Studies in the Sierra 



237 



Fig. 13. 



boulder of hard 

 metamorp h i c 

 slate, which, af- 

 ter withstanding 

 many a crush 

 and blow in its 

 winter history, 

 until its angles 

 were worn and 

 battered, at 

 length, on the 

 recession of the 



glacier to which it belonged, came to rest on a smooth hard 

 pavement, so level that it could not have rolled or fallen to its 

 present position. Yet it is now split in two, having fallen apart 

 by its own weight, on the ripening of one of its cleavage planes, 

 just as the valves of seeds ripen, open, and fall. 



Fig. 14 is a profile view of a rock 200 yards from the head 

 of the Yosemite Fall, which is now weak and ready to fall 

 apart by the development of the vertical north 35° east cleavage 

 planes, the edges of which are seen in front; yet it is certain 

 that this rock was once subjected to the strain of the over- 

 sweeping Yosemite basin glacier, when on its way to join the 

 main trunk Yosemite glacier in the valley. 



Fig. 15 is a ruinous dome-top on the divide between Yosemite 

 Creek basin and cascade. The beginner in such studies would 

 not perceive that it had been overswept ; yet hard portions near 

 the base show clear evidence of glacial action, and, though 

 ruinous and crumbling, it will at once appear to the educated 

 eye that its longer diameter is exactly in the direction of the 

 oversweeping ice-current, as indicated in the figure by the 

 arrows. Rock masses, hundreds or even thousands of feet in 

 height, abound in the channels of the ancient glaciers, which 

 illustrate this argument by presenting examples in every stage 

 of decay, the most decayed always occurring just where they 

 have been longest exposed to disintegrating and general 

 weathering agents. The record of ice phenomena, as sculp- 

 tured, scratched, and worn upon the mountain surfaces, is like 

 any other writing, faint and blurred according to the length of 

 time and hard usage to which it has been exposed. It is plain, 

 therefore, that the present sculptured condition of the Sierra 



