THE HUKONIAN SEEIES. 



281 



copper. The following description of the Hnronian or 

 Cambrian system is from the little work before re- 

 ferred to.* 



" The shores of Lakes Huron ' and Superior offer a 

 series of schists, sandstones, limestones, and conglomerates 

 interstratified with heavy beds of greenstone, and resting 

 unconformably upon the Lauren tian formation. As these 

 rocks underlie those of the Silurian system, and have not 

 as yet afforded any fossils, they may probably be referred 

 to the Cambrian system (lower Cambrian of Sedgwick), 

 the schists of this system upon Lake Superior are bluish 

 in colour, and contain beds of cherty silex, marked by 

 calcareous bands, and holding anthracite in its fissures. 



"These are covered by a considerable thickness of 

 trap, upon which repose massive beds of red and white 

 sandstone which sometimes becomes conglomerate and 

 contains pebbles of quartz and jasper. Beds of a red- 

 dish argillaceous limestone are often interstratified with 

 these sandstones, which are intersected and overlaid by a 

 second eruption of greenstone of great thickness and 

 columnar in its structure. This formation, which, accord- 

 ing to the observations of Sir William Logan, has, on 

 Lake Superior a total thickness of about 12,000 feet, 

 is traversed by a vast number of trappean dykes. 



" In the corresponding formation on the north shore of 

 Lake Huron, the sandstones are more vitreous and the 

 conglomerates more abundant than on Lake Superior ; 

 they are, however, associated with conglomerates and 

 schists similar to those we have just described, and the 

 formation offers great intercalated masses of greenstone. 

 A band of limestone, fifty feet in thickness, forms a part of 

 this series, to which Sir William Logan assigns a thickness 



* A Sketch of the Geology of Canada, &c, by Sir William Logan and 

 Mr. Hunt. 



