Atlantic Monthly, Volume 3, No. 20, June, 1859 by Various

V >> Various >> Atlantic Monthly, Volume 3, No. 20, June, 1859

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Stretch up your white arms towards me,
Climb and never despair;
Come! the blue sky is above you,
Sunlight and soft warm air.
Shake off the sleep from your eyelids,
Work in the darkness awhile,
Trust in the light that's above you,
Win your way up to its smile.

Ah! do you know how the May-flowers,
Down on the shore of the lake.
Are whispering, one to another,
All in the silence, "Awake!"
Blushing from under the pine-leaves,
Soon they will greet me anew,--
But still, oh, my beautiful violets,
I'll be watching and longing for you.

THE STEREOSCOPE AND THE STEREOGRAPH.

Democritus of Abdera, commonly known as the Laughing Philosopher,
probably because he did not consider the study of truth inconsistent
with a cheerful countenance, believed and taught that all bodies were
continually throwing off certain images like themselves, which subtile
emanations, striking on our bodily organs, gave rise to our sensations.
Epicurus borrowed the idea from him, and incorporated it into the famous
system, of which Lucretius has given us the most popular version. Those
who are curious on the matter will find the poet's description at the
beginning of his fourth book. Forms, effigies, membranes, or _films_,
are the nearest representatives of the terms applied to these
effluences. They are perpetually shed from the surfaces of solids, as
bark is shed by trees. _Cortex_ is, indeed, one of the names applied to
them by Lucretius.

These evanescent films may be seen in one of their aspects in any clear,
calm sheet of water, in a mirror, in the eye of an animal by one who
looks at it in front, but better still by the consciousness behind the
eye in the ordinary act of vision. They must be packed like the leaves
of a closed book; for suppose a mirror to give an image of an object a
mile off, it will give one at every point less than a mile, though this
were subdivided into a million parts. Yet the images will not be the
same; for the one taken a mile off will be very small, at half a mile as
large again, at a hundred feet fifty times as large, and so on, as long
as the mirror can contain the image.

Under the action of light, then, a body makes its superficial aspect
potentially present at a distance, becoming appreciable as a shadow or
as a picture. But remove the cause,--the body itself,--and the effect is
removed. The man beholdeth himself in the glass and goeth his way, and
straightway both the mirror and the mirrored forget what manner of man
he was. These visible films or membranous _exuviae_ of objects, which
the old philosophers talked about, have no real existence, separable
from their illuminated source, and perish instantly when it is
withdrawn.

If a man had handed a metallic speculum to Democritus of Abdera, and
told him to look at his face in it while his heart was beating thirty
or forty times, promising that one of the films his face was shedding
should stick there, so that neither he, nor it, nor anybody should
forget what manner of man he was, the Laughing Philosopher would
probably have vindicated his claim to his title by an explosion that
would have astonished the speaker.

This is just what the Daguerreotype has done. It has fixed the most
fleeting of our illusions, that which the apostle and the philosopher
and the poet have alike used as the type of instability and unreality.
The photograph has completed the triumph, by making a sheet of paper
reflect images like a mirror and hold them as a picture.

This triumph of human ingenuity is the most audacious, remote,
improbable, incredible,--the one that would seem least likely to be
regained, if all traces of it were lost, of all the discoveries man has
made. It has become such an everyday matter with us, that we forget its
miraculous nature, as we forget that of the sun itself, to which we owe
the creations of our new art. Yet in all the prophecies of dreaming
enthusiasts, in all the random guesses of the future conquests over
matter, we do not remember any prediction of such an inconceivable
wonder, as our neighbor round the corner, or the proprietor of the small
house on wheels, standing on the village common, will furnish any of us
for the most painfully slender remuneration. No Century of Inventions
includes this among its possibilities. Nothing but the vision of a
Laputan, who passed his days in extracting sunbeams out of cucumbers,
could have reached such a height of delirium as to rave about the time
when a man should paint his miniature by looking at a blank tablet, and
a multitudinous wilderness of forest foliage or an endless Babel of
roofs and spires stamp itself, in a moment, so faithfully and so
minutely, that one may creep over the surface of the picture with his
microscope and find every leaf perfect, or read the letters of distant
signs, and see what was the play at the "Varietes" or the "Victoria,"
on the evening of the day when it was taken, just as he would sweep the
real view with a spy-glass to explore all that it contains.

