338 ' THE JOURNAL OF GEOLOGY. 



makes it at least very probable that in this eastern area also the 

 erosion took place in pre-Cambrian times. 



It is a very remarkable fact that the roche moutonne 

 character possessed by these eroded Laurentian rocks and which 

 is usually attributed to the glaciation which they underwent in 

 Pleistocene times, was really impressed upon them in the first 

 instance in these pre-Cambrian times, for all along the edge of 

 the nucleus from Lake Superior to the Saguenay, the Paleozoic 

 strata, often in little patches, can be seen to overlie and cover up 

 a mammillated and roche moutonne surface showing no traces 

 of decay and similar to that exposed over the uncovered part of 

 the area. The conclusion therefore seems inevitable that not 

 only were these Laurentian rocks sharply folded and subjected 

 to enormous erosion, but that they had given to them in pre- 

 Cambrian times their peculiar hummocky contours so suggestive 

 of ice action.^ The pre-Paleozoic surface of the Fundamental 

 Gneiss of Scotland, as Sir Archibald Geikie has shown, also 

 presents the same hummocky character.^ On this surface the 

 Upper Huronian, Cambrian, and later Paleozoic rocks were 

 deposited. 



To what extent the seas of Cambrian, Silurian and Devonian 

 times passed over this area cannot be determined with certainty. 

 A great series of rocks referred to by Dr. G. M. Dawson as 

 probably of Lower Cambrian age and analogous in character to 

 the Keweenawan and Animikie series occur overlying the Lauren- 

 tian in many parts of the Protaxis, not only along its margin, 

 but as outliers at many places in the interior. It occurs exten- 

 sively developed about the Arctic Ocean and about Hudson's 

 Bay, and a large area of rocks referred to the same age also 

 occur near the height of land about Lake Mistassini. "Through- 

 out the whole of the vast northern part of the continent this 

 characteristic Cambrian formation, composed largely of volcanic 

 rocks, apparently occupies the same unconformable position with 



^ A. C. Lawson. — "Notes on the Pre - Palaeozoic surface of the Archean Terranes 

 of Canada." Bulletin of the Geological Society of America. Vol. i, 1890. 

 = "A Fragment of Primeval Europe." Nature, August 26, 1888. 



