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Sierra Club Bulletin 



ciated surfaces become corroded sooner. The lowest patches 

 are found at elevations of from 3000 to 5000 feet above the 

 sea, and thirty to forty miles below the summits, on the sunni- 

 est and most enduring portions of vertical walls, protected 

 from the drip and friction of water and snow by the form of 

 the walls above them, and on hard swelling bosses on the bot- 

 tom of wide cations, protected and kept dry by broad boulders 

 with overhanging eaves. 



MORAINES 



In the summit region we may watch the process of the form- 

 ation of moraines of every kind among the small glaciers still 

 lingering there. The material of which they are composed has 

 been so recently quarried from the adjacent mountains that 

 they are still plantless, and have a raw, unsettled appearance, 

 as if newly dumped, like the stone and gravel of railroad em- 

 bankments. The moraines belonging to the ancient glaciers 

 are covered with forests, and extend with a greater or less de- 

 gree of regularity down across the middle zone, as we have 

 seen in Study No. III. Glacial rock forms occur throughout this 

 region also, in marvelous richness, variety, and magnitude, 

 composing all that is most special in Sierra scenery. So also 

 do canons, ridges and sculpture phenomena in general, descrip- 

 tions of whose scenic beauties and separate points of scientific 

 interest would require volumes. In the lower regions the pol- 

 ished surfaces, as far as my observations have reached, are 

 wholly wanting. So also are moraines, though the material 

 which once composed them is found scattered, washed, crum- 

 bled, and reformed, over and over again, along river-sides and 

 over every fiat, and filled-up lake-basin, but so changed in po- 

 sition, form of deposit, and mechanical condition, that unless 

 we begin with the undisturbed moraines of the summit region 

 and trace them carefully to where they become more and more 

 obscure, we would be inclined to question the glacial character 

 of these ancient deposits. 



The cafions themselves, the valleys, ridges, and the large rock 

 masses are the most unalterable and indestructible glacial phe- 

 nomena under consideration, for their general forms, trends, 

 and geographical position are specifically glacial. Yet even 



