ures can be adjusted and brilliantly illuminated by
artificial light. The effect of their optical combination can thus
be easily studied; any errors of adjustment can be rectified, and
the composite may be photographed at once.

It must not be supposed that any one of the components fails to
leave its due trace in the photographic composite, much less in the
optical one. In order to allay misgivings on the subject, a small
apparatus is laid on the table together with some of the results
obtained by it. It is a cardboard frame, with a spring shutter
closing an aperture of the size of a wafer, that springs open on the
pressure of a finger, and shuts again as suddenly when the pressure
is withdrawn. A chronograph is held in the other hand, whose index
begins to travel the moment the finger presses a spring, and stops
instantly on lifting the finger. The two instruments are worked
simultaneously; the chronograph checking the time allowed for each
exposure and summing all the times. It appears from several trials
that the effect of 1000 brief exposures is practically identical
with that of a single exposure of 1000 times the duration of any one
of them. Therefore each of a thousand components leaves its due
photographic trace on the composite, though it is far too faint to
be visible unless reinforced by many similar traces.

The composites now to be exhibited are made from coins or medals,
and in most instances the aim has been to obtain the best likeness
attainable of historical personages, by combining various portraits
of them taken at different periods of their lives, and so to elicit
the traits that are common to each series. A few of the individual
portraits are placed in the same slide with each composite to give a
better idea of the character of these blended representatives. Those
that are shown are (1) Alexander the Great, from six components;
(2) Antiochus, King of Syria, from six; (3) Demetrius Poliorcetes,
from six; (4) Cleopatra, from five. Here the composite is as usual
better looking than any of the components, none of which, however,
give any indication of her reputed beauty; in fact, her features are
not only plain, but to an ordinary English taste are simply hideous.
(5) Nero, from eleven; (6) A combination of five different Greek
female faces; and (7) A singularly beautiful combination of the
faces of six different Roman ladies, forming a charming ideal profile.

My cordial acknowledgment is due to Mr