Many crude systems of using lights for signaling were employed. Lines of watch-towers were arranged which served as signal-stations. The ruins of the old Roman and Gallic towers may still be found In France. Hannibal erected them in Africa and Spain. Colored tunics and spears were also used for military signals in the daytime. For instance, a red tunic displayed meant prepare for battle; while a red spear conveyed the order to sack and devastate.
An ancient system of camp signals from columns is especially interesting as showing a development away from the prearranged signals of limited application. For these camp signals the alphabet was divided into five or six parts, and a like number of columns erected at each signal-station. Each column represented one group of letters. Suppose that we should agree to get along without the Q and the Z and reduce our own alphabet to twenty-four letters for use in such a system. With six columns we would then have four letters for each column. The first column would be used to signal A, B, C, and D. One light or flag shown from column one would represent A, two flags or lights B, and so on. Thus any word could be spelled out and any message sent. Without doubt the system was slow and cumbersome, but it was a step in the right direction.
The American Indians developed methods of transmitting news which compare very favorably with the means 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.