98 A. WINCHELL — A LAST WORD WITH THE HURONIAN. 



the northeast, through the region of Maskinonge and Sturgeon rivers (tribu- 

 taries of Lake Nipissing), as far as Lake Temiscaming. He continues : 



" The group on Lake Huron we have computed to be about 10,000 feet thick, and 

 from its volume, its distinct lithological character, its clearly marked date posterior 

 to the gneiss, its economic importance as a copper-bearing formation, it appears to 

 me to require a distinct appellation and a separate color on the map. Indeed, the 

 investigation of Canadian geology could not conveniently be carried on without it. 

 We have, in consequence, given to the series the title of Huronian. 



" A distinct name being given to this portion of the Azoic rock renders it necessary 

 to apply one to the remaining portion. The only local one that would be appropriate 

 in Canada is that derived from the Laurentide range of mountains, which are com- 

 posed of it from Lake Huron to Labrador. We have, therefore, designated it as the 

 Laurentian series."* 



Mature Definition of " Huronian'^ — With a view to attaining as exact a 

 comprehension as possible of the conception of the Huronian system enter- 

 tained by Sir William Logan and his eminent collaborators, it may be best 

 to make a few citations from the " Geology of Canada," published in 1863, 

 and embodying more matured views than those contained in the annual 

 reports. In this work Sir William Logan makes statements from which the 

 following extracts are drawn (p. 90) : 



" On Lake Temiscaming the Laurentian orthoclase is followed by a slate conglom- 

 erate. The finer parts of the rock are dark gray, weathering to dark green. They 

 are of a uniform grain, and, being at the same time argillaceous and silicious, they 

 present the characters of a hard, compact slate. Some parts, not so fine in texture, 

 are a hard, dark-gray sandstone, weathering to a dingy olive-green. In both cases 

 the rock frequently exhibits the character of a compact conglomerate, holding pebbles 

 and bowlders, sometimes a foot in diameter, of the subjacent gneiss, from which they 

 appear to be principally derived." 



Some other conditions of the formation are described as finer textured, 

 penciled in transverse fracture by fine-colored lines ; another as a " very 

 close-grained, compact, dark-gray mica slate. When cleavage exists, the 

 planes cut the pebbles in common with the matrix." It is never fit for roof- 

 ing-slates. To this slate conglomerate succeeds a quartzite apparently 400 

 to 500 feet thick. 



The Huronian system was most specially studied along that part of the 

 northern shore of Lake Huron which lies between the Missisagui and Ste. 

 Marie rivers. A general section of the Huronian, generalized from obser- 

 vations in this portion of Canada, is given on pages 55-57, and an abstract 

 of this is here appended : 



Feet. 



13. White quartzite, imperfectly examined 400 



12. Yellowish chert and impure limestone, similar to 10 200 



11. Quartzite, white, frequently of vitreous aspect 1,500 



*See also the Canadian Journal, vol. II, 1857, pp. 439-442; Canadian Naturalist and Geologist, vol. 

 II, 1857, pp. 255-258. 



