174 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
direct line. Through very nearly all this distance, the floor is covered 
by the basal (Tonto) sandstones of the paleeozoic series. When the 
actual contact is seen, it is found to be ragged, but in the twenty-mile 
stretch that I saw, the vertical inequalities of the floor were trifling in 
comparison to its horizontal extent. A few miles west of the Grand 
view trail into the canyon, a broad flat mound of the crystallines rose 
high enough in the northern wall of the canyon to interrupt the whole 
ere 
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Figure 15. 
The canyon in the erystallines, looking down the river (northwest) from Coppermine spur, 
Grand View trail. The crystalline floor is generally covered by the Tonto sandstone; 
but a low crystalline monadnock rises through the Tonto in the distance. Drawn from 
a sketch. 
thickness of the Tonto sandstones (Figure 15), but this was the only 
significant unevenness of the surface between the Tonto and the schists 
visible in that direction. A short distance east of the apex of the 
“wedge,” the more resistant members of the older series are not so well 
planed down as are the crystallines just west of the same point, and the 
Tonto sandstone is there greatly reduced in thickness or altogether 
wanting for large fractions of a mile. But these inequalities in the 
