I am happy to present this text to you today, dear readers of Dagnews. Although this text is much longer than what I usually wish to present in this format, it is one of the best in describing the workings of a daguerreian gallery. Although no author is indicated in the issue, the "Household Words" Office Book gives the authors as William Henry Wills and Henry Morley. An error in the text regarding the use of pyrogallic acid as a fixitive was corrected in a later "Household Words" article, "The Stereoscope" (Vol. 8, No. 181 [10 September 1853] pp.37-42.) I'll also mention that the text was also reprinted in "The Photographic Art-Journal" Vol. 5, No. 6 (June 1853) pp. 325-333. On this day (March 19) in the year 1853, the following text appeared in "Household Words" (London) Vol. 7, No. 156 (19 March 1853) pp. 54-61. - - - - - - - - PHOTOGRAPHY. ________ WE have been ringing artists' bells. We have been haunting the dark chambers of photographers. We have found those gentlemen--our modern high priests of Apollo, the old sun god--very courteous, and not at all desirous to forbid to the world's curiosity a knowledge of their inmost mysteries. We rang a bell in Regent Street--which was not all a bell, for it responded to our pull not with a clatter; but with one magical stroke--and instantly, as though we had been sounding an enchanted horn, the bolts were drawn by unseen hands, and the door turned upon its hinges. Being well read in old romance, we knew how to go on with the adventure. There were stairs before us which we mounted; swords we had none to draw. In a few seconds we reached another open door, that led into a chamber, of which the walls and tables were in great part overlaid with metal curiously wrought. A thousand images of human creatures of each sex and of every age--such as no painter ever has produced--glanced at us from all sides, as if they would have spoken to us out of the hard silver. Here a face was invisible: there it burst suddenly into view, and seemed to peep at us. Beautiful women smiled out of metal as polished and as hard as a knight's armour on the eve of battle. Young chevaliers regarded us with faces tied and fastened down so that, as it seemed, they could by no struggle get their features loose out of the very twist and smirk they chanced to wear when they were captured and fixed. Here a grave man was reading on for ever, with his eyes upon the same line of his book; and there a soldier frowned with brow inanely fierce over a rampart of moustachios. The innumerable people whose eyes seemed to speak at us, but all whose tongues were silent; all whose limbs were fixed (although their faces seemed in a mysterious way to come and go as the lights shifted on the silver wall)--what people were these? Had they all trodden the steps by which we had ourselves ascended? Had they all breathed and moved, perhaps, about that very room. "They have," answered the genius of the room, "they have all been executed here. If you mount farther up you also may be taken." The figures in the room were not all figures of enchantment. There were present four unmetamorphosed people; three of them were ladies, of whom of course it would be rude flatly to say that there was nothing of enchantment in their figures; but the fourth was a belted soldier with a red coat, a large cocked hat, and a heavy sword. Imprudently we had come out without even so much weapon as an umbrella. The taker of men himself came down to us, affable enough; but smiling faces have been long connected with mysterious designs. The soldier was, in fact, a man of peace, a lamb in wolf's clothing; an army doctor, by whose side, if army regulations suffered it, there should have hung a scalpel, not a sword. And the expert photographer--the magic of whose art is fostered by no worse feeling than vanity, or by a hundred purer sentiments--was followed very willingly upstairs. It was all wholesome latter-day magic that we went up to see practised under a London skylight. Light from the sky is, in fact, the chief part of the stock-in-trade of a photographer. Other light than the sun's can be employed; but, while the sun continues to pour down to us a daily flow of light of the best quality, as cheap as health (we will not say as cheap as dirt, for dirt is a dear article), sunlight will be consumed by the photographers in preference to any other. A diffused, mellow light from the sky, which moderates the darkness of all shadows, is much better suited to the purpose of photography than a direct sun-beam; which creates hard contrasts of light and, shade. For in the picture formed by light, whether on metal, glass, or paper, such hard contrasts will be made still harder. Lumpy shadows haunt the chambers of all bad photographers. He who would not be vexed by them and would produce a portrait in which the features shall be represented with the necessary softness, finds it generally advantageous not only to let the shades be cast upon the face in a room