ys usually below, to give any prowling, thieving
prairie-wolf, or other carnivorous intruder, the worst of the bargain,
should he attempt to dig out the architect of this subterranean abode.
But for this nice little family arrangement, the last prairie-dog would
long since have been unearthed and eaten. As it is, the rattlesnake gets
a den for nothing, while the prairie-dog sleeps securely under the
guardianship of his poison-tongued confederate. The owl, I presume,
either pays _his_ scot by hunting mice and insects for the general
account, or by keeping watch against all felonious approaches. Even man
does not care to dig out such a nest, and prefers to drown out the
inmates by pouring in pail after pail of water till they have to put in
an appearance above ground. The only defense against this is to
construct a prairie-dog town as far as possible from water, and this is
carefully attended to. I heard on the Plains of one being drowned out by
a sudden and overwhelming flood; but of the hundreds I passed, not one
was located where this seemed possible.

Absence of rock in place--that is, of ridges or strata of rock rising
through the soil above or nearly to the surface--has determined the
character not only of the Plains but of much of the roll of the great
rivers east and south of them. Even at the very base of the Rocky
Mountains, the Chugwater shows a milky though rapid current, while the
North Platte brings a considerable amount of earthy sediment from the
heart of that Alpine region. After fairly entering upon the Plains,
every stream begins to burrow and to wash, growing more and more turbid,
until it is lost in 'Big Muddy,' the most opaque and sedimentary of all
great rivers. I suspect that all the other rivers of this continent
convey in the aggregate less earthy matter to the ocean than the
Missouri pours into the previously transparent Mississippi, thenceforth
an unfailing testimony that evil company corrupts and defiles.
Louisiana is the spoil of the Plains, which have in process of time
been denuded to an average depth of not less than fifty and perhaps to
that of two or three hundred feet. I passed hills along the eastern base
of the Rocky Mountains where this process is less complete and more
active than is usual,--hills which are the remaining vestiges of a
former average level of the plain adjacent, and which have happened to
wear away so steeply and sharply that very little vegetation ever finds
support