r 



No. 6.] DOUGLAS— LAKE SUPERIOR COPPER MINES. 321 



the range in the Ontonagon district, became even more famous 

 from the enormous masses of copper it produced. Here, like- 

 wise, the copper occurs in veins which, though running with the 

 strata, are palpably subsequent formations consisting chiefly of 

 quartz, calc spar, and laumonite. The vein stone is difi"erent 

 from the enclosini^ rock, the walls are well-defined and often 

 grooved. In the Minnesota, the masses were not only large, but 

 frequently threw off branches into the enclosing rock, which 

 interfered with their being detached in the usual manner by re- 

 moving the country rock adjacent. The prosperity of the mine 

 ceased after the extraction of a mass of 90 per cent copper, weigh- 

 ing 525 tons, in 1857. No mines here are flourishing at present, 

 nor does there seem to be a like revival of mining industry to 

 what is taking place in the Keweenah Point district on the ash 

 bed, under the infection of the successful development of certain 

 beds near Portage Lake. 



Portage Lake and River extend so nearly across the promon- 

 tory at about 60 miles from its point, that a canal less than 

 three miles long suflices to give water communication between 

 the east and west shores. The lake is an irregularly-shaped 

 body, as much as two miles wide where excavated out of the 

 low-lying sandstone, but tapering rapidly where the high, 

 bluff cliffs of the trap beds of the copper-bearing series confine 

 it. While still in the low-lying horizontal sandstone, it throws 

 off towards the north-east a long arm, which expands into Torch 

 Lake, a considerable body of water whose north-west shore almost 

 defines the line of contact between the horizontal sandstone and 

 the steeply-tilted copper-bearing rocks. 



As the steamer enters the narrows, and there come into view 

 the towns of Hancock and Houghton facing one another on 

 the opposite banks, the large mills on the lake shore, and the 

 mine buildings and tramways on the heights above, the contrast 

 between the modes of activity and the aims of civilised man, and 

 of the Indians, with whom the traveller, if he has been long on 

 the lake, must have come into close contact, strikes the mind 



very forcibly. 



Where the copper-bearing rocks are exposed by the deep fis- 

 sures, whose bottom is occupied by Portage Lake, the width of 

 the range is seven miles, and the beds dip at an angle of 54^^ to 

 the north-west. They consist of traps of varying degrees of 

 Vol. VII. V No. 6, 



