decreasing the size of its successive portions more rapidly than demanded
by perspective alone. The same principal can be applied in many ways. For
example, in Fig. 89 the roof appears quite extensive when viewed so that
the end-walls of the structure are not seen. Such illusions find
applications in the moving-picture studio where extensive interiors, great
fortresses, and even villages must be erected within small areas.
Incidentally the camera aids to create the illusion of magnitude in
photographs because it usually magnifies perspective, thereby causing
scenes to appear more extensive in the photographs than in the reality.
[Illustration: Fig. 88.--Some simple geometrical-optical illusions in
architecture.]
Balance in architecture is subject to illusions and might be considered an
illusion itself. For example, our judgment of balance is based largely
upon mechanical laws. A composition must appear to be stable; that is, a
large component such as a tower must not be situated too far from what we
take as a center of gravity, to appear capable of tipping the remainder
of the structure. In physics we would apply the term "moment." Each mass
may be multiplied by its distance from the center of gravity, thus
determining its moment. For a building or other composition to appear
stable the sum of these moments must be zero; that is, those tending to
turn the figure in one direction must be counterbalanced by those tending
to turn it in another direction. In appraising a composition, our
intellect summates the effects of different parts somewhat in this manner
and if satisfactory, balance is considered to have been attained. The
colors of the various components exert an influence in this respect, so it
is seen that illusions may have much to do with the satisfactoriness of
architectural compositions.
[Illustration: Fig. 89.--By decreasing the exposed length of shingles
toward the top a greater apparent expanse is obtained.]
Various illusions of height, of ceiling, composedness, etc., may be
obtained by the color of the ceiling. A dark cornice in an interior may
appear to be unsupported if the walls below are light in color, without
any apparent vertical supports for the cornice. We are then subjected to
the illusion of instability or incongruity. Dark beams of ceilings are not
so obtrusive because our intellect tells us that they are supports passing
over the top of the walls and are therefore able to support themselves.
Color and brightness in such cases are very important.
The architectural details on exteriors evolved under daylighting outdoors
so that their form has been determined by the shadows desired. The
architect leads his lights and shadows around the building modeling it as
he desires. An offset here and a depression there models the exterior in
light and shade. The forms must be powerful enough to resist the
obliterating effect of overcast skies but notwithstanding all precautions
the expression of an exterior varies considerably with nature's lighting.
Indoors the architect has a powerful controllable medium in artificial
light which he may draw upon for producing various expressions or moods in
rooms. The effect of shadows is interesting when viewing some structures
flood-lighted at night. In those cases where the light is directed upward
there is a reversal of shadows which is sometimes very unsatisfactory.
It is interesting to experiment with various ornamental objects lighted
from various directions. For example, a Corinthian capital lighted from
below may produce an unpleasant impression upon the observer. We do not
like to have the dominant light from below, perhaps because it is annoying
to the eyes. Possibly this is an instinct acquired by experience in
snow-fields or on the desert, or it may be a heritage of ancestral
experience gained under these glaring conditions. This dislike manifests
itself when we appraise shadow-effects and therefore our final impression
is tempered by it.
All sculptured objects depend for their appearance upon the lighting, and
they are greatly influenced by it. In sculpture, in a strict sense,
illusions play a lesser part than in other arts. Perhaps in those of very
large proportions various corrections have been applied. A minor detail of
interest is the small cavity in the eye, corresponding to a reversed
cornea. This depression catches a shadow which gives considerable
expression to the eye.
XIV
MIRROR MAGIC
Strictly speaking there are fewer illusions found in the practice of the
magician than is generally supposed; that is, the eye usually delivers
correctly to the intellect, but the judgment errs for various reasons. The
"illusion" is due to false assumptions, to the distracting words, to
unduly accented superfluous movements of the magician; or in general to
downright trickery. Much of the magician's success is due to glibness of
tongue and deftness of fingers, but many of the more notable "tricks" were
those involving the use of mirrors and the control of light. Black
curtains, blackened assistants, and controlled light have played prominent
parts in the older magic, but the principles of these are easily
understood. However, the mirror perhaps has done more to astound the
audience than any other device employed by the magician. For this reason,
and because its effects are commonly termed illusions, some representative
examples will be presented.
In a previous chapter attention was called to the simple but usually
overlooked fact that, for example, the image of a face in a mirror is
reversed as to right and left. When this fact is overlooked we may be
astonished at the changed expression of an intimate friend as we view the
face (reversed) in the mirror. Similarly our own features are reversed as
to right and left and we are acquainted with this reversed image rather
than the appearance of our face as it is. Inasmuch as faces are not
accurately symmetrical and many are quite unsymmetrical the effects of the
mirror are sometimes startling. It might be of interest for the reader to
study his face in the mirror and note that the right ear is the left ear
of the image which he sees. He will also find it of interest to compare
the face of a friend as viewed directly with the appearance of its image
in the mirror. If he desires to see himself as others see him, he can
arrange two mirrors vertically almost at a right-angle. By a little
research he will find an image of his own face, which is not reversed;
that is, an image whose right ear is really his right ear.
