the Mound-Builders are much more
than two thousand years old.

Those familiar with the facts established by geologists and
palaeontologists are aware that remains of human skeletons have been
discovered in deposits of the "Age of Stone" in Western Europe; not to
any great extent, it is true, although the discoveries are sufficient to
show that fragments of skeletons belonging to that age still exist. It
is not without reason, therefore, that the condition of decay in which
all skeletons of the Mound-Builders are exhumed from their burial-places
is considered a proof of their great antiquity. There is no other
explanation which, so far as appears, can be reasonably accepted.

3. The great age of these mounds and inclosures is shown by their
relation to the primeval forests in which most of them were discovered.
I say _primeval_ forests, because they seemed primeval to the first
white men who explored them. Of course there were no unbroken forests at
such points as the Ohio Valley, for instance, while they were occupied
by the Mound-Builders, who were a settled agricultural people, whose
civilized industry is attested by their remains. If they found forests
in the valleys they occupied, these were cleared away to make room for
their towns, inclosures, mounds, and cultivated fields; and when, after
many ages of such occupation, they finally left, or were driven away, a
long period must have elapsed before the trees began to grow freely in
and around their abandoned works. Moreover, observation shows that the
trees which first make their appearance in such deserted places are not
regular forest trees. The beginning of such growths as will cover them
with great forests comes later, when other preliminary growths have
appeared and gone to decay.

When the Ohio Valley was first visited by Europeans it was covered by an
unbroken forest, most of the trees being of great age and size; and it
was manifest that several generations of great forest trees had preceded
those found standing in the soil. The mounds and inclosures were
discovered in this forest, with great trees growing in them. Eight
hundred rings of annual growth were counted in the trunk of a tree
mentioned by Sir Charles Lyell and others, which was found growing on a
mound at Marietta. In the same way, successive generations of forest
trees had grown over their extensive mining works near Lake Superior,
and many of those works are still hidden in what seem to be pri