382 DESCRIPTION OF THE COUNTRY BORDERING 



is variegated by yellowish-red spots and stripes, precisely like those found in the 

 shaly sandstones of some parts of the south shore. A short distance above the 



h a 



mouth of Kamanosisatikag River, are some small rock-islands, near the lake-shore, 

 two of which are connected by a natural arch, as seen in the following sketch by 

 Major R. Owen. The space between the abutments has been cut out of the soft, 



NATURAL ARCH, LAKE SUPERIOR. 



shaly amygdaloid by the action of the waves, while the bridge which spans it is 

 made by the more unyielding overlying trap-bed. At some points in this vicinity 

 the bedded trap is from twelve to twenty feet thick, and overlaid by a deposit of 

 drift. 



17. Kamanosisatikag River. — At the mouth of this river, the lowest rock is an 

 earthy, red amygdaloid, from eight to ten feet thick, in beds, with very thin lamina? 

 of clayey matter between them, and over the amygdaloid is about twelve feet of 

 volcanic grit, with thin bands of No. 133 intercalated between the beds. 



About half a mile from the Lake, the river runs through a narrow gorge, not over 

 two feet in width at some points, with perpendicular walls from twenty to thirty feet 

 high. This gorge is represented on the opposite page, from a point a short distance 

 below, as sketched by Major R. Owen. The section up to this place shows, in de- 

 scending order, 1st, the rock seen at the mouth; 2d, shaly amygdaloid; 3d, metamor- 

 phosed, siliceous shale ; all dipping to the southeast at an angle of 9°. Ascending the 

 river a short distance further, a purplish-coloured, metamorphosed slate comes up 

 (No. 139), over which there is a fall of twenty-five feet, in four or five cascades. This 

 rock contains occasional crystals of flesh-coloured felspar disseminated through it. 

 About three-quarters of a mile above this, is a ridge, of which No. 137 forms the 

 summit. It rises to the height of five hundred and eleven feet above the lake-level, 

 according to the measurement of Major Owen, and is the first ridge met with in 



