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Show THE A WAP A PLATEAU. 273 masses constituting the High Plateaus. The slopes of the entire mass all converge towards a central depression called Rabbit Valley. It is not an inclined plane or roof, but the segment of a dish. Everywhere the general inclination is very slight, though undulating with low hills. The western boundary is a wall from 1,800 to 3,000 feet high, plunging down into Grass Valley, sometimes by a grand precipice, sometimes by a steep, difficult slope and always abruptly. The length of the plateau, though its boundaries are for the most part difficult to locate with precision, is about 35 miles and its breadth about 18 miles. It is a dreary place. Upon its broad expanse scarcely a tree lifts its welcome green, save a few gnarled and twisted cedars. Its herbage consists only of the ubiquitous artemisia and long nodding grasses. Not a spring or stream of water is known upon all its area, except at the lowest part, where its slope merges into the floor of Rabbit Valley. And yet most of its surface is at an altitude where verdure and moisture abound, and where the summer is like the spring of more favored regions. But here the snows of winter are melted early, and the summers are nearly as hot and dry as those of the plains below. A ride across it is toilsome and monotonous in the extreme. It takes us over an endless succession of hills and valleys, clad with a stony soil, usually just steep enough to worry the animals, but not enough so to require us, or to even encourage us, to dismount. Here and there a sharp canon opens across the path in an unexpected manner, compelling a long detour to find a crossing. These are usually shallow, rarely exceeding 400 or 500 feet in depth, but are as typical in their forms or sections as the canons in the sedimentary strata. The whole mass of the Awapa consists of volcanic materials. The only localities where sedimentary beds are seen are in Rabbit Valley and low down in the western flank opposite East Fork Canon in Grass Valley. In the latter locality the great fault has brought them to daylight, and the ravines have still further opened them to view. They are Lower Tertiary, corresponding to the Bitter Creek beds of the northern plateaus. Above them are 3,000 feet of volcanic conglomerates and lavas. In Rabbit Valley beds presumed to be of the same age are also discovered beneath thin cappings of trachyte and basalt. Hence it appears that the 18 h p |
