Yakutat and Pinnacle Systems. 131 



almost eveiywhere bare of snow and too steep and rugged to be 

 scaled. They form a strongly drawn boundary line in the 

 geology of the region, and furnish the key to the structure and 

 geological character of an extended area. All the rocks to the 

 soutliAvard are sandstone and shale belonging to a well-defined 

 series, and differ materially from the rocks in the fault-scarp. I 

 have called the rocks toward the south, the Yakutat system, and 

 those exposed in the faces of the fault-scarp the Pinnacle sys- 

 tem. Directly north of Pinnacle pass, and at the base of Mount 

 Owen, the rocks of the Yakutat system are exposed, and from 

 their position and association it is evident that they are younger 

 than the Pinnacle system and belong above it. If these con- 

 clusions are sustained by future investigation, they will carry 

 with them certain deductions which are among the most remark- 

 able in geological history. On the crest of the Pinnacle pass 

 cliffs I afterwards found strata containing fossil shells and leaves 

 belonging to species still living. These records of animal and 

 plant life show that not only were the rocks of the Pinnacle sys- 

 tem deposited since living species of moUusks and plants came 

 into existence, but that the Yakutat system is still more recent. 

 More than this, the upheaval of the mountains, the formation of 

 numerous fault-scarpfe, and the origin of the glaciers, have all 

 o"ccurred since Pliocene times. 



The discovery of Pinnacle pass left no question as to the route 

 to be traversed in order to reach the mountains to the westward. 

 We returned to Camp 12, and the following day, with Crumback 

 and Lindsley to assist us, advanced our camp across Pinnacle 

 pass and far down the western snow-slope. 



The day we crossed the pass was bright and clear in the morn- 

 ing, but clouds gathered around all the higher peaks about mid- 

 day, vanishing again at nightfall. As it was desirable to occupy, 

 for topographic and other purposes, a station on the top of the 

 cliffs overlooking Pinnacle pass, we made an effort to reach the 

 crest of the ridge by climbing up the steep scarp just at the 

 divide, where the cliffs are lowest. While Crumback returned 

 to Camp 12 for an additional load and Lindsley went ahead to 

 discover a new canaping place, Kerr and myself, taking the neces- 

 sary instruments, began the ascent ; but we found it exceedingly 

 difficult. The outcrops of shale in the lower portion of the cliff 

 furnished but poor foothold, and crumbled and broke away at 

 every step. Once my companion, losing his support, slid slowly 