A famous "illusion" which astounded audiences was the sphinx illustrated
in Fig. 90. The box was placed upon a table and when opened there was
revealed a Sphinxian head, but why it was called a Sphinx is clothed in
mystery because upon some occasions it talked. As a matter of fact it
belonged to a body which extended downward from the table-top and this
kneeling human being was concealed from the audience by two very clean
plate-glass mirrors _M_ shown in the accompanying diagram. The table
actually appeared to have three legs but the audience if it noticed this
at all assumed the fourth leg was obscured by the foremost leg. The walls,
floor, and ceiling of the box-like recess in which the table was placed
were covered with the same material. It is seen by the diagram that the
mirrors _M_ reflected images of the side walls _W_ and these images were
taken by the audience to be portions of the rear wall _W_. Thus the table
appeared to be open underneath and the possibilities of the apparatus are
evident.
[Illustration: Fig. 90.--An example of a "mirror" illusion.]
The magician with a fine flow of language could dwell at length upon the
coming to life of the head of an ancient statue which he had in the box in
his hand. Walking to the table he could place the box over a trap-door and
by the time he had unlatched the door of the box, the assistant kneeling
under the table could have his head thrust upward through the trap-door of
the table-top into the box. After a few impressive words, supposed to be
Hindoo but in reality were Hoodoo, presto! and the Sphinx was revealed.
It conversed after a period of silence extending back to the days of
Rameses when a wrathful god condemned an unfortunate king to imprisonment
in the stone statue. The original trick awed audiences for many nights and
defied explanation until one night a keen observer noted finger-prints on
what proved to be a mirror. Doubtless a careless accomplice lost his job,
but the damage had been done, for the trick was revealed. This "illusion"
is so effective that it, or variations of it, are still in use.
[Illustration: Fig. 91.--Another example of "mirror magic."]
Another simple case is illustrated in Fig. 91. A large plate-glass mirror
_M_ was placed at an angle of approximately 45 degrees from the floor.
Through a hole in it an assistant's head and shoulders projected and the
edge of the opening was covered with a draped cloth. The audience saw the
image of the ceiling _C_ of the alcove reflected by the mirror but being
ignorant of the presence of the mirror, assumed this image to be the rear
wall. This trick was effective for many years. Obviously the mirrors must
be spotlessly clean and the illuminations of the walls, ceiling, and in
some cases, the floor must be very uniform. Furthermore, no large
conspicuous pattern could be used for lining the box-like recess.
The foregoing examples illustrate the principles involved in the
appearance of ghosts on the stage and of a skeleton or other gruesome
object in place of a human being. The possibilities of mirrors in such
fields are endless and they can be studied on a small scale by anyone
interested. The pseudoscope which produces effects opposite to those of
the stereoscope is an interesting device.
The foregoing is the faintest glimpse of the use of the mirror, but it
does not appear advisable to dwell further upon its use, for after all the
results are not visual illusions in the sense of the term as usually
employed throughout this book.
XV
CAMOUFLAGE
Illusions played many roles in the science and art of deception during the
World War, but they served most prominently in the later stages of the war
upon the sea. Inasmuch as the story of the science of camouflage is not
generally available, it appears worth while to present it briefly. Besides
being of interest, it will reveal to the reader the part that the science
of light, color, lighting, and vision played in deception. Furthermore,
the reader will sense the numberless illusions which are woven into
camouflage as developed in nature, and in human activities. The word
_camouflage_ by origin does not include all kinds of deception; however,
by extension it may and will here signify almost the entire art and
science of deception as found in nature and as practiced in the World War.
_Terrestrial Camouflage._--Camouflage is an art which is the natural
outgrowth of our instinct for concealment and deception when pitting our
wits against those of a crafty prey or enemy. It is an art older than the
human race, for its beginnings may be traced back to the obscurity of the
early ages of the evolution of animal life. The name was coined by the
French to apply to a definite art which developed during the Great War to
a high state, as many other arts developed by drawing deeply upon the
resources of scientific knowledge. With the introduction of this specific
word to cover a vast field of activity in scientifically concealing and
deceiving, many are led to believe that this is a new art, but such is not
the case. However, like many other arts, such as that of flying, the
exigencies of modern warfare have provided an impetus which has resulted
in a highly developed art.
