DEAINAGE SYSTEM OF THE KAIBAB. 
U)3 
De Motte Park is a portion of the same depression. Farther north it diverges 
Irom this median or axial position, and trends off slight!}^ toward the south- 
west, ending at last upon the brink of the great chasm. In several places 
the valley bottom, as we follow it from north to south, reverses its grade. 
But in general there is a slight upward slope for more than forty miles, 
until we reach the “Sylvan Gate,” at the foot of the larger De Motte Park. 
Passing through the gate the grade of the valley descends toward the south. 
Wlien the geologists first visited the plateau they were considerably per- 
plexed by this long valley or chain of valleys. They observed that from 
the summits which overlook them on either side nearly all the drainage 
channels flowed away from it, and very few flowed into it. Upon these 
summits the numberless ravines took their rise — those upon the western side 
flowing away from it like rays in every direction west of the meridian, those 
upon the eastern side also flowing away from it, but not in the same man- 
mer. The origin of these summit ravines, their courses, and their distribu- 
tion, were easily explained, but the origin of the median chain of parks which 
separated the eastern drainage-plexus from the western was a mystery. 
Powell and Gilbert were at first inclined to suspect that a long, narrow 
wedge on the summit of the plateau had dropped between two faults, but 
no faults could be discerned, and they abandoned the supposition. Duiing 
the last season a thorough survey of the drainage system was made, and I 
think the mystery may now be cleared up. In the first place, the existence 
of the supposed faults was positively disproven by the discovery of the cross- 
bedded sandstone of the Aixbrey group just where it ouglit to be in case no 
faults exist, or where it could not be if the faults did exist. In the second 
place, the chain of valleys is the locns of an ancient river which once flowed 
from the north and emptied into the Colorado. Tliis river was far more 
ancient than any of the other drainage channels now scoring the surface of 
the Kaibab, which are all of comparatively recent origin. What antiquity 
should be assigned to it may not be altogether established, but by far the 
most probable supposition is that it is as old as the Colorado itself and its 
tributaries, the Kanab, Paria, and Little Colorado. We are not concerned, 
liowever, to find an origin so remote as these, but only to find that it ante- 
dates the Pliocene. That it belongs to the system of drainage which pre- 
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