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 that the current was
hastening away; still more by the formation of swamps and marshes, which
arrest the sweep of fires, and so protect the youth and growth of trees
and forests.
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