224 Notice of Messrs. Foster and Whitney^ s Report 

 narrow island of Isle Royal between, proving, as the authors state, 



that this part of the lake must he the course of a great synclinal 



valley, arising from two parallel axes of elevation on opposite 

 sides of the lake. We might add farther, that this course is at 

 right angles to the great range of lakes that extends from Erie 

 and Michigan northwest to the Northern ocean, which range is 

 parallel to the Rocky Mountains and the Northwest coast of 

 America on one side, and to Hudson's Bay and the shores of 

 Davis Straits on the other.* 



We cite with regard to the mountains, from pages 34, 35. 



" L Two granite belts occur in the Northwest — one forming 

 the axis between the waters of Lake Superior and Hudson's Bay; 

 the other between I^ake Superior on the north and Lake Michi- 

 gan and the Mississippi river on the south. The outline of the 

 Canada range is N. 60"^ E., though subject to minor irregularities. 

 It forms the rim of the Canada shore for more than two-thirds of 

 its extent. The summits of this range are generally rounded, 

 and rarely elevated 1,500 feet above the lake- 



On the southern shore, a belt of granite approaches the lake 

 near Dead river, and thence stretches westward, sinking down 

 into a somewhat broken plain southwest of Keweenaw bay. Its 

 widest expansion is about thirty miles. This belt constitutes the 

 Huron mountains, which in places attain an elevation of 1,200 

 feet above the lake. They do not range in continuous chains, 

 but exist in groups, radiating from a common centre, presenting 

 a series of knobs, rising one above another, until the summit-level 

 is attained. Their outline is rounded or waving — their slope 

 gradual. The scenery is tame and uninteresting. Hemmed in 

 by these knobs, it is not unusual to find numerous lakes and 

 meadows covered with grass, forming an agreeable feature in the 

 landscape. These meadows appear at one time to have been 

 lakes, which have been filled with the detritus brought down 

 from the surrounding hills, or drained in consequence of the 

 water having worn down the barriers which existed at their out- 

 lets. Towards the western extremity of the district, the granite 

 reappears in low ridges, and crosses the Montreal within twelve 

 miles of its mouth. There are subordinate patches of granite in 

 other portions of the district, attaining no great elevation, which 

 will be described in the detailed report. 



The metamorphic belt folded around the granite is traversed 

 by numerous detached ridges of hornblende and feldspar rocks, 

 ranging in E. and \Y, direction, and rarely rising more than 200 

 feet above the surrounding country, and present a more rugged 

 aspect than the granite. A quartz range starts from the lake 



Origin of tlie Graad Outline Features of the Earth, bv J. D. Dana, this Journal, 

 [2,] iii, 382 and 389. 



