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Daguerre And His Photographic Discoveries

( Originally Published 1898 )

IN the meanwhile another Frenchman had been engaged in a similar line of investigation to that which had so long riveted Niepce's attention. This was Louis Jacques Mande Daguerre, to whom for many years was given the chief honor in connection with the discovery of photography. Daguerre was born at Cormeilles, a village in the department of the Seine-et-Oise, not far from Paris, in 1787. Occupied at first as an Inland Revenue officer, he after a while threw up that avocation, and turned his attention to scene-painting for the opera. He studied under Degote, and soon surpassed both him and his predecessors Bibiena and Munich, especially in the remarkable power he developed of representing light and shade. He was, for a time, engaged with M. Prevost in the production of panoramic views of Rome, Naples, London, Jerusalem, and other places, and in 1822, in conjunction with another, he produced his famous Diorama, the pictorial effects of which were heightened by the alternate use of reflected and transmitted light. In the preparation of his pictures Daguerre frequently employed the camera obscura to obtain his first sketches from nature; and it appears to have been the hopelessness of imitating the perfection and beauty of the originals as presented on the screen of the dark chamber, that turned his thoughts to the finding out of some means of rendering the evanescent shadows permanent. The Diorama enjoyed great vogue in Paris until 1839, when it was accidentally destroyed by fire. This stroke of ill-luck, however, was soon more than compensated for by the fame the artist achieved as the inventor of the Daguerrotype process of photography.

How far Daguerre had gone in his investigations when, in the early part of 1826, he learned that the problem on which he was engaged had already been solved by a gentleman at Chalonssur-Saone we do not know. But, putting himself in communication with Niepce, he received from him several plates of metal acted upon by his heliographic process, and also some engravings taken from them. In return, however, he either would not, or could not, give any specimens of his own labours, or particulars of the results he had achieved, beyond affirming that he had constructed a greatly improved camera, which afforded a more certain means of effecting the fixation of images. Finally they met, and Niepce proposed that they should unite their efforts with a view to making the most of their inventions. To this Daguerre agreed, and the deed of partnership, already referred to, was drawn up and signed at Chalons-sur-Saone in 1829, at which time Niepce made his process fully known to his collaborator.

From this time until the death of Niepce in 1833 the two investigators worked together for the perfecting of the heliographic process, and it is said that Daguerre succeeded in making such improvements in the invention that Niepce was as much surprised as rejoiced at the results obtained.

Daguerre, in the place of bitumen, experimented with the resin obtained from the distillation of the essence of lavender. When a plate covered with this substance had been exposed to the action of light, he subjected it to the vapour of the essence of lavender. This method, however—whether by the use of asphalt or the lavender resin—required a long exposure to the light, and after a time the picture was in part effaced.

Abney has a theory that it was from the experiments with bitumen that Daguerre obtained his first idea of the method that bears his name. The image formed by the asphalt on the silver plates (which Niepce employed) was brown, the shadows being represented by the metallic surface. "In order to produce a proper effect, it was necessary that the parts covered by the bitumen should be whitened and the bare parts darkened. After various experiments he applied iodine to the picture, subsequently removing the bitumen. It is to be presumed that Daguerre noticed the action that the light produced on those portions of the plate which had been covered with iodine. At any rate to Daguerre belongs the glory of the discovery that an image could be produced on a silver plate which had been exposed to the action of iodine." *

These images were produced by exposing plates of silver to the vapour of iodine (a peculiar and very volatile chemical element). Under this treatment the silver assumes a pale yellow colour. When exposed to the light plates thus prepared assume a brown colour, and when exposed to the action of light in the camera a picture is formed upon them. But in order to produce such a picture a very long exposure to the light is necessary.

At length—some time subsequent to the death of Niepce—Daguerre was accidentally led to the discovery that an image is formed by the luminous rays upon a plate covered with iodide of silver which is invisible under ordinary conditions, but which appears as soon as the plate is exposed to the vapour of mercury. Thanks to this discovery, photography upon metallic plates, or daguerrotype, was created.

The way in which this discovery was made is both curious and interesting. One day Daguerre placed several plates that had been exposed too short a time to the light in a closet where were some chemicals. They were condemned as useless because no image had appeared. But, after a time, happening to look at the plates, he was astonished to see a picture upon them. He immediately came to the conclusion that this effect must have been produced through the operation of some chemical substance which was lying in the closet. By removing the chemicals one after another, and placing in the closet plates that had been exposed too short a time to the light, and still finding images produced upon them, he concluded that the culprit was a dish containing mercury; that substance giving off vapour at an ordinary temperature.

In order to test the truth of his supposition, Daguerre again took a plate that had been exposed for a short time in the camera obscura, and on which no picture was yet visible. Subjecting it to the action of the vapour of mercury, he found, to his intense delight, that the picture appeared. Thus by a happy accident, the world was made the richer by a most valuable discovery.

