LINEAMENTS OK. THE DESERT 



25 



CoroTE Mou>'TAix, AitizoN'A, risiug 3,<J0U I'et-t above the plaiu. Devoid of soil ; 

 impotency of water-action shown in the small volume of fans at the base. 



westward and then northward again until it passes into the British 

 possessions. The simile is as striking as it is apt. 



To the average mountaineer, one of the strangest characteristics of 

 the desert ranges is the absence of foot-liills. The main eminences of 

 the mountains rise directly from the plains. The line where plain and 

 mountain meet is as sharply defined as if drawn with a pen. Often 

 this line is represented by high mural faces that can be scaled at Imt 

 few points. For this reason it is, chiefly, that the mountains appear 

 to be half buried by the drifting sands. It is on this account largely 

 that the plains areas appear to be leveled by the waters of former seas, 

 of which the mountains formed the coastal cliffs. The illusion is all 

 but completed by the fact that the phenomenon is perfectly inde- 

 pendent of geologic sti-ucture. This surprising feature is really one 

 of the most novel peculiarities of eolian action under conditions of 

 aridity. 



That the substructure of the intermont plains is made up of the 

 softer or non-resistant rocks is an observation the full significance of 

 which has been only lately appreciated. Under conditions of a moist 

 or wet climate it is not an unlooked-for fact that the belts of weak 

 rocks coincide with the valleys or lowlands. It is unexpected, however, 

 that this is also true in an arid country, especially since the intermont 

 plains are commonly considered as areas of extensive accumulations of 

 mountain waste. On the whole they are now thought to be areas of 



