BIOGRAPH, an apparatus that displays in rapid sequence a long series of photographs. It belongs to a class of apparatus which fol lowed the invention of the lcinetoscope, and includes the vitascope, cinematograph, phan toscope, etc. It differs from the kinetoscope in that instead of showing small pictures through an enlarging lense by reflected light, it projects them on a screen. The biograph may be described as a stereopticon combined with such mechanism as is requisite for the precise manipulation of the celluloid picture film. When the apparatus is set in motion the long band of celluloid passes quickly, though not continuously, behind the projecting lens, between spools or bobbins which revolve at a uniform rate. While thus passing from its original spool to the winding reel the film en counters certain pulleys and toothed rollers that serve to direct its movements accurately. Along its edges are numerous small perfora tions into which the teeth of the rollers fit with precision, and by this means the small transparencies are made to occupy exactly simi lar positions when their images are projected upon the canvas. As each picture in its turn attains this critical position it is momentarily brought to a standstill. At the same time a shutter is opened and an image of the picture flashes for an instant upon the screen. The shutter is then quickly closed, the picture re suming its motion, while its successor in the series is brought into a similar fixed situation. This temporary stoppage of the film (or rather of a portion thereof), as each picture attains its proper place behind the projecting lens, is a very essential feature of the process.
At the instant of its arrival a portion of the film on the preceding side of the picture will be in an unstrained or slack condition. The ((slack)" is then taken up by a continu ously- moving sprocket pulley, whereupon a rod or roller is quickly brought to bear against the now tightened film, pressing_it to one side and as quickly releasing it. By this move ment the next picture is pulled into its fixed position, while the film is made taut (or nearly so) on the following side of this pic ture. These operations are repeated contin uously until the entire film has passed through the holding device in rear of the lens.
The camera .used in taking the negative from which motiOn pictures are made is pro vided with a similar mechanism to that em ployed in showin,g the finished photographs. T.he picture roll is replaced by a roll of sen sitized film, upon which the exposures are made at the rate of from 25 to 50 per second. The films range in length from 50 to 200 feet, and contain, when finished, from 800 to 3,000 negatives. After the film has been sub jected to the usual photographic operations it is made to pass, in contact with a second sensitized film, beneath an incandescent lamp, and by this means the photographs are printed upon the sensitized surface. This second film is then in turn passed through the various photographic processes, and when complete it is wound on a spool which may then be placed in the machine used for exhib iting the pictures.