full of diffused rays--that is to say, under a skylight--but also by the waving of large b1ack velvet screens over the head to moderate and stint the quantity of light that falls on features not thrown into shadow. For this reason few very good photographic pictures can be taken from objects illuminated only by a side light, as in a room with ordinary windows. The diffused light of cloudy weather, if the air be free from fog, hinders the process of photography only by lengthening the time occupied in taking impressions. Light, when it is jaundiced by a fog is quite as liable as jaundiced men to give erroneous views of mankind. Photography, out of England has made its most rapid advances, and produced its best results in the United States and in France ; but, although both the French and the Americans have the advantage of a much purer and more certain supply of sunlight, it is satisfactory to know that the English photographers have throw as much light of their own on the new science as any of their neighbours. Led by the military gentleman, whose cocked hat elevated him in our civilians' eyes to something like the dignity of general, we mounted to the door; through which we poured our forces into the room under the skylight, where we found several defences thrown up in the shape of folding screens, and faced an unusually heavy fire from a round tower of a stove. To maintain a high and dry temperature is customary in the room used by the daguerreotypist for his operations; partly in order to protect more thoroughly the delicate surface of the plates carried about in it, partly to ensure to the sitter so much warmth as shall make perfect repose of all the features, in the most natural way, quite easy. For while the work of the photographer is done with an astonishing rapidity, he is one of the few men who especially desire of those with whom they have to deal that they should not look sharp. A group was to be made of Doctor Sword, and one lady, his wife. Another lady, probably his mother-in-law, declared candidly that when her turn came she must be held in some way, for she was too nervous to sit still. A younger lady, a friend to Mrs. Doctor S., looked interested. The group of two was to be first executed. Now the lady's dress was not at all ill chosen for a photographic sitting or a masquerade. It included extensive scalp-fixings of a savage style introduced lately into this country, consisting of a ragged tuft of streamers, knotted with Birmingham pearls nearly as large as coat buttons; a great deal of gauze, wonderfully snipped about and overlaid with divers patterns; with a border of large thick white lilies round the cape. The lady was placed on a chair before the camera, though at some distance from it. The gentleman leaned over the back of the chair; symbolically to express the inclination that he had towards his wife: he was her leaning tower, he was her oak and she the nymph who sat secure under his shade. Under the point of the gentleman's sword the Pilgrim's Progress by John Bunyan was placed to prop it up; and one or two trifling distortions were made at the extremity of the proposed picture to neutralise the contrary distortions that would be produced on that portion of the image in the camera. We then peeped under a black pall into the machine itself, where we beheld the gentleman and lady on a piece of ground-glass, standing on their heads. Leaving Doctor and Mrs. Sword to stand at ease and talk to one another, we, Messieurs Pen, departed from the camera for a few minutes and accompanied the artist to his den behind the scenes. The den of the photographer, in which he goes through those mysterious operations which are not submitted to the observation of the sitter, is a small room lighted by a window, and communicating into a dark closet, veiled with heavy curtains. Our sense of the supernatural, always associated with dark closets, was excited strongly in this chamber, by the sound of a loud rumbling in the bowels of the house, and the visible departure of a portion of the wall to lower regions. We thought instinctively of bandits who wind victims up and down in moveable rooms or turn them up in treacherous screw bedsteads. But, of course, there was no danger to be apprehended. What we saw was, of course, only a contrivance to save labour in conveying pictures up or down for colouring or framing. Our consciences having been satisfied on this point, the expert magician took a plate of the prescribed size, made ready to his hand. Such plates consist of a thin layer of silver fixed upon copper, and are provided to the artist highly polished; but a final and superlative polish is given to each plate, with a "buff" or pad like a double handled razor strop, tinged with a fine mineral powder. Simple as it appears, the final polishing of the plate is an operation that can only succeed well under a practised pair of hands, that regulate their pressure by a refined sense of touch. The plate thus polished