TRUE VOLCANOES. 387 



on approaching the Rocky Mountains from the east, belong 

 perhaps to old eruptions of the Cerrito, or of the stupendous 

 Spanish Peaks (37° 32 7 ). This easterly volcanic district of 

 the isolated Eaton Mountains forms an area of 80 geograph- 

 ical miles in diameter ; its centre lies nearly in latitude 

 36° o(K. 



On the western slope most unmistakable evidences of an- 

 cient volcanic action are discernible over a wider space, which 

 has been traversed by the important expedition of Lieutenant 

 Whipple throughout its whole breadth from east to west. 

 This variously-shaped district, though interrupted for fully 

 120 geographical miles to the north of the Sierra de Mogo- 

 yon, is comprised (always on the authority of Marcou's geo- 

 logical chart) between latitude 33° 48 / and 35° 40', so that 

 instances of eruption occur farther south than those of the 

 Raton Mountains. Its centre falls nearly in the parallel of 

 Albuquerque. The area here designated divides into two 

 sections, that of the crest of the Rocky Mountains nearer 

 Mount Taylor, which terminates at the Sierra de Zuiii,* and 

 the western section, called the Sierra de San Francisco. The 

 conical mountain of Mount Taylor, 12,256 feet high, is sur- 

 rounded by radiating lava streams, which, like Malpays still 

 destitute of all vegetation, covered over with scoriae and pum- 

 ice-stone, wind along to a distance of several miles, precisely 

 as in the district around Ilecla. About 72 geographical miles 

 to the west of the present Pueblo de Zuiii rises the lofty vol- 

 canic mountain of San Francisco itself. It has a peak which 

 has been calculated more than 16,000 feet high, and stretches 

 away southward from the Rio Colorado Chiquito, where, far- 

 ther to the west, the 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 vil- 

 lage of the Mohave Indians (lat. 34°, long. 114°); for, on 



* We must be careful to distinguish, to the west of the mountain 

 ridge of Zuiii, where the Paso de Zuivi attains an elevation of as much 

 as 7943 feet, between Zuiii viejo, the old dilapidated town delineated 

 by Mollhausen on Whipple's expedition, and the still inhabited Pueblo 

 de Zuiii. Forty geographical miles north of the latter, near Port De- 

 fiance, there still exists a very small and isolated volcanic district. Be- 

 tween the village of Zuiii and the descent to the Eio Colorado Chiquito 

 (Little Colorado) lies exposed the petrified forest which Mollhausen 

 admirably delineated in 1853, and described in a treatise which he 

 sent to the Geographical Society of Berlin. According to Marcou 

 {Resume expiic. cfune Carte Geol., p. 59), fossil trees and ferns are min- 

 gled with the silicified coniferse. 



