312 B. WILLIS LEWIS AND LIVINGSTON RANGES, MONTANA 



of the activity of valley glaciers in strongly jointed flat-bedded rocks. 

 None of the high summits were ever submerged beneath a general ice- 

 sheet, although glaciers accumulated to great depth in the valleys. The 

 spurs which extend from the crest northeasterly have summit characters 

 resembling those of the crest in its immediate vicinity and sometimes to 

 a distance of several miles away from it. 



Differences of elevation along the- crest of the Lewis range are scarcely 

 less pronounced than they are across it. Its rugged backbone is accent- 

 uated by high peaks between which are deep U-shaped wind gaps. 

 The elevations of the highest summits range from 8,500 to 10,400, and 

 those of the wind gaps from 5,500 to 6,500. Many small glaciers still 

 linger in the shadows of the high peaks, and the Harrison and Blackfoot 

 glaciers are nearly continuous for 5 i miles along the summit between 

 Harrison creek and Saint Mary river. 



Water ton- McDonald valley. — West of the Lewis crest and between it and 

 the Livingston crest lies the central valley of the Front range. It has 

 the trend common to all the major features, north 10 to 20 degrees west, 

 and is drained by two streams, one of which, Waterton river and its 

 head tributaries, flows north, the other, the McDonald lake drainage, 

 flowing south and southwesterly. The divide between these streams is 

 known as Flattop mountain, but should not be confused with the Flat- 

 top mountain east of the Lewis range. It has an elevation of about 6,800 

 feet, and is a broad expanse of slight relief, which was in fact the floor 

 of an older valley under a previous condition of drainage lines. The 

 head of Waterton river, Little Kootna creek, lies in a canyon 3,000 feet 

 deep, across the northern end of Flattop mountain, and Mineral and 

 McDonald creeks, which unite to flow to McDonald lake, lie respectively 

 on the northeast and southwest sides of the mountain, also in deep, 

 steep-sided canyons (see figures 1 and 1, plates 50 and 51, in panorama). 

 These canyons represent the latest work of the streams in engraving 

 their channels on the old valley floor. Remnants of the higher and ear- 

 lier valley extend as broad benches along the western slope of the Lewis 

 crest and the eastern slope of the Livingston crest. Northwestward be- 

 yond Little Kootna creek and southeastward beyond the canyon of 

 Mineral creek are high mountain masses which attain very nearly the 

 extreme altitudes of the eastern and western crests. The exact relations 

 of these several physiographic features, the date of the ancient valley o 1 * 

 Flattop mountain, and its relation to one or more episodes of glacial 

 occupation, are not yet fully made out. 



Livingston range. — North of McDonald lake and surrounded at its 

 eastern and southern base by McDonald creek is a conspicuous height 

 known as mount Heavens. During much of the summer season it is 