was brushed over finally and very lightly, as with the touch of a cat's paw, with a warm pad of black velvet freshly taken from an oven. To witness the next process we went into the dark closet itself, the very head quarters of spectredom. There, having carefully excluded daylight, the operator lifted up the lid of a small bin, rapidly fixed the plate, silver side downwards, in a place made underneath for its reception, shut down the lid, and began to measure seconds by counting, talking between whiles, thus:--"One--that box--two--contains--three-- chloride of iodine--four--strewn--five--six--at the bottom. Now!" Presto, out came the plate in a twinkling, and was held against a sheet of white paper, upon which it reflected a ghastly straw colour by the light of a small jet of gas.) "Ah, tint not deep enough!" The plate was popped into its vapour bath again with magic quickness. "Seven--the action of the iodine" (continued the operator, counting seconds, and teaching us our lesson in the same breath) "rising in vapour upon the surface--eleven--of the plate--twelve--causes it to take in succession --thirteen--fourteen--fifteen--all the colours of the spectrum--sixteen --seventeen; and deposits upon it a film. As he went on solemnly counting we asked how long he exposed the plate to the visitation of that potent vapour. A very short time," he replied; but it varies-- thirty--thirty-one--according to the light in the next room--thirty-five --thirty-six--thirty-seven. Adjusting the plate to the weather, thirty-eight--is the result of an acquired instinct--thirty-nine--forty. Now it is ready." The plate was out and its change to a deeper straw colour was shown. The lid of an adjoining bin was lifted and the iodized plate was hung in the same way over another vapour; that of the chloride of bromine, that the wraiths of the two vapours might mingle, mingle, mingle as black spirits with white, blue spirits with gray. In this position it remained but a very short time, while we stood watching by in the dark cupboard. The plate having had its temper worked upon by these mysterious agencies was rendered so extremely sensitive, that it was requisite to confine it at once, in a dark hole or solitary cell, made ready for it in a wooden frame; a wooden slide was let down over it and it was ready to be carried to the camera. Before quitting this part of the subject, we must add to the preceding description two or three external facts. We have been discussing hitherto the kernel without touching the nutshell in which these, like all other reasonable matters in this country, may be (and usually are) said to lie. The nutshell is in fact as important to a discussion in this country as the small end of the wedge or the British Lion:--In the action of light upon surfaces prepared in a certain manner lies the whole idea of photography. The camera obscura is an old friend; how to fix chemically the illuminated images formed in the camera by light, was a problem at which Sir Humphrey Davy, half a century ago, was one of the first men who worked. Sir Humphrey succeeded no farther than in the imprinting of a faint image, but as he could not discover how to fix it, the whole subject was laid aside. Between the years 1814 and 1828, two Frenchmen, M. Daguerre and M. Niepce, were at work upon the problem. In 1827 M. Niepce produced before the Royal Society what he then called heliographs, sun-pictures, formed and fixed upon glass, copper plated with silver, and well-polished tin. But, as he kept the secret of his processes, no scientific use was made of his discovery. M. Daguerre, working at the same problem, succeeded about the same time in fixing sun-pictures on paper impregnated with nitrate of silver. M. Daguerre and M. Niepce having combined their knowledge to increase the value of their art, the French government--in the year 1839--acting nobly, as it has often acted in the interests of science, bought for the free use of the world the details of the new discovery. For the full disclosure of their secrets there was granted to M. Daguerre a life pension of two hundred and forty pounds (he died not many months ago), and a pension of one hundred and sixty pounds to the son of M. Niepce, with the reversion of one half to their widows. Six months before the disclosure of the processes in France, Mr. Fox Talbot is England had discovered a process leading to a like result--the fixing of sun-pictures upon paper. As the English parliament buys little for science, nothing unfortunately hindered the patenting of Mr. Talbot's method. That patent in certain respects very much obstructed the advance of photography in this country and great credit is due to Mr. Talbot for having recently and voluntarily abandoned his exclusive rights, and given his process to the public for all purposes and uses, except that of the portrait-taker. By so doing he acted in the spirit of a liberal art born in our own days, and peculiarly marked with the character of