and aerial perspective, which distinguishes the distance of objects by the relative brilliancy of their colour and effect.
Phenakistoscope. See Zoetrope.
Phosphorescence. See Luminous Paint and Radiography.
Phosphorus. P = 3i. A non-metallic element widely dis-tributed throughout the animal and vegetable kingdom, but never occurring in the free state. It is insoluble in water, soluble in ether, chloroform, benzine, turpentine, and other oils, and bisulphide of carbon. It is altered by light, and methods rather curious than practical have been based on this fact.
Photoaquatint. See Gum-Bichromate, and for hints as to photoaquatint in colours see Photography in Natural Colours. Photogravure is sometimes called Photoaquatint.
Photochromoscope. Synonymous with Kromskop.
Photocrayon. Sarony, in 1870, used a paper backing, shaded or hatched with cross lines, and placed under a transparency to simulate a crayon effect. •
Photo-Engraving. Numerous processes are in everyday use. See Photogravure, Obernetter's Process, Fish Glue Process, Galvanography, Daguerreotype (etching of), Electrotyping, Woodbury type, Zincography, Asphalt Process, Chemigraphy, Types (originating by Photography). Collateral subjects are Lithography (Photo), Litho-photo-gravure, Leimtype, Filigrane, Collotype, Prism Rever-sing, and Collotype.
Photofiligrane. See Filigrane.
Photogalvanography. See Galvanography.
Photogene. (1) A name applied by Gaudin to a sensitive emulsion. (2) A bichromated gum mixture for the powder process.
Photoglyph. A photo engraving. .
Photoglyptie. Synonymous with Woodburytype.
Photogram. (1) Synonymous with Photograph. (2) A record obtained by Photogrammetry.
Photogrammetry. The art of making surveys or geodetical measurements by the aid of photography. (See Cylindograph,