12 
THE GRAND CAlJON DISTRICT. 
here and there shade into each other. The westernmost is the Slieavwits 
Plateau. Its western boundary is a gigantic escarpment, overlooking the 
Grand Wash, a broad and deep valley descending from the north to the 
Colorado, and reaching the river at the mouth of the Grand Cafion. This 
“wash” carries the drainage from a considerable area lying to the north- 
westward, and also from the western wall of the plateau. No river runs 
there, but only occasional deluges of mud, whenever the storms from the 
southeast are flung against the lofty battlements and break in torrents of 
winter rain. The plateau wall had its origin in a great fault along the 
course of which the country east of it has been hoisted several thousand feet 
above the country on the west. The shear of this fault diminishes to the 
northward and appears to vanish about forty miles north of the Colorado, 
but its details remain to be studied. From the crest of the escarpment the 
plateau has a veiy gentle slope towards the east and northeast, for a dis- 
tance of about 30 miles. Its surface is diversified by some volcanic masses, 
and by a few large Permian outliers, capped by basaltic sheets. One con- 
siderable mass of basalt forms Mount Dellenbaugh, in the southern part of 
the plateau, and around its base spreads out a large basaltic field. The 
eastern limit of the Sheavwits is at the foot of the Hurricane Ledge, one 
of the most striking of the strong geological and topographical features of 
the region. The profile of the country, which has gradually declined from 
the western verge of the Sheavwits, suddenly leaps upward 1,600 to 1,800 
feet. Here begins the Uinkaret Plateau. 
It is the naiTowest of the four, but is strongly marked in its features. 
Its southern portion has been the scene of basaltic eruptions of consider- 
able magnitude, though far inferior in extent and mass to those of other 
districts around the borders of the Plateau Province. But they are very 
interesting in consequence of their connection Avith other features of the 
plateau and with their history. The cones and coulees are in an excellent 
state of preservation, and some of them have a singular freshness and an 
aspect of great recency. The positions of many of the basaltic masses 
amid the stupendous scenery of the great chasm and its tributary valleys, 
are highly impressive and siaggestive. On this plateau also the basalt 
has preserved the Permian beds in several localities, and the manner of 
