Naval signals are frequently mentioned by the classical writers, and recent investigation has discovered the fact that the system which prevailed during the naval supremacy of Greece and Carthage bore a striking resemblance to our present army code, invented by Gen. A. J. Myer, U. S. A. Signal flags began to be used in the English navy in the time of Elizabeth, or perhaps a little earlier. In the reign of James II. their use was somewhat systematized, and in 1790 or thereabouts, under Earl Howe and Kempen-felt, a regular code of day and night signals was perfected. Besides flags during the last century, arbitrary signs were used as signals, which were well known to all seafaring people. The signal to unmoor ship, for example, was the loosing of the maintopsail; that to prepare for sailing was loosing the foretopsail and firing one gun. In general there are three classes of signals: those for the day, made by square flags and triangular pennants variously colored of red, blue, white, and yellow; night signals, made with colored lights, rockets, etc.; and fog signals made by steam whistles, fog horns, bells, or guns.

By means of the " International Code of Signals for the use of all Nations," all maritime countries use the same kind of signal flags, and having the signal book of each country printed in its own language, ships of different nationalities communicate as readily with each other as ships sailing under the same flag. In most systems the signal flags represent the numerals from 1 to 10, and in the signal book, corresponding to the numbers from 1 up to several thousand, are words and phrases most likely to be used by ships. But in the code just referred to the consonants of the alphabet were used in preference to numerals, by which means it was found that with 18 flags more than 78,000 distinct signals could be made without displaying more than four flags at a time. The number of flags and their position are also significant. Thus, when but two flags are shown, "danger " or "urgency " is implied. If in a signal consisting of two flags a burgee (a swallow-tail flag) is uppermost, it is known at once to be an " attention " signal. If a pennant is uppermost, it is a compass signal. A square flag above indicates an "urgent" signal. Three flags in one hoist express "latitude, longitude, time," and all ordinary signals required for communications. Four flags indicate geographical signals.

The flags representing the alphabet are for spelling out words not found in the vocabulary. With a pennant above, the name of a ship of war is indicated; with a square flag uppermost, that of a merchant vessel. Observing, then, the colors of each flag, we seek in the signal book the same combination of letters and the corresponding message. Let us suppose, for example, that on the meeting of two ships at sea one is observed to hoist two flags. We know at once it is an urgent signal, and on closer examination find the upper one divided vertically, in white and red, the lower one a red burgee. The upper flag • represents the letter H, the lower one the letter B. The combination H B in the signal book stands opposite the sentence, " Want immediate assistance." Thereupon the second ship hoists a white and red vertical flag (H), and beneath a red pennant with white ball in centre (F). II F in the signal book corresponds to the sentence, "We are coming to your assistance." As each ship has a signal book printed in the language of its country, this code furnishes a kind of universal language. If the ship first mentioned had found herself on a strange coast, she might have made the same signal to a shore station, and received the friendly aid of a life boat.

Should the distance between two points be too great to distinguish colors, the shape alone indicates the value of the signal, for which purpose a ball, a long pennant, and a square flag are used, known as "distance signals." In addition to the above, each national marine has a system of signals adapted to its own particular wants, not only for holding free communication among the ships of a fleet, the transmitting of orders, conveying of intelligence, etc, but to enable the commander-in-chief of a naval force to signal orders to his ships for the various evolutions of naval tactics. A complete naval signal book comprehends therefore a system of evolutionary tactics. For night signals, red, green, and white lights are used to represent those colors in the flags of the day signals, the green light taking the place of the blue bunting. The night signals known as the "Coston lights" are the best in use. - The greatest improvement of recent times in signalling is that made by Gen. A. J. Myer, already referred to. For its perfect simplicity and comprehensiveness it is now considered indispensable to both branches of the public service. The letters of the alphabet are represented by combinations of the numerals 1 and 2 for spelling the words of a message.

Each word is punctuated by a comma represented by the numeral 3; 1, 2, and 3 being represented by arbitrary signs. A, for instance, is represented by 2-2, B by 2-1-1-2, 0 by 1-2-1, etc.; 3 indicates the end of a word, 3-3 the end of a sentence, and 3-3-3 the end of the message. There are also abbreviations. The signals commonly used to represent these numbers are as follows : The signalman, facing his correspondent, waves a flag (at night a lighted torch) to his right to indicate 1, bringing his flag to a rest in a vertical position; to the left to denote 2; and to his front for 3. By waving his flag or torch to his right and left he spells out the words of his message, using frequent abbreviations, so that two expert signalmen may transmit long communications with great rapidity and exactness.