SUPERFICIAL GEOLOGY OE BRITISH COLUMBIA. 121 



taken into account. As these latest glaciers retired, after their 

 short advance, the waters also appear to have fallen, the partly 

 water-modified moraine-mounds remaining as evidences of this joint 

 action. 



If glaciation of the mainland by a great northern ice-cap, whether 

 of polar origin or arising within the country itself, ever occurred, 

 Vancouver Island and the region of the Strait of Georgia must have 

 been buried under a still greater accumulation of ice ; but if the 

 glaciation of the continent was effected during a submergence of 

 4000 or 5000 feet, very little of the island would remain above the 

 surface of the sea, and the hollow between it and the Coast range 

 would be below the level and sheltered from the action of the 

 floating ice. In either case, however, the dimensions attained by the 

 glaciers during their latest extension, taking into account the 

 favourable position with regard to gathering-grounds of the Strait of 

 Georgia, would appear to be quite sufficient to explain the forma- 

 tion of the great glacier of the Strait. 



The supposed general submergence of the region to a maximum 

 depth of 5270 feet may at first seem a very startling hypothesis, 

 though it may be softened by such reference to its insignificance 

 when compared with the diameter of the globe as that used by some 

 of the advocates of a great northern ice-cap. It may, however, I 

 think, be said to have been shown in the course of a former examina- 

 tion of the facts of glaciation of the Great Plains to be extremely 

 probable, if not absolutely certain, that the whole interior of the 

 continent, from the Laurentian axis to the Rocky Mountains, was 

 submerged, and that the sea reached a height of at least 4400 feet 

 on the flanks of the latter range*. With this terrace, and some of 

 those described by Dr. Hector, those of Tatlayoco Lake, in the Coast 

 range of British Columbia, correspond as closely as can be expected, 

 taking into account the distance apart of the two localities (500 

 miles). Is it, then, surprising that, in a region further north and 

 better suited for their preservation, water-marks should be formed 

 at a yet greater elevation of about 900 feet ? To explain some of 

 the features of the last Glacial period, we are called upon to repro- 

 duce mentally conditions of which we can scarcely hope to appreciate 

 the magnitude ; but it does not appear that even 5000 feet of water 

 should be considered so vast a conception as the like thickness of 

 glacier ice. In Eastern America few localities present themselves 

 where the effects of subsidence to an amount equal to this can be 

 studied. We find terraces, however, to a height of 1425 feet on the 

 Laurentian axis f ; and it is worthy of remark that a depression of 

 about the amount above indicated would serve to account for the 

 glaciation and erratics of the higher mountains of the New-England 

 states. 



* Quart. Journ. Greol. Soc. vol. xxxi., 1875, p. 603 ; ' Geology and Eesources 

 of the 49th Parallel/ p. 244. 



t Geology and Eesources of the 49th Parallel, p. 256. 



