170 W. N. THAVER 
various members of the mountain system are bound together in one 
great structure by a chain of batholiths, the intrusion of which 
seems to have begun in the north and continued progressively 
southward during a long period of time.* 
The members of this mountain system in the United States are 
the Sierra Nevada, the Klamath Mountains, and the Cascade 
Mountains. To these might be added the Blue Mountains of 
Oregon. The Northern Cascade Mountains are generally regarded 
as ending at the International Boundary, but as a matter of fact 
they terminate naturally a few miles beyond the boundary at the 
canyon of Fraser River. Daly? has selected this as a dividing 
line, according to his plan of limiting physiographic units by master- 
valleys and trenches. ) 
This province includes a section in Canada known as the Coast 
Range of British Columbia—a mountainous belt about 100 | 
miles wide which extends along the coast for nearly goo 
miles from the canyon of Fraser River northwestward beyond the 
head of Lynn Canal. Dawson} early objected to admitting the 
Coast Range to the same classification as the Cascades because of 
the decided difference in rock composition. Physiography, how- 
ever, gives preference to structure and topography as criteria for 
classification, and, as Daly‘ has pointed out, “‘it has become more 
and more evident as the study of the Cordillera progresses that 
rock composition can never rival crest continuity as a primary 
principle in grouping the western mountains.” 
At its northern end the Coast Range passes behind the St. Elias 
Range and gradually blends with the Interior Plateaus near Lake 
Kluane.’ Although this particular member terminates here, the 
province, following the trend of the other Cordilleran divisions, 
continues along a great arc to the northwest and embraces an 
Alaskan section of several members—in succession the Chigmit 
Mountains, the Alaskan Range, and the Aleutian Range.° In all 
t A. C. Lawson, Jour. Geol., 1, 579-86. 
2R. A. Daly, Geol. Survey Canada, Mem. 38, Part I, p. 41. 
3G. M. Dawson, Trans. Royal Soc. Can., sec. 4, p. 4. 
4R. A. Daly, op. cit., p. 40. 
5 J. A. Bancroft, Geol. Survey Canada, Mem. 23, p. 13. 
6 A. H. Brooks, op. cit., pl. 7. 
