antern;
the whole can be moved to and fro.

_r_ The reflector inside the camera.

_m_ The arm outside the camera attached
to the axis of the reflector; by
moving it, the reflector can be
moved up or down.

_g_ A ground-glass screen on the roof,
which receives the image when the
reflector is turned down, as in the
diagram.

_e_ The eye-hole through which the image
is viewed on _g_; a thin piece of
glass immediately below _e_, reflects
the illuminated fiducial lines in the
transparency at _f_, and gives them
the appearance of lying upon _g_,--the
distances _f e_ and _g e_ being
made equal, the angle _f e g_ being
made a right angle, and the plane
of the thin piece of glass being
made to bisect _f e g_.

_f_ Framework, adjustable, holding the
transparency with the fiducial lines
on it.

_t_ Framework, adjustable, holding the
transparency of the portrait.

C is a travelling carriage that supports the portraits in turn, from
which the composite has to be made. I work directly from the
original negatives with transmitted light; but prints can be used
with light falling on their face. For convenience of description I
will confine myself to the first instance only, and will therefore
speak of C as the carriage that supports the frame that holds the
negative transparencies. C can be pushed along the board and be
clamped anywhere, and it has a rack and pinion adjustment; but it
should have been made movable by rack and pinion along the whole
length of the board. The frame for the transparencies has the same
movements of adjustment as those in the stage of a microscope. It
rotates round a hollow axis, through which a beam of light is thrown,
and independent movements in the plane, at right angles to the axis,
can be given to it in two directions, at right angles to one another,
by turning two separate screws. The beam of light is furnished by
three gas-burners, and it passes through a condenser. The gas is
supplied through a flexible tube that does not interfere with the
movements of C, and it is governed by a stop-cock in front of the
operator.

The apparatus, so far as it has been described with any detail, and
ignoring what was said about an eye-hole, is little else than a
modified copying-camera, by which an image of the transparency could
be thrown on the ordinary focusing-screen, and be altered in scale
and position until it was adjusted to fiducial lines drawn on the
screen. It is conceivable that this