cene to be
photographed. On turning the main shaft of the camera the sprocket, G,
is moved intermittently, and its teeth, catching in the holes in the
sensitized film, draws it downward, bringing a new portion of its length
in front of the lens, the film then remaining stationary for an instant.
In the mean time, through gearing connecting the main shaft with the
shutter, the latter is rotated, bringing its opening, D, coincident with
the lens, and therefore exposing the film while it is stationary, after
which the film again moves forward. So long as the action is continued
these movements are repeated, resulting in a succession of enormously
rapid exposures upon the film during its progress from reel H<1S> to its
automatic rewinding on reel H<2S>. While the film is passing through the
various parts of the machine it is guided and kept straight by various
sets of rollers between which it runs, as indicated in the diagram.

By an ingenious arrangement of the mechanism, the film moves
intermittently so that it may have a much longer period of rest than
of motion. As in practice the pictures are taken at a rate of twenty or
more per second, it will be quite obvious that each period of rest is
infinitesimally brief, being generally one-thirtieth of a second or
less. Still it is sufficient to bring the film to a momentary condition
of complete rest, and to allow for a maximum time of exposure,
comparatively speaking, thus providing means for taking clearly defined
pictures. The negatives so obtained are developed in the regular
way, and the positive prints subsequently made from them are used for
reproduction.

The reproducing machine, or, as it is called in practice, the Projecting
Kinetoscope, is quite similar so far as its general operations in
handling the film are concerned. In appearance it is somewhat different;
indeed, it is in two parts, the one containing the lighting arrangements
and condensing lens, and the other embracing the mechanism and objective
lens. The "taking" camera must have its parts enclosed in a light-tight
box, because of the undeveloped, sensitized film, but the projecting
kinetoscope, using only a fully developed positive film, may, and,
for purposes of convenient operation, must be accessibly open. The
illustration (Fig. 2) will show the projecting apparatus as used in
practice.

The philosophy of reproduction is very simple, and is illustrated
diagrammatically in Fig. 3, reference letters b