"A Manual of Signals: For The Use Of Signal Officers In The Field."
Washington, D.C., 1864.
POSITION OF FLAGMEN,
ATTEMPTS TO ATTRACT THE ATTENTION OF A STATION.
The position of a flagman, transmitting a message, must be exactly facing the point to which the message is being sent; and this must be the case, whatever the style or character of the signal he is using. Signals, of whatever description, made by the flag man, must also be exactly shown on his right and left. In other cases, they will not be clearly displayed to the observer. To determine this exact position, a line, direct to the other station, should be sighted, as over a straight rod for instance, and a line following this direction should be marked on the ground in front of the signal man. A line drawn at right angles with this line should extend on each side of the signal-man. If the common signal equipment is to be used, a marking stake should be drawn on the line in front of the flagman, and twelve feet distant from him; and a similar marker should be placed at the same distance on the side lines on either side.
All signals must be made with reference to the directions indicated by these stakes. These lines must be established by daylight, if possible. The use of the markers, secure the most perfect display of the signals by day, and is even more manifestly valuable at night, when the communicating station becomes invisible. The flagman has three other guides, by which to determine the proper direction in which his signals must be shown.
A signal-man, transmitting messages, should always be placed a little in advance of the person at the glass, in order that errors made in forming any signal may be noticed and corrected.
When signals are made with torches and the ordinary apparatus, at night, the signal-man must stand immediately behind the foot-light, a relates to the other station, and the flying-light be so handled that when brought to the front and lowered to the ground, as to make pause-signals. Its flame, observed from the communicating station, will seem to mingle with the foot-light. When large, common fires are burning at or near the station at night, care must be taken that they are so placed as not to confound the view of the torch-signals, or other lights that may be shown. The signal-man must be placed well to one side of the fire, and his signals must be displayed out of the line of sight from the fire to the communicating station.
The light of large fires, burning near, will often interfere, at night, with the use of the glass. The best location for the glass is, in these circumstances, in advance of the fire. The signalman; making either day or night-signals, ought to be placed a little in advance of, and to one side of the officer at the glass in charge of the station.
Care must be taken to so place the signal-man that the glare of the torches or lights will not interfere with the use of the telescope.
ATTEMPTS TO ATTRACT THE ATTENTION OF A STATION.
In order to be persistence, should never be abandoned, until every device has been exhausted; and they should be renewed and continued at different hours of the day and night. It must always be remembered, that attempts which have failed, may have failed because the observer's attention has been drawn in another direction, and that the effort may, at any other moment, be a success, if the observing glass chances to bear on the calling signals.
When a station is found, fix the telescope steadily upon it, and keep it observed while signals are made for its attention. As soon as it is perceived, and the attention is gained, signal its number, or call or answer any signals it may make.
Communicating stations should always arrange a few pre-concerted signals for either day or night use. These signals should be of such character as this: "Wait a moment." "I see you, but cannot reply." "Cease signalling: will call you soon." This will prevent the sometimes occurring annoyance of calling a station for hours when the signals, though seen cannot, for some reason, be answered.
A signallist, observing from an elevated station, and finding his own view of the communicating station uninterrupted, may be led to imagine that the station on which he stands, is more prominently visible, from the communicating station, than is the case in fact. Thus a person viewing, from the top of a house, may think the whole house is in view from the observing station, when in fact nothing but the roof can be thence seen. To determine whether any station is clearly in view from any other, the observing station must be viewed from the ground, and from different positions close to the station. If the station can be well seen from these different points, that form which the observations are made must of course be plainly visible.
When any station has signalled all the messages on hand, the signal to cease signalling must invariable be made. When nothing more is to be for the time sent from either station, both will make the "cease signalling" signal. The observer, or officer, must never leave his station, or cease to watch the communicating station, until this signal has been exchanged by both stations. It must never be presumed that a station has ceased to work until it has announced this fact by signal.
Stations ceasing to work for a short time only, will display a flag flying, and stationary. This is a signal that the communicating station may be called at any moment.
So long as this signal is made, an observer will be kept at the glass.
When a number of stations are in view from one dominant station, some preconcerted signal, as a rocket, a red light, or some peculiar flag or torch-signal, or cartridge-puff, should be agreed upon as a signal for general attention. Upon noticing this signal, all the stations reply, and then observe the dominant station. This plan is useful when two or more stations can at the same time read the signals from the prominent station, and thus together receive any information to be transmitted from it.
When a number of stations are working in concert, certain fixed hours of the day and night should be named by proper authority for the especial exchange of messages; at which hours, each station may be certain that those on duty at every other station will be observant and ready for business.
