CHAPTER VI.
Light and its phenomena—Magic pictures—The optical paradox—Chinese metallic mirrors—Effect of an optical instrument on a superstitious mind—Origin of photography—The Talbotype—The Daguerreotype—Sunlight pictures.
Light and its phenomena—Magic pictures—The optical paradox—Chinese metallic mirrors—Effect of an optical instrument on a superstitious mind—Origin of photography—The Talbotype—The Daguerreotype—Sunlight pictures.
Thecause of those sensations which we refer to the eyes, or that which produces the sense of seeing, is light. The phenomena of vision have always been regarded as among the most interesting branches of natural science. The knowledge of the laws which regulate the phenomena of light, constitutes the science of optics, which explains the cause of many most striking illusions.
Magic pictures have been produced, which, when seen in a certain point through a glass, exhibit an object different from that be held by the naked eye. Niceron tells us that he executed at Paris, and deposited in the library of the Minimes of the Place Royale, a picture of this kind; when seen by the naked eye, it represented fifteen portraits of Turkish sultans, but, when viewed through the glass, it was a portrait of LouisXIII.
The writer has often seen a singular transformation effected by an ingenious device, called the optical paradox: thus an eagle may be changed into a lion, and a dog into a cat.
B: shallow drawer; C: rod rising from drawer to D: bar holding glass tube
small flat pyramid
For this purpose, a wooden three-sided box must be prepared, and through the open part may slide the various drawings to be used, asB. Connected with this, there must be a pillar,C, and a horizontal bar holding a tube,D, having in it a glass placed exactly over the centre. The change is partly dependent on the glass, the sides of which are flat and diverge from its hexagonal base upwards, to a point in the axis of the glass, like a pyramid,E, forming an isosceles triangle. All that is now necessary to the completion of the change, is in the border of the drawing, in which the various parts required for the new figure are cleverly introduced; so that when the distance of the glass from the eye is rightly adjusted, each angular side will take up its portion from the border, and present to the eye the various parts in an entire figure. The shape of the glass prevents the appearanceof any particular figure in the centre, as the eagle, for instance; while the lion, arranged in portions and drawn on the circle of refraction at six different parts of the border, yet artfully disguised by blending with it, the transformation will be completely produced.
A paper has lately been read to the Academy of Sciences at Paris, by M. Stanislaus Julien, on the metallic mirrors made in China, and to which the name of “magic mirrors” has been given. Hitherto all attempts by Europeans to obtain information as to the process, in the localities where they are manufactured, have proved failures, some of the persons applied to being unwilling to reveal the secret, and others being ignorant of the process. These mirrors are called magical, because, if they receive the rays of the sun on their polished surface, the characters, or flowersin relief, which exist on the other side, are faithfully reproduced. The following information has been obtained by M. Julien, from the writings of an author named Ou-tseu-hing, who lived between 1260 and 1341:—“The cause of this phenomenon is the distinct use of fine copper and rough copper. If, on the under side, there be produced, by casting in a mould, the figure of a dragon in a circle, there is then engraved deeply on the disc a dragon exactly similar. Then, the parts which have been cut are filled with rather rough copper; and this is, by the action of fire, incorporated with the other metal, which is of a finer nature. The face of the mirror is nextprepared, and a slight coating of tin is spread over it. If the polished disc of a mirror so prepared be turned towards the sun, and the image be reflected on a wall, it presents distinctly the clear portion and the dark portion, the one of the fine, and the other of the rough copper.” Ou-tseu-hing states, that he had ascertained this by a careful inspection of the fragments of a broken mirror.
It is easy for an ignorant and superstitious mind to confound a very harmless and simple instrument with one of magical power. We have an example of this in Dodwell’s description of his residence at Athens. On his first admission within the venerable walls of the Acropolis, it was necessary to offer a small present to the disdar, or Turkish governor, and an additional sum to make drawings and observations without being molested by the servants of the garrison. The disdar proved to be a man of bad faith and insatiable rapacity, and, after experiencing numerous vexations from the mercenary Turk, Dodwell was at length released from his importunities by a singular circumstance. As he was one day engaged in drawing the Parthenon, with the aid of his camera obscura, the disdar, whose surprise was excited by the novelty of the sight, asked, with a sort of fretful inquietude, what new conjuration he was performing with that extraordinary machine. Dodwell endeavoured to explain it, by putting in a clean sheet of paper, and making him look at the instrument;but he no sooner saw the Temple of Minerva reflected on the paper in all its lines and colours, than he imagined the effect was produced by some magical process; his astonishment appeared mingled with alarm, and, stroking his long black beard, he repeated several times the words Allah, Masch-Allah—a term of admiration with the Turks, signifying that which is made by God.
