HELIOGRAPH (from Gr. Helios, solar, and graphos to write down) an instrument for reflecting the rays of the sun (or the sunshine obtained from some other source) over a considerable distance. Its principal software is in military signalling. An analogous instrument to the heliotrope, used principally for outlining distant factors in geodetic surveys, akin to in the triangulation of India, and in the verification of the African arc of the meridian. It is obligatory to differentiate the tactic of signalling termed heliography from the new photographic technique of the same name.
This is the primary identified photograph. There is little benefit in this picture apart from that fact. It is tough to interpret; the constructing is on the left, a tree a third in from the left, and a barn immediately in front. The exposure lasted eight hours, so the sun had time to move from east to west, appearing to shine on each side of the constructing.
This instrument, invented by Sir Henry C. Mance, receives on a mirror, and thence casts upon the distant station, the rays of the sun; the working of a small key controls the flashes by throwing the mirror barely off its alignment and thus obscuring the sunshine from the get together reading indicators. The truth that the heliograph requires sunlight, as mentioned above, militates against its employment in Great Britain, but the place it’s possible to make use of it, it’s by far the very best technique of signalling. Secrecy and rapidity are its chief advantages.
The main part of the instrument is the mirror, which ought to be about four in. square, set in a wooden body and swung on trunnions product of two square-head bolts, each 1/4 in. in diameter, and 1 in. long, which are firmly held to the frame with brass strips, 1/2 in. huge, and three in. lengthy. The strips are drilled centrally to admit the bolts, and then drilled at every end for a screw to fasten them to the frame. This construction is clearly proven in Fig. 1.
The first recorded use of heliograph comes from 405 BC when the Historical Greeks used polished shields to sign in battle. In about 35 ADVERT, the Roman emperor Tiberius, by then very unpopular, dominated his vast empire from a villa on the Isle of Capri. It is thought he used a heliograph to ship coded orders every single day to the mainland, eight miles away.