COPPER ORES. 305 



out that the crystalline grain has disappeared, and the copper when cut 

 through has a silky polished appearance, and the color is light red. 

 It is then ladeled out into moulds, usually 12 inches in width by 18 long. 

 Lead is sometimes added in the purification, to aid by its own oxyda- 

 tion in the oxydation of the iron present. 



The process of melting copper on the continent is done by blast fur- 

 naces instead of the reverberatory, and they are said to be more eco- 

 nomical in fuel, and produce a less waste of copper in the slags. Thia 

 mode is used at the works at Boston, while the Swansea mode haa 

 been adopted at the Baltimore furnaces, Maryland. At the Ha'ford 

 works, South Wales, a furnace of three tiers of hearths has been intro- 

 duced, which answers the double purpose of calcination and fusion at 

 the same time. 



Galvanism has been turned to account in the reduction of copper 

 ores. The ore is converted into a sulphate by roasting with the free 

 access of the atmosphere. From this sulphate the copper is deposited 

 in a pure state by galvanic decomposition. See on this subject Ameri- 

 can Journal of Science, ii ser., volume iv, p. 276, or Franklin Journal, 

 volume xi, p. 128. 



Copper Mines. The principal mines of copper in the world are those 

 of Cornwall and Devon, England ; of the island of Cuba ; of Copiapo, 

 and other places in Chili ; Chessy, near Lyons, in France ; in the 

 Erzgebirge, Saxony ; at Eisleben and Sangerhausen, in Prussia ; at 

 Goslar, in the Lower Hartz ; at Schemmitz, Kremnitz, Kapnik, and 

 the Bannat, in Hungary ; at Fahlun, in Sweden ; at Turinsk and Nisch- 

 ni-Tagilsk, and other places in the Urals ; also in China and Japan. 

 Lately extensive mines have been opened in Southern Australia. 



In the United States, considerable quantities have been raised from 

 the mines of New Jersey, and those of Simsbury, Conn. At Bristol, 

 Conn., is a fine vein of vitreous copper, now under profitable exploration. 

 The Hiwassee mine, Tennessee, and the mine at Corinth, Vermont, 

 are at present productive. 



The most extensive deposits are those of Northern Michigan, near 

 L. Superior. The Michigan mines are vertical veins mostly in the trap 

 rock which intersects a red sandstone, probably identical in age with 

 the red sandstone of Connecticut and New Jersey. The first discov- 

 eries of copper ore in this place were made at Copper harbor, where the 

 chrysocolla and carbonate occur. Near Fort Wilkins the black oxyd 

 was afterwards found in a large deposit, and 40,000 pounds of this ore 

 were shipped to Boston. On farther exploration in the trap, the Cliff 

 mine, 25 miles to the westward, was laid open, where the largest masses 

 of native copper have been found, and which still proves to be highly 

 productive. Other veins have since been opened in various parts of the 

 region, at Eagle harbor, Eagle river, Grand Marais, Lac La Belle, 

 Agate Harbor, Torch Ldke, on the Ontonagon, in the Porcupine moun- 

 tains, and elsewhere. At Mineral Point, Wisconsin, a blue siliceous 

 carbonate is found. Other mines are opened in Missouri. The country 

 north of Lakes Superior and Huron, also afford copper ores. 



What is the process of reduction on the continent of Europe ] Where 

 are the principal foreign mines of copper 1 Where is copper found iu 

 the United States] 



