TELEGRAPHY BY LIGHT SIGNALS.

New Zealand Herald, Volume XVI, Issue 5496, 28 June 1879, Page 7

TELEGRAPHY BY LIGHT SIGNALS.

The heliostat has lately become a recognised article of army, equipment for signalling purposes. Only the other day ColoDel Stanley explained in the House of Commons that four of these reflecting instruments had been forwarded to the Cape, and a letter from Jellalabad has recently told us how the heliograph was employed for signalling along the Khyber Pass. The only drawback to the value of these useful instruments is tbe circumstance that sunshine is indispensible. The plan of operating is very simple. The men who communicate with one another are each provided with a mirror placed at a certain angle; as the snn is continually travelling, or rather the earth, the mirror has of course to be continually shifted to reflect the rays of that luminary, and this is what the clockwork movement of the heliostat does. Once properly set, the mirror follows the sun. Under these circumstances, the signallers have simply to move the mirror backwards and forward to flash light signals to one another. How bright these flashes are may be judged when we see the declining sun reflected by a window pane. Any one who has noticed this phenomenon at sundown, a bright spot more intense than the most vivid fire, can readily understand the distance to which sun-signals may be made to travel, and how readily they are perceived. Any code of signals will answer the purpose; but the Morse alphabet is that in general use by our army Bignallers. Once set in order for the day, any trained soldier can despatch and read heliostat signals so long, that is, as he is favoured with sunshine. Signalling by mirror is no novelty, but has frequently been resorted to both by civilised and uncivilised nations. The United States forces captured & tribe of Indians but very recently, who were known by the name of the Nez-Perces, and the chief of these carried a small looking-glass for signalling. More than thirty years ago, when Admiral . Sheriff was at Gibraltar, he carried out many experiments in light signalling, using for the purpose a common, toilet glass, and with this simple apparatus he was in the habit of oommuntcatiDg . with a friend at Tangier s, right across the Mediterranean from Europe to the African main. Iu India and other sunny lands, from the fact that the flashes are seen at much greater distance than flags or ehutters, we may expect to see this eystem of telegraphy firmly established.