52 STEPHEN R. CAPPS 



in that part of the White River Valley which lies west of the inter- 

 national boundary, are very extensive. The area of deposition varies 

 in width from about two miles, just below the glacier, to about nine 

 miles, south of Mount Natazhat. For the first ten miles below the 

 glacier the valley is flat from side to side and is for the most part 

 bare of vegetation. East of Ping Pong Mountain, the White River 

 itself occupies only a narrow valley close to the base of a rock ridge. 

 The remainder of the broad valley to the south slopes upward toward 

 the mountains, and consists of a compound alluvial fan built up by 



Fig. io. — Mount Natazhat, and the great cirques on its flanks. Each of these 

 cirques is occupied by a glacier. Photograph by F. H. Mofiit. 



the tributaries from the south. This fan is heavily timbered except 

 for narrow belts along the streams. The present course of the White 

 River has been determined by this alluvial fan which has crowded the 

 river north against the base of Ping Pong Mountain. 



Fig. 1 1 is a diagrammatic cross-section of the White Valley, five 

 miles west of the boundary. If we can assume that the wide valley 

 north of Mount Natazhat was eroded by the great glacier to an average 

 depth equal to the present level of the White River (a), then the valley 

 filling of alluvial gravel must be more than 400 feet thick in the center 

 of the old valley {b) . Since the White River was nowhere observed to 

 have cut its valley down to bedrock, and since the bedrock level at (b) 

 is probably lower than at (a) , the thickness of the gravels in the deepest 

 portions of the old valley may greatly exceed 400 feet. 