our own time. It does one good to think how photographers, even while exercising the new art for money, have pursued it with a generous ardour for its own sake, and emulate each other in the magnanimity with which they throw their own discoveries into the common heap, and scorn to check the progress of their art for any selfish motive. After the completion of the French discovery two daguerreotype establishments were formed in London armed with patent rights, and their proprietors, Messrs. Claudet and Beard, do in fact still hold those rights, of which they have long cheerfully permitted the infringement. Mr. Beard tried to enforce them only once, we believe; and M. Claudet with distinguished liberality, never. At first the sitting was a long one, for the original daguerreotype plate was prepared only with iodine. We see it stated in the jury reports of the Great Exhibition, that to procure daguerreotype portraits, it was then "required that a person should sit without moving for twenty-five minutes in a glaring sunshine." That is a glaring impossibility, and in fact the statement is wrong. It is to M. Claudet that the public is indebted for the greater ease we now enjoy in photographic sittings, and it is the same gentleman who informs us that five minutes--not five-and-twenty--was the time required for the formation of a good picture on the plates prepared in the old way. The discovery of the accelerating process, by the use of the two chlorides of iodine and bromine, was at once given to all photographers by M. Claudet; it having been made public by him. In England, through the Royal Society, and in France, through the AcadŽmie des Sciences. By the use of this double application, plates are made so sensitive that portraits may be taken in a period varying, according to the measure of the light, between a second and a minute. We have said something about varying the degree of sensitiveness in the plate according to the weather. In the account just given of our visit to a photographic studio, it will be seen that a very skilful artist (Mr. Mayall) lessens at times the sensitiveness of the plate, but in this respect the practice is not uniform. In illustration of the extreme sensitiveness that can be communicated to the prepared plate, reference has often been made to an experiment performed at a meeting of the Royal Society, the account of which we quote from Dr. Lardner. "A printed paper was fastened upon the face of a wheel, which was put in revolution with such rapidity that the characters on the paper ceased to be visible. The camera, with the prepared photographic surface, being placed opposite the wheel and properly adjusted, the room was darkened. The room and wheel were then illuminated, for an instant, by a strong spark taken from the conductor of a powerful electric machine. This instantaneous appearance of the wheel before the camera was sufficient to produce a perfect picture." In reading of this experiment we are not to direct our attention to the sensitiveness of the plate so much as to the power of the light. Such a spark as was taken for the purpose produced an instantaneous light, greatly surpassing in intensity the ordinary sunlight used by the photographers. M. Claudet, in reply to our questions about the adjustment of the sensitiveness of his plates, replied simply, "I always try to make my plates as sensitive as possible." A walk through his gallery satisfied us that if; by so doing, he increases the demand on his dexterity in sunny weather, the demand is met. His results fully justify his practice. We may say the same for Mr. Mayall, the photographer whose operations led us into the preceding digression. From the dark cupboard, cleared by a strong up draught of escaping fumes, we brought the prepared plate in its frame, carefully excluded from the light by a protecting slide. The frame was made to fit into the camera, but before placing it, the final adjustment of the sitters had to be made. The Doctor and his lady having resumed their positions, we again observed, upon the ground glass of the camera, the artistic effect of the group in an inverted miniature, coloured of course. This observation was made with the head thrust under a black velvet pall. Upon the ground glass we saw drawn four squares, one within another, and we remembered well what pictures we had seen of trines and squares and houses of the planets drawn by Albertus Magnus and Agrippa. These were, however, squares, the adept told me, corresponding respectively in size to the plates, differing in price, on which it is in the choice of the sitter to have a likeness taken. A frame corresponding to each size has the plate so fixed in it that, when placed in the camera, it occupies precisely the position of the square marked on the glass. Our picture was to be of the third size--the third square was to be the house of Mars and Venus--and the object of the operator was to arrange the sitters and the camera in such a way as to