Page:Encyclopædia Britannica, Ninth Edition, v. 6.djvu/377

Rh name about 35 miles from the sea, in 27 36 S. lat., 70 23 W. long. The streets of the town, which was founded in 1731 by Count Jose deManso, are straight and wide, with side pavements ; but the houses are low and of timber, excepting in the streets Chafiarcillo and Atacama, where they are built with more elegance and of more solid material. The principal square is 403 feet on each side, with flowers and shrubs in the centre surrounded by rows of shady pepper trees ; while at the western end of the town is an avenue 52 feet broad and half a mile long with four rows of willow trees. Copiapo is connected by rail with the port of Caldera, 50 miles westward, and with the surrounding great mining districts, to which it owes its importance. From its situation in one of the driest regions of America, water is scarce, and the stream Copiapo is all utilized before it reaches the sea. Population, 12,000.  COPLEY, (1737-1815), historical painter, was born of Irish parents at Boston, Massachusetts. He was self-educated, and commenced his career as a portrait-painter in his native city. The germ of his reputation in England was a little picture of a boy and squirrel, exhibited at the Society of Arts in 1760. In 1774 he went to Rome, and thence in 1775 came to England. In 1777 he was admitted Associate of the Royal Academy; in 1783 he was made Academician on the exhibition of his most famous picture, the Death of Chatham, popularized immediately by Bartolozzi s elaborate engraving ; and in 1790 he was commissioned to paint a portrait picture of the defence of Gibraltar. The Death of Major Piers Dn, now in the national collection, also deserves mention. Copley s numerous other works are little esteemed, being feeble and lifeless in drawing, and cold and dull in colour. His powers appear to greatest advantage in his portraits. He was the father of Lord Chancellor Lyndhurst. See.  COPPER is a metal svhich has been known to and used by the human race from the most remote periods. Its alloy with tin (bronze) was the first metallic compound in common use by mankind, and so extensive and characteristic was its employment at an early stage in pre-historic times that the epoch is known in archaeological chronology as the Bronze Age. Metallic relics of that age in the form of arms, ornaments, and domestic implements are still very abundant. By the Greeks and Romans both the metal and its alloys were indifferently known as ^aX/co s and &amp;lt;xs, As, according to Pliny, the Roman supply was chiefly drawn from Cyprus, it came to be termed &amp;lt;.es cyprium, which was gradually shortened to cyprium, and corrupted into ciiprum, whence comes our copper, the French cuivre, and the German hipfer. Copper (chemically, Cuprum, Cu) is a brilliant metal of a peculiar red colour, in which respect it differs from all others excepting, perhaps, titanium, The atomic weight of copper is 63 - 3, and its specific gravity varies between 8 91 and 8 9 5, according to the treatment to which it may have been subjected. It takes a brilliant polish, is in a high degree malleable and ductile, and in tenacity it only falls short of iron, exceeding in that quality both silver and gold. By different authorities its melting point is stated at from 1000 C. to 1398 C. In electric conduc tivity it stands next to silver ; the conducting power of silver being equal to 100, that of perfectly pure copper is given by Matthiessen as 96 4 at 13 C. On solidifying from its molten condition it expands. Copper is not affected by exposure in dry air, but in a moist atmosphere it becomes coated with green carbonate. When heated or rubbed it emits a peculiar disagreeable odour. Copper, according to Walchner, is as widely distributed in^ nature as iron, and occurs in all soils, and ferruginous mineral waters and ores. It has been discovered in sea weed ; in the blood of certain Cephalopoda and Ascidia, and of a species of Limulus ; in straw, hay, eggs, cheese, meat, and other food-stuffs ; in the liver and kidneys, and, in traces, in the blood of man and other animals ; it has also been shown by Church to exist to the extent of 5 - 9 per cent, in turacin, the colouring-matter of the wing-feathers of the Turaco. The ores containing copper in suffi cient proportion to render its extraction economically practicable are numerous. It occurs not unfrequently native, sometimes in very great masses, as on the south shores of Lake Superior, where pieces of 150 tons weight have sometimes been obtained. Native copper most frequently occurs in masses of irregular form in rocky fissures, and often crystallized. The principal ores of copper are Cuprite, Melaconitc, Malachite, Chessyllte, Atacamite, Chrysocolla, Chalcocite, Chalcopyrite, Erubescite, and Tetrahedrite. Cuprite, or red oxide of copper,, Cu 2 O, is a mineral which crystallizes in the cubic system, and con tains 88 78 of metal. It occurs in most cupriferous mines, but never by; itself in large quantities. Melaconite, or black oxide of copper, CuO, contains, when pure, 79 -85 of the metal. It was formerly largely worked in the Lake Superior region, and is abundant in some of the mines of Tennessee and the Mississippi valley. Malachite, or green carbonate of copper, CuCO 3, Cu(HO) 2, is a beautiful and valuable ore containing about 56 per cent, of the metal ; it is obtained in very large quantities from South Australia, Siberia, and other localities. Frequently intermixed with the green carbonate is the blue carbonate of copper, chessy- Jite or azurite, 2CuCO 3, Cu(HO) 2 , an ore containing when pure 55 - 16 per cent, of the metal. It was formerly char acteristic of Chessy, near Lyons. Atacamite is a hydrated oxychloride of copper, occurring chiefly in Chili and Peru ; it crystallizes in the rhombic system. Chrysocolla is a hydrated silicate of copper, CuSi0 3, 2H 2 0, containing in the pure state 30 per cent, of the metal ; it is an abundant ore in Chili, Wisconsin, and Missouri. The sulphur compounds of copper are, however, the most valuable in an economical point of view. Chalcocite, redruthite, copper-glance, or vitreous copper, is a sulphide, Cu 2 S, containing very nearly 80 per cent, of copper. Copper pyrites, or chalcopyrite, a sulphide of copper and iron, CuFeS 2, crystallizes in the pyramidal system and contains 34 6 per cent, of copper when pure; but many of the ores, such as those worked specially by wet processes on account of the presence of a large pro portion of sulphide of iron, contain less than 5 per cent, of copper. Cornish ores are almost entirely pyritous ; and indeed it is from such ores that by far the largest pro portion of copper is extracted throughout the world. In Cornwall copper lodes usually run east and west. They occur both in the killas or clay-slate, and in the growan^ or granite. Erubescite, bornite, or horseflesh ore is a sulphide of copper and iron much richer in copper than the ordinary pyrites, and containing 56 or 57 or, according to the for mula FeCiioSo, 62-5 per cent, of copper. Tetrahedrite, fahlerz, or &quot;grey copper, a sulphide crystallizing in the cubical system, contains from 30 to 48 per cent, of copper, with arsenic, antimony, iron, and sometimes zinc, silver, or mercury. The numerous other compounds of copper have more interest from a mineralogical than from a metal lurgical point of view. Copper is obtained from its ores by two principal methods, which may be denominated (1) the pyro-metal- lurgical or dry method, and (2) the hydro-metallurgical or wet method ; and a small proportion of metallic copper is procured by (3) the electro-metallurgical method. The methods of working vary according to the nature of the ores treated and local circumstances. The dry method, or ordinary smelting, cannot be profitably practised with 