1855.] ISBISTER — NORTH AMERICA, ETC. 501 



of the rugged and lofty coast-range of Labrador and Baffin's Bay, 

 as well as of the west coast of Greenland. 



By carrying the eye over the map from point to point along the 

 western edge of the crystalline belt running through the Hudson's 

 Bay Territories, it will be seen that the average direction is the same ; 

 though, as it proceeds northwards it inclines slightly towards the 

 Rocky Mountains, which, it is to be observed however, begin here 

 to lose their continuity ; several of the western ranges being found 

 to deviate from the general direction of the chain, and to develope 

 themselves in irregular masses through the interior of Russian 

 America. 



We possess little reliable information respecting the structure of 

 the mountain ranges of Labrador (on the east) or of the Rocky 

 Mountains (on the west) north of the forty-seventh parallel, where 

 they were crossed by Lewis and Clarke, in 1805, and no organic re- 

 mains (so far as I am aware) from either locality. Sir John Richard- 

 son, who is in possession of all the information respecting the Rocky 

 Mountain range, collected from the traders of the Hudson's Bay 

 Company and from the botanists Douglas and Drummond, who crossed 

 it between the sources of the Elk and Peace Rivers, describes the 

 eastern slopes as consisting of conglomerate and sandstone, to which 

 succeed limestone and clayslates, probably of Silurian age, and gra- 

 nite. This view is to some extent borne out by the section of this 

 range given by Marcou, at Fort Laramie, in lat. 42°, from the 

 Surveys of the United States' geologists. Farther north, where the 

 chain was explored by myself, near its termination in the Arctic Sea, 

 the prevailing formations were found through their organic remains 

 (as will be subsequently noticed) to be referable to certain members 

 of the Carboniferous series, corresponding probably to the Mountain 

 Limestone of English geologists. From the highest part of the 

 range, near latitude 55° N., where it attains an elevation of 16,000 feet 

 above the sea, the four largest rivers of North America — the Missouri, 

 the Saskatchewan, the Mackenzie, and the Columbia take their rise. 

 It may be added, that these four feeders of opposite oceans not only 

 take their origin from the same range of mountains, but three of 

 them almost from the same hill, — the head-waters of the Columbia 

 and the Mackenzie being only about "two hundred yards" apart, 

 and those of the Columbia and the Saskatchewan, not more than 

 *' fourteen paces." It may be mentioned also as a singular fact, that 

 one branch of the Mackenzie, the *' Peace River " of Sir Alexander 

 Mackenzie, actually rises on the western side of the Rocky Moun- 

 tains within 300 yards of another large river flowing into the Pacific, 

 the Tacoutchetesse, or Eraser's River, which discharges itself into 

 the Gulf of Georgia, opposite Vancouver's Island. 



Central Plateau of Crystalline Rocks. — Marcou, in his recently 

 published Geological Map of the United States, has traced the cry- 

 stalline formation of the Laurentine Mountains a considerable distance 

 to the westward of Lake Superior, where it appears to form the chief 

 constituent of the low watershed which separates the waters of the 



