now imported from the Malay Peninsula. In and around Swansea, also, there are smelting works for the treatment of copper, lead, and zinc. Pembroke on Milford Haven is a naval dockyard.