A coin of Nero, analysed by Arthur Phillips, was found to consist of 81·07 per cent. copper, 1·06 tin, and 17·73 zinc; another, of Hadrian, of 85·78 copper, 1·19 tin, 1·81 lead, 6·43 zinc, and 0·74 iron. The chief zinc-producing countries of Europe are Prussia and Belgium. The Prussian mines, which in 1866 yielded 1,204,419 hundredweight, or about 60,000 tons, are situated in Silesia, Westphalia, and the Rhenish provinces. In the same year Belgium produced 35,500 tons, chiefly from the mines of the Vieille Montagne, near Aix-la-Chapelle, where calamine occurs in a large mass, imbedded in chalk, and is worked like an open quarry. In England calamine is, next to galena, the most important ore obtained from the Derbyshire mines, and of late years large quantities of blende or sulphuret of zinc—an ore which, on account of the special difficulties offered by its treatment, had hitherto been neglected—are likewise furnished by the Isle of Man, Denbighshire, Flintshire, and Cornwall. In 1864 our entire production of zinc amounted to no more than 4,040 tons; but since that period it has been considerably increased by the importation of immense quantities of Sardinian, Swedish, and Spanish ores, which are for the most part reduced in the works of Messrs. Vivian, at Swansea. For many years the United States depended upon Europe for their whole supply of zinc; but as nature seems to have denied none of her mineral riches to the great republic, the discovery of immense deposits of calamine and blende in the state of Tennessee has enabled them to compete successfully with foreign produce, and the works of Leehigh and Lasalle now furnish a large proportion of the zinc consumed in the country. Platinum, the heaviest body in nature, was first discovered by the Spaniards, in the gold mines of Darien, probably in the first half of the sixteenth century;[62] but as it remained infusible in the strongest heat, and no method was known for purifying its ore, in which it is remarkably combined with six or even seven other metals, it continued for a long time to be a mere object of curiosity. In 1772 Count Sickingen discovered that it can be welded like iron when urged to a white heat, and first succeeded in producing platinum wire and platinum leaves. A few years after the celebrated Swedish chemist, Bergmann, isolated it from the metallic substances associated with its ore, and proved it to be a peculiar metal. Footnote 62: Kopp, ‘Geschichte der Chemie,’ vol. iv. p.221.