is recorded of the Argonautic Expedition. Theseus devised the use of
colored sails to convey messages from ship to ship of the fleet, and
caused the death of his father by his failure to handle the signals
properly. Theseus sailed into conflict with the enemy with black sails
set, a signal of battle and of death. With the battle over and himself
the victor, he forgot to lower the black flag and set the red flag of
victory. His father, the aged Ægeus, seeing the black flag, believed
it reported his son's death, and, flinging himself into the sea, was
drowned.

In time it occurred to the great monarchs as their domains extended
to establish relays of couriers to bear the messages which must be
carried. Such systems were established by the Greeks, the Romans, and
the Aztecs. Each courier would run the length of his own route and
would then shout or pass the message to the next runner, who would
speed it away in turn. Such was the method employed by our own
pony-express riders.

An ancient Persian king thought of having the messages shouted from
sentinel to sentinel, instead of being carried more slowly by relays
of couriers. So he established sentinels at regular intervals within
hearing of one another, and messages were shouted from one to the
other. Just fancy the number of sentinels required to establish a line
between distant cities, and the opportunities for misunderstanding and
mistake! The ancient Gauls also employed this method of communication.
Cæsar records that the news of the massacre of the Romans at Orleans
was sent to Auvergne, a distance of nearly one hundred and fifty
miles, by the same evening.

Though signaling by flashes of light occurred to the ancients, we have