absence of talus or morainic material, the steepness and 

 height of the valley walls, the ragged nature of the upper 

 1,200 or 1,500 feet of the same, the absence on this upper 

 portion of the valley walls of glacial scratches or polish 

 from Glacier Point down stream, the general parallelism 

 of the walls themselves and the hanging nature of the 

 tributary valleys. The accompanying figure is a represen- 

 tation of the thalweg of the valley from El Portal to the 

 Little Yosemite as taken from Matthes' topographic map. 

 Above in dotted lines is shown what appears to have been 

 the position of the thalweg during the period immediately 

 preceding the most recent Ice Age. 



It will be seen that the narrow floor of the Merced Valley 

 ascends rapidly from El Portal until the meadow immedi- 

 ately down stream of El Capitan is reached. Here the 

 meadow or flat which is about half-a-mile in width is 

 entered upon, and through it the Merced stream winds in 

 sluggish meanders. Upstream the flat floor suddenly ends 

 and the thalwegs of the Tenaya and Merced rise in pro- 