Some years ago, we sent a page or two to one of the magazines,--the
"Knickerbocker," if we remember aright,--in which the story was told
from the "Arabian Nights," of the three kings' sons, who each wished to
obtain the hand of a lovely princess, and received for answer, that he
who brought home the most wonderful object should obtain the lady's hand
as his reward. Our readers, doubtless, remember the original tale, with
the flying carpet, the tube which showed what a distant friend was
doing by looking into it, and the apple which gave relief to the
most desperate sufferings only by inhalation of its fragrance. The
railroad-car, the telegraph, and the apple-flavored chloroform could and
do realize, every day,--as was stated in the passage referred to, with
a certain rhetorical amplitude not doubtfully suggestive of the
lecture-room,--all that was fabled to have been done by the carpet, the
tube, and the fruit of the Arabian story.

All these inventions force themselves upon us to the full extent of
their significance. It is therefore hardly necessary to waste any
considerable amount of rhetoric upon wonders that are so thoroughly
appreciated. When human art says to each one of us, I will give you
ears that can hear a whisper in New Orleans, and legs that can walk six
hundred miles in a day, and if, in consequence of any defect of rail
or carriage, you should be so injured that your own very insignificant
walking members must be taken off, I can make the surgeon's visit a
pleasant dream for you, on awaking from which you will ask when he
is coming to do that which he has done already,--what is the use of
poetical or rhetorical amplification? But this other invention of _the
mirror with a memory_, and especially that application of it which has
given us the wonders of the stereoscope, is not so easily, completely,
universally recognized in all the immensity of its applications and
suggestions. The stereoscope, and the pictures it gives, are, however,
common enough to be in the hands of many of our readers; and as many of
those who are not acquainted with it must before long become as familiar
with it as they are now with friction-matches, we feel sure that a few
pages relating to it will not be unacceptable.

Our readers may like to know the outlines of the process of making
daguerreotypes and photographs, as just furnished us by Mr. Whipple, one
of the most successful operators in this country. We omit many of those
details which are everything to the practical artist, but nothing to
the general reader. We must premise, that certain substances undergo
chemical alterations, when exposed to the light, which produce a change
of color. Some of the compounds of silver possess this faculty to a
remarkable degree,--as the common indelible marking-ink, (a solution of
nitrate of silver,) which soon darkens in the light, shows us every day.
This is only one of the innumerable illustrations of the varied effects
of light on color. A living plant owes its brilliant hues to the
sunshine; but a dead one, or the tints extracted from it, will fade
in the same rays which clothe the tulip in crimson and gold,--as our
lady-readers who have rich curtains in their drawing-rooms know full
well. The sun, then, is a master of _chiaroscuro_, and, if he has a
living petal for his pallet, is the first of colorists.--Let us walk
into his studio, and examine some of his painting machinery.

* * * * *

1. THE DAGUERREOTYPE.--A silver-plated sheet of copper is resilvered by
electro-plating, and perfectly polished. It is then exposed in a glass
box to the vapor of iodine until its surface turns to a golden yellow.
Then it is exposed in another box to the fumes of the bromide of lime
until it becomes of a blood-red tint. Then it is exposed once more, for
a few seconds, to the vapor of iodine. The plate is now sensitive to
light, and is of course kept from it, until, having been placed in the
darkened camera, the screen is withdrawn and the camera-picture falls
upon it. In strong light, and with the best instruments, _three
seconds'_ exposure is enough,--but the time varies with circumstances.
The plate is now withdrawn and exposed to the vapor of mercury at 212 deg..
Where the daylight was strongest, the sensitive coating of the plate has
undergone such a chemical change, that the mercury penetrates readily to
the silver, producing a minute white granular deposit upon it, like
a very thin fall of snow, drifted by the wind. The strong lights are
little heaps of these granules, the middle lights thinner sheets of
them; the shades are formed by the dark silver itself, thinly sprinkled
only, as the earth shows with a few scattered snow-flakes on its
surface. The precise chemical nature of these granules we care less
for than their palpable presence, which may be perfectly made out by a
microscope magnifying fifty diameters or even less.

