The Dictionary Of Photography

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

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same time; and when test slips from this develop a blue image on a yellow ground the exposure is sufficient. The developer is a 20 per cent, solution of ferrocyanide of potassium. The edges of the print are turned back so as to form a sort of dish, or protecting shield, so that no developer gets on the back of the paper. The print is then carefully floated on to the developer and left for about thirty minutes, and then examined at one corner till blue spots begin to appear, when the print should be immediately removed, floated carefully again on a dish of clean water and left for some minutes, and then immersed in dilute hydrochloric acid 1 : 100, and any blue spots removed by carefully brushing ; and, finally, the print should be laid at the bottom of an empty dish and a vigorous stream of water from a rose or tap allowed to play on it. Corrections are made by the same solution previously mentioned, the spots being touched with a fine pencil and blotted off with clean blotting-paper.
Cydograph. 1. A form of the Panoramic Camera (<?-v.) due to M. Damoizeau. 2. A device of Mr. A. H. Smith for photo-graphing the whole circumference of a cylindrical object. The object rolls along a smooth edge in front of the lens, and a narrow slit travels with it. Under these circumstances a fixed lens and plate may be used. A full description of Smith's cyclograph, and of modifications to suit it for cones and other forms, is to be found in The Journal of the Royal Photographic Society, May 30th, 1895, p. 253.
Cylindrograph. A panoramic camera designed by Captain Moessard, and which includes an angle of 1700. The sensitive surface - generally gelatino-bromide on a celluloid base - is bent into a half circle, and during exposure the lens is made to rotate on a vertical axis, which axis passes through what is virtually the optical centre of the lens. The sketch given (Fig. 40), together with a reference to the article Panoramic Camera, will make the nature of the cylindograph sufficiently clear. In order that views taken with the cylindograph may be seen as in correct perspective, the Cylindroscope (which see) is used. The cylindrograph has been used with much success as an aid in surveying by photography (see Photogrammetry), especially in connection with railway work in the United States, as if care is taken in producing the original the resulting print can be