POOLE— ON THE GREAT AMERICAN DESERT. 217 



soil, and to the miner desirous of the aid of steam to help him ex- 

 tract from the mine his expected fortune. 



The scarcity of water restricts the growth of timber to certain 

 districts, and explains the application of the term " treeless wastes," 

 which has been applied to the plains. 



In summer, showers are of much more frequent occurrence on the 

 mountains, and fall much heavier on the timbered ranges than on 

 the foothills and valleys. In general a summer storm which 

 drenches the mountain sides affords but at most a gentle shower or 

 temporary shade to the treeless plain. Even the snows of winter 

 fall lightly on the plain, while storms almost daily rage among the 

 peaks of the Wahsatch. Looking at any mountain range, it will 

 be noticed that the Southern slopes of the spurs, parched by the rays 

 of a constantly blazing sun, are utterly barren, while the opposite 

 sides, having a Northern aspect, are heavily clothed with timber. 

 The dark shade of the pine trees deepens the shadows cast in the 

 ravines, and heightening the contrast, throws the crests of the 

 mountain spurs into greater relief. 



Wherever in the valleys there is a constant supply of water, trees 

 will grow, as they naturally do along the courses of the streams or 

 artificial irrigation ditches. Again on the foothills clumps of cedar 

 grow wherever springs, which may not even show themselves at 

 the surface, keep the ground moist. I lately referred to the enor- 

 mous quantity of detrital matter which torn from the mountain sides 

 had been ground down, comminuted and carried oiF into the 

 depressions between the ranges until it had filled them up and made 

 the present great stretches of plain and valley. The period of time 

 necessary to produce changes so extensive must at least have been 

 great if not incalculable. The very changes themselves would 

 produce such modifications of the surftice as to bring fresh elements 

 into the calculation, and reduce the most careful estimates to but 

 wild guesses. 



Besides the silting up of the valleys other evidences remain to 

 show the extent of the denudation. Even on the mountain sides 

 there are monuments to point to the wear and tear due to the 

 elements. Castle rock and Pulpit rock in Echo Canon^ and the 

 " red buttes " on the plains of Laramie, are some of these. 



