From Nile's National Register (Baltimore) Vol. 57 (28 September 1839) pg. 73.
The secret of M. Daguerre's wonderful invention, or discovery, by which he is enabled to transfer an exact transcript of rural scenery, buildings, &c. to paper, and fix the colors permanently, is disclosed in the following article, copied from the London Globe. For disclosing the secret, M. Daguerre is said to have received from the French government 6,000 francs, and M. Niepce, who also made discoveries in the same direction, 4,000 francs.
From the London Globe of August 23.
It having been announced that the process employed by M. Daguerre for fixing images of objects by the camera obscura would be revealed on Monday, at the sitting of the academy of sciences, every part of the space reserved for visiters was filled as early as one o'clock, although it was known that the description of the process would not take place until three. Upward of two hundred persons who could not obtain admittance remained in the court yard of the palace of the Institute. The following is an analysis of the description given on this occasion by M. Arago:
The influence of light upon colors was known long ago. It had been observed that substance exposed to its action were affected by it; but beyond this fact nothing was known until 1536, when a peculiar ore of silver was discovered, to which was given the name of argent corne, and which had the property of becoming black when exposed to the light. Photographic science remained at this point until it was discovered that this argent corne (chloruret of silver) did not become black under all the rays of light. It was remarked that the red ray scarcely effected any change, whilst the violet ray was that which produced the greatest influence.M.J.Baptiste Porta then invented the camera obscura, and numerous efforts were made to fix the pretty miniature objects which were seen upon the table of it, and the transitory appearance of which was a subject of general regret. All those efforts were fruitless up to the time of the invention of M. Niepce, which preceded that of M. Daguerre, and led to the extraordinary result that the latter gentleman has obtained.
M. Niepce, after a host of attempts, employed sheets of silver, which he covered with bitumen (bitume de Judee) dissolved in oil of lavender, the whole being covered with varnish. On heating these sheets, the oil disappeared, and there remained a whiteish powder adhering to the sheet. Thus prepared, it was placed in the camera obscura; but when withdrawn the objects were hardly visible upon it. M. Niepce then resorted to new means for rendering the objects more distinct. For this purpose, he put his sheets, when removed from the camera obscura, into a mixture of oil of lavender and oil of petroleum. How M. Niepce arrived at this discovery was not explained to us; it is sufficient to state that, after this operation, the objects became as visible as ordinary engravings, and it only remained to wash the sheet with distilled water to make the drawings permanent. But as the bitume de Judee is rather ash-colored than white, M. Niepce had to discover the means of increasing the shadows by more deeply blackening the lines, (hachures). For this purpose he employed a new mixture of sulphuret of potassium and iodine. But he (M. Niepce) did not succeed as expected to do, for the iodine spread itself over the whole surface, and rendered the object more confused. The great inconvenience, however, of the process was the little sensitiveness of the coating, (enduit) for it sometimes required three days for the light to produce sufficient effect. It will easily be conceived, therefore, that this means was not applicable to the camera obscura, upon which it is essential that the object should be instantaneously fixed, since the relative positions of the sun and the earth being changed, the objects formed by it were destroyed. M. Niepce was therefore without hope of doing more than multiplying engravings, in which the objects, being stationary, are not effective by the different relative positions of the sun. M. Duguerre was devoting himself to the same pursuit as M. Niepce when he associated himself with that gentleman, and brought to the discovery an important improvement. The coating employed by M. Niepce had bee laid on by means of a tampon, or dabber, similar to the process used in printing, and consequently the coating was neither of a regular thickness nor perfectly white. M. Daguerre conceived the idea of using the residuum which is obtained from lavender by distilling it; and, to render it liquid and applicable with more regularity, he dissolved it in ether. Thus a more uniform and whiter covering was obtained, but the object, notwithstanding, was not visible at once, it was necessary to place it over a vase obtaining some kind of essential oil, and then the object stood forth. This was not all that M. Daguerre aimed at. The tints were not deep enough, and this composition was not more sensitive than that of M. Niepce. Three days were still necessary to obtain designs.
We now come to the great discovery in the process for which M. Daguerre has received a national reward. It is to the following effect: A copper sheet, plated with silver, well cleaned with diluted nitric acid, is exposed to the vapour of iodine, which forms the first coating, with is very thin, as it does not exceed the millionth part of a metre in thickness. There are certain indispensable precautions necessary to render this coating uniform, the chief of which is the using of a rim of metal round the sheet. The sheet thus prepared, is placed in the camera obscura, where it is allowed to remain from eight to ten minutes. It is then taken out, but the most experienced eye can detect no trace of the drawing. The sheet is now exposed to the vapor of mercury, and when it has been heated to a temperature of sixty degrees of Reaumur, or one hundred and sixty-seven degrees Fahrenheit, the drawings come forth as if by enchantment. One singular and hitherto inexplicable fact in this process is, that the sheet, when exposed to the action of the vapor, must be inclined; for if it were placed in a direct position over the vapor, the results would be less satisfactory. The angle used is 48 degrees. The last part of the process is to place the sheet in a large quantity of distilled water. The description of the process appeared to excite great interest in the auditory, amongst whom we observed many distinguished persons connected with science and the fine arts.
Unfortunately the locality was not adjusted suitable for the performance of M. Daguerre's experiments, but we understand that arrangements will be made for a public exhibition of them. Three highly curious drawings, obtained in this manner, were exhibitedone of the Pont Marie, another of M. Daguerre's atelier, and a third of a room containing some rich carpeting, all the minutest threads of which were represented with the most mathematical accuracy, and with wonderful richness of effect.
(End of text. Please refer to our textnote regarding this text.)