to bind the pictures together in book form by
one edge, and then release them from the other in rapid succession by
means of the thumb or some mechanical device as the book is bent
backwards. In this case the subject is viewed, not by projection, but
directly, either with the unaided eye or through a magnifying glass.

Cinematograph films produced by ordinary photographic processes, being
in black and white only, fail to reproduce the colouring of the subjects
they represent. To some extent this defect has been remedied by painting
them by hand, but this method is too expensive for general adoption, and
moreover does not yield very satisfactory results. Attempts to adapt
three-colour photography, by using simultaneously three films, each with
a source of light of appropriate colour, and combining the three images
on the screen, have to overcome great difficulties in regard to
maintenance of register, because very minute errors of adjustment
between the pictures on the films are magnified to an intolerable extent
by projection. In a process devised by G.A. Smith, the results of which
were exhibited at the Society of Arts, London, in December 1908, the
number of colour records was reduced to two. The films were specially
treated to increase their sensitiveness to red. The photographs were
taken through two colour filters alternately interposed in front of the
film; both admitted white and yellow, but one, of red, was in addition
specially concerned with the orange and red of the subject, and the
other, of blue-green, with the green, blue-green, blue and violet. The
camera was arranged to take not less than 16 pictures a second through
each filter, or 32 a second in all. The positive transparency made from
the negative thus obtained was used in a lantern so arranged that beams
of red (composed of crimson and yellow) and of green (composed of yellow
and blue) issued from the lens alternately, the mechanism presenting the
pictures made with the red filter to the red beam, and those made with
the green filter to the green beam. A supplementary shutter was provided
to introduce violet and blue, to compensate for the deficiency in those
colours caused by the necessity of cutting them out in the camera owing
to the over-sensitiveness of the film to them, and the result was that
the successive pictures, blending on the screen by persistence of
vision, gave a reproduction of the scene photographed in colours which
were sensibly the