Again he looked into the camera obscura, with a kind of cautious diffidence, and, at that moment, some of his soldiers happening to pass before the reflecting-glass, were beheld by the astonished disdar walking upon the paper. He now became outrageous; he assailed Dodwell with various opprobrious epithets, one of which was Bonaparte—the appellation being at the time synonymous to that of magician, or of any one supposed to be endowed with supernatural talents—and declared that, if Dodwell chose, he might take away all the stones in the temple, but that he would not permit his soldiers to be conjured into a box. “When I found,” says Dodwell, “that it was no use to reason with his ignorance, I changed my tone, and told him that, if he did not leave me unmolested, I would put him into my box; and that he should find it a very difficult matter to get out again. His alarm was now visible; he immediately retired, and ever after stared at me with a mixture of apprehension and amazement. When he saw me come to the Acropolis, he carefully avoided my approach;and never afterwards gave me any further molestation.”
camera obscura
The portable camera obscura, represented by the diagram, has often yielded much pleasure in the domestic circle, while the larger ones, which are publicly exhibited, are highly interesting. No person, perhaps, has witnessed the neatness of outline, the precision of form, the truth of colouring, and the sweet gradations of tint, thus apparent, without regretting that an imagery so exquisite and faithful to nature could not be made to fix itself permanently on the tablet of the machine. Yet, in the estimation of all, such a wish seemed destined to take its place among other dreams of beautiful things; the splendid but impracticable conceptions in which men of science and ardent temperament have sometimes indulged. Such a dream, however, has been realized of late.
A: lens at left end of portable camera obscura; B: glass reflector at right end
Mr. Thomas Wedgewood, the celebrated porcelain manufacturer, so early as 1802, published, in the journals of the Royal Institution,a method of copying paintings upon glass, and of making profiles by the agency of light upon nitrate of silver. The experiments he made were repeated by sir Humphry Davy; but several years after, MM. Niepcé and Daguerre, and Mr. Fox Talbot, laid the foundation of the present state of photographic drawing. The former engaged in a long series of experiments to render metallic surfaces peculiarly sensitive; the aim of the latter was to produce this effect on paper. The camera obscura used for this purpose is a rectangular box, with a double convex lens,A, at one end, and a glass reflector,B, which is generally a piece of looking-glass, at the other. Now, supposing the rays of light to proceed from an extensive landscape, and pass through this small convex lens, as we well know they may do, what will be the effect produced? The scene will, in the first place, be thrown on the reflector, which is fixed at an angle of forty-five degrees to the horizon. Now it follows, from a law well known to opticians, that these rays will be reflected to the top of the box, immediately over the mirror; so that if a ground glass, or any other medium capable of receiving thereflected image, be placed there, a representation of the landscape may be observed. As then, it is proved, by innumerable experiments, that reflected light has, in proportion to its power, as much influence on prepared or photographic paper, as the direct rays of the sun; it follows that, if a piece of it be placed in the same situation as the ground glass, the reflected image, be it a landscape, a figure, or an artificial object, will be formed on it. All that is, therefore, required to be done, in using the camera obscura for photographic drawing, is to place upon the opening at the top of the box the prepared paper, and immediately to cover it with the lid,C, so that it may not be acted upon by any other light than that reflected from the mirror. The time required for producing the necessary effect will depend on several circumstances, such as the preparation of the paper and the intensity of the light when the experiment is made; the latter, however, is by far the more important. On a bright sun-shining day, the drawing will be produced in one-half the time, and with far more sharpness of outline, than on a dull wintry day, when the sun struggles with the mists by which its radiant beams are encumbered. “The Pencil of Nature,” is the expressive title of a collection of photographic drawings, produced by Mr. Talbot. Upon the third part of this work, we find the following acute criticism in theAthenæum, No. 920.
