112 W J MCGEE — SHEETELOOD EROSION. 



Plate 12. — Coyote Mountain, looking eastward. 



Coyote mountain is an en echelon extension northward of Baboquivari range. 

 The prevailing rocks are gray granites, with schists toward the base and on the 

 adjacent plains. The altitude of the crest is probably about 5,500 feet, or 3,000 

 feet above the Indian village (Coyote) in the foreground. The conspicuous features, 

 as at Fresnal, are steepness, ruggedness, and the small dimensions of taluses, fans, 

 and foothills. The mountain face shown is practically inaccessible, and has never 

 been climbed. Several low fans are shown, particularly at the right and somewhat 

 left of the center ; these have the form of alluvial accumulations, but actually con- 

 sist of sharply carved mountain rocks, veneered thinly with granitic loam and 

 gravel littered with great boulders. The plain in the foreground is thoroughly 

 typical ; the surface deposit is granitic debris, averaging less than a yard in thick- 

 ness (so far as could be determined from several exposures), resting on the planed 

 edges of rocks similar to those of the mountain. The view shows well the sharp 

 transition from rugged mountain to smooth plain. 



Plate 13. — Torrential Aprons of Papagueria. 



The view represents the eastern side of the valley of Rio Magdalena, about twenty 

 miles above Imuris. The mesquite-clothed foreground is alluvial, though under- 

 rocks crop out occasionally and appear m terraciform bluffs. The great aprons 

 forming the background have the appearance of alluvial fans, such, e. g. 5 as those 

 described by Drew in northern India (Quarterly Journal of Geological Society, 

 vol. xxix, 1873, p. 441, et seq.), yet analogy with all of the plains examined indi- 

 cates that they are in greater part baseleveled mountain rocks thinly veneered with 

 alluvial deposits. They were not visited. The sierra in the right background was 

 somewhat doubtfully identified as belonging to the main Sierra Madre, in which 

 case it is seventy-five or a hundred miles distant. Since the locality approaches 

 the high Sierra, the slopes are steeper than those characteristic of the lower plains ; 

 the altitudes range from some 2,000 feet in the foreground valley to 3,500 in the 

 aprons and 5,000 and upward in the nearer sierras. 



