MICHIGAN AND WISCONSIN. 



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Professor Irving in reply to Mr. Selwyn stated that "the copper- 

 bearing rocks underlie unconformablj — and with an immense uncon- 

 formity — a series of sandstones holding Cambrian fossils." He further 

 remarked " that the copper-bearing strata also underlie unconformably 



* 



the eastern sandstone of the south shore of the eastern half of Lake 

 Superior." He also complains that the evidence of himself, Sweet, and 

 Chambcrliu regarding the Taylor's Falls locality had been ignored by 

 others. (Science, 1883, I., pp. UO, Ul, 359, 360, 422.) 



It was in reply immediately pointed out by Dr. Wadswortb, that 

 the above mentioned observations had neither been ignored nor denied ; 

 but that the trouble was that the Wisconsin geologists themselves 

 had ignored tlie simplest principles of the geology of eruptive rocks, 

 which they themselves admit these to be. (Science, 1883, I., pp. 248, 

 249.) 



In the mean while Dr. Hunt stated that the 



*' view of the continuity of the cupriferous series with the Potsdam (St. Mary) 

 sandstone was maintained by Whitney ; but Logan, in 1803, put forth strong, 

 and to most minds conclusive, reasons for believing that the highly inclined 

 cupriferous rocks at the east end of the lake pass unconformably below this 

 sandstone." (Science, 1883, I., pp. 218, 219.) 



It was then pointed out by Dr. Wadsworth, that 



'* the evidence advanced by Logan, which Dr. Hunt finds so convincing, was 

 mainly a difference in dip between the traps and sandstones at localities several 

 miles apart ; and that all the evidences, as Logan himself says, only 'seem to 

 Siipport the suspicion that the sandstones m^ay overlie unconformably those 

 rocks, which, associated with the trap, conatitute the copper-bearing series.' " 

 (Science, 1883, L, p. 307.) 



Prof. N. H. Winchell then, in agreement with Foster and Whitney, 

 and with Solwyn, remarked with reference to the statements of the 

 latter : — 



" I concur with hira in the sweephig affirmation, * that there is, at present, 

 no evidence whatever of their [the cupriferous rocks] holding any other place 

 in the geological series ' than that of the * Potsdam and primordial Silurian * ; 

 and I would also add, that there is nuich incontestible evidence that they can 

 hold no other." (Science, 1883, L, p. 334.) 



Later, Proi. T. C. Chamberlin summed up the various reasons for 

 supposing that the Keweenaw rocks were distinct from the adjacent 

 sandstones. They were : the diifcrcut stratigraphical relations ; differ- 

 ences in thickness and in constitution; unconformity; the inherent 



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