outlines. Whenever any group of brain elements has been excited by a
sense impression, it becomes, so to speak, tender, and liable to be
easily thrown again into a similar state of excitement. If the new
cause of excitement differs from the original one, a memory is the
result. Whenever a single cause throws different groups of brain
elements simultaneously into excitement, the result must be a
blended memory.
We are familiar with the fact that faint memories are very apt to
become confused. Thus some picture of mountain and lake in a country
which we have never visited, often recalls a vague sense of identity
with much we have seen elsewhere. Our recollections cannot be
disentangled, though general resemblances are recognised. It is also
a fact that the memories of persons who have great powers of
visualising, that is, of seeing well-defined images in the mind's eye,
are no less capable of being blended together. Artists are, as a
class, possessed of the visualising power in a high degree, and they
are at the same time pre-eminently distinguished by their gifts of
generalisation. They are of all men the most capable of producing
forms that are not copies of any individual, but represent the
characteristic features of classes.
There is then, no doubt, from whatever side the subject of memory is
approached, whether from the material or from the mental, and, in
the latter case, whether we examine the experiences of those in whom
the visualising faculty is faint or in whom it is strong, that the
brain has the capacity of blending memories together. Neither can
there be any doubt that general impressions are faint and perhaps
faulty editions of blended memories. They are subject to errors of
their own, and they inherit all those to which the memories are
themselves liable.
Specimens of blended portraits will now be exhibited; these might,
with more propriety, be named, according to the happy phrase of
Professor Huxley, "generic" portraits. The word generic presupposes
a genus, that is to say, a collection of individuals who have much
in common, and among whom medium characteristics are very much more
frequent than extreme ones. The same idea is sometimes expressed by
the word "typical," which was much used by Quetelet, who was the
first to give it a rigorous interpretation, and whose idea of a type
lies at the basis of his statistical views. No statistician dreams
of combining objects into the same generic group that do not cluster
towards a common centre; no more should we attempt to compose
generic portraits out of heterogeneous elements, for if we do so the
result is monstrous and meaningless.
It might be expected that when many different portraits are fused
into a single one, the result would be a mere smudge. Such, however,
is by no means the case, under the conditions just laid down, of a
great prevalence of the mediocre characteristics over the extreme
ones. There are then so many traits in common, to combine and to
reinforce one another, that they prevail to the exclusion of the rest.
All that is common remains, all that is individual tends to disappear.
The first of the composites exhibited on this occasion is made by
conveying the images of three separate portraits by means of three
separate magic-lanterns upon the same screen. The stands on which
the lanterns are mounted have been arranged to allow of nice
adjustment. The composite about to be shown is one that strains the
powers of the process somewhat too severely, the portraits combined
being those of two brothers and their sister, who have not even been
photographed in precisely the same attitudes. Nevertheless, the
result is seen to be the production of a face, neither male nor
female, but more regular and handsome than any of the component
portraits, and in which the common family traits are clearly marked.
Ghosts of portions of male and female attire, due to the
peculiarities of the separate portraits, are seen about and around
the composite, but they are not sufficiently vivid to distract the
attention. If the number of combined portraits had been large, these
ghostly accessories would have become too faint to be visible.
The next step is to compare this portrait of two brothers and their
sister which has been composed by optical means before the eyes of
the audience, and concerning the truthfulness of which there can be
no doubt, with a photographic composite of the same group. The
latter is now placed in a fourth magic-lantern with a brighter light
behind it, and its image is thrown on the screen by the side of the
composite produced by direct optical superposition. It will be
observed that the two processes lead to almost exactly the same
result, and therefore the fairness of the photographic process may
be taken for granted. However, two other comparisons will be made
for the sake of verification, namely, between the optical and
photographic composites of two children, and again between those of
two Roman contadini.
The composite portraits that will next be exhibited are made by the
photographic process, and it will now be understood that they are
truly composite, notwithstanding their definition and apparent
individuality. Attention is, however, first directed to a convenient
instrument not more than 18 inches in length, which is, in fact, a
photographic camera with six converging lenses and an attached screen,
on which six pictures 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. R. Stuart Poole, the learned
curator of the coins and gems in the British Museum, for his kind
selection of the most suitable medals, and for procuring casts of
them for me for the present purpose. These casts were, with one
exception, all photographed to a uniform size of four-tenths of an
inch between the pupils of the eyes and the division between the lips,
which experience shows to be the most convenient size on the whole
to work with, regard being paid to many considerations not worth
while to specify in detail. When it was necessary the photograph was
reversed. These photographs were made by Mr. H. Reynolds; I then
adjusted and prepared them for taking the photographic composite.
