190 THE CAMBRIAN. [bull. 81. 



the south coast dips regularly northerly, while the upper or gray sandstone dips 

 equally regularly south or southeasterly, in which respect the last-mentioned rock 

 conforms to the limestones resting upon it, while it rests itself upon the uptilted edge 

 of the red sandrock below. 1 



The upper sandrock, like the lower, abounds in clearly denned ripple marks, and 

 its Hue of cleavage is very irregular, frequently being opposed to the line of stratifi- 

 cation over very considerable districts of country. Two indistinct species of fucoides 

 were all the fossils noticed in connection with it. 



I was unable to obtain any observations upon the thickness of the upper sand rock 

 which were satisfactory, but from the imperfect observations which were obtained I 

 was led to conclude that the average thickness as far westerly as the Pictured Rocks 

 does not vary far from 700 feet. The upper sandrock, like the rocks before mentioned, 

 wedges out as far as we proceed in an easterly direction. 2 



When presenting to the Boston Society of Natural History an ac- 

 count of his visit to Lake Superior Prof. H. D. Rogers states that he 

 discovered in the neighborhood of Chocolate and Carp Rivers the fol- 

 lowing conditions of stratification : 



First, a group of rocks, the equivalents, undoubtedly, of the Primal sandstone and 

 Primal slate of Profs. W. B. Rogers and H. D. Rogers, denominated, in the nomen- 

 clature of the New York survey, the Potsdam sandstone, and these rocks, highly in- 

 clined, and traversed by parallel east and west axes. Secondly, upon the uptilted 

 edges of this earliest Paleozoic formation rests, in an unconformable position and 

 with a very gentle northern dip, the conglomerates and shales of the red sandstone 

 series- Specimens of the conglomerate were displayed, in which the pebbles were 

 all from the older rocks. Mr. Rogers thought this fact of unconformable superposi- 

 tion an almost conclusive proof of a post-Paleozoic date ; and he proceeded to argue, 

 from various points of analogy between the red sandstone itself, its trappean dikes, 

 and their mineral associations, with similar components of the Mesozoic or new 

 red sandstone of the Atlantic States, that the formation in question is of equivalent 

 age and origin with this last-named interesting group of rocks. 3 



In his reconnaissance of the Chippewa land district of Wisconsin, Dr. 

 D. D. Owen examined a portion of the shores of Lake Superior. He 

 noted the red sandstone, its mode of occurrence, and character. He 

 states that various views have been advanced by different writers re- 

 garding the age of the red sandstone, marls, and conglomerates of Lake 

 Superior. Some authors have referred them to the date of the oldest 

 sandstones of the New York system ; others believe them to be con- 

 temporaneous with the New Red sandstone of Great Britain and the 

 hunter Sandstein of Germany. He further states : 



Judging, however, from lithological and mineralogical character, there certainly 

 is strong presumptive evidence that they were deposited subsequently to the Carbon- 

 iferous era. 



He calls attention to the strong resemblance between them and the 

 formations above the Coal Measures, not only of the State, but of some 

 parts of Europe. 



Ranging through Connecticut, New Jersey, Maryland, and Virginia there are red 

 sandstone and marly beds that are almost a counterpart of some portion of the Lake 

 Superior formations, as well in aspect as in composition ; like them, too, they are 



•Op. cit., pp.41, 42. __ 



8 Op. cit., pp. 42, 43. 



* On the mineralogy and geology of the south shore of Lake Superior. Boston Soc. Nat. Hist. Proc. 

 vol 2, 1816, p. 126. 



