heliograph

Meanings

1. 1
   noun

   an instrument that sends coded signals over a distance by reflecting flashes of sunlight with a mirror

   The survey party used a heliograph to signal the fort across the valley.

2. 2
   verb

   to send a message or signal by heliograph

   The lookout heliographed the warning to the troops below.

Formed in the nineteenth century from helio-, 'sun,' + -graph, 'an instrument for writing or recording,' both from Greek. The name treats reflected sunlight as a means of writing messages across distance.

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