Colorado
River, on the same spot where our boat-party had camped the year before.
Leaving the party in charge of Mr. Graves and Mr. Bishop, while they are
building a ferryboat, I take some Indians to explore the canyon of the
Paria. We find steep walls on either side, but a rather broad, flat
plain below, through which the muddy river winds its way over
quicksands. This stream we have to cross from time to time, and we find
the quicksands treacherous and our horses floundering in the trembling
masses.

These broad canyons, or canyon valleys, are carved by the streams in
obedience to an interesting law of corrasion. Where the declivity of the
stream is great the river corrades, or cuts its bottom deeper and still
deeper, ever forming narrow clefts, but when the stream has cut its
channel down until the declivity is greatly reduced, it can no longer
carry the load of sand with which it is fed, but drops a part of it on
the way. Wherever it drops it in this manner a sand bank is formed. Now
the effect of this sand bar is to turn the course of the river against
the wall or bank, and as it unloads in one place it cuts in another
below and loads itself again; so it unloads itself and forms bars, and
loads itself with more material to form bars, and the process of
vertical cutting is transformed into a process of lateral cutting. The
rate of cutting is greatly increased thereby, but the wear is on the
sides and not on the bottom. So long as the declivity of the stream is
great, the greater the load of sand carried the greater the rate of
vertical cutting; but when the declivity is reduced, so that part of the
load is thrown down, vertical cutting is changed to lateral and the rate
of corrosion multiplied thereby. Now this broad valley canyon, or "box
canyon," as such channels are usually called in the country, has been
formed by the stream itself, cutting its channel at first vertically and
afterwards laterally, and so a great flood-plain is formed.

For a day we ride up the Paria, and next day return. The party in camp
have made good progress. The boat is finished and a part of the camp
freight has been transported across the river. The next day the
remainder is ferried over and the animals are led across, swimming
behind the ferryboat in pairs. Here a bold bluff more than 1,200 feet in
height has to be climbed, and the day is spent in getting to its summit.
We make a dry camp, that is, without water, except that which has