THE 



CANADIAN NATURALIST, 



SECOND SEEIES. 



ON THE ROCKS AND CUPRIFEROUS BEDS OF 

 PORTAGE LAKE, MICHIGAN. 



By Thomas Macfarlane. 



During the summer of 1865 I was employed on the Geological 

 Survey of Canada in making certain explorations on the north and 

 east shores of Lake Superior. I had instructions to visit also the 

 mines of the south shore," in order to acquire some idea of the 

 experience there gained in mining the deposits of native copper, it 

 being anticipated that such might be advantageously applied in 

 explorations on the Canadian side of the lake. The observations 

 which I made on the south shore, although sufficiently interesting, 

 could not well find a place in a report having reference to Cana- 

 dian territory, and, Sir William Logan having kindly consented, 

 I have made them the subject of the following paper. 



One of the most conspicuous geographical features of the south 

 shore of Lake Superior, is Keweenaw Point. Like the rocks 

 constituting it, it strikes out into the lake in a north-easterly 

 direction for a distance of fifty miles. Portage Lake is situated 

 near its base, and together with Sturgeon River, which flows into 

 Keweenaw Bay, almost severs the point from the main land. The 

 north-western part of Portage Lake intersects the various strata of 

 trap and other rocks which run along the whole length of Kewee- 

 naw Point. While to the north-eastward, at Eagle River and 

 elsewhere, the mines of greatest note are generally situated upon 

 veins crossing the strike of the trap, those in the neighbourhood of 



Vol. III. a No. 1. 