Scientists have recognized for many years, and perhaps more or less
vaguely for centuries, that Nature exhibits wonderful examples of
concealment and deception. The survival of the fittest, as Darwin
expressed his doctrine, included those individuals of a species who were
best fitted by their markings and perhaps by peculiar habits to survive in
the environment in which they lived. Naturally, markings, habits, and
environment became more and more adapted to each other until the species
became in equilibrium with Nature sufficiently to insure its perpetuity.
If we look about us upon animal life we see on every hand examples of
concealing coloration and attitudes designed to deceive the prey or enemy.
The rabbit is mottled because Nature's infinite variety of highlights,
shadows, and hues demand variety in the markings of an animal if the
latter is to be securely hidden. Solid color does not exist in Nature's
landscapes in large areas. The rabbit is lighter underneath to compensate
for the lower intensity of illumination received on these portions. As
winter approaches, animals in rigorous climates need warmer coats, and the
hairs grow longer. In many cases the color of the hairs changes to gray or
white, providing a better coating for the winter environment.
Animals are known to mimic inanimate objects for the sake of safety. For
example, the bittern will stand rigid with its bill pointed skyward for
many minutes if it suspects an enemy. Non-poisonous snakes resemble
poisonous ones in general characteristics and get along in the world on
the reputation of their harmful relatives. The drone-bee has no sting, but
to the casual observer it is a bee and bees generally sting. Some animals
have very contrasting patterns which are conspicuous in shape, yet these
very features disguise the fact that they are animals. Close observation
of fishes in their natural environment provides striking examples of
concealing coloration. Vast works have been written on this subject by
scientists, so it will only be touched upon here.
There are many examples of "mobile" camouflage to be found in Nature.
Seasonal changes have been cited in a foregoing paragraph. The chameleon
changes its color from moment to moment. The flounder changes its color
and _pattern_ to suit its environment. It will even strive to imitate a
black and white checkerboard.
In looking at a bird, animal, insect, or other living thing it is
necessary to place it in its natural environment at least in the
imagination, before analyzing its coloration. For example, a male mallard
duck hanging in the market is a very gaudy object, but place it in the
pond among the weeds, the green leaves, the highlights, and the shadows,
and it is surprisingly inconspicuous. The zebra in the zoo appears to be
marked for the purpose of heralding its presence anywhere in the range of
vision, but in its reedy, bushy, grassy environment it is sufficiently
inconspicuous for the species to survive in Nature's continuous warfare.
Thus studies of Nature reveal the importance of general hue, the necessity
for broken color or pattern, the fact that black spots simulate shadows or
voids, the compensation for lower illumination by counter-shading, and
many other facts. The artist has aided in the development of camouflage,
but the definite and working basis of all branches of camouflage are the
laws and facts of light, color, and vision as the scientist knows them.
Just as lower animal life has unconsciously survived or evolved by being
fitted to do so, mankind has consciously, or at least instinctively,
applied camouflage of various kinds to fool his prey or his enemy. Many of
us in hunting ducks have concealed the bow of our sneak-boat with mud and
weeds, or in the season of floating ice, with a white cloth. In our quest
of water fowl we use decoys and grass suits. The Esquimau stalks his game
behind a piece of ice. In fact, on every hand we find evidences of this
natural instinct. The Indian painted his face and body in a variety of
colors and patterns. Did he do this merely to be hideous? It seems very
possible that the same instinct which made him the supreme master of
wood-craft caused him to reap some of the advantages of concealment due to
the painting of his face and body.
In past wars there is plenty of evidence that concealment and deception
were practiced to the full extent justifiable by the advantages or
necessity. In the World War the advent of the airplane placed the third
dimension in reconnaissance and called for the application of science in
the greatly extended necessity for concealment and deception. With the
advent of the airplane, aerial photography became a more important factor
than visual observation in much of the reconnaissance. This necessitated
that camouflage in order to be successful had to meet the requirements of
the photographic eye, as well as that of the human eye. In other words,
the special characteristics of the colors used had to be similar to those
of Nature's colors. For example, chlorophyl, the green coloring matter of
vegetation, is a peculiar green as compared with green pigments. When
examined with a spectroscope it is seen to reflect a band of deep red
light not reflected by ordinary pigments. In considering this aspect it is
well to bear in mind that the eye is a synthetic apparatus; that is does
not analyze color in a spectral sense. An artist who views color
subjectively and is rarely familiar with the spectral basis may match a
green leaf perfectly with a mixture of pigments. A photographic plate, a
visual filter, or a spectroscope will reveal a difference which the
unaided eye does not.
Some time before the Great War began, it occurred to the writer that
colored filters could be utilized in aiding vision by increasing the
contrast of the object to be viewed against its surroundings.[9] Studies
were made of various filters, made with the object of the experiment in
mind, in viewing the uniforms of various armies. Further developments were
made by applying the same principles to colored lights and painted
pictures. Many of these have been described elsewhere. With the
development of the science of camouflage, filters came into use for the
detection of camouflage. As a result of the demand for avoiding detection
by photographic plates and by various colored filters, some paints
provided for the camoufleur were developed according to the spectral
requirements. Many other applications of science were developed so that
camouflage can now be called an art based upon sound scientific
principles.
