BRITISH COLUMBIA AND ADJACENT REGIONS. 283 



General Remarks and Conclusions. 



It is somewhat difficult to connect the various observed facts of 

 the glaciation of British Columbia in a general theory of glaciation, 

 owing to the complexity of its physical features and their marked 

 character. Several conjectural schemes were advanced in a former 

 communication ; but, abandoning the seemingly untenable theory 

 of a great polar ice-cap, two probable hypotheses appear to remain. 

 A general north-to-south movement of ice is indicated by striation 

 in a number of places in the central-plateau zone, extending now 

 for a length of over 400 miles. This region, from elevations ex- 

 ceeding 5000 feet downward, is also covered thickly with drift-de- 

 posits requiring, by their character and mode of arrangement, the 

 action of water. To account for these facts it was thought that 

 either the flow of strong arctic currents bearing heavy ice during a 

 period of great submergence might be supposed, or that the whole 

 region may have been buried under a massive confluent glacier, the 

 drift-deposits being laid down as it retreated in the water of the 

 sea during a period of subsidence, or in that of a great lake held 

 in by glacier-dams in the valleys of the several mountain-ranges. 



It was presumed that the gaps of the Peace and Pine rivers in the 

 Rocky-Mountain range might have sufficed for the entrance from the 

 north-east of such currents and masses of ice as would be required 

 by the first theory ; but the examination of the region, with this 

 supposition in view T , has convinced me that, notwithstanding the 

 general decrease in elevation and width of the Rocky Mountains, 

 the valleys of the rivers are too narrow and indirect, and the sur- 

 rounding mountains too high, to allow the inflow of sufficient cur- 

 rents with the degree of subsidence which would be required by 

 most of the localities of glaciation and by the superficial deposits. 

 Neither is there any evidence of the passage of drift-material in this 

 region across the mountains either from east to west or in the oppo- 

 site direction. 



It therefore appears to remain as the most probable hypothesis 

 that a great glacier mass resembling the inland ice of Greenland 

 has filled the region which may be called the Interior Plateau, be- 

 tween the Coast Mountains and the Gold and Rocky Mountain 

 ranges, moving (though perhaps very slowly) southward and south- 

 eastward from the region of great precipitation and high mountains 

 of the northern part of the province*, and discharging by the 

 Okanagan depression and through the transverse valleys of the 

 coast range. It still appears to me most probable, however, that 

 this stage of the glacial period was closed by a general submergence, 

 during which the deposit referred to as Boulder-clay was laid down 

 in the interior plateau, and that as the land again rose it assumed 

 its present terraced character. Conditions may be suggested to 

 account for the temporary existence of a great lake in the interior 



* Explorations in the northern part of the province in 1879 have shown 

 that the mountains here are even higher and more extensive than had been 

 supposed, several ranges exceeding 8000 feet in great portions of their extent. 



