﻿214 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 9, 



Still farther north the Mackenzie drains seventeen degrees of lati- 

 tude, and takes a course directly opposite to that of the Mississippi. 



Now, referring to the map, and beginning with Lakes Michigan, 

 Huron, and Superior, we can trace a chain of lakes that succeed each 

 other in a line parallel to the Rocky Mountains, or more nearly per- 

 haps to that of the strike of the granite and gneiss formation, viz. 

 Rainy Lake, Lake of the Woods, Lake Winipeg, Deer Lake, Wol- 

 laston Lake, Athabasca Lake, Great Slave Lake, and Great Bear 

 Lake, with Liverpool and Franklin Bays on the Arctic coast. All 

 these (except the two bays) are excavated in Silurian strata with one 

 end running in among the granite and gneiss rocks. 



The Saskatchewan or Nelson River and the Churchill River run at 

 right angles nearly to the line of lakes, crossing the granite and gneiss 

 formation, and, if we examine the lake-basins individually, we shall 

 find that often they take the same direction. For instance, if we 

 take the most northern lake-basin, Great Bear Lake and Coronation 

 Gulf, we find their axis to be about north-east. 



The next in succession, Great Slave Lake, viewed in conjunction 

 with the valley of the Great Fish River, is rather more nearly at right 

 angles with the channel of the Mackenzie. 



Athabasca Lake, with the large sheets of freshwater which discharge 

 themselves into Chesterfield Inlet, have a similar direction. 



More to the south, in the interval between the great N.N.W. and 

 S.S.E. valleys of the Mackenzie and Mississippi, there is a change, the 

 axes of the lakes running along the line of junction of the Silurian 

 with the gneiss and granite rocks, while the rivers flow transversely 

 and nearly parallel to the more northern lake-basins. 



This parallelism is preserved by the River St. Lawrence, its lakes, 

 and up to the west end of Lake Erie ; but I^akes Huron, Michigan, 

 and Superior, taken in the aggregate, make the northern bend parallel 

 to the axis of the Rocky Mountains. The whole water-course of the 

 St. Lawrence valley is in fact bent round the gneiss and granite 

 formation above-noticed, and which sends out a projecting point 

 between Lakes Huron and Ontario at the place of flexure. The 

 southern brim of this basin, except at the New York highlands, is 

 low, so that easy canal communications with the Mississippi valley 

 have been established at various places. The basins of the lakes 

 themselves and their southern borders are sunk in the strata of the 

 Silurian or Carboniferous series. 



Perhaps the instances I have adduced will serve to show, that two 

 great lines of fracture cross the continent, cutting each other at a 

 large angle, approaching to a right angle, and that one of these lines 

 preserves a parallelism to the gneiss, granite, trap, and conglomerate 

 formation which lies between the Rocky Mountains and the Alle- 

 ghanies, and in its course northward inclines a little to the former. 

 In an account of my late journey through the country, now in the 

 press, I shall offer further details, and enter more fully into the phy- 

 sical geography of the continent. In the mean time I shall be glad 

 if this short notice elicits opinions from gentlemen more conversant 

 with the science of geology than I am, and more able to judge of the 

 bearing of such investigations. 



