252 THE CANADIAN NATURALIST. [Jan. 



consisting of reddish-grey felspar, soft dark-green iron-chlorite 

 (delessite), and occasional spots of yellowish-green epidote. From 

 this they graduate into finer-grained varieties, but they very 

 seldom become impalpable, or their constituents altogether indis- 

 tinguishable. Sandstone was not observed in contact with the 

 traps, but a large mass of quartzose porphyry is seen at a short 

 distance from the shore. 



Another large development of traps and sandstones occurs to 

 the north of Pointe-aux-Mines, where an occasional bed of 

 tufaceous melaphyre is also found. 



Besides the rocks above described, there are found on the low 

 ground betwixt Goulais and Bachewalmung Bays, betwixt the latter 

 and Pancake Bay, and on many of the islands of the east shore, 

 large areas of red sandstone, almost horizontal, which are supposed 

 to be the continuation of that occurring at Sault St. Marie, and 

 usually called the St. Peter Sandstone. The true relations of this 

 rock to those of the upper group of the Upper Copper-bearing series 

 have not yet been made out. It closely resembles, in lithological 

 character, the sandstone described above as occurring in almost 

 vertical strata on the south shore of Bachewahnung Bay. The 

 disturbance of the latter is reasonably attributable to the neigh- 

 bouring melaphyres, in which case the sandstone would be the 

 earlier rock. On the other hand, as Sir W. E. Logan observes, 

 " the contrast between the general moderate dips of these sand- 

 " stones and the higher inclination of the igneous strata at 

 " Gargantua, Mamainse, and Gros Cap, combined with the fact 

 " that the sandstones always keep to the lake side of these, while 

 " none of the many dykes which cut the trappean strata, it is 

 " believed, are known to intersect the sandstones (at any rate on 

 " the Canadian side of the lake), seem to support the suspicion 

 " that the sandstones may overlie unconformably those rocks 

 (l which, associated with the trap, constitute the copper-bearing 

 " series."* The following facts are confirmatory of this view. 

 In the bay immediately south of Point- aux-Miues, where the 

 Mamainse series adjoins the Laurentian rocks, the lowest member 

 of the former is unconformably overlaid by thin bedded bluish and 

 yellowish-grey sandstones, striking N. 50° E., and dipping la° 

 north-westward. The lowest layer is a conglomerate, with granitic 

 and trappean boulders, and a bluish, fine-grained and slaty matrix. 



* Geology of Canada, p. 85. 



