TELGRAPHY BY LIGHT SIGNALS.

Nelson Evening Mail, Volume XIV, Issue 163, 10 July 1879, Page 4

TELGRAPHY BY LIGHT SIGNALS.

The beliostat has lately become a recognised article of army equipment for signalling purposes. Only tbe other day Colonel Stanley explained in tbe House of Commons tbat four of these reflecting instruments bad been forwarded to the Cape, and a letter frotn Jellslabad has recently told us how the heliograph was recently employed for signalling along the Kbyber Pass. The only drawback to tbe value of these useful instruments is tbe circumstance tbat sunshine ia indiepenaible. Tbe plan oi operating is very simple. Tbe men who communicate with one another are each provided with a mirror placed at a certain angle ; as the sun is continually travelling, or rather the eartb, tbe mirror has, of course,to be continually shifted to reflect the rays of that luminary, and this is what the clockwork movement of the helioßtat does. Once properly set, the mirror follows the sun. Under thesis circumstances, the

signallers have simply to move tbe mirror backwards and forwards to flash light signals to one another. How brigbt these flashes are may be judged wben we see the declining son reflected by a window pane. Anyone who has noticed this phenomenon at sundown,* a bright spot more intense than the most vivid fire, can readily understand tbe distance at which sun signals may be mode to travel, and bow readily they are perceived. Any code of signals will answer the purpose; but the Morse alphabet is that in general use by our army signallers. Once set in order for the day, any trained soldier oan despatch and read beliostat signals, so long, tbat is, as bo is favored with sunshine. Signalling by mirror is no novelty, but has frequently been resorted to both by civilised and uncivilised nations. The United Stateß forces captured a tribe of Indianß very recently who were known by the name of the N. z-Percefl, and the chief of these carried a small looking-glass for signalling. More tban thirty years ago, wben Admiral Sheriff was at Gibraltar, he carried cut msny experiments in ligbt signalling, using for the purpose a common toilet-glass, and with this simple apparatus he was in the habit ot communicating with a friend st Tangier?, rigbt across the Mediterranean from Europe to the African maie. Ir India and olher sunny iunds, from ihe fact that tbe flashes bre seen at in acb greater distance than flags or abutters, we may expect to see this system of telegraphy firmly established.