n. - Photography.
n. - The description of the sun.
n. - The system, art, or practice of telegraphing, or signaling, with the heliograph.
n. - An early photographic process invented by Nicephore 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.