STUDIES IN THE SIERRA* 



By John Mum 



NO. III. ANCIENT GLACIERS AND THEIR PATHWAYS 



THOUGH the gigantic glaciers of the Sierra are dead, their 

 history is indeHbly recorded in characters of rock, moun- 

 tain, canon, and forest; and, although other hieroglyphics are 

 being incessantly engraved over these, "line upon line," the 

 glacial characters are so enormously emphasized that they rise 

 free and unconfused in sublime relief, through every after in- 

 scription, whether of the torrent, the avalanche, or the restless 

 heaving atmosphere. 



In order to give the reader definite conceptions of the mag- 

 nitude and aspect of these ancient ice-rivers, I will briefly out- 

 line those which were most concerned in the formation of Yo- 

 semite Valley and its cafion branches. We have seen (in the 

 previous paper )t that Yosemite received the simultaneous thrust 

 of the Yosemite Creek, Hoffmann, Tenaya, South Lyell, and 

 Illilouette glaciers. These welded themselves together into one 

 huge trunk, which swept down through the valley, receiving 

 small affluents in its course from Pohono, Sentinel, and Indian 

 canons, and those on both sides of El Capitan Rock. At this pe- 

 riod most of the upper portions of the walls of the valley were 

 bare ; but during its earliest history, the wide mouths of these 

 several glaciers formed an almost uninterrupted covering of 

 ice. All the ancient glaciers of the Sierra fluctuated in depth 

 and width, and in degree of individuality, down to the latest 

 glacial days. It must, therefore, be distinctly borne in mind that 

 the following sketches of these upper Merced glaciers relate 

 only to their separate condition, and to that phase of their sep- 

 arate condition which they presented toward the close of the 

 period when Yosemite and its branches were works nearly ac- 

 complished. 



* Reprinted from the Overland Monthly of July, 1874. This is the third of a 

 series of seven studies in which Mr. Muir developed his theories of the geology of 

 the Sierra. — Editor. 



t Reprinted in Sierra Club Bulletin, Vol. X, No. i, January, 1916. 