“The subjects are ‘The Entrance Gateway ofQueen’s College, Oxford;’ ‘The Ladder,’ in which we have three figures from the life; and ‘A View of the Author’s Residence, Lacock Abbey, in Wiltshire.’ In the first of these, the truth-telling character of photographic pictures is pleasingly shown. It appears, by the turret clock, that the view was taken a little after two, when the sun was shining obliquely upon the building. The story of every stone is told, and the crumbling of its surface under the action of atmospheric influences is distinctly marked. The figures in ‘The Ladder’ are prettily arranged, but the face of the boy is distorted, from the circumstance of its being so very near the edge of the field of view embraced by the lens of the camera obscura. In looking at this photograph, we are led at once to reflect on the truth to nature observed by Rembrandt, in the disposition of his lights and shadows. We have no violent contrasts; even the highest lights and the deepest shadows seem to melt into each other, and the middle tints are but the harmonizing gradations. Without the aid of colour, with simple brown and white, so charming a result is produced, that, looking at the picture from a little distance, we are almost led to fancy that the introduction of colour would add nothing to its charm.”
The following is the patent process for obtaining a negative picture:—Take a sheet of paper, with a smooth surface, and a close and even texture, and without the water-mark, andwash one side of it, by means of a soft camel’s-hair brush, with a solution composed of one hundred grains of crystallized nitrate of silver dissolved in six ounces of distilled water, having previously marked with a cross the side which is to be washed. When the paper has been dried cautiously at the fire, or spontaneously in the dark, immerse it for a few minutes (two minutes, at a temperature of sixty-five degrees,) in a solution of iodide of potassium, consisting of five hundred grains to one pint of distilled water. The paper is then to be dipped in water, and then dried, by applying blotting-paper to it lightly, and afterwards exposing it to the heat of a fire, or allowing it to dry spontaneously. The paper thus prepared is called iodized paper, and may be kept for any length of time in a portfolio not exposed to light. When a sheet of paper is required for use, wash it with the following solution, which we shall call No. 1; take one hundred grains of nitrate of silver, dissolved in two ounces of distilled water, and add to this one-third of its volume of strong acetic acid. Make another solution, No. 2, by dissolving crystallized gallic acid in cold distilled water, and then mix the two solutions together in equal proportions, and in no greater quantity than is required for immediate use, as it will not keep long without spoiling. This mixture, called gallo-nitrate of silver, by the patentee, is then to be spread, by a soft camel’s-hair brush, on the marked side of the iodized paper;and, after allowing the paper to remain half-a-minute to absorb the solution, it should be dipped in distilled water and dried lightly; first with blotting-paper, and then by holding the paper at a considerable distance from the fire. When dry, the paper is ready, and it is advisable to use it within a few hours.
The paper, which is highly sensitive to light, must now be placed in the camera obscura, in order to receive on its marked surface a distinct image of the landscape or person whose picture is required. After remaining in the camera from ten seconds to several minutes, according to the intensity of the light, it is taken out of the camera in a dark room. If the object has been strongly illuminated, or if the paper has been long in the camera, a sensible picture will be seen on the paper; but, if the time of exposure has been short, or the illumination feeble, the paper will “appear entirely blank.” An invisible image, however, is impressed on the paper, and may be rendered apparent by the following process:—Take some of the gallo-nitrate of silver, and, with a soft camel’s-hair brush, wash the paper all over with this liquid, then hold it before a gentle fire, and, in a short time, the image will begin to appear; and those parts upon which the light has acted most strongly will become brown or black, while the others remain white. The image continues to grow more and more distinct for some time, and, when it becomes sufficiently so, the operation must be terminated,and the picture fixed. In order to effect this, the paper must be dipped first into water, then partly dried by blotting-paper, and afterwards washed with a solution of bromide of potassium, consisting of one hundred grains of the salt, dissolved in eight or ten ounces of water. The picture is then finally washed in water and dried as before. In place of bromide of potassium, a strong solution of common salt may be used.
By this process we get a negative picture—having the lights dark and the shades light—and from it positive pictures may be obtained as follows:—Dip a sheet of good paper in a solution of common salt, consisting of one part of a saturated solution, to eight parts of water, and dry it first with blotting-paper, and then spontaneously. Mark one of its sides, and wash that side with a solution of nitrate of silver, which we shall call No. 3, consisting of eighty grains of salt, to one ounce of distilled water. When this paper is dry, place it with its marked side uppermost on a flat board or surface of any kind, and above it put the negative picture, which should be pressed against the nitrated or positive paper by means of a glass plate and screws. In the course of ten or fifteen minutes of a bright sunshine, or of several hours of common daylight, a fine positive picture will be found on the paper beneath the negative picture. When this picture has been well washed or soaked in water, it is washed over with the solution of bromide of potassium, alreadymentioned, or plunged in a strong solution of common salt.F
A singular result of the application of this invention occurred to an accomplished traveller, who ascended Mount Etna, in order to obtain representations of that remarkable volcano. No sooner was the camera fixed on the edge of the crater, and the sensitive paper introduced, than a partial irruption took place, and the traveller had to fly for his life. On the cessation of the irruption, he returned; doubtless, with the expectation of merely collecting the fragments of his valuable instrument; when, to his great astonishment and delight, he discovered not only that his camera was absolutely uninjured, but that it contained an admirable representation of the crater and the irruption.