All persons on duty should make it a point to be faithfully at their posts at these hours, even if communication may seem to be impossible.
It will be found sometimes possible to signal between elevated peaks, when all the landscape of the lower country is deeply buried in fog; and, conversely, a peak will sometimes be wrapped in clouds, when lower down the view is unobstructed. In the former case, messages may be sent by ascending to mountain summits and in the latter case, by descending so as to be below the cloud stratum.
When two stations are communicating at dusk, or when it is growing dark, and a light is shown at the receiving station, it is a signal to the sending station to use there after torches, or lights instead of flags. A light similarly shown at dawn and then extinguished, or a flag then displayed, indicated to the sending station, to cease using lights and to commence using day signals.
While the message is being transmitted by signals, the sending station should constantly observe the receiving station with the telescope, in order that any signals there made to stop the transmission of the message may be instantly seen. These stop signals may be made necessary by any accident at the receiving station. For instance, the telescope there may be thrown out of adjustment, or the connection of the message may have been lost, or by numerous other causes which will render a brief cessation of the signalling desirable. A signal to stop, should be at once recognized by the sending station, and the further sending of the message must be suspended until the receiving station again announces its readiness for work. Stop-signals, of this character, cause much loss of time, and should never, unless absolutely necessary, be made by a receiving station. If part of a message is lost, it is better to receive the remainder, and to then ask for the repetition of the missing portion. In sending very lengthy messages, the precaution should be observed to cease signalling from time to time, and to inquire form the receiving station, if the forgoing has been correctly received. This inquiry may be made by any signal, to which the receiver replies by the usual signal, of message understood, or by other preconcerted signal, as the case may be. Signals in the field, are generally made by a signal-man who, previously drilled, makes each signal by order. These orders, "calling off signals," must be uttered with careful distinctness and precision. A pause is made after each letter combination. When a message is lengthy, a longer pause is made at the end of each sentence, to allow the sentence to be written down by the receiver. Messages must be grammatically correct, and be correctly spelled. The receiver is sometimes confounded by signals made for a word so spelled that it is not recognizable.
The presence of visitors, other than official, should not be encouraged at signal stations of any importance. In an enemy's country, visitors are generally spies, who come under various pretenses, the most innocent, to gather information as to what precise points are in view from the station in order that the enemy may avoid them, and such other items of useful intelligence as they may glean from unsuspecting officers. Visitors should never by allowed to tamper with glasses, to examine messages, or to do any act by which the enemy may gain unnecessary knowledge.
It is sometimes necessary for stations to change positions while working. In this case, the observing station should carefully watch the flag of the moving station, which must be carried flying, in order that it may be readily traced to the new situation. A movement of a station sometimes becomes necessary at the request of a communicating station, to improve the back ground, or the view of the moved station. These movements are often for a few yards only. In such case, the moving station, carrying its own flag flying, must carefully watch the flag of the observing station, which is kept in view in order that it may be so watched, and the movement must be instantly stopped at a signal from the observing station, which indicates when the moving flag has reached the precise position desired.
When stations are certainly in sight of each other, preparations for continued work should be carefully made before the transmission of official messages is commenced.
Officers will always avail themselves of proper precautions to locate their men and themselves in unexposed positions. When in an exposed position, officers and men will lie down, except while transmitting messages. The flag will be kept flying, to indicate the position of the station to those who may be seeking for it, and to the other signal stations with which it may be in communication.
When there is danger of capture, all messages or important papers must be destroyed.
When there is any trouble about the visibility of signals, the largest and brightest flags, or other signals, should at once be used. It will often happen, that after working thus for a short time, the signallist, becoming accustomed to the range, will work successfully with smaller signals.
When, at the receiving station, it is noticed that a change in the color of the signals shown at the sending station would render them more visible, the fact should be immediately stated. When there is any question as to the color of signals to be shown at the different stations, each station should indicate to the other that color most distinctly visible from its own point of view.
Each signallist should have a particular signal by which he can be known.
This signal may be that for any letter or letters of the alphabet. It is known as the "officers signature, or call." It serves to distinguish him, and any message sent by him, and for the correctness of which he is to be held responsible.
By it is also designated the station at which the officer commands. A call, or particular signal, is in like manner generally assigned for each station, to distinguish that station from others.
Whenever these particular calls are seen signalled, it is known that the attention of the officers or the station is desired. The officer or the station should at once respond, making at the close of the response, this same particular signal by which they are identified. The calling station, or officer, should give his own call or signal. There is thus established between the parties a mutual knowledge as to the parties with which each is in communication.
