GENERAL EBPOET. 23 



The following analysis of the soil is given by Dr. Oscar Loew, chemist 

 and mineralogist of the Survey, vol. iii, p. 587 : 



Physical condition : color, dark : consistency, loose. 



Per coiit. 



Saud 42.20 



Silt and clay 37.98 



Hygroscopic moisture 10.97 



Humus and chemically bound water 8.84 



Chemical constituents : 



Per cent. 



Potassa 0.015 



Soda 1 



„..,. > - traces 



Lithia J 



Magnesia 0.029 



Lime , 0.153 



Phosphoric acid 0.058 



Oxide of iron ) 



Alumina C by diff 2.013 



Sulphuric acid j 



Total soluble in hydrochloric acid, water included 22.188 



Insoluble quartz aud clay 77.812 



The rock from which the above soil was derived is a red sandstone. 



The San Francisco Mountains may be regarded as a northward exten- 

 sion of Mogollon Mesa, having the same average altitude (7,000 feet) and 

 the same dense timber-growth, with here and there fertile valleys and open 

 glades. 



South of the Mogollon Mesa, the altitude of the country decreases 

 until at Camp Apache we are but 5,000 feet above tide-water, and in Tonto 

 Basin to the west of Camp Apache lower still, probably between 3,500 and 

 4,500 feet. The word basin correctly represents this canon cut and crossed 

 depression, of which we have yet so much to learn. 



Crossing a series of mesa lands at an elevation of 6,000 to 7,000 feet, 

 we begin the descent to the parched, superheated valley of the Gila River. 

 A complete change comes over the flora. If verdure and superabundant 

 vitality were the expression of plant life on the timber clad Mogollon Mesa, 

 in the valley of the Gila, hardness of texture and contraction of form would 

 be characteristic of the flora. The attempt to make an analysis of one's 



