CINEMATOGRAPH, an instrument designed to picture persons and things while in motion. The invention is to be credited to two brothers, Lumiere of Lyons, France. The principle on which it is founded is the same as that of Edi son's kinetoscope, namely, the persistencb of vision. The device consists of a photo. graphing band or film about an inch and a quarter wide, and with a minimum length of 50 feet. This is exposed in a cinematograph. The band is wound around a drum and passes from this to a series of compensating drums into a posi tion behind the lense of the camera. The shutter of this lense opens sixteen times a second for a period of perhaps one hundredth of a second. In the intervals of the shutter being closed the film is pulled forward for about three-quarters of an inch for a second exposure, and so on. The mechanism is usually worked by a crank which turns at a rate of twice a second. After the exposure the film is developed and wound upon a large drum. To produce positives from these negatives a second film is exposed be neath it and is in turn developed.
The instrument itself is a projecting lantern which throws the pictures upon the screen in rapid succession. The speed with which the pictures are shown is usually at the rate of sixteen per second.
Of course, the picture is not strictly con tinuous, but the interval is so slight between the showing of one picture and the next that the eye fails to notice it, and the effect produced is that of con tinuity. The movement of the successive pictures is usually operated by hand, but in some cases a small electric motor is at tached which operates automatically. The former method is preferable when skill fully done, because there may be cases when the effect of the picture is increased by dwelling a trifle longer on one part than on the other. The film commonly used in exhibitions ranges from 200 to 350 yards. This, at the ordinary rate of speed used, requires from 10 to 16 minutes for presentation on the screen. Of course, any number of reels can be used, depending upon the importance or interest of the picture exhibited. Great care must be taken by the operator against fire, owing to the sensitive nature of the materials used and the concen trated light employed for projecting the picture on the screen. Several automatic inventions have been made that reduce the danger to a minimum. See MOVING PICTURES.