202 BULLETIN UNIVERSITY OF MONTANA 



perfectly plain grooves in the rocks, showing plainly the direction of the 

 ice movement. Also, on the east is the rounded surface made as the ice 

 was forced upward, and on the west is the jagged cliff, unaffected by the 

 ice as it broke off and tumbled over. 



The larger ice mass extended across the Mission valley, pushed over 

 the hills south of St. Ignatius Mission, where it left stranded boulders 

 high on the summits, and on past Arlee to the Cabinet range. Whether it 

 passed over or through these mountains I cannot say at this writing. The 

 southern end of the Mission valley is marked by a high moraine. Its 

 exact height has not been determined, but it is several hundred feet. 

 This moraine is much broken, with many inequalities. From this re- 

 gion to the second moraine at the foot of Flathead lake is about thirty-five 

 miles. This territory shows many evidences of glaciation, stranded bould- 

 ers, hundreds of potholes, banks of pebbly nature, and the like. 



As stated previously, the moraine at the foot of Flathead lake is 4.50 

 feet above the lake. It extends from the Mission mountains on the east 

 to the Cabinets on the west. Its location may readily be seen by con- 

 sulting the map again, Figure 4. 



At the time this was made the outlet of the lake was through the 

 arm at Wild Horse bay, and through the present Little Bitter Root river. 

 An unusual amount of water caused the lake to rise unusually high, when 

 it overflowed the moraine. The cutting was rapid, resulting in a lower 

 lake level and a new outlet. The terraces at both ends of the lake show 

 the successive levels of the lake at different times. There are at least 

 three, and possibly four.* 



The partial drainage of the lake laid bare a large stretch of country 

 to the north, much of which was flat and swampy. It seems apparent 

 that the Swan river flowed northward along the base of the Swan range, 

 and close to the range, emptying into Flathead river near the present 

 town of Columbia Falls. Evidence for this may be seen in the partially 

 filled swamp lakes, while a distinct old bed may be traced through the 

 timber for the greater distance, a veritable bog swamp for most of the 

 season. 



By some unknown means, most likely an unusual ice flow from Mac- 

 Dougal peak, 7,725 feet high, the river must have been dammed, causing 

 a temporary lake. The overflow was across a low pass by short cut to 

 Flathead lake, resulting in a new channel, the present bed, with its beau- 

 tiful rapids and cascades. 



In the earlier time Flathead river must have entered the lake imme- 

 diately after leaving the mountains. When the lake was partially drain- 

 ed by the overflow of the moraine at the southern end the river meander- 

 ed over the level mud plain until it found the lake. It cut a very tor- 

 tuous channel for the greater distance, and has changed many times. In 

 a distance of fifteen miles the river course covers thirty miles. 



By the recession of the main ice sheet northward a large amount of 

 morainal material was deposited in the valley, showing most plainly in a 

 line north of the end of the Mission range. This line of morainal material 



* This view is confirmed by Eliot Blackwelder, from the University 

 of Chcago, who visited the region in 1902. 



