194 
THE GEAND CANON DISTEIOT. 
vailed when the structural conformation of the country was very different 
from the present one is self-evident. The course of its valley for the most 
part is against the structural and topographical slopes, and therefore the 
river was older than those slopes. That is to say, when this valley carried 
a living stream, the Kaibab as a distinct plateau had no existence. 
Two causes may be readily discerned which destroyed this river. The 
first was the arid climate of the Pliocene, which greatly reduced its water 
supply. The second was the peculiar distribution of the uplifting, which, 
being greater along the lower courses of the river than along the upper 
reaches, had a tendency to reverse the slope of its channel. But Kanab 
Creek has persisted to the present day in spite of similar adverse condi- 
tions, and has maintained itself by cutting down its channel as fast as the 
country rose. But in the extinct river of the Kaibab a still more adverse 
arrangement of the uplifting destroyed it. For the uplifting was of such a 
distribution that the river was left upon the axis of a water-shed instead of 
in a broad drainage-basin, and was thus deprived of tributaries and feeders. 
At what epoch was this river destroyed! It perished at the epoch 
when the Colorado was running in the cross-bedded sandstone of the Upper 
Aubrey group, 5,000 feet above its present bed! If we follow its channel 
from the park toward the confluence with the Colorado, we find it sinking 
to the surface of this adamantine stratum, and a few yards into it. At last 
the valley ends suddenly in the mighty wall of the chasm, and from its 
trough we look down upon the great river a mile below and three or four 
miles beyond us. When the valley sustained a living stream it must have 
done just what the other tributaries did — cut down its bed in harmony with 
the Colorado itself. When its waters ceased to flow the valley ceased to 
deepen. It has never carried a stream since, and has never grown materi- 
ally deeper. Its present floor marks the horizon upon which its waters 
ceased to run, and where the Colorado left it and continued to sink deeper 
through the succeeding ages. But the cross-bedded sandstone is within 600 
or 700 feet of the summit of the canon wall, and when the Colorado was 
running over it the work of excavating the present Glrand Canon had just 
begun. Already the reasons have been given for referring this epoch to the 
beginning of the Pliocene. 
