472 GEOLOGICAL EXCURSION TO THE ROCKY MOUNTAINS. 



The greater of these, Oanyon Diablo, has a depth of 250 feet (7.") m.) 

 and has given name to the railway station just cast of it. 

 At Flagstaff the mode of travel changes; the, party is conveyed by 



wagons and saddle horses, takes its meals out of doors, and sleeps in 

 tents.* 



FLAGSTAFF TO THE GRAND CANYON."-' 

 By Q. K. Gilbert. 



Flagstaff Stands at the southern base of San Francisco Mountain. 

 The road to the brink of the Grand canyon curves eastward about the 

 mountain and then takes a northerly course. In the vicinity of the 

 mountain are a great number of basaltic cinder cones from 500 to 1,500 

 feet (150 to 450m.) in height, and most of these are so newly formed 

 that their craters are well preserved. A few are not yet clothed with 

 vegetation, and one, Sunset peak, is associated with a black lava field 

 equally barren. The sides of this cone are of black lapilli, but its 

 crest is tipped with red in a way to suggest that it catches the last 

 rays of the setting sun. In the crest of another com; are artificial 

 caves dug by Indians to serve as dwellings, but long abandoned. 



The general altitude of the plateau is 7,000 feet (2,100 m.), and it is 

 beautified by forests of pine, which give peculiar delight to eyes wearied 

 with treeless plains and mesas, but water is nevertheless scanty. There 

 are no streams, and springs are rare. Hull spring, the first one seen 

 by the party, is a day's journey from Flagstaff and determines a point 

 of encampment. The degradation of the country has here progressed 

 several hundred feet since the spreading of a great field of basaltic 

 lava, and the beds of resistant basalt cap a mesa, facing toward the 

 north. Beneath are soft shales of Permian age, and the water stored 

 in the crevices of the basalt escapes slowly at the plane of contact. 



The sloping Permian outcrop is sheathed by fragments of the basalt, 

 which breaks away in huge blocks as it is sapped. One of these blocks, 

 separated from the main cliff by a chasm a hundred yards across, was 

 chosen as the site of an Indian village and covered with stone houses. 

 The ruined walls remain, with fragments of pottery, and chips of flint 

 and obsidian. 



From Hull spring northward the road descends below the /.one of 

 trees and for 20 miles (30km.) traverses a prairie floored by Aubrey 

 limestone. Continuing on the same terrane, it then rises again into 

 the zone of pine forest, and there remains till the brink of the canyon 

 is reached. This timbered upland is the Oosnino plateau, the compan- 

 ion and counterpart of the Kaibab plateau north of the river. Indeed 

 the two are parts of one uplift divided by the corrading river. 



"The prophecy of "tents" was not verified; the party bivouacked, and was so 

 unfortunate as to encounter storms of rain, snow, and wind. 



