to battle. The Spaniards marched on to sufferings
and death, and darkness again closed around the Etowah Mound. When
the Europeans next beheld it around it was the silent wilderness; the
warriors had departed; the trees of the forest overspread it.

We have now described the principal mound structures, and shown the
different classes into which they are divided. But a large class of
mounds are found scattered all through the Mound Builders' territory
that were probably used as signal mounds. Burial mounds were also often
used for this purpose.<41> This was because their location was always
very favorable for signal purposes. Signaling by fire is a very ancient
custom. The Indians on our western plains convey intelligence by this
means at the present day. Some tribes use such materials as will cause
different shades of smoke, using dried grass for the lightest, pine
leaves for the darkest, and a mixture for intermediate purposes. They
also vary the signal by letting the smoke rise in an unbroken column,
or cover the fire with a blanket, so as to cause puffs of smoke. The
evidence gathered from the position of the mounds, and traces of fire on
their summit, is that the Mound Builders had a very extensive system of
signal mounds.

Illustration of Hill Mounds.---------------

To illustrate this system, we would state that the city of Newark, Ohio,
was the site of a very extensive settlement of the Mound Builders.
This settlement was in a valley, but on all the surrounding hills were
located signal mounds. And it is further stated that lines of signal
mounds can be traced from here as a center to other and more distant
points. The large mound at Mt. Vernon, twenty miles to the north, was
part of this system. As the settlements of the Mound Builders were
mostly in river valleys, we would expect to find all along on the bluffs
fronting these valleys traces of signal mounds. In the Scioto Valley,
from Columbus to Chillicothe, a distance of about forty miles, twenty
mounds "may be selected, so placed in respect to each other that it is
believed, if the country was cleared of forests, signals of fire might
be transmitted in a few minutes along the whole line." Some think
the chain is much more extensive than this, and that the whole Scioto
Valley, from Delaware County to Portsmouth, was so provided with mounds
that signals could be sent in a very few minutes the whole distance.<42>

Illustration of Miamisburg Mound.-----