The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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cylinder and to make this rotate slowly in front of the observer, when the effect will be somewhat similar to that of the observer turning round at the position where the panoramic camera was originally stationed. (See Panoramic Camera and Cylindro-graph.)
Daguerreotype. An early process for obtaining a camera picture; discovered by Daguerre. A sensitive surface of silver iodide and bromide was formed by exposing a silvered copper plate to the direct action of the metalloids. After exposure, which was inordinately prolonged, the development was effected by exposing the plate to the vapour of metallic mercury, which was deposited on the plate as an amalgam of silver and mercury. The unacted-upon iodide and bromide were then dissolved by cyanide of potassium or hyposulphite of soda, and the image toned by sel d'or. (See Gold Hyposulphite.) The first intaglio photogravures were made by Mr. Justice Grove in 1840, by the electrolytic etching of the daguerreotype plate. ■ The plates were too shallow to give good prints. General Waterhouse has shown that the latent image on a Daguerreotype plate may be developed by ordinary developers, also by physical developers. An interesting illustrated account of the daguerreotype process, and of M. Daguerre's early work is to be found in Tissandier's " History and Handbook of Photo-graphy," translated by J. Thomson, London, 1876 (Sampson Low & Co.)
Daguerreotype, To Clean and Copy. Carefully remove the
daguerreotype from its frame and separate from its covering glass, and place face upwards in a dish of cold water. Be extremely careful not to touch the front of the plate, as the slightest touch will leave a permanent mark. Lift the plate by the corners, and remove the paper from the back when suffi-ciently soaked; rinse the plate thoroughly, and, should the water be repelled as though the plate were greasy, flow over a little methylated spirit. If the tarnish on the edges be blue in colour, immersion in an ordinary fixing bath will remove the same; but if any bronzing is visible, make a solution of cyanide of potas-sium, ten grains to the ounce, and keep pouring this on and off till all tarnish is removed. Wash the plate thoroughly to free from cyanide, and rinse well with distilled water; then take hold