400 REACTION OF THE INTEMOK OF THE EAETII 



at the Monte del Diablo (3672 feet), which has been ex- 

 amined by Dr. Trask, in the gold-yielding longitudinal 

 valley of the Eio del Sacramento, and in a fallen-in 

 trachytic crater called the Sacramento Butt, which has 

 been drawn by Dana. Further to the north, the Shasty 

 or Tshashtl Mountains, contain basaltic lavas ; obsidian, 

 used by the natives for arrow-points ; and the talcose 

 serpentines, which at many points of the earth's surface 

 occur in near connection with volcanic formations. But 

 the proper seat of still-subsisting volcanic activity is 

 found in the Cascade Mountains, where several peaks, 

 covered with perpetual snow, rise to heights of 15,000 

 and 16,000 feet. I subjoin a list of such moun- 

 tains, proceeding from south to north, and, as before, 

 marking by an asterisk those which are still more or 

 less active volcanoes. The lofty conical mountains not 

 so marked are probably in part extinct volcanoes, and in 

 part unopened trachytic summits. 



Mount Pitt or M'Laughlin, in 42 30', rather to the 

 west of Lake Tlamat, height 9549 feet. 



Mount Jefferson or Vancouver, in 44 35' ; a conical 

 mountain. 



Mount Hood, in 45 10' ; certainly an extinct volcano, 

 covered with cellular lava: according to Dana, it 

 and Mount St. Helen's are between 15,000 and 

 16,000 feet high, Mount St. Helen's being a little 

 the highest. ( 549 ) Mount Hood was ascended in 

 August 1853, by Lake, Travaillot, and Heller. 



MountSwalalahos, or Saddle Hill, S.S.E.of Astoria ( 55 ), 

 with a fallen-in extinct crater. 



Mount St. Helen's *, north of the Columbia River, in 



