MUSEUM OF COMPARATIVE ZOOLOGY. 93 



chemical agencies, decomposing some soluble salt, most probably the 

 sulphate, of copper. Such changes may have been aided by the remain- 

 ing heat of portions of the volcanic masses, by the presence in them of 

 large quantities of iron in low states of oxidation, and by the further 

 oxidation of that metal evidenced in the red jasper and red laumonite 

 of the veins, and the red conglomerate and sandstone associated with 

 the trap The main fact in relation to the origin of the metallic cop- 

 per, is that it is a product, not of the fusion of the trap, but of subse- 

 quent processes, by which the fissures of that rock were filled by mate- 

 rials regarded as of aqueous origin." (/. c, pp. 8, 9.) 



In 1857, Dr. J. D. Dana* stated that the veins occur "mostly in the 

 trap rock which intersects a red sandstone, probably identical in age 

 with the red sandstone of Connecticut and New Jersey." April 6, 1859, 

 Dr. Jackson inclined to the view that the zeolites had been formed 

 "under the heat of the trap rocks, and the influence of heated saline 

 waters." t Prof. James Hall, in his Pal?eontology of New York,t says : 

 " In the region of Lake Superior, the sandstone, of the age of the Pots- 

 dam sandstone, has accumulated to a degree unparalleled in any other 

 known locality of that rock. In this region there are not only massive 

 accumulations of trappean matter, but outflows which have spread over 

 the strata during their deposition ; the beds of stratified amygdaloid 

 trap alternating with the shale and sandstone, often equalling or exceed- 

 ing the sedimentary matter." 



In 1861', Dr. T. Sterry Hunt, following Logan, referred the sandstone 

 with its accompanying trap to the Quebec group.§ Prior to this,|| Prof. 

 W. B. Rogers supported the view that this sandstone was of Potsdam 

 age, and was opposed in this by Dr. Jackson. 



In his Manual of Geology,^! Dr. Dana refers the sandstone partly to 

 the Potsdam and partly to the Calciferous epoch. In the edition of 

 1874, it is regarded as Calciferous. Dr. Dana further remarks concern- 

 ing the copper, that " the native copper of the Lake Superior region is 

 intimately connected in origin with the history of the trap and sandstone. 

 The copper occurs in irregular veins in both of these rocks near their 

 junction ; and whenever the trap was thrown out as a melted rock, the 



* Man. of Min., 2J ed., p. 305. 

 t Proc. Bost. Soc. Nat. Hist, 1859, VII. 45-47. 

 X Vol. III. p. 79, 1859. 



§ Am. Jour. Sci., (2,)»1861, X.XXI. 216-220, 392-414 ; 1862, XXXIII. 320- 

 327. Canadian Xat and Geol., 1861, VI. 81-105, 199-207. 

 II Proc. Bost. Soc. Nat. Hist., Nov. 17, 1860, VII. 394-399. 

 ir 1862, pp. 172-174. 



