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"A Manual of Signals: For The Use Of Signal Officers In The Field."
Washington, D.C., 1864.
Part III
" TO WORK SIGNALS IN THE FIELD."
"Cavalry Raids.---When the presence of a cavalry force is heard of in the vicinity of an army, or as moving through any section of the country, a signal party should at once be sent to follow it as closely as they may, to report upon its movements, and to annoy it by indicating its position to such of our troops as may be in pursuit. These signal parties fire, at different times, at night, rockets or roman candles, to show the general direction in which the enemy may be. During the day, cartridge-puffs or heavy smokes should be raised, for the same purpose. To this end of attracting attention and directing the march of friendly troops upon the enemy, if there is a known chance to capture or destroy them, hay-stacks, wood-piles, or out-buildings, ought to be fired (using proper judgment), anywhere they may be found in the country lying near the line of the enemy's march; the officer ordering the firing, giving a certificate to the owners, that the property was fired for Government uses. The firing of these signals, of any kind, must follow the track of the enemy from place to place. It is the object to thus mark his course, that preparations may be made in his advance to intercept him, or that troops in pursuit may know in what direction to march or to concentrate. So in front of an enemy, presumed to be advancing on any roads, small signal parties should be sent out on every road. These parties are to fall back, firing signals, raising smokes, or kindling fires, as the enemy advances. Some of the parties ought to conceal themselves near the roads, to gain all the information they can before reporting; others to wait, with the signals ready to be fired, and only light them when the foe drives them from their position. Thus a cartridge-puff may be raised at the last moment it is safe to remain at a station. A few daring men can thus cause infinite annoyance to an enemy, whose success is often depending on the secrecy of his movements. In all cases of this kind, a dominant station or stations, must be chosen somewhere, from which the signals made, in any part of the country, can at once be noted and reported, and whence reports must frequently go to the senior commander in the vicinity, and to the General Commanding. A constant watch must be kept from this position; and signals seen, in any part of the country, must be at once reported as to the distance, kind, and direction.
If communication is to be between ships in a bay or river, the officers will consult together, if possible, before parting, as to the place at which the ships will probably be, the color of the flags it will be best to use, and in what direction, by compass, the vessels will be from each other. They will consider, also, whether signals will be preferably made from the decks or the rigging, as the "tops," and whether the make of the land or river bank, is such that is is likely the hulls of the vessels will be hidden from each other, as by rising grounds or by trees. It is possible this will be the case. It will be considered, also, whether the masts will show above the trees, and how much of them will show. To ascertain this point, the officers should, together, ascent the rigging and estimate the height of the obstacles in the direction in which it is supposed the signalling will be necessary.
When vessels, co-operating with land forces, are to go into action, the post of the signal officer is on the "fore," or in the "maintop." A signal flag should always be kept flying from some prominent position on every vessel carrying a signal officer. Signal officers, serving with troops, or on other vessels, can thus know with what ships it is possible to have verbal communication.
The officers at each signal station must take care that a look-out through the glass, is kept at each station so constantly that no signal can be shown, at any time, at the communicating station, for more than ten minutes without receiving an answer. For this reason, when not at the glass himself, he will cause his men, or any one on duty at the station, to keep a regular "glass-watch," assigning the men by turns, and fixing particular hours for each, that responsibility for neglect may be easily traced. These details will relieve each other every two or four hours, day and night. The watchmen on duty must be seated at the glass; and before assuming his station must, with the aid of the soldier last on duty, make certain that he knows the exact position of the observed station, and that it is plainly in the field of the glass. This precaution is particularly necessary at night, when the least movement of the glass may have thrown the station out of view. All land marks being then invisible, there is nothing by which to detect the error; and signals might be long shown in vain at one station, while the glass not bearing upon them is attentively watched at the other.
Torches.---As a general rule, if stations are not more than ten miles distant, the regulation torch-light, shown in motion at one, will be seen with the naked eye, or the marine glass, at the other, as a light sufficiently strong to attract attention.
Establishing Signal Stations.---When high winds interfere with the proper display of flags, or other signals, at any position, the signal station there ought to be established in the lee of a grove, or sheltered by a house or hill. It will sometimes happen that, signals made from a given position, cannot be seen; while, near that position, is a point at which a sky-exposure, or other advantage, can be had, which will make the signals there visible. In such case, the receiving station should direct the sending station where to place the flag man. This may be done by the usual signal of the codes prepared for the purpose, or by an especial message.
