From the North British Review.

HISTORY OF DISCOVERIES IN PHOTOGRAPHY.

The following able article is from the pen of Sir David Brewster, the greatest living authority in the department of science to which it belongs. It is an eloquent and comprehensive history of the most remarkable discoveries of Talbot and Daguerre, and though sufficiently minute in its scientific de

"Soon shall thine arm, unconquer'd Steam! afar Drag the slow barge, or drive the rapid car."

There are other inventions and discoveries, on the contrary, on which are stamped

scription, is written for the entertainment and instruction of imperishable names, or with which these

the general reader. -ED.]

THE history of science presents us with very few instances in which great inventions or discoveries have burst upon the public view like meteors, or startled the public mind by their novelty and grandeur. The greatest feats of intellect have, like the intellect itself, been of tardy growth. A suggestion from one mind and in one age, has become a fact in another; and some sickly embryo of thought, which has preserved its vitality for a century, has often assumed the form and beauty of a living truth, when the public taste or the wants of society have stimulated research, or created a demand for the productions of genius. So slow, indeed, has been the march of great ideas, and so obscure the path by which they reached their gigantic consummation, that the historian of science has often been unable to trace their steps, and the arbiter of genius to discover the brow upon which he might plant the laurel which they deserved. The astronomy which in one century gave immortality to a priest, in the next immured a philosopher in prison; and geological truth passed through the phases of a presumptuous speculation, and of an atheistical dogma, before it became the handmaid of piety and the creed of the Church. It is with much difficulty and some uncertainty that we can trace even the telescope and the microscope to their humble origin. The steam-engine has not yet owned its obligations to a single mind, and little more than half a century has elapsed since an English court of law came to the decision that James Watt had made no improvement on this mighty instrument of civilization. The steam-ship and the railway-chariot-the locomotives on water and on iron-at once the benefactors and the wonders of the age, will continue to be disputed or unclaimed inventions till society has forgotten the prediction of the poet, or lamented its fulfilment :

names are inseparably associated. Kepler's laws are engraven on the planetary heavens. Newton will never cease to be named, while satellites revolve and terrestrial bodies fall; and while Neptune bears his trident across the firmament, the fame of Adams and Le Verrier will endure. The electro-magnetic power which speeds over the globe the telegraphic message, will carry the name of Wheatstone to its most distant terminus whether in space or time; and the thunderbolt which Franklin drew from heaven, and which, when untaught and untamed, shattered in its course the structures of organic and inorganic life, will acknowledge its apprenticeship to Faraday, while it is imparting new organizations to matter, playing round the solar ray, and guiding even the particles of light in their fantastic gyrations. Other discoveries have associated themselves, even in their nomenclature, with individual names; and in the very terminology of the two great arts which we are about to expound-the Daguerreotype and Talbotype-a grateful age has already embalmed the names of their distinguished inventors.

The two inventions which we have just mentioned possess a character, and occupy a place, essentially different from that of any of the sister arts. While the painter delineates on canvas, or the sculptor embodies in marble those images in their eye to which the law of vision gives an external place, the photographer presents to Nature an artificial eye, more powerful than his own, which receives the images of external objects, and imprints on its sensitive tablet, and with indelible lines, their precise forms, and the lights and shadows by which these forms are modified. He thus gives permanency to details which the eye itself is too dull to appreciate, and he represents Nature as she is neither pruned by his taste, nor decked by his imagination. From among the countless images of surrounding objects which are actually accumulated in every part of space, he excludes, by means

of his darkened chamber, all but the one he face, the part concealed by it remains wishes to perpetuate, and he can thus ex-white, and the other parts speedily become hibit and fix in succession all those floating dark. For copying paintings on glass, the images and subtle forms which Epicurus solution should be applied on leather, and fancied, and Lucretius sang." in this case it is more readily acted upon than when paper is used. After the color has been once fixed upon the leather or paper, it cannot be removed by the application of water, or water and soap, and it is in a high degree permanent."

The art of Photography, or that of delineating objects by the agency of the light which they radiate or reflect, is substantially a new invention, which we owe to two individuals, Mr. Talbot and M. Daguerre, although, like all other arts, Mr. Wedgewood endeavored by repeated some approximation had been made to it washings, and by thin coatings of fine varby previous inquirers. So early as 1802, nish, to prevent the white parts of his picMr. Thomas Wedgewood, the celebrated tures from becoming dark when exposed to porcelain manufacturer, published in the light; but all his attempts were fruitless, Journals of the Royal institution, A me- and he was obliged therefore either to exthod of copying paintings upon glass, and hibit them in candle-light, or for a short of making profiles by the agency of light time in the shade. This process was apupon nitrate of silver, which was accompa- plied by its author to taking profiles, and nied with some observations by Sir Hum-making delineations of all such objects as phry Davy. Having ascertained "that are possessed of a texture partly opaque white paper or white leather, moistened and partly transparent, such as the woody with a solution of nitrate of silver, under- fibres of. leaves and the wings of insects." goes no change when kept in a dark place," He tried also, but without much success, but "speedily changes color" when "ex- to copy prints; and he failed still more sigposed to the daylight," Mr. Wedgewood found "that the alterations of color took place more speedily in proportion as the light was more intense;" that the full effect was produced by the sun's light in two or three minutes, whereas two or three hours were required in the shade; that the red rays have little action upon it, the yellow and green more, and the blue and violet most of all. "Hence," says Mr. Wedgewood, "when a white surface covered with a solution of nitrate of silver, is placed behind a painting on glass exposed to the solar light, the rays transmitted through the differently painted surfaces, produce distinct tints of brown or black, sensibly differing in intensity, according to the shades of the picture, and where the light is unaltered the color of the nitrate becomes deepest. When the shadow of any figure is thrown upon the prepared sur

