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Sierra Club Bulletin 



rounded forms, may be designated the dome cleavage, inas- 

 much as the dome is apparently the most perfect typical form 

 of the group. 



Domes of close-grained silicious granite are admirably cal- 

 culated to withstand the action of atmospheric and mechanical 

 forces. No other rock form can compare with it in strength; 

 no other offered so unflinching a resistance to the tremendous 

 pressure of the glaciers. A dam of noble domes extends across 

 the head of Yosemite Valley, from Mount Starr King to North 

 Dome, which was effectually broken through by the combined 

 force of the Hoffmann and Tenaya glaciers; but the great 

 south Lyell glacier, which entered the valley between Starr 

 King and Half Dome, was unable to force the mighty barrier, 

 and the approach of the long summer which terminated the 

 glacial epoch, found it still mazing and swedging compliantly 

 among the strong unflinching bosses, just as the winds are 

 compelled to do at the present time. 



The Starr King group of domes (Fig. 7) is perhaps the most 

 interesting of the Merced basin. The beautiful conoid, Starr 

 King, the loftiest and most perfect of the group, was one of the 

 first to emerge from the glacial sea, and ere its new-born bright- 

 ness was marred by storms, dispersed light like a crystal island 

 over the snowy expanse in which it stood alone. The moraine 

 at the base is planted with a very equal growth of manzanita. 



There appear to be be no positive limits to the extent of dome 

 structure in the granites of the Sierra, when considered in all 

 its numerous modifications. Rudimentary domes exist every- 

 where, waiting their development, to as great a depth as ob- 

 servation can reach. The western flank was formerly covered 

 with slates, which have evidently been carried off by glacial 

 denudation from the middle and upper regions ; small patches 

 existing on the summits and spurs of the Hoffmann and Mer- 

 ced mountains are all that are now left. When a depth of two 

 or three thousand feet below the bottom of the slates is reached, 

 the dome structure prevails almost to the exclusion of others. 

 As we proceed southward or northward along the chain from 

 the region adjacent to Yosemite Valley, dome forms gradually 

 become less perfect. Wherever a broad sheet of glacier ice has 



