TRUE VOLCANOES. 389 



taut from the shore, are the Blue Mountains,* which rise in 

 their centre to a height of from 7000 to 8000 feet. In the 

 central portion of Old California, a little farther to the north, 

 near the eastern coast or bay in the neighborhood of the 

 former Mission of San Ignacio, in about 28° north latitude, 

 stands the extinct volcano known as the " Volcanes de las 

 Virgenes," which I have given on my chart of Mexico. This 

 volcano had its last eruption in 1746 ; but we possess no re- 

 liable information either regarding it or any of the surround- 

 ing districts. (See Venegas, Noticia de la California, 1757, 

 t. i., p. 27; and Duflot de Moras, Exploration de V Oregon et 

 de la Californie, 1844, t. i., p. 218 and 239.) 



Ancient volcanic rock has already been found in the coast 

 ran^e near the harbor of San Francisco, in the Monte del 

 Diablo, which Dr. Trask investigated (3673 feet), and in the 

 auriferous elongated valley of the Rio del Sacramento, in a 

 trachytic crater now fallen in, called the Sacramento Butt, 

 which Dana has delineated. Farther to the north, the Shasty, 

 or Tshashtl Mountains, contain basaltic lavas, obsidian, of 

 which the natives make arrow-heads, and the talc-like ser- 

 pentine which makes its appearance on many points of the 

 earth's surface, and appears to be closely allied to the vol- 

 canic formations. But the true seat of the still-existing igne- 

 ous action is the Cascade Mountain range, in which, covered 

 with eternal snow, several of the peaks rise to the height of 

 16,000 feet. I shall here give a list of these, proceeding from 

 south to north. The now ignited and more or less active 

 volcanoes will be (on the plan heretofore adopted ; see above, 

 p. 68, note *) distinguished by a star. The high conical 

 mountains not so distinguished are probably partly extinct 

 volcanoes, and partly unopened trachytic domes. 



Mount Pitt, or M'Laughlin (lat. 42° 30'), a little to the 

 west of Lake Tlamat ; height 9548 feet. 



Mount Jefferson, or Vancouver (lat. 44° 35'), a conical 

 mountain. 



Mount Hood (lat. 45° 10'), decidedly an extinct volca- 

 no, covered with cellular lava. According to Dana, this 

 mountain, as well as Mount St. Helen's, which lies more 

 northerly in the volcanic range, is between 15,000 and 



* Dana, p. 616-G20; Blue Mountains, p. 649-651 ; Sacramento Butt, 

 p. G30-613 ; Shasty Mountains, p. 614 ; Cascade range. On the Monte 

 Diablo range, perforated by volcanic rock, see also John Trask, on 

 the Geology of the Coast Mountains and the Sierra Nevada, 1854, p. 

 13-18. 