A brief account of the process of the Daguerreotype may now be given. A plate of silvered copper, about as thick as a shilling, is well cleaned and polished by rubbing it with cotton, fine pumice powder, and dilute nitric acid, and afterwards exposed to the heat of a spirit-lamp, placed below it, till a strong white coating is formed on the polished surface. On the plate being cooled suddenly by means of a cold slab of stone or of metal, the white coating is removed by repeatedly polishing it with dry pumice and cotton, and then three times more with the dilute nitric acid and pumice powder.
A careful cleaning being thus given to the plate, it is placed in a box containing iodine, tillit becomes visibly covered with a golden film of that substance, which must neither be pale nor purple. It is then placed in the camera till a distinct picture of whatever appears before it is formed upon the surface; it remains there for a period depending on the intensity of the light, and is then removed to a metallic box, having in it a cup containing at least three ounces of mercury. Placed below the cup is a spirit-lamp, which throws off the mercurial vapour; and, in exact proportion as this vapour deposits itself on the parts of the plate which have been acted upon by the light, is the picture developed on the surface of the plate, by the adhesion of the white mercurial vapour to the different parts which had been impressed by the light. As soon as the picture appears complete, the plate is placed in a trough of sheet-copper, containing either a saturated solution of common salt, or a weak solution of hyposulphite of soda. Thus, the coating of iodine will be dissolved, the yellow colour quite disappearing; hot, but not boiling, distilled water is then poured over the plate, and any drops which remain are removed by blowing upon them.
The picture being now finished, is preserved from dust by placing it in a frame, and covering it with glass. In every successful operation, the picture is almost as perfect in its details as that of the camera obscura itself; but, as the light of the sun is only white, there can be, of course, none of the varied tints of nature. Theshades are supplied by the black polish of the metallic surface which, when it reflects a luminous object, the white vapour of the mercury appears in shade, and thus gives us either a positive or a negative picture, according to the light in which it is viewed.
Various improvements have gradually been made in the processes of the Daguerreotype and the Talbotype, which our limited space forbids us to describe. Mr. Beard has added colour to his Daguerreotype portraits, which is uniform and so transparent as not to affect the likeness in any degree, while the life-like effect is greatly heightened. M. Claudet has found that, when the sun is rendered red by the vapours of the atmosphere, it not only produces no effect upon the Daguerreotype plate, but that it destroys the effect previously produced by the white light. If the image of the red sun be taken in the camera obscura, it produces upon the Daguerreotype plate a black image. By covering a Daguerreotype plate previously affected by light with a red, orange, or yellow glass, the radiation through these coloured media has also the property of destroying the action produced by white light. The most interesting part of M. Claudet’s statement refers to the fact that, after the destroying action of the red, orange, and yellow radiations, the plate is restored to its former sensitiveness; so that, after having been affected by white light, and restored by the destructive action of the red, orange, and yellow radiations, it is possible to produce a photographiceffect, as upon a plate just prepared with iodine and bromine. This alternate acting and destroying action may be repeatedad infinitum, without altering the final state of the plate. This curious fact proves, evidently, that, in the Daguerreotype process, light does not alter the chemical compound on the plate, and that the affinity for mercury is the result of some new property imparted by the action of the rays of light. M. Claudet’s experiments prove, also, that the red and yellow rays are endowed with a photographic action of their own, which, as well as that of the blue and violet rays, gives an affinity for mercurial vapour. The photographic action of the red ray is destroyed by the yellow, that of the yellow by the red; the red and yellow destroy the photographic action of the blue, and the blue destroys the action of the others. The photographic, or the destroying action of any particular ray cannot be continued by any other. It appears, therefore, that each radiation changes the state of the plate, and each change produces the sensitiveness to mercurial vapour when it does not exist, and destroys this sensitiveness when it does exist.G