* Dico igitur, rerum effigias, tenuisque figuras
Mittier ab rebus summo de corpore earum;
Quæ quasi membrana, vel cortex nominitanda'st
Quod speciem, ac formam similem gerit ejus
Imago,

Quojuscunque cluet de corpore fusa vagari.

Next, for 'tis time, my muse declares and sings
What those are we call images of things,
Which like thin films from bodies rise in streams,
Play in the air and dance upon the beams.-
A stream of forms from every surface flows,
Which may be called the film or shell of those,
Because they bear the shape, they show the frame
And figure of the bodies whence they came.

CREECH.

nally in what was his leading object, to copy the images in the camera-obscura. In following these processes, Sir H. Davy found "that the images of small objects produced by means of the solar microscope, may be copied without difficulty on prepared paper-the paper being placed at but a small distance from the lens ;" and he ascertained that about 1 part of nitrate to about ten of water, gave the best solution. Mr. Wedgewood likewise ascertained that the muriate was more susceptible than the nitrate of silver, and that both were most readily acted upon while wet. He impregnated his paper with the muriate, either by diffusing it through water, and applying it in this form, "or by immersing paper moistened with the solution of the nitrate in very diluted muriatic acid. The impossibility of removing the coloring from the white parts of the pictures, sug gested to Mr. Wedgewood the idea tha

them with iodine of potassium greatly diluted with water; but the method which he proposed, as being safer and simpler, was to immerse the picture in a strong solution of common salt, and then to dry it after wiping off the superfluous moisture.

At this period Mr. Talbot's pictures were negative, like those of Mr. Wedgewood, but yet he has distinctly shown how positive pictures, or those in which the lights and shades are given as in nature, may be obtained.

This beautiful process, which, notwithstanding its defects, it required neither science nor skill to repeat, seems to have excited no interest whatever. The writer of this Article gave a notice of it in a Scottish Journal, so early as 1803, but he has not been able to learn that the experiment of Mr. Wedgewood was repeated. Without knowing what had been done by Mr. Wedgewood, Mr. Henry Fox Talbot, of Lacock Abbey, was led by accidental circumstances to turn his attention to the subject of giving a permanent existence to those beautiful but evanescent pic- "In copying engravings," says Mr. Talbot, tures, which the camera-obscura presents "by this method, the lights and shadows are to our view. Recollecting that nitrate of reversed, consequently the effect is wholly altered. silver was changed or decomposed by light, (fixed) so as to bear sunshine, it may be afterBut if the picture so obtained is first preserved he began, early in 1834, that series of exwards itself employed as an object to be copied, periments which led him to the beautiful and by means of this second process the lights and art which now bears his name. Anxious shadows are brought back to their original disposito perfect the new art which he had disco- tion. In this way we have indeed to contend with vered, Mr. Talbot continued his experi- the imperfections arising from two processes inments till the year 1839, when he commu- stead of one; but I believe this will be found nicated to the Royal Society Some Ac-merely a difficulty of manipulation."* count of the Art of Photogenic Drawing, or the process by which natural objects may be made to delineate themselves without the aid of the artist's pencil. In this paper, which was read to the Society on the 31st January, 1839, several months before M. Daguerre had published his photogenic processes, Mr. Talbot enumerates the various purposes to which the new art could be applied; but it was not till the 21st February that he communicated to the Society

his

The communications of Mr. Talbot to the Royal Society could not fail to draw the attention of philosophers to so curious an art, and we accordingly find that the Rev. J. B. Reade, F.R.S., a gentleman to whom the sciences owe valuable obligations, had made important additions to the photogenic processes, and had himself applied them to the delineation of objects of natural history, of which he took pictures by the solar microThe following process was commuscope. nicated by Mr. Reade, on the 9th of March, 1839, to E. W. Brayley, Esq., who explained the process and exhibited the drawings referred to, at one of the soirées of the London Institution on the 10th April,

1839.

