(1):
(n.) The description of the sun.
(2):
(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.
(3):
(n.) The system, art, or practice of telegraphing, or signaling, with the heliograph.
(4):
(n.) Photography.