Studies in the Sierra 



305 



rectly into the sea, and so perhaps did all first-class glaciers 

 when in their prime; but now the world is so warm, and the 

 snow-crop so scanty, most glaciers melt long before reaching 

 the ocean. Schlagenweit tells us those of Switzerland melt on 

 the average at an elevation of about 7400 feet above sea-level ; 

 the Himalaya glacier, in which the Ganges takes its rise, does 

 not descend below 12,914 feet;* while those of our Sierra melt 

 at an average elevation of about 11,000 feet. In its progress 

 down a mountain-side a glacier follows the directions of great- 

 est declivity, a law subject to very important modifications in 

 its general application. Subordinate ranges many hundred feet 

 in height are frequently overswept smoothly and gracefully 

 without any visible manifestations of power. Thus, the Ten- 

 aya outlet of the ancient Tuolumne mer de glace glided over 

 the Merced divide, which is more than 500 feet high, impelled 

 by the force of that portion of the glacier which was descend- 

 ing the higher slopes of Mounts Dana, Gibbs, and others, at a 

 distance of ten miles. 



The deeper and broader the glacier, the greater the horizon- 

 tal distance over which the impelling force may he transmitted. 

 No matter how much the courses of glaciers are obstructed by 

 inequalities of surface, such as ridges and canons, if they are 

 deep enough and wide enough, and the general declivity be suf- 

 ficient, they will flow smoothly over them all just as calm 

 water- streams flow over the stones and wrinkles of their chan- 

 nels. 



PRESENT CONDITION OF THE SIERRA CONSIDERED WITH 

 REFERENCE TO GLACIAL ACTION 



The most obvious glacial phenomena presented in the Sierra 

 are: first, poUshed, striated, scratched, and grooved surfaces, 

 produced by the glaciers slipping over and past the rocks in 

 their pathways. Secondly, moraines, or accumulations of mud, 

 dust, sand, gravel, and blocks of various dimensions, deposited 

 by the glaciers in their progress, in certain specific methods. 

 Thirdly, sculpture in general, as seen in canons, lake-basins, 

 hills, ridges, and separate rocks, whose forms, trends, distribu- 

 tion, etc., are the peculiar offspring of glaciers. 



* According to Captain Hodgson. 



