122 A. R. C. SELWYN ON THE GEOLOGY OF LAKE SUPERIOR. 
and in all respects closely resembling those of Thunder Bay are again found resting on the 
red marls and sandstones, and also, in some instances, clearly cutting them as intrusive but 
not columnar masses, of which Burnt Island, Isle Verte, and La Grange Island, in 
Nipigon Bay, are examples. Nimilar strata are largely developed northwards to Lake 
Nipigon, and in the valleys of the Pike, Jack Fish, Cypress and Naomikan Rivers, 
which empty into the north side of Nipigon Bay, a region of which as yet no exam- 
ination has been made, but in which important facts bearing on this question will, I have 
no doubt, be found. At present the ascertained facts respecting the details of the distribu- 
tion of the several series of strata which together constitute the so-called Copper-bearing 
Rocks are far too few and too scattered to authorize any but the most general statements 
concerning them, and that this is so, nothing proves more conclusively than the various 
and entirely discordant opinions that have been expressed concerning them. In conclusion, 
I may refer to the close correspondence in lithological and physical characters with the 
Lake Superior rocks of those so extensively developed on the east coast of Hudson’s Bay, as 
described by Dr. Bell in the Reports of the Geological Survey, and also another series of 
quartzose sandstones, schists and dolomites described by Dr. G. M. Dawson, on the 49th 
parallel, in the Rocky Mountains, which, though without the contemporaneous traps so 
characteristic of the other localities, will, I venture to predict, be eventually found to occupy 
the same Lower Cambrian horizon. These however, are matters of speculation which can 
only be brought within the domain of certainty by much careful stratigraphical examina- 
tion and comparison of the facts yet to be observed in the several areas. 
That the discussion is an interesting one is perhaps best proved by the fact that in 
the pages of the new American Journal, Science, of which the 15th number only is issued, 
we find the names of Winchell, Irving, Whitney, Hunt and Wadsworth taking part in it, 
in Nos. 2, 5, 8, 9, 10, 12, and 13, following on a letter from me in No.1. It is to be hoped, 
therefore, that a much larger array of observations, carefully made and recorded, will be 
brought to bear in any future discussion which may arise on the subject, as only by such 
means can the true interpretation of the structure be ascertained. 
I hope the labours of the Geological Survey during the present summer will achieve 
something towards this end, and that the few remarks I have now made will help to : 
stimulate observation on the points referred to. 

