This most interesting and useful arm of the military service is perhaps, less heard of by the public than any other; and its invaluable labors, as well as its frequent imminent perils, are alike unrecorded, and, therefore, unappreciated. The signal officer who would bring late and full news to the commanding General must undergo not a little fatigue and hardship. He must climb high trees to watch the enemy; he must penetrate through tangled thickets and forests, in search of eligible stations; he must climb the sides of steep and rugged mountains, and his bright and showy flag never fails to attract the rebel sharpshooter’s fire when he is in reach, which he must often be to secure a good post, or observe the enemy.
When once a station is established, his flag must never droop by day nor his torch grow dim by night, till he has orders from his chief to abandon his post for a new one. And yet so great is the mystery with which he must enshroud his art, so profoundly secret must he keep the weighty messages and orders confided to him, and so silent are his operations, that the world and even the army know little about him. He alone is proof against the wiles of those “universal walking interrogation-points,” the correspondents, though he, above all others, is the man whom they would delight to be permitted to “use.” But he has his reward for all this. In the clear upper air where he dwells, he sees, as with a hawk’s eye, the whole great drama played out beneath him; he sees the long lines of men deployed through the valleys, and knows where they go, and why; his eyes feast upon the field of battle, where the columns of attack rush impetuously down a wooded slope, across an open field, and up into another piece of wood, and all is clear to him and intelligible, while, to others who must grovel on the ground, there is nothing but an exasperating muddle.
Signal stations are of two kinds; reflecting stations and stations of observation; the former for transmitting dispatches, the latter for watching the enemy and communicating the results to the commander. Both are constructed on the same principles, and employ the same instruments. The latter are few and simple. The flag is made of different colors, to contrast with the line of the background, white, black, or red. The one usually employed is but four feet square; for the largest distances it is made six feet square, and mounted on a third joint of staff to give it wider range. The marine glass is used for scanning the horizon rapidly, and making general observations; the telescope for reading signals at a great distance, and observing fixed points minutely. Besides these there is a certain mysterious pasteboard disc, stamped with a circle of figures, and a sliding interior one of letters corresponding to each. This is the key and clew of the whole matter, and to the uninitiated is, of course, impenetrable.
When a message is about to be sent, the flagman takes his station upon some elevated object, and “calls” the station with which he desires to communicate by waving the flag or torch slowly to and fro. The operator, seated at the glass, watches closely the distant flag, and as soon as it responds by dipping, he is ready to send his dispatch. Holding the written message before him, he calls out to the flagman certain numbers, each figure or combination of figures standing for a letter. The flagman indicates each separate figure by an ingenious combination of a few very simple motions. For instance, one stroke of the flag from a perpendicular to a right horizontal, indicates one figure; a stroke to the left horizontal, indicates another; a stroke executing a half circle, another, &c. After each motion indicating a figure, the flag returns always to a perpendicular. There are a few syllables which are indicated by a single stroke of the flag; otherwise the word must be spelled out letter by letter. Experienced signal officers, however, employ many abreviations by omitting vowels, &c., so that scarcely a single word, unless a very unused one, is spelled out in full.
When a message is being received, the operator sits at the glass, with the flagman near to record it. This the operator then interprets, for not even the General himself is in the secret, and by supplying the omitted vowels, &c., makes out an intelligible piece of the king’s English.
The rapidity with which all this is executed by experienced operators is astonishing. The flag is kept in such rapid motion that the eye of the inexpert can scarcely follow, and his wonder is increased by being told that the reader, of whom he cannot see the slightest indication with his naked eye, is ten or twelve miles away. An ordinary message of a few lines is despatched in ten minutes; a whole pge of foosscap occupies about thirty minutes in its transmission. Officers who have long worked together, and are intimately acquainted with each other’s abbreviations and peculiar expressions, can improve upon even this speed.
The distance also through which signals can be transmitted, without an intermediate station, is surprising. Captain Leonard, a chief signal officer of the Fourth Corps, sent despatches regularly from Ringgold to Summerville, on Lookout Mountain, a distance of eighteen miles. Lieut. William Reynolds, formerly of the Tenth Corps, signalled from the deck of a gunboat twenty miles into Port Royal harbor. N. Daniels was sent by the Secretary of War, to Maryland Heights to give information of the enemy’s movements, and he succeeded in sending messages rapidly over the extraordinary distance of twenty-four miles–from the Heights to Sugar-loaf Mountain–four miles from Frederick. But these instances require remarkably favorable conditions of the atmosphere, locality, &c. Ordinarily. messages were not sent a greater distance than six or eight miles.