CONSTITUENTS OF THE LAURENTIAN SERIES. 275 



Logan's approximate estimate of the thickness of the 

 various constituent parts of the mass, arranged in as- 



cending order ; — - 



Feet. 



1. Gneiss 5,000 



2. Crystalline Limestone . . . . 1,500 



3. Gneiss 4,000 



4. Crystalline Limestone ...... 2,500 



6. Gneiss . . . . . . . 3,500 



6. Crystalline Limestone . 750 



7. Gneiss 5,000 



8. Crystalline Limestone . 500 



Total 22,750 



The area occupied by the Laurentian series in the 

 Basin of Lake Winnipeg is indicated on the geological 

 map. The country between Lake Superior and the Height 

 of Land has been described by Mr. Alexander Murray, of 

 the Canadian Geological Commission * ; the geology of 

 Eainy Lake and of the Lake of the Woods by Dr. Bigsby f ; 

 the country on the Pigeon Eiver route by Dr. Norwood J ; 

 and a general view of the whole country between Lake 

 Superior and Lake Winnipeg by Dr. Hector §, &c. 



The intrusive rocks, so numerous throughout the vast 

 extent of this series in the region under review, consist of 

 granites, syenites, greenstones, trap, &c. In Great Dog 

 Lake mica schist rests on each side of syenite outbursts, 

 which have the form of promontories jutting into the 

 lake on the west coast. The valley of Dog Eiver is 

 bounded by low granite ridges which acquire greater 



* Report of Progress, 1846. 



t "On the Geology of Rainy Lake, South Hudson's Bay," by Dr. J, 

 J. Bigsby, F.G.S. &c. — Quarterly Journal of the Geological Society, 1854. 

 Also "On the Geology of the Lake of the Woods," by the same author.— 

 Quarterly Journal, 1852. 



% Geological Survey of Wisconsin, &c. 



§ Papers Relative to the Exploration of British North America, by 

 Captain Palliser.— Blue Book, 1859. 



