GEOLOGY. 251 



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This may seem an argument against the probable pro- 

 ductiveness of the Wisconsin copper mines. Yet the forma- 

 tions in this western hemisphere are on a scale so extensive, 

 compared with those in most parts of Europe (witness a 

 single coal field equalling Great Britain in area), that such 

 an argument must be received with many qualifications. In 

 addition to this, the indications in Wisconsin, as far as they 

 have been observed, and the analysis of the ore, afford strong 

 presumptive evidence that capital and skill alone are required 

 to render copper-mining in this district, at least for some 

 time to come, an advantageous and profitable adventure. 



" One of the difficulties which here occurs in reducing the 

 ore — namely, the lack of fuel — is common to the richest 

 copper countries in Europe. The Cornwall copper ore is 

 conveyed partly to Swansea and other portions of Wales, 

 and partly to Liverpool, to be smelted in a coal region ; and 

 the same vessels which thus convey the less bulky material 

 to the more bulky (the ore to the fuel), return laden with 

 coal to supply the numerous and powerful steam engines 

 required for draining and other purposes at the Cornwall 

 mines. And thus, in Wisconsin, if copper ore be raised in 

 quantities, it may be necessary to convey it soutk to the 

 margin of the great Illinois coal field — say to the mouth of 

 Rock River. This would require a land carriage of from 

 ten to thirty miles, and a water carriage of about 100. The 

 Cornwall ore is transported to a greater distance than this. 



" It may be added, as an additional fact whereby to esti- 

 mate the value of the Wisconsin copper ore, that, in some 

 of the European copper mines, ' this ore does not contain 

 above three per cent, of pure copper, and yet it pays for 

 working.' Also, that in some of the Cornwall mines, the 

 ore is worked profitably at a depth of more than 2000 feet 

 * from the grass,' as the phrase there is. 



