Along the north shore of lake Superior from the Slate islands to Pigeon river, and extending over an area reaching to more than 100 miles north of the Canadian Pacific railway, the most prominent geologic feature is the occurrence of large areas in which trap sheets predominate. Within this area practically every salient feature of the topography is found to be associated with these trap sheets. Along the southern edge of the district, and extending for about 40 miles north of the Canadian Pacific Railway line, the traps are constantly found in association with Keweenawan and Animikie sediments. In the northern part of the area, in the basin of lake Nipigon, residual patches of Keweenawan sediments are frequently found associated with the traps, but there are numerous localities where the igneous rock rests directly upon the older Archean rocks.
The variegated, bold, . . .