No. l.J SELWYN — THE QUEBEC GROUP. 31 



II. Huronian : To include 1. The typical or original Hu- 



ronian of Lake Superior and the conform- 

 ably — or uuconformably as the case may 

 be — overlying upper copper-bearing rocks. 



2. The Hastings, Templeton, Buckingham, 

 and Grenville groups. 



3. The supposed upper Laurentian or Norian 



4. The altered Quebec group as shewn on the 

 map now exhibited, and certain areas not 

 yet defined betw^eeu Lake Matapedia and 

 and Cape Maquereau in Gaspe. 



5. The Cape Breton, Nova Scotia and New 

 Brunswick, pre-primordial sub-crystalline 

 and gneissoid groups. 



III. Cambrian : In many of the areas especially the western 



ones, the base of this is well-defined by un- 

 conformity, but in the Eastern Townships 

 and in vsome parts of Nova Scotia it has 

 yet to be determined. The limit between 

 it and Lower Silurian is debatable ground 

 upon which we need not enter. 



The apparent great unconformity of the Nipigon group to the 

 Huronian around Lake Nipigon may perhaps be explained by 

 our having here the deep-seated parts of an ancient volcanic 

 crateriform vent greatly denuded and the crater now occupied by 

 the waters of the lake. The eruptions from this crater may 

 have commenced in the Huronian epoch and been continued at 

 intervals even up to the Triassic period ; but in the meantime we 

 have no evidence of any of the eruptions being newer than Cam- 

 brian. One point I wish particularly to insist on is that great 

 local unconformities may exist without indicating any important 

 difference in age, especially in regions of mixed volcanic and sedi- 

 mentary strata, and that the fact of crystalline rocks (greenstones, 

 diorites, dolerites, felsites, norites, &c.,) appearing as stratified 

 masses and passing into schistose rocks, is no proof of their not 

 being of eruptive or volcanic origin — their present metamorphic 

 character is as the name implies a secondary phase of their 

 existence, and is unconnected with their origin or original forma- 

 tion at the surface. 



(Read before the Natural History Society, 24th February, 1879.) 



