On the Geology of British Columbia. 237 



beds are not altered by them, the character of the veins traversing 

 them, and an apparent unconformity between these beds and the 

 undoubtedly Carboniferous beds overlying them, the authors come 

 to the conclusion that this deposit is not of Carboniferous, but of 

 Silurian age ; and they indicate certain theoretical conclusions which 

 follow from this determination. 



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

 Mercer Dawson, Esq., F.G.S., Assoc. E.S.M., of the Geological 

 Survey of Canada. 



The author stated that the rock-striation and fluting on the 

 south-eastern peninsula of Yancouver's Island shows that at one 

 time a great glacier swept over it from N. to S., filling the Strait 

 of Georgia, 50 miles broad in places, and having near Victoria a 

 thickness of ice of over 600 feet. Traces of this glacier also occur 

 on San- Juan Island, and on the coast of the mainland. The de- 

 posits immediately overlying the glaciated rocks, besides what may 

 be moraine profonde, locally developed, are sandy clays and sands, 

 arranged in water, and sometimes containing marine shells. The 

 lower beds, at least, of these, were probably formed at the foot of the 

 retreating glacier, the sea standing considerably higher than at 

 present. The northern part of the Strait of Georgia and the fjords 

 opening into it, and the fjords north of the Strait, show ice-action 

 to a height of above 3000 feet. Terraces on the coast of the main - 

 land are rare, and never at great elevations. 



The interior plateau of British Columbia shows a system of 

 glaciation from N. to S., traces of which have been observed above 

 3000 feet. Subsequent glaciation radiating from the mountains 

 also occurs. The superficial deposits here are either unmodified or 

 modified. The former, representing the boulder clay, occurs at nearly 

 all heights up to over 5000 feet ; the latter characterizes nearly all 

 localities below 3000 feet, and is most extensively developed in the 

 northern low country, where it forms a white silt or loess. The 

 interior is marked with shore-lines and terraces up to 5270 feet. 

 Moraines occur in great numbers, most of them marking stages in 

 the retreat of glaciers towards the mountains, although some may 

 have been formed in connexion with the IN", and S. glaciation. 



The sequence of events in the interior, according to the author, 

 seems to have been as foUows : — glaciation from N. to S., with 

 deposit of boulder clay ; formation of terraces by lowering of water- 

 surfaces, accompanied or followed by a warm period; advance of 

 glaciers from the mountains, and formation of lower terraces ; and 

 retreat of glaciers to their present limits. The glaciation of Van- 

 couver's Island may have occurred during both cold periods or during 

 the second only. 



The author considers the assumption of the production of the 

 N.-to-S. glaciation by an ice-cap to be attended with great difficulties, 

 and seems to favour the notion of its being effected by the accumu- 

 lation of ice on the country itself, and especially on the mountains 

 to the N., filling the central plateau in going southward, and passing 

 seaward through the gaps and fjords of the coast-range. 



