108 BULLETIN OF THE 



and conglomerates, by Houghton, Jackson, Shepard, Hubbard, and Mar- 

 cou. They were thought to be in hxva overflows by Hubbard, Foster 

 and Whitney, Jackson, Bigsby, Hall, Hunt, Pumpelly, and Irving. 

 They were regarded as metamorphosed sedimentary rocks by Locke, 

 Rivot, Pumpelly, and Brooks, while the amygdaloidal portion was said 

 to have been formed from fused sandstone by Houghton and Jackson, 

 and from sedimentary material, possibly volcanic mud, by Hunt. The 

 latter author at first taught that the traps were eruptive, but separated 

 the amygdaloids from them. 



The traps were supposed to be of a prior age to the sandstones by 

 Bayfield (who thus long antedated the views of Pumpelly and Brooks), 

 Logan, Whittlesey (who regarded them as conformable with the sand- 

 stones), Alexander Agassiz, Pumpelly, Brooks, Hunt, Ptominger, Irving, 

 and Selwyn. They were said to be younger than the sandstone by 

 Houghton, Jackson, and Marcou. They were taken to be of the same 

 geological age as the sandstones by Hubbard, Foster and Whitney, 

 Jackson, Bigsby, Rivot, Logan, Hall, Dana, Pumpelly, Hunt, and Rom- 

 inger. 



The traps were assigned to a geological age distinct from the eastern 

 sandstone, and given the name Keweenaioan by the Wisconsin geologists, 

 Keweenawian by Brooks, and Keweenian by Hunt. Logan and Selwyn 

 assigned them to the Huronian, the latter doing so principally on ac- 

 count of the erroneous observations of Pumpelly and Brooks. 



The eastern sandstone of Keweenaw Point was regarded as Old Red 

 by Bayfield and Bigsby ; as New Red, by Houghton, Ruggles, Jackson, 

 H. D. Rogers, Shepard, Owen, Marcou, and Dana; as Potsdam, by Hub- 

 bard, Foster and Whitney, Owen, Logan, Hall, AV. B. Rogers, Rivot, 

 Rominger, and Irving ; as partly Potsdam and partly Calciferous, by 

 Logan and Dana ; as Calciferous, by Dana ; as Chazy, by Logan ; as 

 Quebec, by Logan, Hunt, and Pumpelly ; as Permian, by Macfarlane ; 

 and as Permian or Triassic, by Bell. The sandstone was also thought 

 to be older than the Potsdam by Logan and Whittlesey. 



Dr. Houghton at first regarded the sandstone and trap from the Sault 

 St. Marie to the Porcupine Mountains as the same formation ; later, he 

 thought that the sandstone west of Grand Island was unconformably 

 overlaid by that east of that island ; still later, the sandstones east of 

 Keweenaw Bay were said to be older than the Trenton, while the Cop- 

 per-bearing rocks were thought to be New Red. 



The veins were thought to have been formed anterior to the traps by 

 Jackson, and at the time of their eruption by Dana and Marcou, but by 