The picture thus formed would soon fade under the action of light, in
consequence of further changes in the chemical elements of the film
of which it consists. Some of these elements are therefore removed by
washing it with a solution of hyposulphite of soda, after which it is
rinsed with pure water. It is now permanent in the light, but a touch
wipes off the picture as it does the bloom from a plum. To fix it, a
solution of hyposulphite of soda containing chloride of gold is poured
on the plate while this is held over a spirit-lamp. It is then again
rinsed with pure water, and is ready for its frame.

2. THE PHOTOGRAPH.--Just as we must have a mould before we can make a
cast, we must get a _negative_ or reversed picture on glass before we
can get our positive or natural picture. The first thing, then, is to
lay a sensitive coating on a piece of glass,--crown-glass, which has a
natural surface, being preferable to plate-glass. _Collodion_, which is
a solution of gun-cotton in alcohol and ether, mingled with a solution
of iodide and bromide of potassium, is used to form a thin coating over
the glass. Before the plate is dry, it is dipped into a solution of
nitrate of silver, where it remains from one to three or four minutes.
Here, then, we have essentially the same chemical elements that we
have seen employed in the daguerreotype,--namely, iodine, bromine, and
silver; and by their mutual reactions in the last process we have formed
the sensitive iodide and bromide of silver. The glass is now placed,
still wet, in the camera, and there remains from three seconds to one
or two minutes, according to circumstances. It is then washed with a
solution of sulphate of iron. Every light spot in the camera-picture
becomes dark on the sensitive coating of the glass-plate. But where the
shadows or dark parts of the camera-picture fall, the sensitive coating
is less darkened, or not at all, if the shadows are very deep, and
so these shadows of the camera-picture become the lights of the
glass-picture, as the lights become the shadows. Again, the picture is
reversed, just as in every camera-obscura where the image is received on
a screen direct from the lens. Thus the glass plate has the right part
of the object on the left side of its picture, and the left part on its
right side; its light is darkness, and its darkness is light. Everything
is just as wrong as it can be, except that the relations of each wrong
to the other wrongs are like the relations of the corresponding rights
to each other in the original natural image. This is a _negative_
picture.

Extremes meet. Every given point of the picture is as far from truth as
a lie can be. But in travelling away from the pattern it has gone round
a complete circle, and is at once as remote from Nature and as near it
as possible.--"How far is it to Taunton?" said a countryman, who was
walking exactly the wrong way to reach that commercial and piscatory
centre.--"'Baeout twenty-five thaeousan' mild,"--said the boy he
asked,--"'f y' go 'z y' 'r' goin' naeow, 'n' 'baeout haeaf a mild 'f y' turn
right raeoun' 'n' go t'other way."

The negative picture being formed, it is washed with a solution of
hyposulphite of soda, to remove the soluble principles which are liable
to decomposition, and then coated with shellac varnish to protect it.

This _negative_ is now to give birth to a _positive_,--this mass of
contradictions to assert its hidden truth in a perfect harmonious
affirmation of the realities of Nature. Behold the process!

A sheet of the best linen paper is dipped in salt water and suffered to
dry. Then a solution of nitrate of silver is poured over it and it is
dried in a dark place. This paper is now sensitive; it has a conscience,
and is afraid of daylight. Press it against the glass negative and lay
them in the sun, the glass uppermost, leaving them so for from three to
ten minutes. The paper, having the picture formed on it, is then washed
with the solution of hyposulphite of soda, rinsed in pure water, soaked
again in a solution of hyposulphite of soda, to which, however, the
chloride of gold has been added, and again rinsed. It is then sized or
varnished.

Out of the perverse and totally depraved negative,--where it might
almost seem as if some magic and diabolic power had wrenched all things
from their proprieties, where the light of the eye was darkness, and the
deepest blackness was gilded with the brightest glare,--is to come the
true end of all this series of operations, a copy of Nature in all her
sweet gradations and harmonies and contrasts.

We owe the suggestion to a great wit, who overflowed our small
intellectual home-lot with a rushing freshet of fertilizing talk
the other day,--one of our friends, who quarries thought on his
own premises, but does not care to build his blocks into books and
essays,--that perhaps this world is only the _negative_ of that better
one in which lights will be turned to shadows and shadows into light,
but all harmonized, so that we shall see why these ugly patches, these
misplaced gleams and blots, were wrought into the temporary arrangements
of our planetary life.

