Studies in the Sierra 



187 



ness in sculpture and general form to this glacial-shadow action, 

 which in many portions of the summit may still be observed in op- 

 eration. But it is only to the effects of shadows in the segregation of 

 mountain masses that I would now direct special attention. Figure 

 5 is a map of the Merced range adjacent to Yosemite Valley, with a 

 portion of the ridge which unites it to the main axis. The arrows in- 



FiG. 5 



dicate the direction of extension of the deep glacial amphitheaters, 

 and it will be at once seen that they all point in a southerly direction 

 beneath the protection of shadows cast by the peaks and ridges. 

 Again, it will be seen that because the Merced spur (S P) trends in 

 a northerly direction, its western slopes are in shadow in the fore- 

 noon, its eastern in the afternoon, consequently it has a series of gla- 

 cial wombs on both sides; but because the ridge (P G) trends in an 

 easterly direction, its southern slopes are scarcely at all in shadow, 

 consequently deep glacial wombs occur only upon the northerly 

 slopes. Still further, because the Merced spur (S P) trends several 

 degrees west of north, its eastern slopes are longer in shadow than' the 

 western, consequently the ice-wombs of the former are deeper and 



