DAVIS: THE GRAND CANYON OF THE COLORADO. 111 
ment and denudation. The topographical maps prepared by Bodfish 
and Renshawe in 1879 are also of great service to the traveller. The 
main conclusions of the earlier explorers are not to be disputed. The 
great unconformities at the base of the plateau series, the enormous 
volume of nearly horizontal and conformable strata from lower Paleozoic 
to Tertiary, the division of the region into great blocks by displacements, 
either faults or flexures, trending about north and south, the great 
denudation by which the plateaus bordering the canyon have been 
stripped of thousands of feet of strata, the sharp erosion by which the 
canyon has been incised in the plateaus, and the superb development of 
volcanic phenomena, —all these great features are standard examples 
for citation. There are, however, certain subordinate conclusions an- 
nounced in the earlier reports which seem open to question, and it is 
chiefly to a consideration of these debatable points that the present 
essay is devoted. 
The following brief summary of certain aspects of the work of three 
earlier observers may be of service to the reader. 
Newberry, geologist of the Ives expedition to the Colorado river of 
the west in 1857-58, ascended the Grand Wash cliffs to the plateaus 
from the deserts among the Basin ranges on the south of the river, 
descended northward into the Grand canyon near its western end by 
the side canyon of Diamond creek, and, ascending again, traversed the 
southern plateaus past San Francisco mountain from west to east. He 
recognized the fundamental crystalline rocks beneath their heavy un- 
conformable cover of palzeozoic strata (pp. 54-58); he perceived the 
importance and efficacy of ordinary erosive processes not only in the 
excavation of the narrow canyons beneath the plateaus by the larger 
and smaller streams (pp. 45, 46), but also in the broad recession of the 
cliffs upon the plateau (pp. 45, 62), indeed he regarded the opening of 
the broad upland valleys on the plateaus, such as that of the Little 
Colorado, as “a much grander monument of the power of aqueous 
action than even the stupendous cajion of the Colorado” (p. 86). He 
noted a “slight arching of the strata” in passing from what we may 
now call the southern Shivwits to the southern Uinkaret plateau 
(p. 58), and a “curve of the underlying rock” on descending from the 
Coconino plateau (south of the Kaibab) to the platform of the Little 
Colorado valley (p. 61); but he denied the occurrence of other dis- 
placements, not only in the canyons but also along the north-south 
escarpments, saying that “the strata of the table-lands are as entirely 
unbroken as when first deposited” (p. 46) ; and this is not unreasonable 
