ANCIENT OUTLET OF YELLOWSTONE LAKE. 195 



bearing upon the subject. In the present chapter, therefore, it is only 

 necessarv to refer to a few facts as given there, so far as they relate to 

 the geological features of Chicken Ridge. 



PI. XXV is a reproduction from a photograph of the meadow of 

 Outlet Canyon. The view is taken from the top of a low glacial mound, 

 looking eastward toward the crest of the ridge. The Cretaceous rocks 

 forming the walls of the canyon are shown on the right-hand side of the 

 picture, the bare white outcrop marking the contact between the sand- 

 stone and rhyolite. Along the north wall, shown in the picture, the abrupt 

 precipice consists of rhyolite, rising more than 150 feet above the valley. 

 The densely wooded slopes, as depicted in the illustration, represent fairly 

 well large areas of the Park, covered by a vigorous growth of lodge-pole 

 pine (Pinus murrayand), which, although of poor quality as timber, meets 

 every requirement in preserving the soil from being washed away by 

 freshets and in protecting the snows from the hot suns and dry winds. 



Outlet Canyon is a broad, deep gorge, and throughout a long period 

 of time evidently served as the channel for a rapid, powerful stream carry- 

 ing a large volume of water. To-day its bottom is a flat, grassy meadow 

 with dark, rich soil, through which meanders with sinuous course a slug- 

 gish brook of dark, unattractive water. Tall, coarse grasses and low 

 growths of willows line the brook. 



During the ice period Outlet Canyon was undoubtedly occupied by an 

 extensive glacier. Stretching across the bottom of the canyon, between 

 Overlook and Channel mountains, lies an old terminal moraine, whose 

 material consists mainly of sandstone and rhyolite, with occasional frag- 

 ments of andesite and basalt. This obscure morainal heap to-day marks 

 the course of the continental watershed, serving as a barrier between the 

 waters of the Atlantic and those of the Pacific. From this insignificant 

 and unassorted heap of detrital material a small stream having scarcely any 

 eroding force has cut itself a channel in the glacial drift, but nowhere has 

 it penetrated to the underlying rock. Never since the retreat of the ice 

 has it been anything more than a mere rivulet. The glacial material, over- 

 lain by alluvial deposits, completely occupies the bottom of the valley, and 

 only along the abrupt walls of the canyon are Cretaceous rocks exposed. 

 This sluggish stream, which one can easily jump across, emerges from the 

 canyon through a growth of pines, and comes out into the open valley of 