"The more important process, and one probably different fro any hitherto employed, consists in washing good writing paper with a strong solution of nitrate of silver, containing not less than 8 grs. to every drachm of distilled water.

process for preparing the paper, and his method of fixing the images. A sheet of superfine writing paper (of a good firm quality and smooth surface) is dipped into a weak solution of common salt (muriate of soda) and wiped dry. A solution of nitrate of silver, namely, a saturated solution six or eight times diluted with water, is spread with a brush over one surface only, and the paper when dry is fit for use. When leaves of flowers, lace, engravings, &c., are laid upon the nitrated surface of the paper and exposed to the sun, very paper thus prepared is placed in the dark, and perfect images of them are obtained, the allowed to dry gradually. When perfectly dry, lights and shades being reversed, or, what sion of galls prepared according to the Pharmacoand just before it is used, I wash it with an infuis the same thing, the pictures are deline-poeia, and immediately, even while it is yet wet, ated by white in place of black lines, or are throw upon it the image of microscopic objects by negative pictures. In like manner, the means of the solar microscope. pictures thrown upon the nitrated paper placed in the focus of a camera-obscura are negatively delineated. In order to fix these pictures, or prevent the white lines and portions from being blackened by exposure to light, Mr. Talbot first washed

The

"It will be unnecessary for me to describe the effect, as I am able to illustrate it by drawings thus produced. I will only add, with respect to the time, that the drawing of the flea was perfected in

*

London and Edin. Phil. Mag. March, 1839. No. 88, vol. xiv., p. 208.

The paper thus prepared is highly sensitive to light, and it 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 To this most important invention Mr. from 10 seconds to several minutes, accordTalbot gave the name of Calotype, which ing to the intensity of the light, it is taken his friends have now changed into the more out of the camera in a dark room. If the appropriate name of Talbotype, and he se- object has been strongly iHuminated, or if cured the exclusive privilege of using it by the paper has been long in the camera, a a patent for England, which was sealed on sensible picture will be seen on the paper; the 8th February, 1841. The following but if the time of exposure has been short, is the patent process for obtaining the nega- or the illumination feeble, the paper will tive picture :-Take a sheet of paper with appear entirely blank." An invisible a smooth surface and a close and even tex-image, however, is impressed on the paper,

and may be rendered visible by the follow-process; but though it has the advantage of ing process:-"Take some of the gallo- giving sharper lines than the double process, nitrate of silver, and with a soft camel's- it is greatly inferior to it, and is not likely hair brush wash the paper all over with this ever to come into general use. All the liquid, then hold it before a gentle fire, and copies of pictures which it yields are rein a short time the image will begin to ap- versed, and all its portraits and landscapes pear, and those parts upon which the light reversed; but the principal objections to its has acted most strongly will become brown use are two: It requires such a length of or black, while the others remain white. time that portraits could not easily be taken The image continues to grow more and by it, and even when we do obtain a good more distinct for some time, and when it picture, we cannot multiply it as in the becomes sufficiently so the operation must double process. 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 100 grains of the salt dissolved in 8 or 10 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, and from it any number of positive pictures may be obtained in the following manner :Dip a sheet of good paper in a solution of common salt, consisting of one part of a saturated solution to 8 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 80 grains of salt to 1 oz. 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 10 or 15 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 a solution of bromide of potassium already mentioned, or plunged in a strong solution of common salt.

As all the inequalities and imperfections of the paper on which a negative picture is formed, are copied on the positive picture which it yields, attempts have been made to obtain positive pictures by a single process. This was first effected by Dr. Fyfe, of King's College, Aberdeen, and M. Lassaigne of Paris; and Mr. Talbot has included a process of this kind in his specification. We have in our possession one of the pictures taken by Mr. Talbot by this

The following is the single process, as contained in Mr. Talbot's specification:

"A sheet of calotype paper is exposed to the daylight for a few seconds, or until a visible discoloration or browning, of its surface takes place; then it is dipped into a solution of iodide of potassium, consisting of 500 grains to one pint of water. This visible discoloration is apparently removed by the immersion; such, however, is not really the case, for if the solution was dipped into a solution of gallo nitrate of silver, it would speedily blacken all over. When the paper is removed from the iodide of potassium, it is washed with water, and then dried with blotting paper. It is then placed in the camera-obscura, and after five or ten minutes it is removed therefrom, and washed with gallo-nitrate of silver, and warmed as before directed. An image of a positive kind is thereby produced, and represents the lights of objects by lights, and the shades by shades, as required."

The property of hydriodate of potash, to whiten paper that has been darkened by exposure to light, was observed about the same time by Mr. Hunt, Dr. Fyfe, Sir J. Herschel, Mr. Talbot, and M. Lassaigne. Mr. Hunt, in particular, has paid much attention to the photographic processes founded upon this peculiarity of the hydriodate, and has published the results of his inquiries in a very interesting paper, which appeared in the Philosophical Magazine for September, 1840. He has more recently resumed the subject in his very valuable and interesting volume, entitled, Researches on Light, and has there given an explanation of the best method of preparing a good photographic paper, " on which, by the united agency of the hydriodate and the solar rays, perfect pictures may be produced in the camera or otherwise, having their lights and shadows correct as in nature." This branch of photography is more curious than useful; for though the pictures may be perfectly fixed, and retain their color as long as they are kept in a portfolio, and but occasionally exposed to sun-light, yet, when they are occasionally