Natural lighting is so variable that it is often impossible to provide
camouflage which will remain satisfactory from day to day; therefore, a
broad knowledge of Nature's lighting is necessary in order to provide the
best compromise. There are two sources of light in the daytime, namely,
the sun and the sky. The relative amounts of light contributed by these
two sources is continually changing. The sky on cloudless days contributes
from one-tenth to one-third of the total light received by a horizontal
surface at noon. Light from the sky and light reflected from the
surroundings illuminate the shadows. These shadows are different in color
than highlights, although these finer distinctions may be ignored in most
camouflage because color becomes less conspicuous as the distance of
observation increases. In general, the distribution of brightness or light
and shade is the most important aspect to be considered.
The camoufleur worries over shadows more than any other aspect generally.
On overcast days camouflage is generally much more successful than on
sunny days. Obviously, counter-shading is resorted to in order to
eliminate shadows, and where this is unsuccessful confusion is resorted to
by making more shadows. The shape and orientation of a building is very
important to those charged with the problem of rendering it inconspicuous
to the enemy, but little attention has been paid to these aspects. For
example, a hangar painted a very satisfactory dull green will be
distinguishable by its shape as indicated by its shadow and shaded sides.
In this zone a hangar, for example, would be more readily concealed if its
length lay north and south. Its sides could be brought with a gradual
curve to the ground and its rear, which is during most of the day in
shadow, could be effectively treated to conceal the shadow. A little
thought will convince the reader of the importance of shape and
orientation.
Broken color or pattern is another fundamental of camouflage which, of
course, must be adapted to its environment. For our trucks, cannon, and
many other implements of war, dark green, yellow, dark blue, light gray,
and other colors have been used in a jumble of large patterns. A final
refinement is that of the blending of these colors at a distance, where
the eye no longer resolves the individual patches, to a color which
simulates the general hue of the surroundings. For example, red and green
patches at a distance blend to yellow; yellow and blue patches blend to a
neutral gray if suitably balanced, but if not, to a yellow-gray or a
blue-gray; red, green, and blue if properly balanced will blend to a gray;
black, white and green patches will blend to a green shade, and so on.
These facts are simple to those who are familiar with the science of
light and color, but the artist, whose knowledge is based upon the mixture
of pigments, sometimes errs in considering this aspect of color-blending
by distance. For example, it is not uncommon for him to state that at a
distance yellow and blue patches blend to make green, but the addition of
lights or of juxtaposed colors is quite different in result from the
addition of pigments by intimately mixing them.
In constructing such a pattern of various colors it is also desirable to
have the final mean brightness approximate that of the general
surroundings. This problem can be solved by means of the photometer and a
formula provided, which states, for example, that a certain percentage of
the total area be painted in gray, another percentage in green, and so on.
The photometer has played an important role in establishing the scientific
basis of camouflage. The size of the pattern must be governed by the
distance at which it is to be viewed, for obviously if too small the
effect is that of solid color, and if too large it will render the object
conspicuous, which is a disadvantage ranking next to recognizable.
Where the artist is concerned with a background which does not include the
sky, that is, where he deals only with _illuminated_ objects on the earth,
his trained eye is valuable provided the colors used meet the demands made
by photographic plates and visual color-filters. In other words, the sky
as a background gives trouble to all who are unfamiliar with scientific
measurements. The brightnesses of sky and clouds are outside the scale of
brightnesses ordinarily encountered in a landscape. Many interesting
instances of the artist's mistakes in dealing with these backgrounds could
be presented; however, the artist's trained eye has been a great aid in
constructing patterns and various other types of camouflage. One of the
most conspicuous aspects of the earth's surface is its texture. From great
heights it appears flat, that is, rolling land is ironed out and the
general contour of the ground is flattened. However, the element of
texture always remains. This is the chief reason for the extensive use of
netting on which dyed raffia, foliage, pieces of colored cloth, etc., are
tied. Such network has concealed many guns, headquarters, ammunition
dumps, communication trenches, roadways, etc. When this has been well done
the concealment is perfect.
One of the greatest annoyances to the camoufleur is the lack of dullness
or "flatness" of the paints, fabrics, and some of the other media used.
When viewed at some angles the glint of highlights due to specular
reflection renders the work very conspicuous. For this reason natural
foliage or such material as dyed raffia has been very successful.
Systems of network and vertical screens have been extensively employed on
roadways near the front, not for the purpose of concealing from the enemy
the fact that the roadways exist, but to make it necessary to shell the
entire roadway continually if it is hoped to prevent its use.