ON THE SUPERFICIAL GEOLOGY OF BRITISH COLUMBIA. 



9. On the Superficial Geology of British Columbia. By George 

 Mercer Dawson, Esq., D.Sc, F.G.S., Assoc. R.S.M., Assistant 

 Director of the Geological Survey of Canada. (Read June 20, 



1877.) 



[Plate V.] 



Contents. 



1. Outline of Physical Geography. 



2. Vancouver Island and the Coast. 



a. Glaciation of Eock-surfaces. 



b. Superficial Deposits. 



c. Observations northward in the Strait of Georgia &c. 



3. Interior of British Columbia. 



a. Striation and Rock-polishing. 



b. Superficial Deposits. 



Preglacial Gravels. 



Unmodified Drift. 



Modified Drift. 



Shore-lines, Terraces and Benches. 



Moraines. 



4. Mode of Glaciation and Formation of the Superficial Deposits. 



The following notes give, in a summarized form, the chief observed 

 facts of the Glacial period in British Columbia, obtained during the 

 season's work in that province on the Geological Survey of Canada. 

 They are offered as an extension to the Pacific coast of the observa- 

 tions carried in a former paper* to the Rocky Mountains. 



1. Outline of Physical Geography. 



For the purposes of this paper the eastern boundary of British 

 Columbia may be regarded as coinciding with the Rocky-Mountain 

 range, from which the province stretches westward to the Pacific 

 including Vancouver and the Queen-Charlotte Islands. Southward,' 

 the 49th parallel separates it from Washington Territory and parts 

 of Idaho and Montana. To the north the Province-line is drawn on 

 the 60th parallel. The area of British Columbia is roughly com- 

 puted at 330,000 square miles, its exteme length, from corner to 

 corner, being about 900 miles (see Map, PI. V.). 



The Rocky Mountains, many peaks in which surpass 9000 feet, 

 are defined to the south-east by a remarkably deep and straight 

 valley, in which are considerable portions of the courses of several of 

 the largest rivers of the country. South-westward, beyond this great 

 valley, is a second and broader mountain region, called by various 

 names in different parts of its length, but which may be generally 

 named the Selkirk or Gold range. Many of the summits of these 

 mountains are scarcely less in altitude than those of the Rocky Moun- 

 tains ; and in many places they appear to be broad and plateau-like, 



* Quait. Journ. Geol. Soc, Nov. 1875, vol. xxxi. p. 603. 



