23 



a sharp turn, sweepi off in a north-westerly direction to the Arctic 

 Ocean. The two arms of this band thus form tangents to the Ai'ctic 

 Circle. The northern limits of those Laurentian rocks is not as yet 

 exactly known. The Gulf St. Lawrence forms its southern limit 

 from Belle Isle to Cape Tourmente, a distance of about six hundred 

 miles. For the next two hundred miles their southern limit runs west 

 south-west, and is distant from the St. Lawrence in rear of Montreal, 

 about thirty miles. It then follows the Ottawa for a hundred miles, turns 

 south toward the St. Lawrence, meeting it again at the Thousand Islands, 

 which arc caused by the passage of this belt of hard rocks across the river. 

 Crossing at the Thousand Islands, the Laurentian expands into an area 

 of about ten thousand square miles in the State of New York, forming 

 the Adirondacks. The southern limit then runs off toward Lake 

 Huron, whose east and north shores it forms, and then continues on, as 

 before stated, to the Arctic Ocean. We thus see that this great Y 

 shaped area of Laurentian rocks has its longer arm approximately 

 parallel to the Rocky Mountain chain and Pacific border, and its shorter 

 one parallel to the smaller Appalachian chain and Atlantic border. 

 "Hence," says Prof. Dana, " in the very inception of the continent not 

 only was its general topography foreshadowed, but its main mountain 

 chains appear to have been begun, and its great intermediate basins to 

 have been defined — the basin of New England and New Brunswick on 

 the east ; that between the Appalachians and the Rocky Mountains 

 over the great interior • that of Hudson's Bay between the arms of the 

 northern V^. The evolution of the grand structure lines of the con- 

 tinent was hence early commenced, and the system then initiated was 

 the system to the end. Here is one strong reason for concluding that 

 continents have always been continents; that, while portions may have at 

 times been submerged some thousands of feet, the continents have never 

 changed places with the oceans." * 



These old crystalline rocks give a peculiar character to the scenery 

 wherever they occur, producing, with but few exceptions, a surface 

 covered with low hills having a peculiar rounded contour, quite distinct 

 from the serrated and rugged outlines often seen in hills and mountains 



* 3Iamtal of Geology, p. 160. 



