3o6 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



River above Little Yosemite Valley, yet the overflow from 

 the Tuolumne glacier, comprising, as it probably did, the 

 larger part of the ice that came down the Lyell fork of the 

 Tuolumne River, was so considerable as to form an ice 

 sheet 2,000 feet or more in thickness, extending from Mount 

 Hoffmann to, or nearly to. Cathedral Peak. Nearly all of 

 the huge domes between the Tuolumne Meadows and Lake 

 Tenaya, as well as the domes between the lake and the east 

 end of the Yosemite, were covered by this ice sheet. Prob- 

 ably Mount Watkins was so covered, and pretty certainly 

 both Basket Dome and North Dome; for about one-fourth 

 of a mile north of Basket Dome there was found a boulder 

 of a metamorphic rock, rich in biotite, which undoubtedly 

 came from an area in which such rocks are found on the 

 east slope of Mount Hoffmann. The absolutely bare char- 

 acter of the upper portion of all the domes named suggests 

 that they were cleaned off b^ ice, but only those in the 

 neighborhood of Lake Tenaya still show definite glacial 

 markings. The probability is that that portion of the Tuol- 

 umne glacier which became tributary to the Merced glacier 

 was forced over the low divide between the Tuolumne 

 drainage by the pressure of the enormous ice-mass moving 

 southward from near Mt. Conness. 



The next most considerable mass of ice which entered 

 Yosemite Valley came down the upper Merced River, pass- 

 ing through Little Yosemite Valley. The neve basin of 

 this glacier was quite extensive, and this accession of ice 

 was very considerable. According to Professor Whitney, 

 a certain amount of ice from the Tuolumne glacier also 

 came over the divide at the head of Echo Creek ; and if 

 such was the case, this ice-mass would contribute to the 

 glacier passing through Little Yosemite Valley. The third 

 tributary to the Merced ice river was the Yosemite Creek 

 glacier. The neve field of this glacier was on the west and 

 north slopes of the high and jagged ridge of which Mount 

 Hoffmann is the culminating point. At an advanced time 

 in the Glacial Period, when the Yosemite had already 

 attained about its present depth, this Yosemite Creek glacier 

 must have fallen in avalanches over the Yosemite Falls 



