ON THE NORTHWEST SHORE OF LAKE SUPERIOR. 



387 



The rock which forms the points of the bay at this place is greenstone (No. 

 102). Then succeeds, in passing up the stream, a volcanic gritstone, No. 95, highly 

 metamorphosed, and overlaid by a bed of trap. These beds dip northwest at an 

 angle of 19°. Above this, on the east side of the creek, is an exposure of No. 98, 

 ten feet in thickness where it first shows itself, but continues to increase in thick- 

 ness and dip as the creek is ascended, until it dips 39° northwest. The next rock 

 is a trap-bed, conforming to the dip of the rocks with which it is associated, and a 

 short distance beyond that, a dike of columnar trap, bearing nearly east and west, 

 traverses all the beds. 



On the top of the first ridge, which is about one hundred and fifty feet above the 

 level of the lake, the surface for the space of several acres, is almost entirely bare, 

 and. presents numerous scratches and grooves. They are of all sizes, from a mere 

 scratch to two inches in depth, and from one to four inches in width at the top. 

 Their general direction is east-southeast, and southeast. The ridge slopes gradually 

 towards the Lake in a southeast direction, the bearing being northeast and south- 

 west. The northwest side of the ridge is abrupt, and presents a mural escarpment 

 from twenty to thirty feet in height, with a wide talus below. The highest point 

 of this ridge is about three hundred feet above the Lake. Beyond this ridge, the 

 shales continue for about a quarter of a mile, dipping to the northwest, when they 

 are concealed by clay and marl beds, and when they again appear, the dip is to the 

 southeast, at an angle of 6°. They are porphyritic at this place. The clays and 

 marls, which are from twenty-five to sixty feet thick, soon cover them again. In 

 the upper part of these beds are many pebbles and small boulders, and on the top, 

 many large boulders of granite. 



Another exposure, on the opposite side of this bay, gives the following section. 



12 0 4 



1. Greenstone ridge, at the lake-shore. 



2. lied sand-rock and shales, the joints and searns full of laumonite. 



3. Breccia, composed of angular and rounded fragments of sand-rock and shales. 



i. Metamorphosed argillaceous slate — rings like clink-stone when struck with a hammer. It is very thinly laminated. 

 5. Greenstone. 



On a small creek near this place is a great exposure of sandy shales and sand- 

 stone, like those on the lake-shore. The shales are in layers, from one to six inches 

 thick. Some of them are hard, while others are soft and disintegrate easily. They 

 all dip to the southeast, at an angle of 7°. A quarter of a mile up the creek, in the 

 vicinity of a trap-dike, the joints and seams of these beds are filled with laumonite. 



These beds come up, as the creek is ascended in the following order : 



1. Thin shales (No. 103), with seams of clay and nests of laumonite. 



2. Thicker layers of shale, more indurated, with occasional cells filled with calcite and zeolites. 



3. Beds of Nos. 104, 105, from two to four feet thick, hard, of a deep red colour, and showing dark 

 greenish-coloured lines, when broken. Some of these beds are ripple-marked. 



4. Beds of No. 106, still harder and more compact ; pebbly near its junction with the other beds. 



