which were the marks of an axe. Cedar shovels,
mauls, copper gads or wedges, charcoal, and ashes were discovered, over
which "primeval" forest trees had grown to full size.

Modern mining on Lake Superior began effectively in 1845. The whole
copper region has not been fully explored. Works of the ancient miners
are found at all the mines of any importance; and they show remarkable
skill in discovering and tracing actual veins of the metal. Colonel
Charles Whittlesey, one of the best authorities on this point, believes
the Mound-Builders worked the copper-beds of that region during "a great
length of time," and more of their works will undoubtedly be explored
when the forests shall be cleared away from those portions of the copper
region not yet worked by modern miners. So far as they have been traced,
they every where show the same methods, the same implements, and the
same peculiarities of both knowledge and lack of knowledge in the old
miners.

II.

ANTIQUITY OF THE MOUND-BUILDERS.

That the Mound-Builders and their works belong to a distant period in
the past is evident; but, of course, we have no means of determining
their antiquity with any approach to accuracy, no scheme of chronology
by which their distance from us in time can be measured. Nevertheless,
some things observed in their remains make it certain that the works are
very ancient.

1. One fact showing this is pointed out by those who have examined them
carefully as follows: None of these works (mounds and inclosures) occur
on the lowest-formed of the river terraces, which mark the subsidence of
the western streams; and as there is no good reason why their builders
should have avoided erecting them on that terrace, while they raised
them promiscuously on all the others, it follows, not unreasonably, that
this terrace has been formed since the works were erected. It is
apparent, also, that in some cases the works were long ago partly
destroyed by streams which have since receded more than half a mile, and
at present could not reach them under any circumstances. Those streams
generally show four successive terraces, which mark four distinct eras
of their subsidence since they began to flow in their present courses.
The fourth terrace, on which none of the works are found, marks the
last and longest of these periods; and it marks also the time since the
Mound-Builders ceased to occupy the river-valleys where it was formed.
The period marked by