30 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



line. Dawson gave the name ' Wilson range ' to a limited group of mountains 

 in which Sheep mountain occurs. However, the title ' Lewis range ' is to be 

 a permanent feature of geographical nomenclature in Montana and must include 

 the Wilson range, which is but a part of a whole first recognized in the scientific 

 exploration of Montana. (Figure 1.) 



West of the Flathead river and east of the Kootenay river, Dawson (follow- 

 ing Palliser) recognized two distinct ranges as including the mountains along 

 the Forty-ninth Parallel. On his 1886 map the more easterly range bears the 

 name ' MacDonald range ', the other bearing the name ' Galton range.' These 

 ranges are separated, for a part of their length, by the straight valley of Wig- 

 wam river. Willis appreciated the undoubted fact that the Galton range 

 continues, with relatively unbroken crest-continuity far to the south of the 

 Boundary line. In his 1902 map of northwest Montana, this range is repre- 

 sented as extending to the main Flathead river at Columbia Falls, the south- 

 western and western limit being fixed at the valleys of Stillwater creek, Tobacco 

 river, and Kootenay river ; and the northeastern limit in Montana being fixed 

 at the valley of the North Fork of the Flathead river. Between the North 

 Fork and the Wigwam the mountains are not named on Willis' map, but, 

 apparently, were considered by him to belong to Dawson's 'MacDonald range.' 

 In this view the MacDonald range is limited on the south by the strong trans- 

 verse valley of Yakinikak creek. According to Dawson's map the northern 

 limit of the Galton range seems to have been fixed at the Elk river and the 

 northern limit of the MacDonald range at the Cretaceous area along the North 

 Kootenay Pass. 



Combining the views of Dawson and Willis we have a convenient subdivi- 

 sion of the western half of the Pocky Mountain system at the Forty-ninth 

 Parallel into the two ranges, the Galton and the MacDonald, each of which, 

 according to the law of crest-continuity, is a fairly distinct unit. 



The sketch-map of Figure 1 illustrates the conclusions reached by the 

 writer as to the most desirable topographic subdivision of this part of the Rocky 

 Mountain system. It is very possible that further mapping of the region may 

 show the necessity of modifying this orographic scheme. In its present form 

 it will be found useful for the purposes of this report and seems to have the 

 advantage of meeting the views of the few trained observers who have pene- 

 trated these mountains. 



PURCELL MOUNTAIN SYSTEM AND ITS SUBDIVISION. 



Westward from Tobacco Plains, on the Forty-ninth Parallel, we cross, in 

 the air-line, sixty miles of ridges belonging to a range unit which is almost as 

 systematic as the great group on the east. (Plate 4 and Figure 2.) The crests 

 of this second group are in unbroken continuity from the wide southern loop 

 of the Kootenay river at Jennings to the angle where the Purcell Trench is 

 confluent with the Rocky Mountain Trench. Throughout this area the drainage 

 is quite evenly divided by the easterly and westerly facing slopes of the unit- 



