rdinary
example of erosion is, of course, the chasm of the Grand Canyon
proper, which, were the missing strata restored to the adjacent
plateau, would be sixteen thousand feet deep. The layman is apt to
stigmatize such an assertion as a vagary of theorists, and until
the argument has been heard it does seem incredible that water
should have carved such a trough in solid rock. It is easier for
the imagination to conceive it as a work of violence, a sudden
rending of earth's crust in some huge volcanic fury; but it appears
to be true that the whole region was repeatedly lifted and
submerged, both under the ocean and under a fresh-water sea, and
that during the period of the last upheaval the river cut its
gorge. Existing as the drainage system of a vast territory, it had
the right of way, and as the plateau deliberately rose before the
pressure of the internal forces, slowly, as grinds the mills of the
gods, through a period to be measured by thousands of centuries,
the river kept its bed worn down to the level of erosion; sawed its
channel free, as the saw cuts the log that is thrust against it.
Tributaries, traceable now only by dry lateral gorges, and the
gradual but no less effective process of weathering, did the rest."

In the innermost depths of this colossal chasm runs the Colorado River.
Descending the stupendous crags and terraces by one of the two or three
"trails," the traveller at last stands upon a sandy rift confronted by
nearly vertical walls many hundred feet high, at whose base a black
torrent pitches in a giddying onward slide that gives him momentarily
the sensation of slipping into an abyss.

"With so little labor may one come to the Colorado River in the heart of
its most tremendous channel, and gaze upon a sight that heretofore has
had fewer witnesses than have the wilds of Africa. Dwarfed by such
prodigious mountain shores, which rise immediately from the water at an
angle that would deny footing to a mountain sheep, it is not easy to
estimate confidently the width and volume of the river. Choked by the
stubborn granite at this point, its width is probably between two
hundred and fifty and three hundred feet, its velocity fifteen miles an
hour, and its volume and turmoil equal to the Whirlpool Rapids of
Niagara. Its rise in time of heavy rain is rapid and appalling, for the
walls shed almost instantly al