Page:Theophrastus - History of Stones - Hill (1774).djvu/65

  Matter, either in detached Pieces of different Figures and Textures; or in whole Veins. The various Kinds of them contain different Quantities of different Metals, but generally too mall to be worth the Charge and Trouble of working. Gold, Silver, Copper, and Iron are frequently found thus in them, But the principal Subtances of which they are formed are Salts, Sulphurs, and Earths. The common Coppers of our Shops is made from different Kinds of them, in different Quantities; and no Species yields it in uch Plenty as the echinated Kind of the Chalk Pits of Kent and Surrey. The Marchaites, as thoe are particularly called which are not in detached Pieces, but run in Veins, or fill the perpendicular Fiures of Strata, often abound with Copper, and with a mineral, arenical Juice, eldom found in the others; ome of thee alo contain Antimony; others Bimuth, and ome Iron and Tin. When they are very rich in thee Metals, they loe the Name of Marchaites, andare called Ores. The Mineral, called in ome Parts of England Mundick, is of this Kind, containing Copper and ometimes other Metals; but the Sulphur is o abundant in thee kinds of Ores, that they are not to be fluxed without great Trouble; the Addition of Lime, or ome imilar Subtance, is often neceary to bring them to fue at all, and at bet they are the mot troubleome, and leat profitable; unles where very rich indeed, of any Ores in the World.

This Author however was not ingle, though erroneous, in his Opinion of the Pyritæ and Molares melting in the Fire; his Mater Aritotle had probably led him into it, who has, ''Met. L.'' 4. c. 6. .

XXI. For ome burt and fly in Pieces in the Fire: as, though not fuible, yet not of Power wholly to reit the Force of the Heat; which is alo