34 DEPARTMENT OF TEE INTERIOR 



2 GEORGE V., A. 1912 



In the present report MacDonald's name ' Moyie range ' will be used to 

 include all the mountains bounded by the Purcell Trench and by the strong 

 valleys of the Moyie and Goat rivers. Similarly the name ' Yahk range ' will 

 be used with limits as follows: on the west and north by the Moyie river; on 

 the south, by the Kootenay; on the east, by the Yahk river from source to 

 mouth. The largest subdivision, the eastern one, will here be called the Mc- 

 Gillivray range, a title taken from one of the earliest names of the Kootenay 

 river.* This range is bounded on the east by the Eocky Mountain Trench; 

 on the south, by the loop of the Kootenay river; on the west, by the Yahk river 

 and the Moyie lakes; on the north, by the Cranbrook plains. (Plate 6.) This 

 three-membered part of the Purcell system is there marked off by two huge 

 trenches and by deep and wide transverse notches, faithfully followed by the 

 two transmontane railroads, the Canadian Pacific and the Great Northern. 

 (Figure 2.) 



SELKIRK MOUNTAIN SYSTEM AND ITS SUBDIVISION. 



The Selkirk Mountain system next on the west likewise forms a range 

 unit considerably longer than the area generally ascribed to the Selkirk group. 

 (Plate 3.) On principles similar to those adopted for the Purcell range, the 

 Selkirk system may be defined as bounded on the east by the Purcell Trench; 

 on the north and northeast by a portion of the Rocky Mountain Trench; on 

 the west by the Selkirk Valley; on the south by the Columbia lava plain, Pend 

 D'Oreille lake, and a short unnamed trench extending from that lake to the 

 Purcell Trench at Bonner's Ferry. For a short stretch the Selkirk system is 

 apparently confluent with the Coeur D'Alene mountains, though a short trench 

 followed by the Great Northern railway may separate them. This extension 

 of the Selkirks across the Boundary has already been indicated on maps of the 

 Encyclopedia Americana, Stieler's Handatlas, and the Yidal-Lablache atlas. 



The whole mountain complex embracing the Purcell range and Selkirk 

 system, as just defined, may be viewed in another way. The Purcell range is 

 thereby considered as part of the Selkirk system, and that division of the whole 

 lying to the westward of the Purcell Trench, might be called the Selkirk range. 

 The Selkirk system would thus include the Selkirk range and the Purcell range. 

 As already noted, Dawson seems to have adopted this alternative view. An 

 objection to it is the chance for confusion in using ' Selkirk ' to mean now a 

 component range, now the inclusive system. In favour of Dawson's view is 

 the fact that in rock composition, structural axes, and geological history, the 

 mountains lying between the Eocky Mountain Trench and the Selkirk Valley 

 form part of a natural unit. On the other hand, the Selkirk range is, struc- 

 turally and lithologically, as closely allied to the Columbia system as to the 

 Purcell range; the Purcell range is, lithologically and historically, as closely 

 allied to the Rocky Mountain system as to the Selkirk range. The practicable 

 orographic classification, being based upon erosion troughs, recognizes the 



* In J. Arrowsmith's map of British Columbia in British Government Sessional 

 Papers relative to the affairs of British Columbia \S'.9. 