For, lo! when the sensitive paper is laid in the sun under the negative
glass, every dark spot on the glass arrests a sunbeam, and so the spot
of the paper lying beneath remains unchanged; but every light space of
the negative lets the sunlight through, and the sensitive paper
beneath confesses its weakness, and betrays it by growing dark just in
proportion to the glare that strikes upon it. So, too, we have only
to turn the glass before laying it on the paper, and we bring all the
natural relations of the object delineated back again,--its right to the
right of the picture, its left to the picture's left.

On examining the glass negative by transmitted light with a power of a
hundred diameters, we observe minute granules, whether crystalline or
not we cannot say, very similar to those described in the account of
the daguerreotype. But now their effect is reversed. Being opaque, they
darken the glass wherever they are accumulated, just as the snow darkens
our skylights. Where these particles are drifted, therefore, we have our
shadows, and where they are thinly scattered, our lights. On examining
the paper photographs, we have found no distinct granules, but diffused
stains of deeper or lighter shades.

Such is the sun-picture, in the form in which we now most commonly meet
it,--for the daguerreotype, perfect and cheap as it is, and admirably
adapted for miniatures, has almost disappeared from the field of
landscape, still life, architecture, and _genre_ painting, to make room
for the photograph. Mr. Whipple tells us that even now he takes a much
greater number of miniature portraits on metal than on paper; and yet,
except occasionally a statue, it is rare to see anything besides
a portrait shown in a daguerreotype. But the greatest number of
sun-pictures we see are the photographs which are intended to be looked
at with the aid of the instrument we are next to describe, and to the
stimulus of which the recent vast extension of photographic copies of
Nature and Art is mainly owing.

3. THE STEREOSCOPE.--This instrument was invented by Professor
Wheatstone, and first described by him in 1838. It was only a year after
this that M. Daguerre made known his discovery in Paris; and almost
at the same time Mr. Fox Talbot sent his communication to the Royal
Society, giving an account of his method of obtaining pictures on paper
by the action of light. Iodine was discovered in 1811, bromine in 1826,
chloroform in 1831, gun-cotton, from which collodion is made, in 1846,
the electro-plating process about the same time with photography; "all
things, great and small, working together to produce what seemed at
first as delightful, but as fabulous, as Aladdin's ring, which is now as
little suggestive of surprise as our daily bread."

A stereoscope is an instrument which makes surfaces look solid. All
pictures in which perspective and light and shade are properly managed,
have more or less of the effect of solidity; but by this instrument that
effect is so heightened as to produce an appearance of reality which
cheats the senses with its seeming truth.

There is good reason to believe that the appreciation of solidity by the
eye is purely a matter of education. The famous case of a young man who
underwent the operation of couching for cataract, related by Cheselden,
and a similar one reported in the Appendix to Mueller's Physiology, go to
prove that everything is seen only as a superficial extension, until
the other senses have taught the eye to recognize _depth_, or the third
dimension, which gives solidity, by converging outlines, distribution
of light and shade, change of size, and of the texture of surfaces.
Cheselden's patient thought "all objects whatever touched his eyes, as
what he felt did his skin." The patient whose case is reported by Mueller
could not tell the form of a cube held obliquely before his eye from
that of a flat piece of pasteboard presenting the same outline. Each of
these patients saw only with one eye,--the other being destroyed, in one
case, and not restored to sight until long after the first, in the
other case. In two months' time Cheselden's patient had learned to
know solids; in fact, he argued so logically from light and shade and
perspective that he felt of pictures, expecting to find reliefs and
depressions, and was surprised to discover that they were flat surfaces.
If these patients had suddenly recovered the sight of _both_ eyes,
they would probably have learned to recognize solids more easily and
speedily.

We can commonly tell whether an object is solid, readily enough with one
eye, but still better with two eyes, and sometimes _only_ by using both.
If we look at a square piece of ivory with one eye alone, we cannot tell
whether it is a scale of veneer, or the side of a cube, or the base of
a pyramid, or the end of a prism. But if we now open the other eye, we
shall see one or more of its sides, if it have any, and then know it to
be a solid, and what kind of a solid.

