276 G. M. DAWSON" ON THE SUPERFICIAL GEOLOGY OF 



Peace and Athabasca river-basins to the east of the Rocky Moun- 

 tains, enables the characters of glacial evidence to be defined further 

 north, and has aided in the decision of some theoretical points 

 referred to in the sequel. Most of the facts observed to the west of 

 the Rocky Mountains resemble so closely those previously described 

 for the regions south and east of this that they do not require 

 lengthened notice. The southward or south-eastward passage of 

 glacier-ice in the valley of Babine Lake is indicated by glacial 

 grooving, while the valley of the Skeena has formed a main channel 

 of discharge of glacier-ice toward the coast. In the mountains 

 between the valley of this river and Babine Lake a somewhat irre- 

 gular, but still, I believe, distinct terrace-flat was observed on the 

 watershed at an elevation of 4300 feet. Its surface is strewn with 

 water-rounded stones differing from those of the mountains of the 

 vicinity. The region north-east of Stuart Lake, extending to 

 M c Leod's Lake and the Parsnip River at the base of the foot hills of 

 the Rocky Mountains, is deeply drift-covered, the surface consisting 

 either of Boulder-clay charged with erratics of varied origin, or 

 terrace-flats formed by its rearrangement. This region lies to the 

 north of and somewhat higher than the Nechaco basin, which is 

 characterized by the white silts of a former paper *. The highest 

 part of its surface crossed by the trail has an elevation of 2900 

 feet. 



In the valley of the Misinchinca, flowing westward from the 

 summit of the Pine pass of the Rocky Mountains, glaciation was 

 observed in a few places parallel to the direction of the main de- 

 pression. In the Pine-River valley, draining eastward and joining 

 the Peace, no glaciated surfaces were seen — a circumstance which 

 may arise from the comparatively soft character of the rocks. 



Peace and Athabasca Basins. 



In the comparatively level country drained by the Peace and 

 Athabasca rivers, to the north-east of the mountains, underlain 

 by unaltered rocks of Mesozoic and Tertiary age, the chief evidences 

 of the glacial period are found in the distribution of erratics, and 

 the existence of extensive " drift " deposits. In travelling eastward 

 from the mountains by the Pine-River valley, a remarkable absence 

 of such deposits is noted in that part of the valley which traverses 

 the eastern foot hills ; but at the Middle Porks the plateau, with an 

 elevation of 1000 feet above the river, or 3000 feet above the sea, 

 and at a distance of thirty miles from the indurated rocks of the 

 mountains, is strewn with rounded pebbles of quartzite &c. from 

 these rocks, though material of local origin preponderates. Eighteen 

 miles further east, at the Lower Porks, the superficial deposits are 

 much more important, covering the surface of the plateau to a 

 considerable depth, and consisting of gravelly beds passing upwards 

 into finer silty materials ; the elevation of the plateau is here 2350 

 feet. In continuing eastward after passing over a summit of 3300 

 feet on the line followed, Laurentian boulders which must have come 

 * Quart. Journ. Geol. Soc. vol. xxxiv. p. 105. 



