ombinations 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.

The introduction of the Morse code and its adaptation to signaling by
sight and sound did much to simplify these means of communication. The
development of signaling after the adoption of the Morse code, though
it occurred subsequent to the introduction of the telegraph, may
properly be spoken of here, since the systems dependent upon sight and
sound grow from origins more primitive than those which depend upon
electricity. Up to the middle of the nineteenth century armies had
made slight progress in perfecting means of communication. The British
army had no regular signal service until after the recommendations
of Colomb proved their worth in naval affairs. The German army, whose
systems of communication have now reached such perfection, did not
establish an army signal service until 1902.