JOHNSON: GRAND CANON DISTRICT. 137 
passing up over the surface of the great double fold to the summit of 
the Kaibab Plateau. Passing down Jacob's Canon we had an oppor- 
tunity to see the West Kaibab Fault where this caiion opens on the 
Kanab Plateau at the face of the fault scarp. At Pipe Spring we 
encountered the Sevier Fault, and followed it southwestward for ten 
or twelve miles. Turning west, we reached the northern end of the 
Toroweap Fault and followed it southwest to a point near the Grand 
Canon. Returning to Pipe Spring along the Toroweap and Sevier 
Faults, we next turned westward, crossing the Hurricane Fault near 
the Arizona-Utah line, and followed it northward into Utah. 
In meeting the expenses of the excursion, we were aided by grants 
from the Massachusetts Institute of Technology and the Sturgis-Hooper 
fund of Harvard University, and by private contributions from Mr. 
George H. Crocker, Sr., and other friends of the Institute. Our 
party included Dr. H. W. Shimer of the Institute, and Mr. C. H. 
Decker, E. M., of Bingham Canon, Utah. 
It is not necessary to preface these notes with any extensive review 
of the literature. A short summary of observations made by previous 
workers in the Grand Canon district, together with a fairly full bibli- 
ography will be found in one of Davis's ('01) papers cited below. 
It is sufficient to note in the present connection that two theories have 
been entertained regarding the relative ages of the displacements 
and the main drainage lines of the district. According to Dutton, the 
courses of the Colorado River and its main tributaries were established 
before the faults and folds came into existence. The development of 
the displacements at a much later period was so gradual that these 
main drainage lines were able to maintain their courses, cutting their 
channels downward as fast as uplift occurred, wherever barriers were 
raised across their paths. In other words, the drainage lines are older 
than the lines of displacement; the Colorado, with its main tributaries, 
is an antecedent river system. The same conclusion had been reached 
by Powell ('75, p. 198) some years earlier. 
An alternative theory has been advanced by Davis ('01, '03). Ac- 
cording to his interpretation the disjjlacements are much older than 
supposed by Powell or Dutton. After the displacements occurred, 
the region was reduced to a penejilain. Across this surface of faint 
relief the Colorado river system found its way, its course havino- 
been determined in part by a series of complex adjustments during 
the cycle which ended in the peneplanation, while in places the stream 
