The negative approved, we are now ready to print the positives. On the negative, as the amateur photographer will know, the light conditions were reversed from the normal. That is, the portions of the film which we would expect to appear white, such as a snow-covered walk, were black, while the dark portions, a railroad train, for example, appeared white. This is the principle explaining the method of printing positives. The negative is superimposed on the positive film stock and light allowed to stream through. Naturally the image on the negative obstructs light in proportion to its density. Our snow-bank, let us say, being black on the negative, will allow no light to pass through and that portion of the positive stock under it will not be exposed. The near-by train, appearing white on the negative, offers no obstruction to the light, and here the positive is strongly exposed. When the positive is later developed it takes on a deposit of silver in equal proportion to the strength of the exposure, the snow-bank taking little, while a heavy deposit of silver clings to that part of the film showing the railroad train, which received so much exposure to the light. Thus the positive print brings the light conditions back to normal again, the train appears dark, the snow white, and the other objects in the scene shaded in ratio to the amount of light they allowed to penetrate through the negative to the positive stock. In practice positive printing is done by a machine using for its essential principles the shutter and feeding devices that we have seen in the motion-picture camera. Negative and positive stock are perforated alike, and when superimposed the perforations fall in alignment. The film-feeding device of the printer engages in these perforations just as we saw it do in the camera, only in this case it is moving the negative and positive film along simultaneously. What would be the lens in the camera is here the place where the light is allowed to pass through. Once more the shutter serves its purpose of shutting off the light while the required length of film for one small picture is shifted into place. As in the camera, care is taken that the light strikes no portion of the film but the three-quarter-inch strip that is being exposed. The action of a printer is practically automatic, but the human touch is evident in determining the brilliancy of the light, its distance from the film, and the speed at which the printer will be run, all points determined by the condition of the negative. [Illustration: (_Selig_) DRYING-ROOM IN THE FACTORY--THE FILM IS WOUND ON THE LARGE DRUMS]