When the color of a signal flag to be used at any station has been determined upon, and the flag-man has been placed, it may yet be necessary to decide, whether there are any obstacles to a clear vision existing between the stations. For this purpose, view the station to which communication is to be had, from the sending station, with a telescope; first from a position close to the ground, at the feet of the flag-man, and then from two other points, close to the ground: one on his right, and one on his left, and at a distance from him, equal to the length of the signal staff to which the flag is attached. If, from these three points, the position of the telescope at the other station, or the whole position on which the flag-man there stands, can be seen, it is certain that every signal made at the first station can be seen at the other. Similar precautions to determine this point, should be had at both; such precautions are particularly called for at night. The foot-torch, lying close to the ground, is often hidden by bushes or high grass near it, and night-signals are thus made unintelligible. Signalling should never be commenced at night, at any station until, with the head as near the ground and in the place at which the foot-torch will be, the receiving station has been observed, and made sure, that the foot-light shown at the first, will be plainly visible there. When a station is occupied and worked during the day, all preparations for night signals, such as filling the torches, properly placing them, determining that, when lighted, they will be in view of the other, etc., should be made before dark. When this is impossible, as when the station is first reached at night, it may be held, that it is fair to presume, that any point at one station from which fires or foot-lights known to be at the other are visible, is in proper view from that station.
Glasses--When a signal station is to communicate with two or more stations, a telescope should be firmly fixed, bearing on each, and so far apart that the reader at one will not be in danger of disturbing the reader at the other by his movements. At permanent stations, the fixed telescopes should not be removed from their supports when signalling has ceased for a time, unless it may be necessary to clean them; but they should be kept in position carefully covered to protect them from the weather.
When the atmosphere is ladened with moisture, the object and other glasses of the telescope being cold, sometimes condense it, and become covered with a thin film or mist; this is especially likely to happen at night. It should always be suspected when, while the might seems clear and lights can be seen with the naked eye, they are seen with difficulty with the glass. To remedy this, the glass ought to be thoroughly warmed at a fire, or with a lamp, and made so warm as to retain its heat while it is being used to receive messages. The eye-glass of the telescope is sometimes obscured by the moisture of the breath condensing upon it while the eye is at the glass; this ought to be carefully guarded against.
Telescopes ought never be allowed to fall into the hands of the enemy. Officers, on dangerous stations, ought to conceal their glasses when not in use. When a glass is to be hidden for precaution, the object lens, or one joint of the telescope, should be hidden separately from the body of the telescope. A single joint or one lens is so small an object, that it can be concealed almost beyond the possibility of discovery. If an officer is in danger of capture, and there are no means of concealment, the telescope glasses must be shattered or rendered worthless rather than surrendered.
If, for any reason, telescopes have not been fixed on communicating stations during the day, they must be fixed and adjusted before dark. After dark, land-marks are lost to view, and distant stations are discovered with difficulty. The glass must have in its field the exact point at which night signals are to appear, and must so remain, properly sheltered, until morning. The neglect of this care, often causes much trouble. The telescope should always, when possible, be first placed in rest and properly adjusted in some sheltered or shaded position, and in one as convenient as attainable, before communication is opened, for after communication is opened, important messages may come so rapidly, that the glass cannot be abandoned, and the station must be worked for hours with much of discomfort and even of suffering, on the part of the reading officer.
To adjust a telescope to its proper focus, view with it some object with well defined outlines at a distance of about half a mile, lengthening or shortening the eye-glass joint until the object is seen with the sharpest distinctness. To adjust a glass at night, fix it upon some brilliant star.
Glasses which are to be used in the field, should have plainly marked upon one of the eye-glass slides a focus mark, so that they may be adjusted at any time without an especial adjustment in every case.
Telescopes, as a general rule, absorb light in proportion as their magnifying power is great. The most powerful glasses are therefore to be used for minute observations on the clearest days, or where there is a strong light upon the observed object. When the light is fading, or there is little light upon the observed object, the clearer view will be had by those glasses of low magnifying power. When telescopes are fitted with a double adjusting focus, the short focus is to be used, where the light is dim, the long focus where the light is strong.
Old newspapers furnish the best material with which to clean lenses. The pieces to be selected, should be free from grit or anything to scratch the glass. Soft paper is better than chamois skin. The telescope glasses ought to be kept scrupulously clean. If the glass is to be carried in the rain, a leather cap must always cover the eye-piece end. Without this precaution, the glass will be filled with water, and may be ruined.
