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Show BABBIT YALLEY. 277 side the valley is girt about by imposing masses; on the north and west by the slopes of the Awapa, and on the south by the Aquarius. Its floor is a broad alluvial plain, receiving the wash of all the surrounding uplifts, and carrying a noble stream, which is fed from all directions by rivulets which have brought down their loads of debris and, reaching the nearly level bottom, have deposited it. Those coming from the Awapa are always dry in summer, excepting one which heads near the foot of the slope, but the other tributaries from the north and south are perennial. The accumulation of detritus through the ages has produced a broad expanse of alluvial plain through which the Fremont River meanders, and nothing but a moist atmosphere is wanting to make this valley an Eden. It is somewhat unusual to find so large an area in this elevated region in which the accumulation is in excess of the power of the rivers to carry it away. But this exceptional condition appears to have prevailed in Rabbit Valley for a considerable time. It was apparently brought about by the last stage in the uplifting to the eastward across the great fault, or, what is the same thing, the downthrow of the valley itself; for these vertical movements must be considered in a purely relative sense and as meaning simply the difference of elevation between the lifted and thrown sides, respectively, of the displacement. The Thousand Lake fault cuts across the outlet of Rabbit Valley, which passes between Thousand Lake Mountain and the northern salient of the Aquarius, and it has had the effect of an increasing barrier to the outflow of the Fremont River and has slackened its waters within the valley. Hence the loads of ditritus which its affluents bring down from the plateaus on every side are thrown down in the valley. Since the last paroxysm of uplifting the river has taken to meandering, in consequence of the progressive building up of its channel and has repeatedly shifted its bed over different parts of its flood plain. Old canons in the borders of the lava sheets coming down from the Awapa have been partially filled up and the river has abandoned them. In truth, a con-siderible number of low canons of this sort are still discernible in the lower portions of these old trachytic beds, and it is apparent at a glance that they have nothing in common with the canons and ravines which descend the slopes of that plateau, except to form the old trunk channel into which the |