This was the cardinal point in Daguerre's discoveries. While others before him had sought to produce a visible picture by means of light, for which long exposure was necessary, he succeeded in hitting upon a process by which he obtained an invisible or "latent " picture after a short exposure, and then by a second process "developed," or brought it to light. By this fortunate discovery an enormous advance was made in photography.

Hardly less important was the discovery which soon followed whereby the image thus obtained could be fixed by immersing the plates after development in a strong solution of common salt, which dissolved and washed away the iodide of silver that had been acted upon by the light, Subsequently, however, Daguerre adopted hypo-sulphite of soda as a solvent of the silver salt. This substance was discovered by Chaussier in 1799, and shortly after the daguerrotype process was made public in 1839 Sir John Herschel pointed out its superior qualities for clearing and fixing the light-produced picture.

According to the terms of the agreement made between Niepce and Daguerre in 1829, the names of both the inventors were to be attached to their discovery ; but after Niepce's death, his son consented to the first agreement being replaced by another, by the terms of which Daguerre was to throw into the partnership a new process he had discovered which would produce pictures ten or twenty times quicker than that discovered by Niepce, on condition that the new process should bear only the name of Daguerre.

Thus it was that practical photography was first presented to the world under the name of daguerrotype.

It has been asserted that the too confiding Niepce was deluded out of the honour of his invention by his sharper and more business-like partner. That may be putting the matter too strongly; but one cannot help feeling that Daguerre acted ungenerously in thus giving his name exclusively to an invention which, to give him all possible credit, was only in part his, and that part perhaps the lesser one.

In order to make the most of his discovery, Daguerre appears to have tried to form a company to work it ; but, failing in the attempt, he made known his process to M. Arago, the celebrated astronomer and physicist, and in accordance with his advice an announcement respecting it was made to the Academy of Sciences on the 9th of January 1839; although the details of it were not communicated until the month of August following. On the 30th of July of the same year, in consequence of the representations made by M. Arago and others to the French Government, the daguerrotype process was purchased by the State and made public, the inventor and his partner receiving each a pension by way of remuneration, that of Daguerre being six thousand francs and that of Claude Niepce four thousand francs. Notwithstanding the invention was thus given to " the world of science and of art," Daguerre took out a patent in England the same year.

According to Arago, Daguerre asked for four thousand francs for himself and four thousand for Niepce, but that an additional two thousand francs was given to him on condition that he should make known his system of transparent and opaque painting in the production of his dioramas, and that he should also give to the public any future discovery he might make in connection with photography. In further recognition of his discovery Daguerre was made an officer of the Legion of Honour.

The only important improvement in his process subsequently made by Daguerre was in the preparation of his plates. This was based on the use of iodine and bromine, and was published in 1844. But prior to this (in 1840) Mr. Goddard, a lecturer on science in London, had made known his method of employing bromine in conjunction with iodine for increasing the sensitiveness of plates. A further impulse in the same direction was given by M. Claudet in the following year by the use of chlorine vapour to the same end. Accelerators of this kind—and a number of them were soon discovered—are not of themselves photogenic, that is to say, capable of being influenced directly by light, but applied to a surface already prepared with iodide, they communicate to the iodine the faculty of being impressed in a few seconds. By means of plates prepared either with bromine or chlorine vapour, the time required to produce a picture in the camera was reduced to a few minutes—indeed, with a bright light, to a fraction of a minute.

Up to this time photographic portraiture had not been possible: through these discoveries it soon became an accomplished fact. The first person to produce an actual portrait from life was Mr. Draper of New York, who was enabled to achieve that result by the use of enlarged lenses, as introduced by Mr. Towson of Liverpool.

Another valuable improvement in the daguerrotype process was introduced by M. Fizeau. Pictures produced by Daguerre's method were extremely perishable ; a very little friction effaced them, while on exposure to the air they were soon darkened almost to obliteration. To do away with this defect M. Fizeau adopted a method of toning or gilding the picture with a solution of gold. Chloride of gold was mixed with hypo-sulphite of soda, and the plate, upon which a little of the solution had been placed; was heated over a spirit-lamp until the required strength was given to the picture. M. Fizeau, in his description of the process, says: " In this operation the silver is dissolved, and the gold precipitated upon the silver and mercury, but with very different results ; in effect, the silver, which by its reflection forms the shades of the picture, is in some way darkened by the thin film of gold which covers it, from which results a strengthening of all the dark parts. The mercury, on the contrary, which, in the state of an infinite number of small globules, forms the lights, is augmented in its solidity and brightness by its union with the gold, from which results a greater degree of permanency and a remarkable increase in the lights of the picture." Most of the daguerrotype pictures still in existence have been subjected to this process.

According to Abney, daguerrotypes may be reproduced by electrotypy, showing that the image, after development, is in relief, although to a very small extent. Sir W. R. Grove introduced a method of etching daguerrotype plates by means of hydrochloric acid, so that they could be printed from. The process, however, does not appear to have been turned to much practical account, having been superseded by more easily manageable and less expensive methods.

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