MUSEUM OF COMrARATIVE ZOOLOGY. 83 



elsewhere, the metulhferous rock is not, as sometimes supposed, a real 

 trap rock, but a mixture of trappean matter, and that of the red sand- 

 stone formation, more or less baked and modified by intense igneous 

 action. These semi-fused materials, in crystallizing, have very fre- 

 quently resulted in the following curious arrangement : the crystalline 

 metallic copper occupies the centre of globular and variously formed 

 concretions ; calcareous spar usually, but not always, invests the cop- 

 per; and very generally the exterior of the kernel is pure crystalline 



chlorite These nodular lumps are dispersed through a base 



which exhibits a sort of pasty mixture of softened red shale and true trap- 

 pean matter ; and many of them are so surrounded as to indicate them 

 to be true segregations from this semi-igneous, semi-aqueous compound." 

 He regarded the sandstone as equivalent to the New Red sandstone of 

 the Atlantic States, and making the same formation throughout the 

 peninsula of Upper Michigan. In a report on the sale of mineral 

 lands by Mr. Relfe we find the following statement : " In the con- 

 glomerate rocks which overlay the trap, are to be found all the varie- 

 ties of copper ore of the richest qualities, offering to the smelter a 

 greater yield than has ever been obtained from the copper ores of 

 England or other countries that have contributed so largely of this 

 important article." * 



Sir "Wm. Logan in the Report of Progresst regarded the copper-bear- 

 ing traps of Lake Superior as of a higher antiquity than the Potsdam 

 Sandstone, and attributes the same view to Dr. Houghton in 1841. 

 Logan's statement seems to be erroneous regarding Dr. Houghton's 

 views in this respect. He considered the traps older than rocks which 

 Logan regards as Potsdam sandstone, but of whose age he expressed no 

 opinion in his Report for 1841, to which Logan refers. In 184:3, as 

 we have seen before. Dr. Houghton not onlj- took the copper-bearing 

 rocks to be of the age of the New Red sandstone, but also considered 

 Logan's Potsdam sandstone as belonging to some formation older than 

 the Trenton. In this way he had reversed his view of the order of 

 succession in 1843, which Logan attributed to him as late as 1847. 

 (1. c, p. 34.)t 



Mr. Bela Hubbard in his report for 1846 § states concerning the trap 



* Reports of Committees, 29th Cong., 1st Sess., Vol. III., Doc. 591, pp. 2,3, 

 1845-46. 



t Geol. of Canada, 1846-47. 



t 1849 and 18.il, Reports of Progress. North Shore of Lake Huron, p. 20 ; Brit. 

 Assoc., pp. 59-62, 1851. 



§ Senate Documents, 1849-50, III. 371-935, p. 887. 



