2 A POPULAR EXPOSITION OF THE 



an economic point of view, the Laureutian Formation is essentially 

 characterised by the vast beds of magnetic and specular iron ore that 

 occur within it : full details of which are given in a preceding page. 

 The formation is many thousands of feet in thickness, and it covers an 

 area of 200,000 square miles — running from Labrador along the north 

 shore of the St. Lawrence to the vicinity of Quebec, and throughout 

 all the more northern and north-western portions of the Province, as 

 shewn in the sketch-maps, figs. 154 and 243. By reference to the 

 latter, it will be seen that in the district between Prescott and 

 Kingston, a narrow belt of this formation crosses the St. Lawrence, 

 and expands over a large extent of country, comprising the Adiron- 

 dack region, in the State of New York. This belt forms a somewhat 

 important featnre in the geology of Western Canada. It will be al- 

 luded to again, in connection with this sketch, under the name of 

 the "gneissoid belt of the Upper St. Lawrence." The Huronian 

 Formation which constitutes the higher division of the Azoic series, 

 consists chiefly of green and greyish slate-conglomerates and other 

 partially altered strata, interstratified with greenstone masses, and tra- 

 versed by numerous trap dykes. It coutains also many quartz veins, 

 holding copper pyrites and other copper ores in workable quantities. 

 The total thickness of the formation is probably not much under 

 20,000 feet. Its strata are chiefly developed along the north shore of 

 Lake Huron (No, 2, in fig. 243), and in places on Lake Superior. 



3. Laurentide Mountains. North and South Basins of Canada. — 

 A high water-shed or range of mountainous country, averaging a 

 height of from one to two thousand feet above the sea, but rising in 

 places to nearly four thousand feet, traverses the greater portion of 

 the Laurentian area, and forms at one part of its course the " Lauren- 

 tide Mountains." It divides the Province into two great basins or 

 geological areas : known, respectively, as the North and South Basins. 



4. Great Northern Basin of Canada. — The area occupied by this 

 basin, lying to the north of the Laurentian water-shed, and sloping 

 towards Hudson's Bay, as regards its geological characters, is still 

 comparatively unexplored. The formations known to occur within 

 its limits, comprise the Laurentian and the Upper Silurian series. 

 The Huroniau rocks are thought to occur also, in the form of Chlo- 

 ritic schists, in the valley of Lake Temiscaming, but no traces of 

 Lower Silurian strata have anywhere been met with. Hence, it is 

 suggested by Sir William Logan, that, the Laurentide mountainous 



