Very superior in visibility and simplicity is Redl's system of cones. This consists of 4 cones fixed to a mast. The cones are collapsable, and are formed in a similar manner to umbrellas.
Their usual condition is shut, and they can only be held open while a rope attached to each is pulled. With cones of 3 ft.
base, signaling is rapid and clear up to 5. m., and the mast can be inserted at any place. The system is very simple: each cone represents a number, 1, 2, 3, or 4; then 1 and 4 shown represent 5; 2 and 4, 6; and so on, as in Fig. 3. This very elegant system can be applied in military or naval operations. But its chief beauty is that a person understanding it can make the same signals without the cones: for example. if a black flag represent anopen cone, and a white flag a shut cone, a ship with 4 back and 3 white flags can make every signal. Again, the arm raised horizontally may represent the open cone; against the body, the shut cone; then two men standing on a cliff are as good as any signal-post—see Fig. 4. Or if one person only be present, he may represent an-open cone by raising his arm with a handkerchief extended, and a shut cone by his arm without the handkerchief. lie has only then to raise his arm four times in -quick succession, with or without the handkerchief, to make the required signal. We have thus arrived at a universal system of the utmost simplicity, which in war, and especially during invasion, might be of inestimable benefit to the nation. The code of signals cannot be too generally diffused by the government, in order that every man among the public may become an amateur signalman on emergency. A secret code, in which the same numbers have different significations, could always be maintained for state purposes.
It only remains to apply the same system to night-signals. The old naval principle has been to hang dingy lanterns in various shapes—triangles, squares, crosses, etc. Besides requiring large bases to be at all visible, this has been found from the motion of a ship to be nearly useless. Redl's system has been applied by hanging four lanterns in a vertical line to represent the cones, and obscuring those which corresponded to shut cones. An improvement was found in introducing a red or green light in the middle, to show the relative position of the four. The best night-signals are, however, flashing lights, as introduced by col. Bolton, and more elaborately by rapt. Colomb, and adopted in the navy. This consists of a bright light, covered by a shade, which shade, by mechanism, can be lifted for any given time, exposing the light meanwhile. A flash of about half a second's duration is negative: a line of 14- seconds, positive. Four exhibi tions of the light then represent a symbol as in Redl's cones. If the same nomenclature be adopted we should signal as in Fig. 5. It will be seen at once that this system pro duces results similar to Morse's electric telegraph. If the distance be within a mile or so, and the weather still, a bugle will answer equally well, long and short notes representing the positive and nega tive cones.
The fundamental principle of the fore going system of universal telegraphy, applicable by night or by day, by sight or by sound, is to employ two signals only—one positive and one negative—and to regulate their exhibition by periods of time.