Heliotrope (instrument)

Heliotrope (c. 1878): B.A. Colonna collection (NOAA). This may be the very one Colonna surveyed from 192 miles away.

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 mathematician Carl Friedrich Gauss.^[1]^[2] The word "heliotrope" is taken from the Greek: helios (Greek: Ἥλιος), meaning "sun", and tropos (Greek: τρόπος), meaning "turn".

^ Dodd, A.; Smith, A. (1822). "The Heliotrope, a New Instrument". Arts and Sciences. The Gentleman's Magazine. 92, Part 2: 358.
^ Dunnington, G. Waldo (1955). Carl Friedrich Gauss: Titan of Science. New York: Exposition Press. pp. 122–127, 119, 221. ISBN 0-88385-547-X.

[1] Dodd, A.; Smith, A. (1822). "The Heliotrope, a New Instrument". Arts and Sciences. The Gentleman's Magazine. 92, Part 2: 358.

[GaussTitan-2] Dunnington, G. Waldo (1955). Carl Friedrich Gauss: Titan of Science. New York: Exposition Press. pp. 122–127, 119, 221. ISBN 0-88385-547-X.

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