Masters of Space - Morse, Thompson, Bell, Marconi, Carty | Page 4

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 of one Roman galley communicated with another came with the introduction of cannon as a naval arm. The use of signal-guns was soon thought of, and war-ships used their guns for signal purposes as early as the sixteenth century. Not long after came the square-rigged ship, and it soon occurred to some one that signals could be made by dropping a sail from the yard-arm a certain number of times.
Up to the middle of the seventeenth century the possibilities of the naval signal systems were limited indeed. Only a few prearranged orders and messages could be conveyed. Unlimited communication at a distance was still impossible, and there were no means of sending a message to meet an unforeseen emergency. So cumbersome were the signal systems in use that even though they would convey the intelligence desired, the speaking-trumpet or a courier was employed wherever possible.
To the officers of the British navy of the seventeenth century belongs the credit for the first serious attempt to create a system of communication which would convey any and all messages. It is not clear whether Admiral Sir William Penn or James II. established the code. It was while he was Duke of York and the commander of Britain's navy, that the James who was later to be king took this part in the advancement of means of communication. Messages were sent by varying the position of a single signal flag.
In 1780 Admiral Kempenfeldt thought of adding other signal flags instead of depending upon the varied positions of a single signal. From his plan the flag signals now in use by the navies of the world were developed. The basis of his system was the combining of distinct flags in pairs.
The work of Admiral Philip Colomb marked another long step forward in signaling between ships. While a young officer he developed a night-signal system of flashing lights, still in use to some extent, and which bears his name. Colomb's most important contribution to the art of signaling was his realization of the utility of the code which Morse had developed in connection with the telegraph.
Code flags, which are largely used between ships, have not been entirely displaced by the wireless. The usual naval code set consists of a set of alphabet flags and pennants, ten numeral flags, and additional special flags. This of course provides for spelling out any conceivable message by simply hoisting letter after letter. So slow a method is seldom used, however. Various combinations of letters and figures are used to indicate set terms or sentences set forth in the code-book. Thus the flags representing A and E, hoisted together, may be found on reference to the code-book to mean, "Weigh anchor." Each navy has its own secret code, which is carefully guarded lest it be discovered by a possible enemy. Naval code-books are bound with metal covers so that they may be thrown overboard in case a ship is forced to surrender.
The international code is used by ships of all nations. It is the universal language of the sea, and by it sailors of different tongues may