This is a process of combining a number of images in such a way that
the result obtained is an aggregate of its components. Francis Galton
was one of the first to employ this system. In the appendix to his
"Inquiries into Human Faculty," Galton has described the very
elaborate and perfect form of apparatus which he has used in his
studies; but entirely satisfactory results may be obtained with much
more simple contrivances. The instrument used by Prof. Bowditch[7] is
merely an old-fashioned box camera, with a hole cut in the top for the
reception of the ground-glass plate upon which the image is to be
reflected for purposes of adjustment. The reflection is effected by a
mirror set at an angle of 45 degrees in the axis of the camera, and
pivoted on its upper border so that, after the adjustment of the
image, the mirror can be turned against the upper side of the box, and
the image allowed to fall on the sensitive plate at the back of the
camera. The original negatives are used as components, and are placed
in succession in a small wooden frame which is pressed by elliptical
springs against a sheet of glass fastened vertically in front of the
camera. By means of this arrangement it is possible to place each
negative in succession in any desired position in a plane
perpendicular to the axis of the camera, and thus to adjust it so that
the eyes and the mouth of its optical image shall fall upon the
fiducial lines drawn upon the ground-glass plate at the top of the
camera. An Argand gas burner with a condensing lens furnishes the
necessary illumination.
[7] From _McClure's Magazine_, September, 1894.
"For our amateur photographers," writes Prof. Bowditch, "who are
constantly seeking new worlds to conquer, the opportunity of doing
useful work in developing the possibilities of composite photography
ought to be very welcome. Not only will the science of ethnology
profit by their labors, but by making composites of persons nearly
related to each other, a new and very interesting kind of family
portrait may be produced. The effect of occupation on the physiognomy
may also be studied in this way. By comparing, for instance, the
composite of a group of doctors with that of a group of lawyers, we
may hope to ascertain whether there is such a thing as a distinct
legal or medical physiognomy."
[Illustration: By Prof. Bowditch. FIG. 84.--COMPOSITE PORTRAITS OF
BOSTON PHYSICIANS AND SAXON SOLDIERS.]