No. 2.] SPENCER — COPPER-BEARING ROCKS. 57 



Between 1819 and 1841, several American exploring; expeditions 

 were sent out. by the government ; but the first of these that 

 could be considered scientific was begun in 1831 by Dr. Hough- 

 ton, State Geologist of Michigan. His report in 1841 drew the 

 attention of capitalists to this region, and it was not long before 

 the development of the mineral wealth about Lake Superior 

 was begun. 



II. — Geology. 



This paper is largely the result of personal observations 

 during parts of the last two years, while engaged in geological 

 and mining operations among the copper mines on Keweenaw 

 Poiut and elsewhere. I have consulted the reports of the Cana- 

 dian and Michigan Geologic al Surveys, and I also acknowledge 

 indebtedness to L. G. Emerson, M.E., for having pointed out 

 many geological phenomena, — the knowledge of which would 

 otherwise only have been gained by much longer study of the 

 region. In this paper, too short for more than a general idea, I 

 bave endeavoured to point out the most striking scientific fea- 

 tures, and to correlate the knowledge of the Copper- Bearing 

 Series, as it has been obtained on both the north and south shores 

 of Lake Superior. 



a. — Geological Distribution* — The deposits of the geological 

 formation known as the Nipigon or Copper-Bearing (formerly 

 Upper Copper-Bjaring) Series is peculiar to L iki Superior. On 

 the south shore of the lake, they skirt it from the extremity of 

 Keweenaw (more correctly Kiewtinona) Point in the Upper 

 Michigan, south- weatwardly for 150 miles into Wisconsin. The 

 exposed brealth varies frooi 4 to 15 miles. Tiiis region is con- 

 sidered the type of the formation, as it is D3st known. Topo- 

 graphically it consists (in part) of two nng3S of hills known 

 locilly as the Greenstone or North, and the South Ranges. The 

 North or true Mineral ft mge rises to heights of 400-700 feet, 

 and slopes gradually to the north- westw ud, till it underlies the 

 lake or (in places) a more recent formation. In the upper p irfc 

 of Keweenaw Peninsula, this has a breadth of about two miles. 

 The south-east side of this range terminates in an abrupt decli- 

 vity, the face of which consists sometimes of an almost vertical 

 wall 20U-300 feet high. The South Range varies in height 



* See Map. 



