But if the apparatus which projects the left side view has a green glass in front of the lens and the one which projects the right side view a red glass, and every person in the audience has a pair of spectacles with the left glass green and the right glass red--a cardboard lorgnette with red and green gelatine paper would do the same service and costs only a few cents--the left eye would see only the left view, the right eye only the right view.

We could not see the red lines through the green glass nor the green lines through the red glass.

In the moment the left eye gets the left side view only and the right eye the right side view, the whole chaos of lines on the screen is organized and we see the pictured room on the screen with the same depth as if it were really a solid room set on the stage and as if the rear wall in the room were actually ten or twenty feet behind the furniture in the front.

The effect is so striking that no one can overcome the feeling of depth under these conditions.
But while the regular motion pictures certainly do not offer us this complete plastic impression, it would simply be the usual confusion between knowledge about the picture and its real appearance if we were to deny that we get a certain impression of depth.

If several persons move in a room, we gain distinctly the feeling that one moves behind another in the film picture.