The next series to be exhibited consists of composites taken from
the portraits of criminals convicted of murder, manslaughter, or
crimes accompanied by violence. There is much interest in the fact
that two types of features are found much more frequently among
these than among the population at large. In one, the features are
broad and massive, like those of Henry VIII., but with a much
smaller brain. The other, of which five composites are exhibited,
each deduced from a number of different individuals, varying four to
nine, is a face that is weak and certainly not a common English face.
Three of these composites, though taken from entirely different sets
of individuals, are as alike as brothers, and it is found on
optically combining any three out of the five composites, that is on
combining almost any considerable number of the individuals, the
result is closely the same. The combination of the three composites
just alluded to will now be effected by means of the three
converging magic-lanterns, and the result may be accepted as generic
in respect of this particular type of criminals.
The process of composite portraiture is one of pictorial statistics.
It is a familiar fact that the average height of even a dozen men of
the same race, taken at hazard, varies so little, that for ordinary
statistical purposes it may be considered constant. The same may be
said of the measurement of every separate feature and limb, and of
every tint, whether of skin, hair, or eyes. Consequently a pictorial
combination of any one of these separate traits would lead to
results no less constant than the statistical averages. In a portrait,
there is another factor to be considered besides the measurement of
the separate traits, namely, their relative position; but this, too,
in a sufficiently large group, would necessarily have a statistical
constancy. As a matter of observation, the resemblance between
persons of the same "genus" (in the sense of "generic," as already
explained) is sufficiently great to admit of making good pictorial
composites out of even small groups, as has been abundantly shown.
Composite pictures, are, however, much more than averages; they are
rather the equivalents of those large statistical tables whose totals,
divided by the number of cases, and entered in the bottom line, are
the averages. They are real generalisations, because they include
the whole of the material under consideration. The blur of their
outlines, which is never great in truly generic composites, except
in unimportant details, measures the tendency of individuals to
deviate from the central type. My argument is, that the generic
images that arise before the mind's eye, and the general impressions
which are faint and faulty editions of them, are the analogues of
these composite pictures which we have the advantage of examining at
leisure, and whose peculiarities and character we can investigate,
and from which we may draw conclusions that shall throw much light
on the nature of certain mental processes which are too mobile and
evanescent to be directly dealt with.
III. COMPOSITE PORTRAITURE.
[_Read before the Photographic Society, 24th June, 1881_.]
I propose to draw attention to-night to the results of recent
experiments and considerable improvements in a process of which I
published the principles three years ago, and which I have
subsequently exhibited more than once.
I have shown that, if we have the portraits of two or more different
persons, taken in the same aspect and under the same conditions of
light and shade, and that if we put them into different optical
lanterns converging on the same screen and carefully adjust
them--first, so as to bring them to the same scale, and, secondly,
so as to superpose them as accurately as the conditions admit--then
the different faces will blend surprisingly well into a single
countenance. If they are not very dissimilar, the blended result
will always have a curious air of individuality, and will be
unexpectedly well defined; it will exactly resemble none of its
components, but it will have a sort of family likeness to all of them,
and it will be an ideal and an averaged portrait. I have also shown
that the image on the screen might be photographed then and there,
or that the same result may be much more easily obtained by a method
of successive photography, and I have exhibited many specimens made
on this principle. Photo-lithographs of some of these will be found
in the _Proceedings of the Royal Institution_, as illustrations of a
lecture I gave there "On Generic Images" in 1879.
The method I now use is much better than those previously described;
it leads to more accurate results, and is easier to manage. I will
exhibit and explain the apparatus as it stands, and will indicate
some improvements as I go on. The apparatus is here. I use it by
gaslight, and employ rapid dry plates, which, however, under the
conditions of a particularly small aperture and the character of the
light, require sixty seconds of total exposure. The apparatus is 4
feet long and 6-1/2 inches broad; it lies with its side along the
edge of the table at which I sit, and it is sloped towards me, so
that, by bending my neck slightly, I can bring my eye to an eye-hole,
where I watch the effect of the adjustments which my hands are free
to make. The entire management of the whole of these is within an
easy arm's length, and I complete the process without shifting my
seat.
The apparatus consists of three parts, A, B, and C. A is rigidly
fixed; it contains the dark slide and the contrivances by which the
position of the image can be viewed; the eye-hole, _e_, already
mentioned, being part of A. B is a travelling carriage that holds
the lens, and is connected by bellows-work with A. In my apparatus
it is pushed out and in, and clamped where desired, but it ought to
be moved altogether by pinion and rack-work.[24] The lens I use is a
I B Dallmeyer. Its focal length is appropriate to the size of the
instrument, and I find great convenience in a lens of wide aperture
when making the adjustments, as I then require plenty of light; but,
as to the photography, the smaller the aperture the better. The hole
in my stop is only two-tenths of an inch in diameter, and I believe
one-tenth would be more suitable.
[Footnote 24: I have since had a more substantial instrument made
with these and similar improvements.]
[Illustration: DIAGRAM SHOWING THE ESSENTIAL PARTS]
_Side View._
_End View._
A The body of the camera, which is fixed.
