The advance of photography : its history and modern applications (1911)

SOME EARLY APPLICATIONS OF PHOTOGRAPHY 225 acids, which often eat sideways into the fine strokes, making them too wide. The sand, in consequence of its direction being at right angles to the plate, cannot widen the lines, and therefore the incisions may be carried to a great depth, and then the plates may be used with letter-press. Tilghman suggested that a gelatine positive should be produced upon a cake of resin ; that this should be blown upon and deeply hollowed out. °' A cast in plaster from this would form a mould for a typemetal cast, which could be used for printing. Animated Photography — Marey's Pistol. — Instantaneous photography could not fail to derive impetus from the introduction of the more highly sensitive gelatine plates. Not only were they more convenient and easy to work with ; they also made it possible to obtain instantaneous images even under an unfavourable light, giving them in detail instead of as mere silhouettes. Attempts to photograph flying birds even proved successful. Marey, of Paris, constructed a " photographic pistol " for this purpose. It was simply a photographer's camera of somewhat peculiar form, resembling a revolver. The object glass was in the barrel, and a small sensitized plate was adjusted in the revolving chamber. If the instrument was pointed at a ^ flying bird and the spring pressed, a ^fck. ^k mechanism was released by which the ^BHk fl^k revolving chamber turned once round ^M jm| A in a second of time, in twelve distinct ■^ jerks ; and at each of the twelve pauses —^^^^^^^^ a spring-shutter opened for r,Tyn of a Fig. 101. second. This is enough to produce an image of the flying bird on the highly sensitive gelatine plate, which thus records twelve succeeding positions of the wings : these are of great value in the study of wing p