procure a telling group within the boundaries of that third square upon the glass. This having been done, and a fixed point supplied, on which the eyes should feast, the velvet pall was thrown over the back of the camera to exclude the light and a black stopper (the obturator) was clapped over the glass in front, making the chamber of the box quite dark. The frame was then inserted in its place, the slide removed, and the prepared silver reposing in the darkness was laid open to receive the meditated shock upon its sensibility. The sitters were requested then to close their eyes for a minute, that the eyelids might be rested, then to look fixedly in the direction indicated by a little picture pinned against a screen. Then "Now, quite still; try to look pleasant--a little pleasanter!" The cap was off, and the two figures, fixed as statues, shone upon the magic mirror in the camera, rigidly pleasant. In half a minute,--counted accurately by the operator--suddenly, the stopper was again clapped over the glass in front; the slide was let down over the tablet, upon which light, haying done its work, must shine no more until the plate was light-proof. Mars and Venus in conjunction having entered the third house, we retired into the necromancer's den to observe what would follow. The necromancer there addressed us in manner following: "The chemical action of light has decomposed the delicate compound formed upon this tablet between the silver and the chlorides of iodine and bromine. The decomposition has been greatest, of course, where the light has been most intense, and its action has been manifested everywhere by the piercing of the sensitive surface with minute holes. Where the light has been the strongest, the number of these microscopic holes, contained upon a space equal to the area of a pin's head, is greater than in those parts on which the chemical action of the light has not been so intense. The portrait is thus minutely and delicately dotted out, dots signifying light. That is the sun picture which I now hold in my hand." After this brief parliamentary address the adept went on with his labour. Still hiding his dark deeds from the face of day he took the plate to a small bath of quicksilver, from which a subtle vapour slowly ascended, the quicksilver being placed over the faint blue flame of a spirit-lamp. Suspended over this bath it received upon its polished surface the fine vapour; which, penetrating into the minute holes formed by light upon the plate, and there condensing into microscopic drops, tinged out with its own substance the surface on which light had fallen--more abundant where its action had been greatest, and less marked where the decomposition had been less. When this process was complete, the picture was complete; all the lights being expressed and graduated by a white metal, and the shadows by the darker ground. There were the allied images of gentleman and lady revealed suddenly before us with a startling accuracy, only unnaturally sensitive and altogether wanting in stability of character. Nothing remained then but to fix the picture; to destroy the sensitiveness of the surface. This was done by pouring over it some dilute pyrogallic acid, and finally submitting it to the action of a salt of gold; of which a solution was washed over the plate, and warmed upon it for one or two minutes. The portrait was in this way perfectly spell-bound. It might be carried about loose in the pocket and indiscriminately handled, without suffering more hurt to its charms than can be worked by those ugly disenchanters, grease and dirt and scratches. For protection, however, against these, and for the better setting off of the picture, it will be delivered to its owner as a well known imp was once sold, in a bottle under glass; and as the Moors were arch magicians, with traditions of Bagdad about them, it will very fitly be enclosed in a morocco case. Truly, a fine picture it is. The lady's dress suggests upon the plate as much delicate workmanship as would have given labour for a month to the most skilful of painters. The lilies that we did not like upon the cape, how exquisite they look here in the picture! But as this group was destined to be coloured, we were courteously invited to the colouring room, a tiny closet in which two damsels were busily at work, one upon a lady's dress, the other upon the forehead of a gentleman, putting in the yellow rather lavishly, but with a good effect. "The faces," she informed us, "must be coloured strongly, or they will be put out by the bright blue sky." We pointed to a small box labelled "Sky," remarking that the fair painters were magicians, to carry the sky in a wafer-box. To which one of them promptly answered "Yes; and Ogres, too, for that pill-box contains gentlemen's and ladies' 'Flesh.'" These terrific creatures--who had quite the ways of damsels able to eat rice pudding in an honest manner--then made us acquainted with a few dry facts. The colours used by