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 communicate through this common medium.  Any message may be conveyed by a very few of the flags in combination.

The wig-wag system, a favorite and familiar method of communication with every Boy Scout troop, is in use by both army and navy.  The various letters of the alphabet are indicated by the positions in which the signaler holds his arms.  Keeping the arms always forty-five degrees apart, it is possible to read the signals at a considerable distance.  Navy signalers have become very efficient with this form of communication, attaining a speed of over fifteen words a minute.

A semaphore is frequently substituted for the wig-wag flags both on land and on sea.  Navy semaphores on big war-ships consist of arms ten or twelve feet long mounted at the masthead.  The semaphore as a means of communication was extensively used on land commercially as well as by the army.  A regular semaphore telegraph system, working in relays over considerable distances was in operation in France a century ago.  Other semaphore telegraphs were developed in England.