Series of operations to which the ore is subjected

—The ores which are smelted in the Swansea works are cupreous pyrites, more or le mingled with gangue (vein-stone). The pyrites is composed of nearly equal proportions of sulphuret of copper and sulphuret of iron. The earthy matters which accompany the pyrites are usually siliceous, though in some mines the metalliferous deposit is mixed with clay or fluate of lime. Along with these substances, pretty uniformly distributed, tin and arsenical pyrites occur occasionally with the copper; and though these two metals are not chemically combined, yet they cannot be separated entirely in the mechanical preparations. The constituent parts of the ore prepared for smelting are, therefore, copper, iron, sulphur, with tin, arsenic, and earthy matters in some cases. The different ores are mixed in such proportions that the average metallic contents may amount to 8 1 ⁄ 2 per cent. The smelting proce consists in alternate roastings and fusions. The following description of it is chiefly taken from an excellent paper, published by John Vivian, esq., in the Annals of Philosophy for 1823. In the roasting operation the volatile substances are disengaged mostly in the gaseous state, while the metals that po e a strong affinity for oxygen become oxidized. In the fusion the earthy substances combine with these oxides, and form gla y scoriæ or slags, which float upon the surface of the melted metal. These calcinations and fusions take place in the following order :— 1. Calcination of the ore. 2. Melting of the calcined ore. 3. Calcination of the coarse metal. 4. Melting of the calcined coarse metal. 5. Calcination of the fine metal (second matt). 6. Melting of the calcined fine metal. 7. Roasting of the coarse copper. In some smelting works, this roasting is repeated four times; in which case a calcination and a melting are omitted. In the Havod works, however, the same saving is made without increasing the number of roastings. 8. Refining or toughening the copper. Besides these operations, which constitute the treatment of copper properly speaking, two others are sometimes performed, in which only the scoriæ are melted. These may be designated by the letters a and b . a is the re-melting of the portion of the scoriæ of the second proce , which contain some metallic granulations. b is a particular melting of the scoriæ of the fourth operation. This fusion is intended to concentrate the particles of copper in the scoriæ, and is not practised in all smelting works.