them were all dry minerals, and were laid on with the fine point of a dry brush; pointed between the lips, and left to become dry before using. A little rubbing caused these tints to adhere to the minute pores upon the plate. Each colour was of course rubbed on with its own brush, and so expertly, that a large plate very elaborately painted, with a great deal of unquestionable taste, had been, as we were told, the work only of an hour. On a subsequent occasion, we saw in the same room our picture of the Doctor under the painter's hands, and undergoing flattery. We admired the subdued tone which the artist had, as we thought, taken the wise liberty of giving to the glare of the red coat. "Yes," she replied, "but I must make it redder presently; when we don't paint coats bright enough, people complain. They tell us that we make them look as if they wore old clothes." And we may observe here that another illustration of our vanities was furnished to us on a different occasion. Daguerreotype plates commonly present faces as they would be seen in a looking-glass, that is to say, reversed: the left side of the face, in nature, appearing upon the right side of the miniature. That is the ordinary aspect in which every one sees his own face, for it is only possible for him to behold it reflected in a mirror. This reversing, of course, alters in the slightest degree the similitude. The sitter himself is generally satisfied. But M. Claudet has taken up the parable of the poet; and has undertaken to be the kind soul who, by virtue of a scientific notion, "Wad the giftie gie us To see ourselves as others see us." Few of us would thank him for it morally, and it is a curious fact that few of us are content to have even our faces shown to us as others see them. The non-inverted daguerreotypes differ too much from the dear images of self that we are used to learn by heart out of our looking-glasses. They invariably please the friend to whom they are to be given, but they frequently displease the sitter. For this reason, though M. Claudet has of course made public the secret of his "giftie," we are not aware that any other photographer has thought it profitable for his use. Somebody asks, "how are those non-inverted images produced?" The question causes us again to drop the kernel of our story, and apply ourselves to a discussion of the nutshell. A daguerreotype formed in the usual way and inverted, if held before a looking-glass, becomes again inverted, and shows therefore a non-inverted picture of the person whom it represents. If the picture in the camera fell, by a previous reflection, inverted on the plate, it would in the same way be restored by a second inversion to its first position. This object could not be attained by any arrangement of glass mirror in the camera, because a piece of looking-glass reflects both from its outer surface and from the quicksilver behind, and this; though unimportant for all ordinary purposes, would make it perfectly unfit for photographic use. A piece of polished metal would have but a single surface; but the exquisite polish necessary would make the preparation of it difficult and costly, and its liability to damage great. The first reflection is made, therefore, by turning the side of the camera to the sitter and causing his image to fall upon one face of a large prism placed before the glasses otherwise in use: an image is then deflected into the camera, which falls in the required manner on the plate. In the present state of photographic art, no miniature can be utterly free from distortion; but distortion can be modified and corrected by the skilful pose of the sitter, and by the management of the artist. The lens of the camera being convex (in order to diminish the object, and to concentrate the rays of light upon the silver plate) the most prominent parts of the figure to be transferred--those parts, indeed, nearest to the apex of the lens--will appear disproportionately large. If you look through a diminishing glass at a friend who holds his fist before his face, you will find the face very much diminished in proportion to the appearance of the fist. The clever artist, therefore, so disposes his sitter, that hands, nose, lips, &c., shall be all as nearly as possible on the same plane in apposition to the lens. In a sitting figure hands placed on the knees would seem prodigious--placed on or near hips, no more prominent than the tip of the nose, they would seem of a natural size. It is for this reason that daguerreotypes taken from pictures instead of living figures, are never distorted, because they are actually on a flat surface. Concerning the action of light in the formation of the picture on the iodized plate within the camera, one or two facts are curious. Light contains rays that are not luminous. In the dark spaces above and below the solar spectrum some of the most decided chemical effects of light are manifested. It is probable that the chemical rays of light are, to our