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



view of the range about Yosemite Valley below the altitude 

 of 10,000 feet presents the aspect of a great plateau, on 

 which are numerous dome-shaped eminences. About this 

 gigantic roches moutonnees-like^ surface rise rugged peaks 

 over which glacial ice has never moved. The surface of 

 this approximate plateau is trenched by glaciated canyons. 

 Along the sides of these there are sometimes benches which 

 could be regarded as remnants of former shallower can- 

 yons. In other words, there are traces of canyons within 

 canyons. The benches just referred to may be regarded 

 as portions of the shallower canyons of the first glacial 

 epoch. During the time when the ice covered the surface, 

 these river valleys, in part inherited from the Tertiary, 

 would not be greatly deepened, but rather would be pro- 

 tected from erosion by the ice sheet. The narrower and 

 deeper canyons of the present day may be supposed to 

 have been cut in an interglacial epoch; then followed the 

 second glacial epoch, when the ice protruded in tongues 

 down the new-cut canyons for long distances but never ex- 

 tended as far from the crest of the range as during the first 

 epoch. The ice of this second period greatly modified the 

 new-cut canyons of the interglacial epoch, and gave them, 

 within the glaciated area, substantially their present 

 form. 



During the field season of 1897 a trip was made through 

 the Yosemite National Park in company with Professor C. 

 R. Van Hise. Mr. Theodore Solomons, a thorough moun- 

 taineer and a member of the Sierra Club, acted as guide 

 and took the party through some of the most rugged and 

 interesting portions of the region. On his return. Profes- 

 sor Van Hise wrote out some rough notes of his interpre- 

 tation of the topography of the higher Sierra Nevada, and 

 kindly placed these at my disposal. He was much im- 

 pressed with the important part that ice seems to have 

 played in moulding the topographic forms, and regarded 

 the benches previously referred to as portions of earlier, 



1 Although the ice has moved over these domes, their shape in the main is due to 

 exfoliation and not to ice erosion. 



