
THE CHASMS OF THE COLORADO, 861 
vines of this description are common; and in these sedimen- 
tary rocks where layer answers to layer on either side of 
the gorge, there can be but little doubt that water has carved 
them out. In the more disturbed localities, however, where 
the stratification is obscured, it becomes difficult to deter- 
mine whether the chasms were not originally great cracks in 
the earth, subsequently enlarged by the grinding and trans- 
porting power of the stream. The Colorado of the West af- 
fords the best illustrations of these two kinds which have yet 
been seen by man. In its lower part the rocky sides of the 
tahons are cut out of strata highly inclined and disturbed, 
where they have been bent upward to form the mountains, 
while in its upper portion they are perfectly horizontal. 
Two rivers, the Green and the Grand, rise at the western 
bases of the Rocky Mountains, ten or twelve thousand feet 
above the sea, one in South-western Nebraska, the other in 
South-eastern Oregon, and are said to unite their streams near 
the southern boundary of Utah, to form the Colorado of the 
West. This then flows south-westerly, and empties into the 
Gulf of California: The descent is accomplished at first by 
* grand cañon cut through a succession of elevated plateaux, 
called Mesas, which spread out westward from the base of 
Rocky Mountains, like a gigantic stairway, each step a 
thousand feet or so in height and many miles in breadth, and 
m Its lower part by a series of cañons through ranges of 
mountains, 
P late 7* shows the north-western prolongation of the Pur- 
ple Hills, which form the first three cañons in the river. The 
two pinnacles of “Chimney Peak,” looming up in the back- 
Stound, are composed of trap. This being much harder than 
ara of the neighboring rocks has yielded less to the 
bps the elements, and shows how vast has been the de- 
On which has destroyed them. Professor Newberry 
S that in some cases tlfe wearing away of the moun- 


*From the Editors of the Ameriean J a af Art 2 Gaian 
* NATURALIST, VOL. 11. 46 

