342 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS, 



4 



Cambrian, and intimately related to the Laurentian, giving among liia 

 reasons its marked similarity, lithologically, to the Laurentian, and the 

 conformity of the Laurentian and Ilurouian ; and stating that in the 

 only place north of Lake Superior where the two systems have been 

 seen in contact, they were found r^nformable. (Quart. Jour. (jJeol. Soc, 

 18G3, XIX.3G-52,) 



Two other localities spoken of by Dr. Bigsby were hypothetical, not 

 actual observed contacts, as he supposed. (See Report on the North 

 Shore of Lake Huron, 1849, pp. 8, 9; Report of Progress, 1848-49, 



p. 36.) 



In the Report on the Geology of Canada, 18G3, the so-called gneisses 

 of the Laurentian series are assumed to be stratified, and although the 

 acknowledgment is made that the supposed beds " when thick, which 

 they usually are, might on first inspection be mistaken for intrusive 

 igneous instead of altered sedimentary masses." That they are really 

 sedimentary is supposed to be shown by the minerals being obscurely 

 arranged in parallel lines " confornuible with the more distinctly banded 

 portion of the strata." {I. c, p. 23, See also p. 587.) 



In fact Mr. Logan states . *' The rocks which compose the Laurentian 

 mountains were shown by the Geological Survey, in 184G, to consist of 



F 



a series of metamorphic sedimentary strata, underlying the fossilifcrous 

 rocks of the Province." We have pointed out that nothing of the kind 

 was shown by the Survey ; but that there was only an announcement 

 of "a theoretic belief that they may be ancient sedimentary formations 

 in an altered condition." (Gedl. Survey of Canada, 1845-4G, p. 40, 

 18G3, p. 22 ; Azoic Rocks, p. G6 ; ante, p. 332.) 



Mr. Logan further states, that it is difficult north of Lake Huron to 

 distinguish the Laurentian gneiss from an intrusive granite. (GeoL of 



Canada, 1863, p. 6L) 



Regarding the relation of the Iluronian to the Laurentian nothing 

 that can be called evidence is advanced, except in one place ; but, as 

 usual, some general assertions are made. The following extract will 

 give an idea of what was actually known of the relations of the two 

 formations, with the exception to be mentioned later. 



" In that part of the country on the north shore of Lake Huron which lies 

 between Misyissagui and St. Mary Rivera, where the Huronian series has Ijeen 

 more completely examined than elsewhere, the immediate contact of the gneiss 

 with the overlying rocks has not been observed. On the coast line between 

 the Mississagni and Thessalon Rivers, a distance of about twenty-five miles, 

 the gneiss extends from within about four miles of the former to within about 



