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DAVIS: THE GRAND CANYON OF THE COLORADO. 127 
cliffs. It is crossed by the road leading from Kanab and Fredonia to 
St. George. The divide does not here separate well-defined valleys, but 
marks the boundary between two long and broad graded platforms of 
gentle declivity, one slowly descending eastward and southeastward to 
Kanab creek, the other westward to a dry branch of Virgin river. 
The eastern platform heads westward in a sharp slope or “ wall” of 
weak lower Triassic shales, two or three hundred feet high and locally 
carved into bad-land spurs, forming a great westward curve, as if a large 
bight had been gnawed into the head of the western platform, whose 
border is appropriately concave. Evidently the eastern slope is gaining 
area by undercutting the western. When we saw first this wall on 
looking west from Pipe spring, it was perplexing, as there was no struc- 
ture known in the lower Trias by which it could be explained ; and 
moreover its even profile, descending gradually to the south, bevelled 
Figure 6. 
View from east of Pipe spring, showing ‘ wall’’ of migrating divide in the background. 
P, Pipe spring; T, Triassic plateau; L, landslide; S, Shinarump mesa; V-R, Sevier- 
Toroweap fault-line. Constructed from map and sections. 
the gentle northern dip of the strata in a curious fashion (Figure 6). 
But later in the day, when we looked northward to the divide from a 
point on the road between Pipe spring and Mount Trumbull (S, Fig- 
ure 6), the origin of the wall was easily discovered. The two graded 
platforms were then seen in opposing profiles, the eastern heading under 
the western, as in Figure 7. Indeed, the northern part of the western 
platform could be seen to extend several miles eastward around the 
head of the eastern platform, forming a bench that obliquely ascended 
the front of the Triassic cliffs independent of structural guidance, un- 
til it must have been a good thousand feet above the eastern plat- 
form. I have never seen so fine an example of the relation between 
two drainage slopes, one encroaching on the other. It was a disap- 
pointment that our hurried movement made closer study of this area 
impossible. 
