PART II. 



CHAPTER VII. 



THE LAURENTIAN AND HURON I AN PERIODS. 



The Laurentian Rocks constitute the base of the entire strati- 

 fied series, and are, therefore, the oldest sediments of which 

 we have as yet any knowledge. They are more largely and 

 more typically developed in North America, and especially in 

 Canada, than in any known part of the world, and they derive 

 their title from the range of hills which the old French geog- 

 raphers named the " Laurentides. " These hills are com- 

 posed of Laurentian Rocks, and form the watershed between 

 the valley of the St Lawrence river on the one hand, and the 

 great plains which stretch northwards to Hudson Bay on the 

 other hand. The main area of these ancient deposits forms 

 a great belt of rugged and undulating country, which extends 

 from Labrador westwards to Lake Superior, and then bends 

 northwards towards the Arctic Sea. Throughout this extensive 

 area the Laurentian Rocks for the most part present themselves 

 in the form of low, rounded, ice-worn hills, which, if generally 

 wanting in actual sublimity, have a certain geological grandeur 

 from the fact that they " have endured the battles and the storms 

 of time longer than any other mountains" (Dawson). In some 

 places, however, the Laurentian Rocks produce scenery of the 

 most magnificent character, as in the great gorge cut through 

 them by the river Saguenay, where they rise at times into verti- 

 cal precipices 1500 feet in height. In the famous group of 

 the Adirondack mountains, also, in the state of New York 

 they form elevations no less than 6000 feet above the level of 

 the sea. As a general rule, the character of the Laurentian 

 region is that of a rugged, rocky, rolling country, often densely 

 timbered, but rarely well fitted for agriculture, and chiefly 

 attractive to the hunter and the miner. 



As regards its mineral characters, the Laurentian series is 



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