104 BULLETIN OF THE 



stone series reposing on the Huronian and Granitic rocks does not ex- 

 ceed the thickness of 300 feet." (L c, pp. 80, 81.) 



" The sandstones lining the eastern shore of Keewenaw Point extend 

 approximating to the centre of the Peninsula, retaining their horizontal 

 position, and also their lithological characters to such a degree that the 

 different strata can be parallelized without difficulty with those of the 

 more eastern localities. Near the centre the horizontal sandstone ledges 

 are found at once abutting against the uplifted edges of a different rock- 

 series — the Cop2Jer-beari)ig rocks — which form the most elevated central 

 crest of the Peninsula." (I. c, p. 95.) " The discordance of the strata 

 on the east side of the axis of elevation, aiid their conformability on the 

 sloping west side, finds its explanation in the hypothesis of a gradual 

 submarine upheaval of the trap range, in its subsequent rupture, and 

 the final emergence of the western margin from the water, while the 

 eastern portion of the fissured earth's crust remains submerged." (I. c, 

 p. 98.) 



In 1874, Prof. Roland Irving discusses the question of the age of 

 the copper-bearing rocks of Wiscoiisin, which were regarded as iden- 

 tical with those of Keweenaw Point. He advocates the same views 

 as those held by Pumpelly and Brooks, and bases his conclusions on 

 similar grounds. The Laurentian, Huronian, Copper-bearing rocks, 

 and Lower Silurian sandstones were never seen in direct contact with 

 one another with one exception. That exception is the junction of a 

 trap supposed to belong to the Copper-bearing series with the Potsdam 

 sandstone. The sandstone, he states, is for three hundred feet from the 

 trap " broken in every conceivable manner, the misplaced layers dipping 

 in all directions, and in its immediate vicinity making a sort of brecciated 



mass of fragments of trap and sandstone These trappean beds 



carry here no intercalated beds of sandstone and conglomerated He ob- 

 jects to the most probable explanation in this case, the protrusion of this 

 trap through the sandstone, as the trap seems to be unlike the Copper- 

 bearing rocks, except in the fact that it is .an old basalt ; but thinks 

 some deep-seated force shoved the old formation, on whose flanks the 

 sandstone was deposited, upwards, and so produced this dislocation.* 



Concerning the relation of the western sandstones to the eastern and 

 to the trap rocks in the Ontonagon district. Dr. Rominger says : " The 

 age of these beds is intermediate between the trap and the horizontal 

 sandstone deposits; but between all three of the indicated groups so great 



* Am. Jour, Sci., (3,) VIII. 46-56; Traas. Wise. Acad. Sei., 18'3-74, II. 

 107-119. 