We see something with the second eye which we did not see with the
first; in other words, the two eyes see different pictures of the same
thing, for the obvious reason that they look from points two or three
inches apart. By means of these two different views of an object, the
mind, as it were, _feels round it_ and gets an idea of its solidity. We
clasp an object with our eyes, as with our arms, or with our hands, or
with our thumb and finger, and then we know it to be something more than
a surface. This, of course, is an illustration of the fact, rather than
an explanation of its mechanism.

Though, as we have seen, the two eyes look on two different pictures, we
perceive but one picture. The two have run together and become blended
in a third, which shows us everything we see in each. But, in order that
they should so run together, both the eye and the brain must be in a
natural state. Push one eye a little inward with the forefinger, and the
image is doubled, or at least confused. Only certain parts of the two
retinae work harmoniously together, and you have disturbed their natural
relations. Again, take two or three glasses more than temperance
permits, and you see double; the eyes are right enough, probably, but
the brain is in trouble, and does not report their telegraphic messages
correctly. These exceptions illustrate the every-day truth, that, when
we are in right condition, our two eyes see two somewhat different
pictures, which our perception combines to form one picture,
representing objects in all their dimensions, and not merely as
surfaces.

Now, if we can get two artificial pictures of any given object, one as
we should see it with the right eye, the other as we should see it with
the left eye, and then, looking at the right picture, and that only,
with the right eye, and at the left picture, and that only, with the
left eye, contrive some way of making these pictures run together as we
have seen our two views of a natural object do, we shall get the sense
of solidity that natural objects give us. The arrangement which effects
it will be a _stereoscope_, according to our definition of that
instrument. How shall we attain these two ends?

1. An artist can draw an object as he sees it, looking at it only with
his right eye. Then he can draw a second view of the same object as he
sees it with his left eye. It will not be hard to draw a cube or an
octahedron in this way; indeed, the first stereoscopic figures were
pairs of outlines, right and left, of solid bodies, thus drawn. But the
minute details of a portrait, a group, or a landscape, all so nearly
alike to the two eyes, yet not identical in each picture of our natural
double view, would defy any human skill to reproduce them exactly.
And just here comes in the photograph to meet the difficulty. A first
picture of an object is taken,--then the instrument is moved a couple
of inches or a little more, the distance between the human eyes, and a
second picture is taken. Better than this, two pictures are taken at
once in a double camera.

We were just now stereographed, ourselves, at a moment's warning, as
if we were fugitives from justice. A skeleton shape, of about a man's
height, its head covered with a black veil, glided across the floor,
faced us, lifted its veil, and took a preliminary look. When we had
grown sufficiently rigid in our attitude of studied ease, and got
our umbrella into a position of thoughtful carelessness, and put our
features with much effort into an unconstrained aspect of cheerfulness
tempered with dignity, of manly firmness blended with womanly
sensibility, of courtesy, as much as to imply,--"You honor me, Sir,"
toned or sized, as one may say, with something of the self-assertion of
a human soul which reflects proudly, "I am superior to all this,"--when,
I say, we were all right, the spectral Mokanna dropped his long veil,
and his waiting-slave put a sensitive tablet under its folds. The veil
was then again lifted, and the two great glassy eyes stared at us once
more for some thirty seconds. The veil then dropped again; but in the
mean time, the shrouded sorcerer had stolen our double image; we were
immortal. Posterity might thenceforth inspect us, (if not otherwise
engaged,) not as a surface only, but in all our dimensions as an
undisputed _solid_ man of Boston.

2. We have now obtained the double-eyed or twin pictures, or
STEREOGRAPH, if we may coin a name. But the pictures are two, and we
want to slide them into each other, so to speak, as in natural vision,
that we may see them as one. How shall we make one picture out of two,
the corresponding parts of which are separated by a distance of two or
three inches?

We can do this in two ways. First, by _squinting_ as we look at them.
But this is tedious, painful, and to some impossible, or at least very
difficult. We shall find it much easier to look through a couple of
glasses that _squint for us_. If at the same time they _magnify_ the
two pictures, we gain just so much in the distinctness of the picture,
which, if the figures on the slide are small, is a great advantage. One
of the easiest ways of accomplishing this double purpose is to cut a
convex lens through the middle, grind the curves of the two halves
down to straight lines, and join them by their thin edges. This is a
_squinting magnifier_, and if arranged so that with its right half we
see the right picture on the slide, and with its left half the left
picture, it squints them both inward so that they run together and form
a single picture.

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