A NEW MODE OF OPTIC TELEGRAPHY.

Globe, Volume XXIII, Issue 2178, 17 February 1881, Page 2

A NEW MODE OF OPTIC TELEGRAPHY.

The use of intermittent luminous signals in ■hips, in lighthouses, &c, is now very general; and the common method is that of bringing & movable diaphragm before a steady source of light. Thus the light is not utilized during eclipse, and it has been estimated that in ordinary systems 65 per cent, of the light is los*; (in lighthouses sometimes 90 per cent.). M. Mercadier has lately proposed a new plan, the essence of whioh lies in varying the souros of light, making it flash up to its maximum at one moment, and reduoing or extinguishing it at another. This can be done either by promptly varying a supply of oxygen to a low flame, or by varying the supply of combustible gas. M. Mercadier describes an arrangement of the former kind, in which he uses a simple petroleum lamp of M. Duboscq; it has a round wick (which does not pass beyond the containing cylinder), and in the centre rises ■ thin vertical tube, dpboucl ing a little below the plane of the wick. Toie lube admits the oxygen coming from a reservoir. The mode of admission is by pressure with the finger on • key, like that of a Morse apparatus; this has the effect of momentarily releasing a caoutchouc tube (by which the oxygen is conveyed) from the pressure of a clip. The flame then brightens. On taking the finger off, the supply of- oxygen is stopped again, and the flame is reduced to very small size. Thif system, M. Mercadier says, has been adapted to apparatuses of optical telegraphy, and has given good results. He will shortly indicate how the same problem is solved with the electric light.