the substantial thing. The stereoscope thus illustrates clearly that the
knowledge of the flat character of pictures by no means excludes the
actual perception of depth, and the question arises whether the moving
pictures of the photoplay, in spite of our knowledge concerning the
flatness of the screen, do not give us after all the impression of
actual depth.

It may be said offhand that even the complete appearance of depth such
as the stereoscope offers would be in no way contradictory to the idea
of moving pictures. Then the photoplay would give the same plastic
impression which the real stage offers. All that would be needed is
this. When the actors play the scenes, not a single but a double camera
would have to take the pictures. Such a double camera focuses the scene
from two different points of view, corresponding to the position of the
two eyes. Both films are then to be projected on the screen at the same
time by a double projection apparatus which secures complete
correspondence of the two pictures so that in every instance the left
and the right view are overlapping on the screen. This would give, of
course, a chaotic, blurring image. 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