employed by the ancients.
Smoke-rings and puffs for the daytime, and fire-arrows at night, were
used by them for the sending of messages. Smoke signals are obtained
by building a fire of moist materials. The Indian obtains his
smoke-puffs by placing a blanket or robe over the fire, withdrawing
it for an instant, and then replacing it quickly. In this way puffs of
smoke may be sent aloft as frequently as desired.

A column of smoke-puffs was used as a warning signal, its meaning
being: Look out, the enemy is near. One smoke-puff was a signal for
attention; two puffs indicated that the sender would camp at that
place. Three puffs showed that the sender was in danger, as the enemy
was near.

Fire-arrows shot across the sky at night had a similar meaning. The
head of the arrow was dipped in some highly inflammable substance and
then set on fire at the instant before it was discharged from the bow.
One fire-arrow shot into the sky meant that the enemy were near; two
signaled danger, and three great danger. When the Indian shot many
fire-arrows up in rapid succession he was signaling to his friends
that his enemies were too many for him. Two arrows discharged into the
air at the same time indicated that the party sending them was
about to attack. Three indicated an immediate attack. A fire-arrow
discharged diagonally across the sky indicated the direction in which
the sender would travel. Such were the methods which the Indians used,
working out different meanings for the signals in the various tribes.

Very slight progress was made in message-sending in medieval times,
and it was the middle of the seventeenth century before even signal
systems were attained which were in any sense an improvement. For many
centuries the people of the world existed, devising nothing better
than the primitive methods outlined above.

II

SIGNALS PAST AND PRESENT

Marine and Military Signals--Code Flags--Wig-wag--Semaphore
Telegraphs--Heliographs--Ardois Signals--Submarine Signals.

In naval affairs some kind of an effective signal system is
imperative. Even in the ordinary evolutions of a fleet the commander
needs some better way of communicating with the ship captains than
despatching a messenger in a small boat. The necessity of quick and
sure signals in time of battle is obvious. Yet for many centuries
naval signals were of the crudest.

The first distinct advance over the primitive methods by which the
commander o