M. Regnault has laid before the Academy of Sciences, at Paris, some photographic specimens on paper, obtained by M. Blanquart-Evrard, by a modification of the usual process. In the preparations hitherto described, one part of the process presented serious difficulties, namely, that of the use of gallic acid in order to producethe impression. It happened frequently, that a proof taken in too mild a light, or of too large dimensions, could not receive the necessary force before disappearing, as it may be said, under the uniform colour produced by the mixture of the gallic acid with the aceto-azotate of silver, with which the paper is imbued. After having ascertained that the gallic acid produces this uniform colour on the impression, only because it is combined in small quantity with the aceto-azotate of silver, M. Blanquart-Evrard removes all the difficulty. After taking the proof from the camera obscura, he plunges it into a vessel of large dimensions, covered with a layer of one centimètre of gallic acid of cold saturation. The bath is agitated during the immersion; and the action may be thus prolonged until the impression has obtained the necessary force to secure a good result. The proof is then washed, and the gallic acid is replaced by a solution of bromure of potassium, or chloruret of sodium, in which it is left for about a quarter-of-an-hour.H
The chromatype, discovered by Mr. Hunt, consists in washing good letter-paper with the followingsolution:—
Papers prepared with this are of a pale yellow colour; they may be kept for any length of time without injury, and are always ready foruse. For copying botanical specimens or engravings, nothing can be more beautiful. After the paper has been exposed to the influence of sunshine, with the objects to be copied superposed, it is washed over in the dark with a solution of nitrate of silver of moderate strength. As soon as this is done, a very vivid positive picture makes its appearance; and all the fixing these photographic pictures require is, well washing in pure water.
M. Niepcé de St. Victor finds that, if a sheet of paper on which there is writing, printed characters, or a drawing, be exposed for a few minutes to the vapour of iodine, and there be applied immediately afterwards a coating of starch, moistened by slightly acidulated water, a faithful tracing of the writing, printing, or drawing, will be obtained. M. Niepcé has also discovered that a great number of substances, such as nitric acid, chlorurets of lime and mercury, act in a similar manner; and that various vapours, particularly those of ammonia, have the effect of vivifying the images which are obtained by photography.
In the words of a writer in theNorth British Review:—“While the artist is thus supplied with every material for his creative genius, the public will derive a new and immediate advantage from the productions of the solar pencil. The home-faring man—whom fate or duty chains to his birth-place, or imprisons in his fatherland—will, without the fatigues and dangers of travel, scan the beauties and wondersof the globe; not in the fantastic or deceitful images of a hurried pencil, but, in the very picture which would have been painted on his own retina, were he magically transported to the scene. The gigantic outline of the Himalaya and the Andes will stand self-depicted upon his borrowed retina—the Niagara will pour out before him, in panoramic grandeur, her mighty cataract of waters, while the flaming volcano will toss into the air her clouds of dust and her blazing fragments. The scene will change, and there will rise before him Egypt’s colossal pyramids, the temples of Greece and Rome, and the gilded mosques and towering minarets of eastern magnificence. But with not less wonder, and with a more eager and affectionate gaze, will he survey those hallowed scenes which faith has consecrated and love endeared. Painted in its cheerless tints, Mount Zion will stand before him, ‘as a field that is ploughed;’ Tyre, as a rock on which the fishermen dry their nets; Gaza, in her prophetic ‘baldness;’ Lebanon, with her cedars prostrate among ‘the howling firs;’ Nineveh made as a grave, ‘and seen only in the turf that covers it;’ and Babylon the great, the golden city, with its impregnable walls, its hundred gates of brass, now ‘sitting in the dust, cast up as an heap,’ covered with ‘pools of water,’ and without even the ‘Arab’s tent,’ or the ‘shepherd’s fold.’ But though it is only Palestine in desolation that a modern sun can delineate, yet the seas which bore on their breast the DivineRedeemer, and the everlasting hills which bounded his view, stand unchanged by time and the elements, and, delineated on the faithful tablet, still appeal to us with an immortal interest. But the scenes which are thus presented to us by the photographer have not merely the interest of being truthful representations: they form, as it were, a record of every visible event that takes place while the picture is delineating. The dial-plate of the clock tells the hour and minute when it was drawn, and with the day of the month, which we know, and the sun’s altitude, which the shadows on the picture often supply, we may find the very latitude of the place which is represented. All stationary life stands self-delineated on the photograph:—the wind, if it blows, will exhibit its disturbing influence; the rain, if it falls, will glisten on the house-top; the still clouds will exhibit their ever-changing forms; and even the lightning’s flash will imprint its fire-streak on the sensitive tablet.”