a certain area. Another is formed elsewhere, and
another, and so on till all drainage is through these tributaries and
away from the brink, by more or less circuitous channels to the main
stream. This backward drainage leaves the immediate brink, or "rim,"
till the last, in its work of erosion and corrasion, and the rim
consequently is left higher than the region away from it. This effect
of a backward drainage is very plain on both sides of the Grand Canyon,
though it is somewhat assisted, on the north at least, by the backward
dip of the strata. It may be modified by other conditions, so that it
would not always be the case.

The basin of the Colorado, excepting that part below the mouth of the
Virgen and a portion among the "parks" of the western slope of the
Rocky Mountain range, is almost entirely a plateau region. Some of the
plateaus are very dry; others rise above the arid zone and are well
watered. The latter are called the "High Plateaus." They reach an
altitude of eleven thousand feet above the sea. They are east of the
Great Basin, and with the other plateaus form an area called by Powell
"The Plateau Province." Eastward still the plateaus merge into the
"parks." The High Plateaus, as a topographical feature, are a southern
continuation of the Wasatch Mountains. They terminate on the south in
the Markagunt, the Paunsagunt, and the Aquarius Plateaus. The extreme
southern extremities of the two former are composed of mighty precipices
of columnarly eroded limestone called the Pink Cliffs. Here is the
beginning of the Terrace Plateaus, likewise bounded by vertical, barren
cliffs. Between the High Plateaus and the parks, the plateaus may be
called, for convenience, Mesa Plateaus, as they are generally outlined
by vertical cliffs. This is the case also south of the end of the High
Plateaus where, stepping down the great terraces, we arrive at the
region immediately adjacent to the Grand Canyon, composed of four
plateaus, three of them of mesa character, the Shewits, Uinkaret, Kanab,
and Kaibab; and up at the head of Marble Canyon a fifth, the Paria,
while still farther to the north-eastward is the Kaiparowitz. The edges
of these Mesa Plateaus, precipitous cliffs, stretch for many miles
across the arid land like mountain ranges split asunder. This region,
lying between the High Plateaus, the Grand Wash, the Henry Mountains,
and the Colorado, is perhaps the most fascinating of all the basin. The
relief map at page