eyes, perfectly dark. Cover a picture with a piece of yellow glass, and you can see it very well. But place it before the camera, and you will get no photographic copy. Cover a picture with a piece of dark-blue glass, and it is totally invisible; but, placed before the camera, the chemical rays pass through and imprint a photographic image as distinct and clear as if there had been no blue glass whatever. The distinct properties of the yellow and blue rays are manifested as strongly in the germination of plants. Germination is prevented by the action of the yellow ray, while to the blue ray it is mainly indebted. The rays that have passed through to form the picture, have been called the photogenic rays: they refract not quite in the same way as the luminous or colorific rays, and therefore the focus of the photogenic picture and that of the picture thrown on the ground glass will not exactly coincide. For this, allowance has to be made in practice, and accurate instruments for ascertaining the true photogenic focus have been invented, one by M. Claudet, and another by Mr. G. Knight. They are called Focimeters. There are hidden mysteries, however, connected with this portion of the subject. Means have been already here and there discovered, by which the colours of the spectrum may be printed at once on photographic tablets, and the sun--most brilliant of artists--may paint his pictures at the same time that he is engraving them. The process is not yet disclosed. Mr. A. Hill, of New York, affirms that he has taken many pictures from Nature, having all the beauty of natural colouring upon them. A new material is said to have been introduced in aid of this effect. When all mechanical details have been perfected, we may therefore expect this new step to be made publicly, by which Apollo will be raised above Apelles in the world of art. The application of photography to the stereoscope produces an extremely pretty toy, that is of no use except as an elegant and valuable illustration of a train of scientific reasoning. The instrument itself was invented some years since by Professor Wheatstone, to illustrate his discovery of the principles of binocular vision. In 1849 Sir David Brewster exhibited to the British Association at Birmingham a stereoscope adapted to the inspection of daguerreotype pictures. Afterwards he happened to describe the instrument to an optician in Paris, M. Duboscq Soleil, who being an enterprising man, constructed a number of such instruments on speculation. At the beginning of 1851 some of these were exhibited at one of the soirees of Lord Rosse; they excited attention, and the photographers of London, seizing the notion, very soon began to take stereoscopic portraits. In the stereoscope two exactly similar pictures are placed side by side under a pair of prisms, which are so adjusted, that one image falls on each eye, and the images on the two eyes do not fall on precisely corresponding parts. This gives the idea of distance. For it is to the use of two eyes that we are indebted for the facility with which we derive ideas of form, solidity, and distance. There is only one point before us, to which both eyes can be turned in the same way at the same time. Every other point before and behind that will fall upon both eyes, will fall upon the retina of each eye in a different place, and the amount of variation presents itself through the optic nerve to the brain as the idea of distance. Upon this hint the stereoscope is formed, and the effects of roundness and distance are presented to the mind by a pair of flat photographic pictures. M. Claudet has constructed an ingenious variation on the ordinary stereoscope, by placing under it two plates not perfectly identical. In one, for example, there are two men fighting: one strikes, the other wards. The companion plate contains precisely the same men; with this difference in their attitude, that the one who struck now wards, and the aggressor stands on the defensive. In looking at this group, and at the same time rapidly moving to and fro a small slide behind the glasses, which covers now one eye and now another, the two impressions run into each other and produce the appearance of an active sparring match. Again, a needle-woman, represented on one plate with her needle in her work, and in the other with her thread drawn out to its full length, appears, when the slide is shifted to and fro, to be industriously sewing. Among ingenious contrivances we ought not to omit to rank Mr. Mayall's very neat method of producing what are called crayon portraits in daguerreotype. His plan is to place between the sitter and the camera a revolving plate, having a hole cut into the middle of it, from which there proceed broad rays as of the sun upon a signboard. The result is a picture upon which the head is engraved with unusual distinctness, and the bust is gradually shaded down into the general colour of the plate, so that the effect is that of a crayon