heliograph

Plural: heliographs

Noun

• an apparatus for sending telegraphic messages by using a mirror to turn the sun's rays off and on
• An apparatus for signalling by means of a moveable mirror which reflects flashes of sunlight.
• A heliogram.
• An instrument for measuring the intensity of sunlight.
• A device for photographing the sun.
• A photograph.

Verb

• signal by means of a mirror and the using the sun's rays
• To send a message by heliograph.
• To send a heliograph.
• To photograph by sunlight.