442 Geological Society. 



the eastward being abrupt, but the slope towards the W. more gra- 

 dual. These mountains join the sea on the west of the Mackenzie ; 

 and at their termination are divided into four groups or chains, to 

 which Captain Franklin has given the names of Richardson s, Buck- 

 land's, the British, and Romanzoff chains. The land again becomes 

 lower to the west of the chain last mentioned, and continues to be so 

 from thence to the remotest point arrived at ; no prominent elevations 

 having been observed to the west of long. 146°. 



2. Another very extensive tract of primitive rocks in the north of 

 America has nearly the same direction with the range of the Rocky 

 Mountains, but the two ranges converge towards the north j the 

 distance between them being, in lat. 50°, 700 miles ; — about 220 miles 

 where it was traversed by Captain Franklin, in going from Hudson's 

 Bay to Lake Winipeg ; — and in lat. 66° only 200 miles. This east- 

 ern primitive tract consists principally of granite and gneiss ; it ex- 

 hibits great uniformity of character, contains no very elevated ground, 

 and is in fact traversed by several rivers which arise in the Rocky 

 Mountains. It is flanked on both sides by extensive calcareous tracts. 



3. The north-eastern extremity of the Rocky Mountain chain, near 

 the mouth of the Mackenzie, consists of grauwacke and other transi- 

 tion-rocks, interposed apparently between the primary and the cal- 

 careous districts. In some of the other places described, a rock 

 resembling the old-red-sandstone of England, occupies a similar si- 

 tuation. 



4. The tract that intervenes between the Rocky Mountains and the 

 eastern primary band above mentioned, consists principally of cal- 

 careous strata, and is remarkable from its including, throughout, a 

 series of great lakes or lake-like rivers, with which a very large pro- 

 portion of the surface is occupied, and the bottoms of which appear 

 in several instances to be below the level of the sea. This interme- 

 diate calcareous band was traced in one place by the author, to the 

 width of about 280 miles from the eastern primary tract j and one of 

 its highest summits, about a mile from Bear Lake, was supposed to 

 be about 950 feet above the sea. The limestone of which this district 

 is composed, as well as that of the calcareous tract on the east of 

 the primary band above mentioned, presents considerable uniformity 

 of character : the ridges of hills are nearly parallel to those of the 

 Rocky Mountains j and a very large proportion of the rocks observed 

 by the author, was found to be magnesian limestone, — apparently 

 belonging either to the magnesian limestone formation of England, 

 or to our mountain-limestone, which it is well known includes in 

 Europe numerous beds of dolomite. 



The fossils also of this calcareous formation, are of the same genera 

 with those of our mountain-limestone and of the magnesian beds in 

 the north of England ; including corallines, products, terebratulites, 

 and a cardium : and in several places the calcareous beds contain a 

 large proportion of chert and flinty slate. The correct determination 

 of the relations of this great calcareous tract, is one of the chief 

 points of interest remaining for future research, in the country de- 

 scribed by the author ; for while he agrees with other geologists in 



assigning 



