188 THE CAMBRIAN. Ibull.81. 



In describing a deep well at Washington, in southeastern Iowa, Prof. 

 S. Calvin states that a gray sandstone 1,230 feet from the surface prob- 

 ably represents the upper part of the Potsdam series. 1 



LAKE SUPERIOR SANDSTONE. 



In an account of a journey along the south shore of Lake Superior, 

 Dr. J. J. Bigsby describes a red and white sandstone, for the most part 

 horizontal, that predominates along the shore, resting in places on 

 granite. 2 He also mentions the red sandstone of Point Keewawoonan 

 and the sandrock described to him by Mr. Thomson. 3 



The description of the geology of Lake Superior, by Capt. H. W. 

 Bayfield, mentions a horizontally stratified sandstoue that he traced 

 from one extremity of the lake to the other, on both the north and 

 south shores, and on many of the islands in the lake. A description 

 of the mode of occurrence of the sandstone on the south shore of the 

 lake is given, with several diagrams illustrating the unconformity be- 

 tween the granite and the sandstone. 4 He considers it quite probable 

 that the formation extended to the west and southwest as far as the 

 foot of the Rocky Mountains, and that it might possibly be the same 

 as the sandstone at the Falls of Niagara, 'etc., but concluded it required 

 much more elaborate investigation than has yet been bestowed to ren- 

 der it certain that the sandstone of Lake Superior and that of the 

 extensive tracts of country mentioned are the same formation. He 

 then gives reasons for terming the sandstone of Lake Superior the Old 

 Red. These are its position immediately on the granite, its structure, 

 and component parts. 5 No fossils were observed. The student will 

 find in this paper of Gapt. Bayfield's a very fair description of the sand- 

 stones as they occur about Lake Superior, and it is worth reading in 

 connection with the controversy in relation to their age. 



As State geologist of Michigan Dr. Douglass Houghton reported 

 upon the strata of the northern peninsula. In the second annual report 

 he says that "the Old Red sandstone 17 has been very much shattered by 

 the protrusion of trap rock through it. 6 In his third report a more ex- 

 tended account is given of the Lake Superior sandstone on the Ste. 

 Marie River. The sandstone passes conformably beneath the super- 

 jacent limestone. 7 Of the bulk of the formation he says: 



The Lake Superior sandstone in its easterly prolongation does not attain a very 

 great thickness, but in proceeding westerly this thickness is vastly increased, attaining 

 on the south shore of Lake Superior to several hundred feet. 



1 Notes on the formations passed through in boring the deep well at Washington, Iowa. American 

 Geologist, vol. 1, 1888, p. 30. 



2 Notes on the geography and geology of Lake Superior. Quart. Jour. Lit., Sci. and Arts (of thelioyal 

 Inst, of Gt Brit.) vol. 18, 1825, p. 33. 



3 Op. cit., p. 260. 



4 Outlines of the geology of Lake Superior. Quebec Lit. and Hist. Soc. Trans., vol. 1, 1829, p. 17, figs. 

 2 and 3, on plate. 



6 Op. cit., p. 19. 



'(Peninsula District.) Second annual report State geologist of Michigan, Detroit, 1839, p. 14. 



7 Third annual report State geologist of Michigan. House Reps. Document, No. 8, 1840, p. 14. 



