CAPT. GAUMET'S OPTICAL TELEGRAPH.
The system of optical communication proposed by Capt. Gaumet, and which he names the Telelogue, is based upon the visibility of colored or luminous objects, and upon the possibility of piercing the opaque curtain formed by the atmosphere between the observer's eye and a signal, by utilizing the difference in brightness that exists between such objects and the atmosphere. It is a question, then, of giving such difference in intensity its maximum of brightness. To do this, Capt. Gaumet proposes to employ silvered signals upon a black background. He uses the simple letters of the alphabet, but changes their value. His apparatus has the form of a large album glued at the back to a sloping desk. Each silvered letter, glued to a piece of black cloth, is seen in relief upon the open register. A sort of index along the side, as in commercial blank-books, permits of quickly finding any letter at will. Such is the manipulator of the apparatus.
The receiver consists of a spy-glass affixed to the board that carries the register. For a range of two and a half miles, the complete apparatus, with a 12×16 inch manipulator and telescope, weighs but four and a half pounds. For double this range, with a 20×28 inch manipulator and telescope, the total weight is thirteen pounds. The larger apparatus, according to the inventor, have a range of seven miles.
For night work the manipulator is lighted either by one lamp, or by two lamps with reflector, placed laterally against it.
This apparatus, although well known, and having been publicly experimented with, has not, to our knowledge, been applied practically. From a military standpoint, its short range will evidently not permit it to compete with optical telegraphic apparatus, properly so called. Perhaps it might rather be of service for private communications between localities not very far apart, since it costs but little and is easily operated.