388 cosmos. 



the other side of the Eio Colorado, at the Soda Lake, sev- 

 eral extinct but still open craters of eruption may be recog- 

 nized." 



Thus we find here, in the present New Mexico, in the vol- 

 canic group commencing at the Sierra de San Francisco, and 

 ending a little to the westward of the Rio Colorado Grande, 

 or del Occidente (into which the Gila falls), over a distance 

 of 180 geographical miles, the old volcanic district of the 

 Auvergne and the Vivarais repeated, and a new and wide 

 field opened up for geological investigation. 



Likewise on the western slope, but 540 geographical miles 

 more to the north, lies the third ancient volcanic group of 

 the Rocky Mountains, that of Fremont's Peak, and the two 

 triple mountains, whose names, the Trois Tetons and the 

 Three Buttes,! correspond well with their conical forms. 

 The former lie more to the west than the latter, and conse- 

 quently farther from the mountain chain. They exhibit 

 wide-spread, black banks of lava, very much rent, and with 

 a scorified surface. $ 



Parallel with the chain of the Rocky Mountains, some- 

 times single and sometimes double, run several ranges in which 

 their northern portion, from lat. 46° 12', are still the seat of 

 volcanic action. First, from San Diego to Monterey (32^° 

 to 36f °), there is the coast range, specially so called, a con- 

 tinuation of the ridge of land on the peninsula of Old, or 

 Lower, California; then, for the most part 80 geographical 

 miles distant from the shore of the South Sea, the Sierra 

 Nevada (de Alta California), from 36° to 40|° ; then again, 

 commencing from the lofty Shasty Mountains, in the parallel 

 of Trinidad Bay (lat. 41° 10 7 ), the Cascade range, which con- 

 tains the highest still-ignited peak, and which, at a distance 

 of 104 miles from the coast, extends from south to north far 

 beyond the parallel of the Fuca Strait. Similar in their 

 course to this latter chain (lat. 43°-4G°), but 280 miles dis- 



* All on the authority of the profiles of Marcou and the ahove-cited 

 road-map of 1855. 



f The French appellations, introduced by the Canadian fur-hunters, 

 are generally used in the country and on English maps. According to 

 the most recent calculations, the relative positions of the extinct vol- 

 canoes are as follows : Fremont's Peak, lat. 43° 5', long. 110° 9' 30"; 

 Trois Tetons, lat. 43° 38', long. 110° 49' 30"; Three Buttes, lat. 43° 20', 

 long. 112° 41' 30"; Fort Hall, lat, 43° 0', long. 111° 24' 30". 



X Lieutenant Mullan, on Volcanic Formation, in the Reports of Ex- 

 phr. Surveys, vol. i. (1855), p. 330 and 348 ; see also Lambert's and 

 Tinkham's Reports on the Three Buttes, Ibid., p. 1G7 and 226-230, 

 and Jules Marcou, p. 115. 



