Magic, Pretended Miracles, and Remarkable Natural Phenomena

by Anonymous

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 the reflected 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 the Athenæum, No. 920.

“The subjects are ‘The Entrance Gateway of Queen’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, and wash 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, already mentioned, 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, till it 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. The shades 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 photographic effect, as upon a plate just prepared with iodine and bromine. This alternate acting and destroying action may be repeated ad 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]