Heliotrope (instrument)
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The heliotrope is an instrument that uses a mirror to reflect sunlight over great distances to mark the positions of participants in a land survey. The heliotrope was invented in 1821 by the German ma
Heliotrope (c. 1878): B.A. Colonna collection (NOAA). This may be the very one Colonna surveyed from 192 miles away.
Gauss's Heliotrope (c. 1822)
Wurdemann's Heliotrope (1866)
Coast Survey, Steinheil, and simple heliotropes c. 1898
Heliograph
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A heliograph is a solar telegraph system that signals by flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shut
Heliotrope (instrument)
…mirror for communicating with the instrument station through heliography, a signalling system using impulsed reflecting surfaces. The inventor of the heliograph, a similar instrument specialized for signaling, was inspired by observing the use of heliotropes in the survey of India. Heliograph, a similar instrument…
Fig. 1: Signaling with a Mance heliograph; Alaska–Canada border, 1910.
Fig. 2: A German heliograph made by R. Fuess in Berlin, on display at the Museum of Communication in Frankfurt
Fig. 3 A Turkish / Ottoman Empire heliograph military crew at Huj during the First World War, 1917
Fig. 4: A U.S. Army Signal Corps heliograph instrument, 1898