144 The Black-Tail Deer. 



dry climate of the plains. Geologically the land is for 

 the most part composed of a set of parallel, perfectly 

 horizontal strata, of clay, marl, or sandstone, which, being 

 of different degrees of hardness, offer some more and some 

 less resistance to the action of the weather. The table- 

 lands, peaks, cliffs, and jagged ridges are caused solely by 

 the rains and torrents cutting away the land into channels, 

 which at first are merely wash-outs, and at last grow into 

 deep canyons, winding valleys, and narrow ravines or 

 basins. The sides of these cuts are at first perpendicular, 

 exposing to view the various bands of soil, perhaps of a 

 dozen different colors ; the hardest bands resist the action 

 of the weather best and form narrow ledges stretching 

 along the face of the cliff. Peaks of the most fantastic 

 shape are formed in this manner ; and where a ridge is 

 worn away on each side its crest may be as sharp as a knife 

 blade, but all notched and jagged. The peaks and. ridges 

 vary in height from a few feet to several hundred ; the 

 sides of the buttes are generally worn down in places so as 

 to be steeply sloping instead of perpendicular. The long 

 wash-outs and the canyons and canyon-like valleys stretch 

 and branch out in every direction ; the dryness of the 

 atmosphere, the extremes of intense heat and bitter cold, 

 and the occasional furious rain-storms keep the edges and 

 angles sharp and jagged, and pile up boulders and masses 

 of loose detritus at the foot of the cliffs and great lonely 

 crags. Sometimes the valleys are quite broad, with steep 

 sides and with numerous pockets, separated by spurs jutting 

 out into the bottom from the lateral ridges. Other ravines 

 or clefts taper down to a ditch, a foot or so wide, from 



