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Show 158 EXPLORATION OF THE OARONS OF THE OOLORADO. passing obliquely through the formations. The great billow or wave liald .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 wavelets, 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 Mounk'tin Canon, and entering the valley below, we run into a down-turned wrinkle, or, in tho 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 tho cuttin<r off of the fold has left the uptm·ned edges of the formations exposed to view. Some of these beds are quite hard, others are composed of very soft material, so there are alternating beds of harder and softer rocks running in an easterly and westerly direction, both on the north and south Bide 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 transvArse . flexures, while the general direction of these ridges is as described, they are turned back and forth from those 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 couutry, hog-backs. In many places these are so steep as to form a complete barrier to progress. |