92 GUIDEBOOK OF THE WESTERN UNITED STATES. 
The boulders are distributed in a fan-shaped, delta-like area, show- 
ing that on emerging from the canyon the current that transported 
them swung first to one side and then to the other 
Brown Canyon. 4 ¢ this great delta fan and, naturally, as it reached 
Elevation 7,324 feet. the open country, lost its transporting power and 
ball eed ae abiuiad its load. The station of Brown Canyon 
is at the point where the stream emerges from the canyon which it has 
cut in the hard granite. (See fig. 20.) 
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Fievure 20.—Ideal section from Sawatch Range to Brown Saeare showing the deep 
gravel filling in the old cremal of the Arkans: 
The canyon is not straight but, as shown in figure 20, winds about 
in the hard rock, and at one place, half a mile beyond thillepost 32 223, 
it touches the very edge of the granite mass, so that the recent cutting 
of the stream has exposed the gravel filling on 
the west (left; see fig. 21), showing conclusively 
that when the river established its present course 
it was flowing on gravel of fairly uniform com- 
position and that the slope of its bed was so 
slight that it meandered over a broad, flat- 
bottomed valley in great well-rounded curves. 
When the uplift came that gave it power to 
trench its valley, the stream cut directly down- 
ward in its established course, and although in 
some places its course was on granite and in 
other places on gravel, the river persisted in 
following that course even to the present day. 
The point of hard rock which the traveler may 
se = see on the left before he reaches the rift in the 
Fieurr 21.—Sketeh canyon wall is a large dike, which was once 
oilers Re PE. rock that was forced up from below 
tion to the granite through some great fissure in the crust of the 
and the gravel. earth. It is now solidified into a mass more 
resistant than the surrounding granite, so that it stands up as a nearly 
vertical wa 
At some iis in this canyon there are great granite boulders, 
around which the water surges furiously when the river is above the 
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