A type of double-exposure work that is, perhaps, even more familiar to readers is that used in showing visions, as, for instance, when the producer desires to show the thoughts that are passing through a character’s mind. The vision may appear in one of the upper corners of the scene, the more common method, or, for novelty’s sake, it may form on the pages of a book the character is reading. The principle in these cases is similar to that explained in the twin-brothers scene. First the action covering most of the scene is photographed, with that part of the film masked on which the vision is to appear. Then the same strip of film is run through the camera to photograph the players enacting the action of the vision. It will be readily apparent that in this work the camera’s perspective must be altered, where in the twin-brother scene it was necessary that there be no change in the position of the camera until both scenes were photographed. The magical appearances and disappearances of characters will be simple to readers who now understand the operation of the motion-picture camera. They will see that it is an easy matter to have a character disappear by ceasing to turn the crank, covering the lens, and then having the character walk off the scene, after which the turning of the crank is resumed. When the picture is developed the player will be seen up to a certain point, then he will suddenly disappear, but the other objects in the scene will appear unchanged. In the same manner a person can be brought suddenly on the scene, appearing to spring from the air. Trick effects may also be secured by running the film through the camera backward, and reversing the actions of the players, that is, making them “do things backward.” When the film is run through the projection-machine correctly, and shown on the screen, you see the player perform such miraculous feats as jumping from the middle of a river clear up a steep bank, when in reality to take the picture he leaped backward from the bank to the river--but the film was reversed.