158 EXPLORATION OF THE CANONS OF THE COLORADO. 
passing obliquely through the formations. The great billow or wave has a 
rippled surface, or wavelets are formed across it, some of which have their 
axis nearly at right angles to that of the great fold, others more or less 
oblique. 
Split Mountain Canon is cut lengthwise through one of the rock wave 
lets, a southward spur of the Uintas. The course of the river does not 
chance to be in the direction of the billow for its whole length, but, running 
down the wavelet for a few miles, it runs out of it to the right, where it 
passes through Island Park, then into it again at the head of Split Mountain 
Canon, and then it divides the fold by a gorge to its foot. 
Leaving Split Mountain Canon, and entering the valley below, we run 
into a down-turned wrinkle, or, in the language of the geologist, into a 
synclinal fold. The axis of the fold is parallel to the Uinta Mountains. 
The valley of the Uinta, on the west, and the valley of White River, on the 
east, mark, in a general way, the bed of this down-turned wrinkle; and 
still continuing to the south, we pass into another up-turned fold. 
It has already been said that the cutting off of the fold has left the 
upturned edges of the formations exposed to view. Some of these beds are 
quite hard, others are composed of very soft material, so there are alternat 
ing beds of harder and softer rocks running in an easterly and westerly 
direction, both on the north and south side of the range. The soft rocks, 
yielding much more readily to atmospheric degradation, have been washed 
out in irregular valleys, between intervening ridges of harder rock, so that 
we have a series of nearly parallel valleys, and also a series of intervening 
parallel ridges, and both valleys and ridges are approximately parallel to the 
range. But as the great fold of the Uinta Mountains is greatly complicated 
by minor oblique and transverse flexures, while the general direction of 
these ridges is as described, they are turned back and forth from these lines 
in gentle or abrupt curves. These ridges are sometimes low mountain 
ranges. 
So, if we approach these mountains from either direction, north or 
south, we first meet with ridges, or, as they are usually called in the western 
country, hog-backs. In many places these are so steep as to form a com 
plete barrier to progress. 