portrait. Photographic processes on glass and paper are even more valuable as aids to knowledge than daguerreotypes. There are many processes by which photographic impressions may be taken upon paper and glass; a book fall of them lies at this moment before us: we have ourselves seen two, and shall confine ourselves to the telling of a part of our experience. We rang the artist's bell of Mr. Henneman in Regent-street, who takes very good portraits upon paper by a process cousin to the Talbotype. By that gentleman we were introduced into a neat little chamber lighted by gas, with a few pans and chemicals upon a counter. His process was excessively simple: he would show it to us. He took a square of glass, cleaned it very perfectly, then holding it up by one corner with the left hand, he poured over the centre of the glass some collodion, which is, as most people know, gun-cotton dissolved in ether. By a few movements of the left hand, which appear easy, but are acquired with trouble, the collodion was caused to flow into an even coat over the surface of the glass, and the excess was poured off at another corner. To do this by a few left-handed movements without causing any ripple upon the collodion adhering to the glass is really very difficult. This done, the plate was left till the ether had almost evaporated, and deposited a film of gun-cotton--which is in fact a delicate paper--spread evenly over the surface of the glass. The glass covered with this delicate paper, before it was yet quite dry, was plunged carefully into a pan or bath, containing a solution of nitrate of silver, about eight grains of it to every hundred of distilled water. In about two minutes it was taken out, and ready for the camera. It was a sheet of glass covered with a fine film of cotton-paper impregnated with nitrate of silver, a colourless salt blackened by light. It was removed in a dark frame to the camera. Then an assistant, opening a book, assumed an attitude and sat for his picture. In a few seconds it was taken in the usual way, and the glass carried again into the operator's room. There it was dipped into another bath--a bath of pyrogallic acid--and the impression soon became apparent. To bring it out with greater force it was then dipped into a second and much weaker bath of nitrate of silver. The image was then made perfect; but, as the light parts were all depicted by the blackest shades, and the black parts were left white, the courteous assistant was there represented as a negro. That negro stage was not of course the finished portrait, it was "the negative"--or stereotype plate, as it were--from which, after it had been fixed with a solution of the sulphate of the peroxyde of iron, any number of impressions could be taken. For it is obvious that if a plate like this be placed on sensitive paper, and exposed to daylight, the whole process will be reversed. The black face will obstruct the passage of the light and leave a white face underneath, the white hair will allow the light to pass, making black hair below, and so on. Impressions thus taken on paper, and afterwards fixed, may either serve for portraits, as they are, or, like the silver plates, they may be coloured. The paper processes, of which we say so little, are in fact practically the most important branches of the art of the photographer. For it is not only--or indeed chiefly--by the reproduction of our own features that we bring photography into the service of our race. One application of the art has produced an apparatus which enables many natural phenomena to register themselves. Mr. Brooke's little cylinder of photographic paper, revolving in measured time under a pencil of light thrown from a small mirror attached to a moving magnet or an anemometer, tells for itself the tale of every twelve hours' work, and has already superseded the hard night-work that was necessary formerly at the Greenwich, and at other great observatories. Photography already has been found available by the astronomer; the moon has sat for a full-face picture, and there is hope that in a short time photographic paper will become a common auxiliary to the telescope. History will be indebted to photography for facsimiles of documents and volumes that have perished; travellers may bring home incontestible transcripts of inscriptions upon monuments, or foreign scenery. The artist will no longer be delayed in travelling to execute his sketches on the spot. He can now wander at his ease, and bring home photographic views, from which to work, as sculptors from the model. Photography is a young art, but from its present aspect we can judge what power it will have in its maturity. The mind may readily become bewildered among expectations, but one thing will suggest many. We understand that a catalogue of the national library of Paris has been commenced, in which each work is designated by a photographic miniature of its title-page. -------------------------------------------------------------- 03-19-98