FORMER VIEWS ON GEOLOGICAL POSITION OF THE SERIES. 13 
minger,! Winchell,? and Wadsworth,’ although these writers differ greatly 
among themselves as to the exact structural relations subsisting between the 
Eastern Sandstone and the trappean series. 
As early as 1846 Logan regarded the copper-bearing rocks of Kewee- 
naw Point as the equivalents of the Huronian of the north shore of Lake 
Huron,‘ and when, later, he abandoned this view, still regarding them as 
older than the Eastern Sandstone, he made them the equivalents of the so- 
called ‘“ Quebec Group” of Canada East.2 In 1872 Pumpelly and Brooks 
advanced excellent reasons for placing the Keweenaw Point rocks below 
the Eastern Sandstone, and as, on the whole, nearer to conformity with 
the Huronian.’ In 1876 Brooks changed his views so far as to abandon 
the conformity with the underlying Huronian, but he still maintained the 
unconformity with the Hastern Sandstone.’ In 1880 the third volume of 
the Geology of Wisconsin presented new and weighty evidence of the 
pre-Cambrian age of the copper-bearing rocks, which are in Northern Wis- 
consin found to be separated from the basal fossiliferous Cambrian sand- 
stones of the Mississippi Valley by a great intervening erosion, while 
from the underlying Huronian the separation did not appear to be so 
great. In that volume the copper-bearing rocks were described under 
the term of the Keweenaw or Keweenawan Series, following the previous 
suggestions of Hunt* and Brooks,’ and the same term will be used in this 
memoir. A few months later appeared the volume of Mr. M. E. Wads- 
worth, in which the copper-bearing rocks are placed as the upper part of a 
series of which the Eastern Sandstone is regarded as the basal member—a 
view which can, I think, be easily shown to be untenable. 
1 Geological Survey of Michigan, Vol. I, Part IL, pp. 80-81. 
2Eighth Annual Report Geological Survey of Minnesota, p. 25. 
3 Op. cit., pp. 115-127. 
4Am. J. Sci. (2), 1857, XXIII, 305-314. 
5 Geology of Canada, 1863, pp. 67-86. 
6Am. J. Sci. (3), III, 428-432. 
7Am. J. Sci. (3), XI, 206-311. 
8 Trans. Am. Inst. Min. Eng., I, 331-342. 
9Am. J. Sci. (3), XI, 206-211. Op cit., p. 66. 
