er races to erect
a mound on which to place their temples, their idols, and altars of
sacrifice.

If mounds were the only works remaining of these ancient people, we
would not take so great an interest in them, and, as it is, we are not
to suppose that all the mounds are the works of those people we call the
Mound Builders. Recent investigation and historical evidence unite in
showing that some comparatively recent Indian tribes formed and used
mound structures. Early explorers have left abundant testimony to show
that in many cases the Indians resorted to mound-burial. Thus, it seems
that it was the custom of the Iroquois every eighth or tenth year, or
whenever about to abandon a locality, to gather together the bones of
their dead and rear over them a mound. To this custom, which was not
confined to the Iroquois, are doubtless to be ascribed the barrows and
bone mounds which have been found in such numbers in various parts of
the country.<17> Although it is well to bear these facts in mind, yet it
is not doubted that the larger number, and especially the more massive
ones, were erected by the same people who built the other mysterious
works, and so it is necessary that they be carefully studied.

Illustration of Altar Mound.-------------------

In the valley of the Ohio there have been found a class of mounds known
as Altar Mounds. These, it should be stated, nearly always occur in or
near inclosures. This cut gives us a good idea of mounds of this kind.
Near the top is seen an instance of what is called "intrusive" burial.
After the mound was completed it had been dug into and a body buried
near the surface. This burial was evidently later in time, and had no
connection with the purpose for which the mound was originally built. We
also notice in this mound the different layers of which it was composed.
These layers are of gravel, earth, and sand, the latter being only a few
inches thick. Mounds made in this manner are called stratified
mounds, and all altar mounds are probably of this kind. The lines of
stratification have been described as curving so as to correspond with
the shape of the mound, and such we are told is the general rule.<18>

Illustration of Plan and Section of Altar.---------

The peculiar feature, however, is the altar at the bottom of the mound,
directly above the natural surface of the ground. The small cut gives us
a clear idea of the altar, the light lines running around it showing