Studies in the Sierra 



fluents, mottled with black slates from the summits, and gray 

 granite blocks from ridges and headlands. One of the most in- 

 teresting facts relating to the early history of this glacier is, 

 that the lofty cathedral spur forming the northeast boundary of 

 its basin was broken through and overflowed by deep ice-cur- 

 rents from the Tuolumne region. The scored and polished gaps 

 eroded by them in their passage across the summit of the spur, 

 trend with admirable steadiness in a northeasterly and south- 

 westerly direction; a fact of great importance, considered in its 

 bearings upon questions relating to the universal ice-sheet. 

 Traces of a similar overflow from the northeast occur on the 

 edges of the basins of all the Yosemite glaciers. 



The principal moraines of the basin occur in short, irregular 

 sections scattered along the sides of the valleys, or spread in 

 rough beds in level portions of their bottoms, without manifest- 

 ing subordination to any system whatever. This fragmentary 

 condition is due to interruptions caused by portions of the sides 

 of the valleys being too precipitous for moraine matter to rest 

 upon and to breakings and down-washings of torrents and ava- 

 lanches of winter snow. The obscurity resulting from these 

 causes is further augmented by forests and underbrush, mak- 

 ing a patient study of details indispensable to the recognition of 

 their unity and simple grandeur. The south lateral moraine of 

 the lower portion of the trunk may be traced about five miles, 

 from the mouth of the north tributary of Mount Clark to the 

 canon of Illilouette, though simplicity of structure has in most 

 places been prevented by the nature of the ground and by the 

 action of a narrow margin glacier which descended against it 

 with variable pressure from cool, shadowy slopes above. The 

 corresponding section of the right lateral, extending from the 

 mouth of Cathedral tributary to Half Dome, is far more per- 

 fect in structure, because of the evenness of the ground, and 

 because the ice-wing which curved against Clouds Rest and 

 descended against it was fully exposed to the sun, and was, 

 therefore, melted long before the main trunk, allowing the lat- 

 ter to complete the formation of this section of its moraine un- 

 disturbed. Some conception of its size and general character 

 may be obtained by following the Clouds Rest and Yosemite 

 trail, which crosses it obliquely, leading past several cross-sec- 