Binocular glasses (marine glasses) have, with a low magnifying power, an extensive field of view, and give much light. They are for use in observation of extensive movements, where large tracts of country must be taken in one field of view, or in sweeping the landscape in view, to find the tents of the enemy, his wagons, etc., or other objects to be afterwards more closely examined with the telescope. They are employed on ship board, or in boats, where the rolling motion interferes with the use of the telescopes. They are used for observations to be made on horseback, or in hasty examinations made on foot or in trees, and generally for all observations not critical, or those to be made under circumstances where the telescope cannot be conveniently handled. The marine glass ought to be held by both hands when in use; and to steady it, the arms ought to be kept close to the body. In following a moving object, to keep it in the field of view, the head ought to be turned with the glass. For reading signals at short ranges, as say, up to five miles, these glasses are better than the telescope. Signals have been frequently read with glasses of this description at the distance of ten miles.
When reading messages through the telescope, or observing any object intently in bad weather, cover the head with a blanket, or the cape of an overcoat, or any dark covering, extending this covering over all the telescope except the object glass: particularly do this when exposed to a dazzling light, or the sun's heat, or in windy weather. The covering shuts out from view all objects near the observer, and thus enables the faculties to be concentrated, and, at the same time, it protects the eye from the disturbing light, the winds, particles floating in the air, etc.
It should be practiced to use both eyes open at the telescope. This can be readily done. The method is more comfortable than to use but one eye, and by it is prevented much of that weariness and injury to the eyes that often follow if they are overstrained, or too much labor is thrown upon them.
To find any small object, as a signal-man or flag near any known position, or to fix the telescope upon it, mark, with the naked eye, some prominent land-mark, or object near which the smaller object is supposed to be, place that telescope carefully adjusted in rest, then sight over the glass upon the marking object near which the smaller object is supposed to be, place the telescope carefully adjusted in rest, then sight over the glass upon the marking object, as sight is taken over a gun-barrel; if the eye, the object being thus covered, is now placed at the eye-glass of the telescope, the prominent or marking object will be found in the field of view. It will be easy then to scan the country near the marker until the smaller object is found. This practice is often necessary at night, when only a point of light is seen, far off through the darkness, and the telescope must be turned upon it. When the compass-bearing of the object to be sought for is known, the telescope, adjusted and placed in rest, may be aligned by a line drawn with the proper compass-bearing. Commencing then with the view at the horizon, the telescope is moved lightly from side to side, taking in, each time, fresh fields of view a little nearer the observer, until the whole country shall have been observed from the horizon to quite near the station. When the general direction only of an object can be given, and it is to be sought for, the whole landscape in that direction to the horizon, is to be divided into sections by imaginary lines, the limits of these sections being bounded between visible land marks through which the bounding lines are supposed to pass. Each section is then to be scrutinized, little by little, until the glass has been passed over every spot. The search can hardly fail to be successful. It must be systematic.
Practice should be had in the use of the telescope held in the hands without rest, in rapidly bringing objects in the field of view, and in the habit of examining an object or point thoroughly, yet quickly. Observations can often be made with such rests as the shoulder of a man, over the back of a saddled horse, or with a cane resting on the ground and held in the hand that steadies the telescope. Very great quickness in the bringing of objects within the field of view can be soon acquired. The eye becomes educated to a remarkable keenness of vision by continual practice. When observations are made with the telescope, or when messages are being received by it by signals, nothing must be taken for granted, and nothing considered as seen, until it has been positively in view, and so clearly as not to admit of doubt. Never presume to anticipate what signals will follow from those already made. A signal must never be considered, or announced as read, until it has been actually seen. Carefully watch the communicating station, until the last signals are made, and be very certain, before ceasing to watch, that the signal for the end of a message has been distinctly given.
The telescope on a signal station should always be fixed. The glass stand or support may be a heap of stones, two saddles lashed together, a temporary tripod of sticks, a post, a stump, fence, anything furnishing a steady rest. Blankets, thickly folded, or any cloth, as an overcoat, a cushion or a pillow, placed under the glass, almost entirely prevents vibration. Stones, or other heavy bodies, ought to be placed on and about the glass, in order to secure it in its place and to steady it. The brass telescope holder, fitted to screw into trees or other wooden supports, is very useful. Trees, having branches and leaves, are apt to be shaken by the wind; for this reason, a fence corner, a stump, or solitary post, or rock should be chosen in preference. It is important so to construct a support, as to allow the person at the glass a comfortable position when reading, and it should be firm enough to withstand any ordinary gust of wind, or other slight disturbing cause. At a post or fixed station, it is well to construct a permanent glass-stand, and to shelter it with a good tent or sentry-box."
