MICHIGAN AND WISCONSIN. 491 



Tn a foot-note Dr. Owen also states that the remains of the shells 

 can be " detected in fraj^ments enclosed in the trap, and so much al- 

 tered as to be distinguished with difficultj from the surrounding green- 

 stone." It seems hardly possible that Owen could have made these 

 statements if part of the trap at least was not intrusive in the sand- 

 stone. 



Mr. J. H. Kloos (Zeits. Deutsch. Geol. Gesells., 1871, XXIII., pp. 417- 

 448 ; Geol. Minn., 10th Ann. Report, for 1881, pp. 175-200) states that 

 he found the sandstone horizontally overlying the trap, or diabase as we 

 — in agreement with Rosenbusch — should prefer to call it. He also 

 observed a conglomerate made up of the ruins of the diabase ; but the 

 relations of the conglomerate to the sandstone were not ascertained. 



Prof X. H. Winchell claims that the sandstone in this locality is not 

 the Potsdam, but belongs to a higher formation. This view he holds 

 on account of the physical characters of the rock, as well as differences 

 in the fossils it contains. (Geol. Minn., 1st Ann. Report, pp. 68-80.) 

 Later, Professor Winchell considered the St. Croix sandstone as belong- 

 ing to the Quebec group, and as overlying the Potsdam sandstone, to 

 •which latter he refeiTed the copper-bearing rocks of Keweenaw Point. 

 (Geol. Minn., 10th Ann. Report, pp. 123-136.) 



From what has been given it can readily be seen that Messrs. Irving 

 and Chamberlin have failed to recognize the simplest features of the 

 geology of mixed eruptive and sedimentary rocks ; and that the condi- 

 tions upon which they place so much reliance to prove the correctness 

 of their views are exactly those which occur (excepting the presence of 

 fossils) whenever a sandstone or conglomerate is found intercalated in 

 the copper-bearing series. If their evidence is good, then we have 

 "proof absolute" that the Keweenawan series — the copper-bearing 

 rocks — is composed of as many distinct geological formations as there 

 are beds of sandstone and conglomerate intercalated in them. So far as 

 their yet published work goes, all their evidence has not advanced one 

 step beyond that which was made known thirty-three years ago, and it 

 is strictly in accord with the views of Foster and Whitney as then 

 stated. Were this not the case, there is as yet not the slightest pub- 

 lished evidence that the St. Croix traps belong to the copper-bearing 

 series : they may be older or younger, while considerable evidence is 

 given by Professor Winchell to show that the sandstone there is more 

 recent than the Potsdam. Moreover, there is positive evidence that 

 the copper-bearing rocks are part of the Eastern sandstone formation on 

 Keweenaw Point. It seems, then, that the Keweenawan series owes 



