During this month (October) in the year 1841, the following article appeared in "The American Journal of Science and Arts" (New Haven) Vol. 16, No. 2 (October 1841;) pages 352-354: - - - - - - - - - ART. X.--Improvement in the Daguerreotype process of Photography; by F. A. P. BARNARD, Prof. of Math. and Nat. Phil. in the Univ. of Alabama. Messrs. Editors,--I commenced, about a year since, in connection with Dr. Wm. H. Harrington of this place, a series of experiments in photography, according to the methods of Mr. Fox Talbot and M. Daguerre. Our attention was directed principally to the Daguerreotype process. From the analogies known to exist between iodine and chlorine, we were strongly impressed with the belief that the latter substance might in some manner be employed to render the surface of silver more sensitive to the action of light than it had yet been made. To determine the correctness of this opinion we instituted a variety of experiments, which, as they proved for the most part unsuccessful, it is unnecessary to detail. The coating formed by the direct action of chlorine gas upon polished silver, was not found to possess the desired photogenic properties. We were led, therefore, to seek whether by the decomposition of some compound of the metal, a sensitive chloride could not be produced. Mr. Talbot had already done this in the preparation of his photogenic paper; but as it was our desire to avail ourselves of the beautiful lights formed by the vapor of mercury, and as the prepared paper, at least so far as our experiments go, is not susceptible of receiving them, we endeavored to produce the decomposition upon the surface of the solid metal. It occurred to us as a possibility that the iodide formed in the usual manner, by exposing a plate over the vapor of iodine, might perhaps give up its silver to chlorine, and thus produce the desired coating. This impression was not verified in our first experiments, owing to a cause which will presently be noticed. Perseverance, however, at length brought its reward. By varying in every possible manner, the circumstances of the experiment, we succeeded in producing a surface so exquisitely sensitive to the action of light, that the image of an illuminated object was formed upon it in the camera in a space of time almost inappreciable. The following is the process by which this result is obtained. Let the plate be prepared in every respect as if an impression were to be taken according to the method of M. Daguerre. Let it be then exposed for the space of half a minute to the action of chlorine gas, diluted with common air to such a degree that it may be inhaled without any particularly unpleasant sensation. It will then be found so extremely sensitive, that on being placed in a camera, with an aperture such as is commonly employed in taking miniature portraits, an impression will be produced upon it in the smallest time in which it is possible to remove and replace the screen. The completion of the picture over mercury is effected in the usual way. A plate thus chlorized, on exposure to light almost immediately assumes a very deep violet color, nearly approaching black. The mercury is not directly tarnished, and in this state the picture is even more beautiful than after being washed with the hyposulphite of soda. But without this washing it cannot be preserved. M. Daguerre has announced that he is able to take images of objects in an instant of time. I have not seen any statement of his method. Some of the artists in the Atlantic cities have been equally successful. Their process is not that which I have here described. I suppose that I am acquainted with the mode of preparation which they employ; but as it was communicated to me under an injunction of secrecy, before I had discovered it myself, although I had actually employed it unskilfully, and therefore without complete success before, I can say nothing of it here. It will, without doubt, soon be made public, if it is not already known. I believe, at any rate, that the chloride coating is more sensitive than any other which has yet been used. It appears to us that the lights produced by this process of preparation are much finer and smoother than those of the original process of M. Daguerre. Some idea of the quickness of the camera operation my be formed from the statement of the fact, that a man walking my be represented with his foot lifted as about to take a step. The quantity of chlorine necessary to produce the effect is exceedingly minute. In our early experiments we employed a quart bottle of the gas, opening it in a deep box, and leaving out the stopper while deliberately counting twenty. Replacing then the stopper, the plate was laid for half a minute over an opening in the top. After fifty experiments the gas in the bottle seemed not to have lost any of its original intensity of color. We have better arrangements at present in preparation. Much care is necessary to avoid an excess of chlorine. The principal cause of our early failures arose from an error of this kind. One may easily determine, with any apparatus, the time and quantity necessary, by laying a plate over the aperture and drawing it partially off at intervals. The action of the gas will then be greatest, of course, upon the part longest exposed. Too much care cannot be taken to exclude the light during the process of preparation. Tuscaloosa, July 1, 1841 -------------------------------------------------------------- 10-04-99