502 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 16, 



Missouri from those of the Saskatchewan and other rivers flowing 

 into Hudson's Bay. 



The zone of crystaUine rocks, chiefly gneiss, with granite and trap, 

 previously alluded to as extending for a very great distance in a 

 north-west direction from Lake Superior, is likewise very little ele- 

 vated for the greater part of its extent above the surrounding country. 

 Sir John Franklin, on his first overland expedition to the shores of 

 the Polar Sea, crossed this granitic chain nearly at right angles to its 

 line of direction in proceeding from Hudson's Bay to Lake Winipeg, 

 where it was 220 miles wide ; it has been since crossed at various 

 other points, and traced nearly along its entire length to the Arctic 

 Sea. We are thus in possession of the requisite data for mapping 

 its course and extent, and indicating its general features with con- 

 siderable accuracy. Branching off" from the Laurentine ranges, 

 it assumes a north-westerly direction from the Lake of the 

 Woods (where it first comes in contact with the limestones which 

 underlie the prairies on the west), until it reaches Lake Winipeg, 

 along the eastern side of which it is then continued for about 280 

 miles in nearly a N.N.W. direction. From Norway Point at the 

 north end of Lake Winipeg to Isle a la Crosse, a distance of 420 

 miles in a straight line, the western boundary has, according to Sir 

 John Richardson, a W.N.W. direction. For 240 miles from 

 Isle a la Crosse to xA.thabasca Lake, its course turns in a somewhat 

 irregular outline northward, enclosing the whole of that lake with 

 the exception of its western extremity. Thence it is continued to 

 MacTavish Bay in Great Bear Lake, a distance of 500 miles in 

 a general direction of about N.W. by W., and is marked, according 

 to Sir John Richardson, " by the Slave River, a deep inlet on the 

 north side of Great Slave Lake, and a chain of rivers and lakes, in- 

 cluding Great Marten Lake, which discharge themselves into that 

 inlet." From Great Bear Lake to the sea it follows the general 

 course of the Coppermine River, its termination being marked by the 

 mouth of that stream in lat. 71° 55' N. and long. 120° 30' W. ; or 

 perhaps more correctly by Richardson's River, a little to the west of 

 it. In this part, for the first time, the chain rises to the altitude of 

 hills, marked on the Map as the Copper Mountains, which attain in 

 some parts a height of 800 feet above the bed of the river. The 

 slight elevations composing the main portion of the chain seldom 

 rise, as has been already observed, much above the level of the sur- 

 rounding country, giving to the entire range the character of a low 

 swampy plateau of crystalline rocks, covered by an immense net- 

 work of small lakes and swamps, connected by narrow and tortuous 

 channels. The low rugged knolls of granite and gneiss, round which 

 these channels wind, "have mostly," says Sir John Richardson, 

 " rounded summits, and they do not form continuous ridges, but are 

 detached from each other by valleys of various breadth, though gene- 

 rally narrow and very seldom level. When the valleys are of con- 

 siderable extent, they are almost invariably occupied by a lake, the 

 proportion of water in this district being very great ; from the top of 

 the highest hill on the Hill River thirty-six lakes are said to be 



