288 



THE GEOLOGIST. 



formation ; but as yet no fossils have been discovered in them. How- 

 ever, from their position and analogies, they must be associated with 

 the equivalents of our Longmynd, " or ''Eottom Eocks," or Lower 

 Cambrian of Sedgwick. 



The schists on the borders of Lake Superior are of a bluish colour, 

 and enclose beds of chert, with bands of limestone, the fissures of which 

 are often filled with anthracite. They are often covered with a con- 

 siderable thickness of trap, upon which are superimposed extensive 

 layers of white and red sands'cone, passing into a state of conglomerate, 

 and inclosing pebbles of quartz and jasper. Beds of red argillaceous 

 limestone are found interposed with these sandstones, which arc often 

 cut through and overlaid by a second sheet of diorite, exhibiting a 

 columnar structure. 



The corresponding rocks on the northern shore of Lake Huron have 

 a more vitreous aspect, and conglomerates are more abundant than at 

 Lake Superior. Great masses of intercalated diorite occur ; and 

 besides these, and of subsequent date to the inter-stratified diorites, 

 there are two sets of dykes of the same mineral, and a third of granite, 

 of a period intermediate between the last two. 



The Huronian formation has been traced over a distance of 450 miles 

 around the Lakes Huron and Superior, and throughout its extent metal- 

 liferous veins occur (of later origin than the volcanic eruptions), which 

 have been as yet little worked, but which, from the proximity of the 

 coal-fields of the neighbouring State of Michigan, must become, at some 

 future period, a source of great riches to Canada. The well-known 

 Bruce" and " Wallace" mines are in this formation. Metalliferous 

 veins also occur in the Laurentian rocks. 



In the accompanying map of the remnants of the primeval lands in 

 Jforth America, the regions coloured pink are the remains of the first 

 dry land — the old gneissic territory or Laurentian formation of the 

 American geologists. The spaces coloured green are fragments of the 

 primeval sediments on its shores—the equivalents of our " Longmynd" 

 or 'M)ottom-rocks" — the Huronian formation" of Logan. 



In our progress we shall add sedimentary formation after formation, 

 until in the end will be produced a perfect map of the in'csent geological 

 eoiulitlons of such part or parts of the globe as ihe acquired knowledge 

 of ihe d:iy will permit us sntisfadorily to attempt ; and by this simple 



