NORTHWEST OF LAKE SUPERIOR. 



349 



nated. At one point, a bed of trap, a foot thick, was found interstratified with it, 

 the underlying shales being very amygdaloidal. Along this part of the coast there 

 are great undulations in the stratified rocks, and the local dip varies from north- 

 west to northeast and southeast, the general dip, however, being southeast, from 

 10° to 16°. The annexed figure represents one of the mural escarpments found 

 here. 



a, Trap, b, Amygdaloidal shales, c, Metamorphosed rock ; syenitic. d, Clay and marl beds. 



At the western point of the west bay, No. 603 shows itself, and also a narrow 

 north 5° east dike. No. 603 disintegrates easily, and the joints are remarkably 

 rusty. The metamorphosed rocks in contact with it are filled with zeolites. From 

 the eastern point of the fourth bay, to the mouth of the Riviere des Francais, the 

 only rocks exposed are the metamorphosed shales, overlaid by No. 603, and dipping 

 at an angle of about 21° to the southeast. The bottoms of the bays are composed 

 of shingle, the rock exposures being confined principally to the points which sepa- 

 rate them. 



4. Riviere des Frangais. — At the mouth of this river there is an exposure of 

 bedded trap (No. 603), overlying metamorphosed siliceous shale (No. 384). About 

 one hundred and fifty yards from the Lake, there is a low uplift of greenstone, and 

 at the junction of this rock with the metamorphosed shales, they contain nests of 

 copper ore, and some grains of native copper. The rock is very amygdaloidal, and 

 the ore seems to be disseminated through it, rather than concentrated in a vein. 

 At the junction of the greenstone with the shales, there is a breccia, through which, 

 also, the ore is distributed, with a great deal of laumonite and calcareous spar. 

 There are no indications of a regular vein of ore. 



The amygdaloid, which is of a dark reddish colour, and rather fine-grained and 

 compact, continues to form the bed of the river for about two miles and a half, with 

 the exception of a short distance, where it is replaced by a bed of trap (No. 383). 

 Where it reappears, it is very amygdaloidal, and resembles No. 399. It dips east, 

 at an angle of 11°. The junction of the shales with the overlying trap, is two hun- 

 dred and thirty-two feet above the lake-level. 



At the distance of two miles and a half from the lake-shore, the river is crossed 

 by a heavy dike of greenstone, which forms an anticlinal axis, the summit of which 

 is two hundred and eighty feet above the level of the Lake. The centre of the 

 greenstone dike is dark-coloured and compact, while the flanks are coarse-grained 

 and decompose somewhat easily. A vein of copper ore traverses this dike, and is 

 exposed for some distance in the bed of the river. From the unfavourable circum- 

 stances in which it is exposed (being under water), no very reliable opinion can be 

 given respecting its value. This much, however, can be said : it presents the 

 best surface indications of any vein met with on the north shore. It is a quartz 



