XV 



GLACIAL PHENOMENA IN NEVADA ^ 



The monuments of the Ice Age in the Great 

 Basin have been greatly obscured and broken, 

 many of the more ancient of them having 

 perished altogether, leaving scarce a mark, 

 however faint, of their existence — a condi- 

 tion of things due not alone to the long-con- 

 tinued action of post-glacial agents, but also 

 in great part to the perishable character of 

 the rocks of which they were made. The bot- 

 toms of the main valleys, once grooved and 

 planished like the glacier pavements of the 

 Sierra, lie buried beneath sediments and detri- 

 tus derived from the adjacent mountains, and 

 now form the arid sage plains; characteristic 

 U-shaped canons have become V-shaped by 

 the deepening of their bottoms and straight- 

 ening of their sides, and decaying glacier head- 

 lands have been undermined and thrown down 

 in loose taluses, while most of the moraines 

 and strise and scratches have been blurred 

 or weathered away. Nevertheless, enough re- 

 mains of the more recent and the more enduring 



1 Written at Eureka, Nevada, in November, 1878. 

 [Editor.] 



184 



