The chief mining district of Devonshire begins at the Tamar and extends across Dartmoor and along its borders. The most important centre was Tavistock, but there were rich mines at North Molton, where several kinds of metal were worked, near Ashburton, and elsewhere. The principal ores are those of copper and tin; some iron is worked, and there are rich veins, believed to be not yet exhausted although not now worked, of galena or silver-lead. The Devonshire mines formerly produced more tin than those of Cornwall; but since the fourteenth century the output of the latter county has been the greater. The quantity now raised in Devonshire is inconsiderable, and in 1907 amounted to only 94 tons. Tin is very largely used in making what is called tin-plate, which is really sheet-iron dipped into the melted metal. It is also mixed with copper to make bronze or machine-brass, and it was for the manufacture of bronze that it was so much sought after by the ancient inhabitants of the country. Copper-mining in Devonshire is believed to be a comparatively modern industry. It is not known whether the ancient Britons made their own bronze from native tin and copper, or whether they imported it from abroad. The Devon Great Consols Mine, four miles from Tavistock, once by far the richest mine in England, and one of the richest in the world, has shipped as much as 1200 tons of copper in a single month, and has produced altogether 3-1/2 million pounds' worth of ore; but it now yields little but arsenic. In 1907 only 652 tons were raised in the whole county. The ore is not exhausted, but the cost of raising it from deep mines is too great to withstand foreign competition. [Illustration: Devon Great Consols Mine] Ores of iron and zinc are widely distributed, but are little worked; and the annual yield, both of these metals and of manganese, of which this county was once a chief source of supply, is inconsiderable. Very rich silver-lead ore was formerly worked at Bere Alston and at Combe Martin, but the mines in both places have been abandoned. A very massive cup, made of Combe Martin silver, given to the Corporation of London by Queen Elizabeth, is still used at the inauguration of each Lord Mayor. Arsenic and arsenical pyrites, ochre, and umber are obtained, especially from some mines whose more valuable ore is exhausted. Cobalt, tungsten, and uranium also occur, and gold has been found in small quantities, generally in streams, as, for instance, in the West Webburn and below Lethitor.