OF THE 



(TY 

 or 



TEUE VOLCA&Om^***** 415 



Bill William Mountain, the Aztec Pass (6279 feet), and the 

 Aquarius Mountains (8526 feet) follow. The volcanic rock 

 does not terminate at the confluence of the Bill William 

 Fork with the great Colorado, near the village of the Mohave 

 Indians (lat. 34, long. 114), for, on the other side of the 

 Rio Colorado at the Soda Lake, several extinct, but still open 

 craters of eruption, may be recognized. 21 



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

 volcanic 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 Te"tons and the 

 Three Buttes, 22 correspond well with their conical forms. 

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

 sequently farther from the mountain chain. They exhibit 

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

 a scorified surface. 23 



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 

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

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



21 All on the authority of the profiles of Marcou and the above-cited 

 road-map of 1855. 



" 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 Tenons, 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". 



- 3 Lieut. Mullan, on Volcanic Formation, in the Reports of Explor. 

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

 Tinkham's Reports on the Three Buttes, ibid. pp. 167 and 226230 

 and Jules Marcou, p. 115, 



