April 24, 2024
RARE BRITISH 5 Inch MARK V HELIOGRAPH SIGNAL MIRRORS
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RARE BRITISH 5 Inch MARK V HELIOGRAPHA black cringle finish British Heliograph (SIGNAL MIRRORS) used for long distance signaling in sunny areas.Model: 5" MK V 1944Serial: B25102Signed: C & D with broad arrow proof markSpare Mirror Case B. W. & M. LTDMirror Diameter: 5 inchesContents: Two signaling mirrors, two spare mirrors, various accessories.Heliographs were used by Commonwealth forces for military line of sight communications from 1875 through WWII and beyond. The disk on the rod behind the mirror was used to tilt the mirror to interrupt the beam and break up the mirror-reflected sunlight into the dots and dashes of Morse Code. With sunlight and clear atmosphere, they could be counted on for 30 mile range.The heliograph was preceded by the "heliotrope", a similar device used by surveyors to provide a daytime beacon survey target by mirror-reflected sunlight. The heliotrope was invented by Carl Friedrich Gauss in 1821, and was used by Colonel Sir George Everest in his Great Trigonometric Survey of India from the early 1830s.Mance began work on his heliograph in late 1869 in Karachi, India, and it became standard equipment in the Indian army in 1875. It was first used in war in 1877, and won fame for its use in the Second Anglo-Afghan War in 1878-1880.With the invention of the radio, the use of the heliograph began a slow decline,
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