on their sides, which every rain is still abrading. At a single
point only do I remember a phenomenon presented by some other mountain
bases,--that of a water-course (dry perhaps half the year, but evidently
a heady torrent at times), which had gradually built up a bed and banks
of boulders, pebbles and gravel, washed down from a higher portion of
its headlong course, so that its current, when it had a current, was
considerably above the general surface on either side of it. Away from
the mountains, however, boulders or loose stones of any size are rarely
seen in the beds of even the largest and deepest channeled streams,
which are usually swift, but never broken by a fall, because never down
to the subjacent rock in place, assuming that such rock must be.

In the rare instances of rocky banks skirting the immediate valley of a
stream, the seeming rock is evidently a modern concrete of clay and the
usual sand or gravel composing the soil,--a concrete slowly formed by
the action of sun and rain and wind, on a bank left nearly or quite
perpendicular by the wearing action of the stream. In the neighborhood
of Cheyenne Pass,--say for a distance of fifty to a hundred miles S.S.W.
of Laramie,--this effect is exhibited on the grandest scale in repeated
instances, and in two or three cases for an extent of miles. Along
either bank of the Chugwater, at distances of twenty to forty miles,
above its junction with the Laramie affluent of the North Platte,
stretch perpendicular rocky terraces, thirty to forty feet high,
looking, from a moderate distance, as regular and as artificial as the
facade of any row of city edifices. I did not see 'Chimney Rock,'
farther down the Platte; but I presume that this, too, is a relic of
what was once the average level of the adjacent country, from which all
around has been gradually washed away, while this 'spared monument' has
been hardened by exposure and the action of the elements from earth to
enduring rock--a gigantic natural _adobe_.

The Plains attest God's wisdom in usually providing surface-rock in
generous abundance as the only reliable conservative force against the
insidious waste and wear of earth by water. Storms, rills, and rivers
are constantly at work to carry off the soil of every island and
continent, and lose it in the depths of seas and oceans. Rock in place
impedes this tendency, by arresting the headlong course of streams, and
depositing in their stiller depths the spoils t