B Lens on a carriage, which can be
moved to and fro.
C Frame for the transparency, on a carriage
that also supports the lantern;
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 should be done, and that the
screen should be replaced by the dark slide, and a brief exposure
given to the plate; then, that a fresh transparency should be
inserted, a fresh focusing adjustment made, and a second exposure
given, and so on. This, I say, is conceivable, but it would be very
inconvenient. The adjusting screws would be out of reach; the head
of the operator would be in an awkward position; and though these
two difficulties might be overcome in some degree, a serious risk of
an occasional shift of the plate during the frequent replacement of
the dark slide would remain. I avoid all this by making my
adjustments while the plate continues in position with its front open.
I do so through the help of a reflector temporarily interposed
between it and the lens. I do not use the ordinary focusing-screen
at all in making my adjustments, but one that is flush, or nearly so,
with the roof of the camera. When the reflector is interposed, the
image is wholly cut off from the sensitised plate, and is thrown
upwards against this focusing-screen, _g_. When the reflector is
withdrawn, the image falls on the plate. It is upon this
focusing-screen in the roof that I see the fiducial lines by which I
make all the adjustments. Nothing can be more convenient than the
position of this focusing-screen for working purposes. I look down
on the image as I do upon a book resting on a sloping desk, and all
the parts of the apparatus are within an easy arm's length.
My reflector in my present instrument is, I am a little ashamed to
confess, nothing better than a piece of looking-glass fixed to an
axle within the camera, near its top left-hand edge. One end of the
axle protrudes, and has a short arm; when I push the arm back, the
mirror is raised; when I push it forward it drops down. I used a
swing-glass because the swing action is very true, and as my
apparatus was merely a provisional working model made of soft wood,
I did not like to use sliding arrangements which might not have
acted truly, or I should certainly have employed a slide with a
rectangular glass prism, on account of the perfect reflection it
affords. And let me say, that a prism of 2 inches square in the side
is quite large enough for adjustment purposes, for it is only the
face of the portrait that is wanted to be seen. I chose my
looking-glass carefully, and selected a piece that was plane and
parallel. It has not too high a polish, and therefore does not give
troublesome double reflections. In fact, it answers very respectably,
especially when we consider that perfection of definition is thrown
away on composites. I thought of a mirror silvered on the front of
the glass, but this would soon tarnish in the gaslight, so I did not
try it. For safety against the admission of light unintentionally, I
have a cap to the focusing-screen in the roof, and a slide in the
fixed body of the instrument immediately behind the reflector and
before the dark slide. Neither of these would be wanted if the
reflector was replaced by a prism, set into one end of a sliding
block that had a large horizontal hole at the other end, and a
sufficient length of solid wood between the two to block out the
passage of light both upwards and downwards whenever the block is
passing through the half-way position.
As regards the fiducial lines, they might be drawn on the glass
screen; but black lines are not, I find, the best. It is far easier
to work with illuminated lines; and it is important to be able to
control their brightness. I produce these lines by means of a
vertical transparency, set in an adjustable frame, connected with A,
and having a gas-light behind it. Below the eye-hole _e_, through
which I view the glass-screen _g_, is a thin piece of glass set at
an angle of 45°, which reflects the fiducial lines and gives them
the appearance of lying on the screen, the frame being so adjusted
that the distance from the thin piece of glass to the transparency
and to the glass-screen _g_ is the same. I thus obtain beautiful
fiducial lines, which I can vary from extreme faintness to extreme
brilliancy, by turning the gas lower or higher, according to the
brightness of the image of the portrait, which itself depends on the
density of the transparency that I am engaged upon. This arrangement
seems as good as can be. It affords a gauge of the density of the
negative, and enables me to regulate the burners behind it, until
the image of the portrait on _g_ is adjusted to a standard degree of
brightness.
For convenience in enlarging or reducing, I take care that the
intersection of the vertical fiducial line with that which passes
through the pupils of the eyes shall correspond to the optical axis
of the camera. Then, as I enlarge or reduce, that point in the image
remains fixed. The uppermost horizontal fiducial line continues to
intersect the pupils, and the vertical one continues to divide the
face symmetrically. The mouth has alone to be watched. When the
mouth is adjusted to the lower fiducial line, the scale is exact. It
is a great help having to attend to no more than one varying element.
The only inconvenience is that the image does not lie in the best
position on the plate when the point between the eyes occupies its
centre. This is easily remedied by using a larger back with a
suitable inner frame. I have a more elaborate contrivance in my
apparatus to produce the same result, which I need not stop to
explain.
For success and speed in making composites, the apparatus should be
solidly made, chiefly of metal, and all the adjustments ought to
work smoothly and accurately. Good composites cannot be made without
very careful adjustment in scale and position. An off-hand way of
working produces nothing but failures.