n. 1. [ Helio- + -graphy. ] The description of the sun. [ Webster 1913 Suppl. ] 2. The system, art, or practice of telegraphing, or signaling, with the heliograph. [ Webster 1913 Suppl. ] 3. An early photographic process invented by Nicéphore Niepce, and still used in photo-engraving. It consists essentially in exposing under a design or in a camera a polished metal plate coated with a preparation of asphalt, and subsequently treating the plate with a suitable solvent. The light renders insoluble those parts of the film which is strikes, and so a permanent image is formed, which can be etched upon the plate by the use of acid. [ Webster 1913 Suppl. ] 4. Photography. [ Archaic. ] R. Hunt. [ 1913 Webster ] |