178 TRANSACTIONS OF THE [FEB. 15, 



but above me the peaks stood clear cut against the sk}'; the snow 

 was glistening in the sun, perhaps I could never come again, so, 

 telling my guide to sit where he was, that I might call to him as 

 I came down, I pushed on alone. 



Cautiously making my way along the loose rocks I reached 

 the ledge, and going on still further I found a place where I 

 could get over and then made my way to a cliff projecting from 

 the side of a mountain, I found I could go up along the base 

 of this cliff and presently came to another ledge extending along 

 the range. I clambered over this and, to my surprise, saw before 

 me a sloping terrace, about three miles long, lying just at the 

 bend in the mountains, where two ridges came together and at 

 the top of this formation the naked rocks of the backbone of all 

 the Sierra Nevadas stood easily accessible and it was only neces- 

 sary to select the point I wished to examine and hurry on to it. 



The terrace had the appearance of an old boulder pavement 

 without the rounding of the material, for there was no evidence 

 of aqueous action, all the broken pieces being sharply angular. 

 There was coarse grass growing among the scattered rocks and 

 wild cattle were feeding there. Granite was everywhere, and I 

 noted as I hurried on that many of the fragments were like flat 

 irregular slabs of rock, yet there was not the slightest trace of 

 schistose structure. 



I had almost reached the last rocky ledge when my attention 

 was suddenly attracted to an uptilted deposit of gray sedimen- 

 tary rock, in texture and appearance almost identical with a com- 

 mon free stone, or the flagstones used on New York sidewalks. 

 It was almost perpendicular, dipping only slightly to the south 

 and striking nearly east and west. It was well defined and lay 

 embedded in granite walls and, though not more than a few 

 inches wide, extended some distance. It was not metamorphosed, 

 indicating that the rocks between which it was folded were 

 cooled before their upheaval and that at the time when the final 

 uplift of these mountains occurred the sediments of a previous 

 period had been deposited and turned to stone, indicating that 

 there was land here before these mountains were intruded and 

 that it was older than all the surrounding parts of South 

 America. 



After examining this seam of rock I hurried on to the top of 

 the range, found a place where I could climb up among the 

 ledges and then sat down in solitude. To the west of where I 

 was I could pitch stones down a deep triangular vallej^ sur- 

 rounded by precipices on two sides. It looked inky black, and 

 I could not see the bottom, though from where I sat one leg was 

 almost hanging over it. On the other side was the terrace and 