There are times when it will be necessary to read messages, while it is known that the signal-man is facing away from the reader. In this case, the messages will be easily legible, if it is remembered that each signal will appear to the reader to be precisely the reverse of that which is made by the signal-man; thus all those signals displayed on the right will seem to the reader to be shown on the left, while those actually made on the left of the signal-man, will seem to be made on his right. Recalling this fact, it will be as easy to read the signals made at any station from the rear of that station as it is from its front.
When working at night with the common signal equipment of the army, the foot-torch is to be filled as often as it becomes exhausted, without stopping signals or extinguishing its light. While transmitting a message, if it becomes necessary to fill the flying torch, drop the torch to the left, extinguish and fill it in that position, and then light it again a the foot torch; bring it, thus lighted, vertically above the head, which is the signal that the message is to proceed and go on as before. To thus drop the flying-torch at any time to the left and there extinguish it, is a signal that the working has been stopped in order to fill that torch. When a stop is made to fill a torch, it should be at the end of a word or a sentence.
It should be observed with care that the wicks of the signal torches are properly adjusted. If the wicks are too tight, the torch will not burn well. If they are too loose, the turpentine will escape, and it will burn too violently. The wick of a flying-torch is properly trimmed when the flame of the burning torch seems to be about three inches in diameter.
When a flying-torch becomes too much heated while working--a fact which will be known by the signing sound and increased size of the flame---the working must stop for a few minutes, and the torch be held up, the signal staff being kept perpendicular until the flame has diminished to a proper size. A flying-torch should be filled, on the average, every fifteen minutes. If the torch is not kept well filled, it will continue to burn, but the wick will be reduced to a cinder; one wick, properly managed and with care to keep the torch well filled while in use, will last for a week.
When the wind blows from such a direction as by driving back the flame of the foot-torch to render the light of that torch indistinct when viewed from the communicating station, so place the torch as to bring the wind-shade upon it in direct opposition to the wind; and if this should not suffice, build behind the torch a screen, about two feet high and two feet long, of stones, earth, boards, or any other material, so that while the foot-torch is in front of the screen, and in view of the communicating station, its flame will be in the dead air, caused by and in front of the screen.
In cases of emergency, torches may be constructed of pitch pine, old cordage, canvas, rags, or other material, saturated with tar, or with any combustible fluid. Fire-brands, or any lights, will answer the purpose. With the preceding instructions of the manual, the signallist need hardly have in question the devises to be used. Any light that can be visible with any other as a point of reference, will afford sufficient means by which to transmit signal messages in any variety of code of signals.
Communicating stations ought not, when it can be avoided, to be located exactly on an east and west line, or the line of the apparent course of the sun. That station which is in the direction from which the sun shines in any part of its course, is very liable to seem to be enveloped in a haze, and the telescope, if turned upon it, is filled with a dazzling light.
The landscape is often seen as perfectly clear and signals are plainly visible in every direction, excepting towards the rising or setting sun. There is a bright haze. It is better, therefore, that the line of the stations should obliquely cross the apparent course of the sun, and care should be taken to so arrange them. If that cannot be done, the stations lying in the apparent course of the sun, should be so located that they may have a sky exposure when viewed from the communicating station. This obviates, to a very great extent, the difficulty of sun haze; and wherever that difficulty exists, resort should at any time, be had to secure such an exposure for the obscured station.
In the same way, when there are temporary interruptions, as often happens from clouds passing the sun, a sky-exposure secured for the obscured, will render all signals, there displayed legible.
Signal stations should always be chosen as much elevated from the ground as possible, when there is difficulty about smoke or haze or dust. The vibration of the atmosphere, noticeable on a hot summer's day, is always less at a distance from the earth's surface. Thus it is sometimes practicable to read, from a tree or house-top, when it is almost impossible so to read from the ground. This undulation is less also over spots well shaded, than in the glare of the sun. This should be borne in mind in all telescopic examinations. Permanent stations should never be placed in hollows, or on low land, when high ground is attainable. The greatest elevation should invariably be sought. In the cool night air, the smoke and dust of the day lie close to the ground, filling the hollows and obscuring low lands, while the higher points emerge in view like islands. So, too the elevated points are free, to a great extent, from heavy moving mists and the malaria of unhealthy locations. There are these advantages, aside form their better location, for working. By careful selection of high ground, stations can often be worked when signals on the lower fields would be invisible; for these reasons, it is well to have, sometimes, a station for night work on a house-top or in a tree, while during the day the station is worked from the ground."