﻿Prohle^ns in Quebec Geology. 493 



problem for some years by Dr. Selwyn, then the Director 

 of the Canadian Survey, this opinion was adopted and was 

 officially announced in the publications of the department 

 for 1877-78, where the whole series was divided into 

 three parts, viz. : 1st, Lower Silurian ; 2nd, a volcanic 

 group, probably lower Cambrian ; and 3rd, the crystalline 

 schist group, probably Huronian, embracing the rocks of 

 the Sutton Mountain anticlinal, etc. 



This change of view placed the study of these com- 

 plicated rocks on an entirely new basis. The careful 

 separation of the fossils found in the pebbles of the lime- 

 stone conglomerates from those which occur in the paste 

 of the rock, served to simplify the difficulty arising from 

 the mixing of widely separated types, since in the earlier 

 days of their study this discrimination was not always 

 attended to, and hence arose the difficulty of reconciling 

 fossils of widely different horizons, said to be obtained froili 

 the same layer. 



The study of the entire series was taken up in detail by 

 the writer in 1885, and since that date the structure of 

 the entire area east of the St. Lawrence and extending to 

 the American boundary, has been mapped, so that several 

 of the most difficult geological problems have now been 

 satisfactorily solved. 



The conclusions arrived at after so many years of con- 

 stant work in this field may be brietiy stated. The results 

 of these investigations involve not only the stratigraphical 

 relations of the several fossiliferous divisions of the Quebec 

 Group, and the definite placing of the schists and associated 

 rocks at their base, but the determination also of the age 

 and relations of the great intrusive masses which are so 

 conspicuous throughout the area east of the St. Lawrence, 

 and which are found both to the east and west of the 

 anticlinal axis of the crystalline schists which compose 

 the greater part of the Sutton Mountain range. 



1st. As regards the crystalline schists, formerly regarded 



