204 Glacial Phenomena in the Yellowstone Park. [M arch, 
of mountainous country on the west, north and east, represent a 
former general elevation of twelve thousand feet or more,. 
Glaciers exist now in the neighboring Wind River and Teton 
mountains at elevations much below twelve thousand feet, and in 
the midst of glacial times descended in immense sheets to four 
thousand and five thousand feet. It would, therefore, be a matter 
of surprise if traces of glaciers were not found here, not only in 
the high valleys, but upon the surfaces of the broad plateaus of 
the park. There is, however, a singular absence of well defined 
glacial moraines. The tens of thousands of granite boulders that 
occur on both sides of the Yellowstone valley, from Cinnabar 
mountain to the north base of Amethyst mountain, generally lie 
upon the smooth surface of the flood planes of the river, or upon 
low ridges of alluvial drift. The significance of this fact may be 
that the transporting glaciers existed in the earlier stages of the 
erosion of the valley, and that the morainal ridges have been 
destroyed by the river as it oscillated from side to side in the suc- 
ceeding stages of its descent from the plateau level to its present 
bed. These great boulders would, in such a case, be the more 
durable masses of the moraines stranded on the various flood 
planes for want of water power to transport them. 
When we come to search for the source of the granite, we are 
led to observe an interesting fact. The only bodies of granite 
rock within the limits of this valley are found either on the north 
side or on the bottom at no considerable elevation above the 
river. But the erratic masses occur to a great extent on the 
south side of the valley and at all elevations. In the vicinity of 
Mt. Evarts they reach the upper surface of the plareau more than 
two thousand feet above the river bed. It is evident that these 
masses of granite were transported to their present resting places 
either before the valley existed or that the ice streams were so 
deep as to fill the valley to the brim and thus carry and strand 
them. Still it is a question whether in the latter case these 
boulders would ever reach their positions on the south side — sup- 
posing the glaciers to follow the course of the valley — as they 
would have to accomplish the feat of crossing the whole width of 
the glacier as a boat would cross a ferry. This could really only 
occur in case there should be such an increase in the masses of 
ice descending from the highlands to the north, as to completely 
fill the valley, sweep across its course and overspread the broad 
