this fourth terrace must be the longest, because
the excavating power of such streams necessarily diminishes as their
channels grow deeper. This geological change, which has taken place
since the latest of the mounds and inclosures were constructed, shows
that the works are very old; no one can tell how old. To count the years
is impossible; but we can see that the date, if found, would take us
back to a remote period in the past.

2. Great antiquity is indicated by the skeletons taken from the mounds.
Every skeleton of a Mound-Builder is found in a condition of extreme
decay. It sometimes appears that the surface of a mound has been used by
the wild Indians for interments; but their skeletons, which are always
found well preserved, can be readily distinguished by their position in
the mounds, as well as by other peculiarities. The decayed bones of
Mound-Builders are invariably found within the mounds, never on the
surface, usually at the bottom of the structure, and nearly always "in
such a state of decay as to render all attempts to restore the skull,
or, indeed, any part of the skeleton, entirely hopeless." Not more than
one or two skeletons of that people have been recovered in a condition
suitable for intelligent examination. It is stated in the work of Squier
and Davis that the only skull belonging incontestably to an individual
of the Mound-Building race, which has been preserved entire, was taken
from a mound situated on a knoll (itself artificial apparently) on the
summit of a hill, in the Scioto Valley, four miles below Chillicothe.

What, save time itself, can have brought these skeletons to a condition
in which they fall to pieces when touched, and are ready to dissolve and
become dust? All the circumstances attending their burial were unusually
favorable for their preservation. The earth around them has invariably
been found "wonderfully compact and dry." And yet, when exhumed, they
are in such a decomposed and crumbling condition that to restore them is
impossible. Sound and well-preserved skeletons, known to be nearly two
thousand years old, have been taken from burial-places in England, and
other European countries less favorable for preserving them. The
condition of an ancient skeleton can not be used as an accurate measure
of time, but it is sufficiently accurate to show the difference between
the ancient and the modern, and in this case it allows us to assume that
these extremely decayed skeletons of