Geology and Mineralogy. 67 
5. The Copper-bearing rocks of the Lake Superior region. — 
In a notice of Professor Irving’s report on these rocks in the last 
volume of this Journal (p. 462), the view of the author is stated 
48 to their relations to the Annimikie on the north shore 
of Lake Superior, and the Lake Superior sandstone, that (1) the 
Annimikie group is Huronian; (2) that the Keweenaw series is 
overlaid unconformably by the “Eastern Lake Superior sand- 
stone ;” (3) that the latter is probably Potsdam in age, as held by 
Most geologists “from Owen to Rominger;” (4) that the unfossil- 
iferous Keweenaw series may be older Cambrian. 
e add here the views of Professor N. H. Winchell, Geologist 
i h Report 
M e 
(1881), of the Geological Survey, and noticed in the Appendix of 
Professor Irving’s Rep 
bov 
ment also; as stated on page 123, “at different places No. 1 
[the light-colored sandstone seen in the Mississippi river bluffs 
and the bluffs of the St. Croix, containing Lingule and trilobites], 
and 2 (the horizontal sandstones of the south shore o ke 
ae sandstone, though Professor Hall refers the St. Croix fossils 
that period. On the fourth point he makes the copper-bearing 
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