DALY : PHYSIOGRAPHY OF ACADIA. 75 



from the Admiralty charts of the coast-line (republished by the 

 Hydrographic Office at Washington), from the maps of the Canadian 

 Geological Survey so far as published, from the wall-map of Mackinlay, 

 and from the small-scale geological map accompanying the text of Daw- 

 son's " Acadian Geology." The physiographic literature treating of 

 Acadia is mainly concerned with glacial and post-glacial problems and 

 with recent crustal movements. The following pages will be restricted 

 almost entirely to the problems of bed-rock forms. The aim will be to 

 express certain conclusions regarding the pre-glacial denudation of this 

 region. Those conclusions do not demand an accurate knowledge of 

 pre-glacial drainage ; it is certain that the body of fact already deter- 

 mined will not permit of our constructing even a tolerable map of the 

 pre-glacial river-systems. 



The Uplands. 



The Southern Plateau. — Bather more than three-fourths of the 

 province of Nova Scotia (excluding Cape Breton Island) is occupied by 

 the largest topographic unit of which I shall have to speak in detail. 

 It may be called the " Southern Plateau." It is sharply defined in its 

 western half by the steep front overlooking the Cornwallis-Annapolis 

 valley, and by the ragged Atlantic shore-line ; in the eastern half, the 

 Atlantic bounds it on the south, the Truro-Pictou lowland, Northum- 

 berland Straits, and St. George's Bay on the north and northeast. 



JStructtire. — The plateau is underlain by a complex of ancient rocks. 

 Most of the area exhibits the outcropping edges of a very thick series 

 of slates associated with a likewise extensive older group of quartzites ; 

 both of these series are presumed by the officers (Bailey, '98, p. 27 If.) 

 of the Canadian Geological Survey to be of Cambrian age. Van Hise 

 ('92, p. 247) regards them as possibly Algonkian. Much less important 

 from the point of view of superficial extent but significant for the 

 unravelling of the history of the plateau, are the isolated patches of 

 fossiliferous Upper Silurian and Devonian sediments occurring in the 

 northern half of the long upland belt. Each of these three ancient 

 members has been involved in the late Devonian mountain-building, 

 which, more than auy other single event, has rendered the structures of 

 the plateau rocks complicated and difficult of interpretation. During 

 that revolution which must have erected over the region an alpine 

 chain of high mountains, the base of the resulting range was punctured 

 and displaced by enormous masses of exotic granites deeply buried at 



