ON THE NORTHWEST SHORE OF 



LAKE SUPERIOR. 



395 



vein of jaspoid rock, having an east-and-west course. No. 64 continues for some 

 distance, when clay and marl beds again occur, from a hundred to a hundred and 

 fifty feet high. On the high ridges fragments of slightly altered red sandstone (No. 

 05), were found in the upper part of the marl. The next rock exposed is a high 

 ridge of greenstone, bearing northeast and southwest. It is a very heavy exposure, 

 and is cut through by the river. It forms a mural precipice on both sides of the 

 stream. 



The next rock is quartzose porphj^ry (No. 07), which seems to be a highly meta- 

 morphosed variety of No. 62. It bears great resemblance in some spots to the 

 slates of Spar Island. It is exposed on both sides of the river. At one point it 

 appears to be overlaid by a heavy bed of greenstone, but the fact could not be esta- 

 blished with certainty. It dips at one of the exposures southwest at an angle of 

 18°. Next comes a high ridge of hornblende rock (No. 06), which seems at some 

 places to graduate into syenite. Some low ridges succeed, and then a high one of 

 No. 08, which is exposed on the slope of the hill for some distance. The bed of 

 the river is much obstructed by fragments of it. This rock continues up to the 

 first lake through which the Wisacode passes. Here we found an old Indian camp- 

 ing-ground. The Grand Portage band come to this place, in the spring of the year, 

 by way of Mud Lake, for the purpose of making sugar. The country beyond this 

 is nearly impassable, except in canoes, on account of the numerous lakes and swamps, 

 and we therefore ceased our explorations at this point. On our way back to the 

 lake, we came to a small stream which flows for several miles through a deep nar- 

 row gorge in No. 02. The walls are perpendicular, and from twenty-five to forty 

 feet in height. At some points, it contains veins of calcite, and small nests of fluor 

 spar (No. 70) . This rock is very thinly laminated in some of the beds, and its 

 stratified character is everywhere to be seen. In a hill near the point where we 

 struck the Lake, which was nearly two miles above the mouth of the Wisacode, is 

 an exposure of greenstone which passes into syenite (No. 71). 



Between the lake-shore and the high greenstone ridge back of the bays above 

 Grand Portage Bay, are four ridges, varying from one hundred and fifty to two 

 hundred and fifty feet in height, the southerly one descending gradually to the Lake, 

 with occasional spots of swampy ground intervening. 



At the bottom of the first bay, proceeding toward the mouth of Wisacode River, 

 is a grayish-coloured anrygdaloid (No. 52). It is shaly, and decomposes easily. 

 The points of the bays, as far as the fourth, are composed of greenstone, and appear 

 to belong to a heavy north-45°-east dike, which has been broken down and nearly 

 carried away by the action of the Lake. From this point, to what I have called 

 the Eastern Palisades, the shore consists mainly of amygdaloid, overlaid by meta- 

 morphosed siliceous slate. The cells of the amygdaloid are filled with laumonite, 

 thalite, and other minerals. The amygdules are from the size of a pea to that of a 

 hazel-nut. Thin seams of the same minerals are also found filling joints and cracks. 

 The dip is southeast, at an angle of 12°, and the height of the exposures above the 

 water-level varies from ten to fifteen feet. The line of junction between the amyg- 

 daloid and the metamorphosed slates is much broken and very irregular. At some 

 localities the amygdaloid weathers into caverns, and many irregularly formed pillars 



