THE DAGUERREOTYPE APPLIED TO PAPER.

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and, by careful management, the process is now generally completed.If, however, the paper is not considered to be sufficiently dark, it mustbe once more washed in the solution of silver, and again subjected tothe action of sulphuretted hydrogen.

If the above paper be allowed to remain in the sulphuretted hydrogengas after the maximum blackness is produced, it is again whitened withsome quickness. This may be accounted for in two wap; the gas maybe mixed with a portion of muriatic acid vapour, or, a quantity of chlo-rine sufficient to produce this effect may be liberated from the pre-paration on the paper, to react on the sulphuret of silver.

The perfection of these papers consists in having a deep black groundto contrast with the mercurial deposit, by which means the pictures liavothe advantage of being seen equally well in all positions, whereas Da­ guerre ’s pictures on the metal plates, can only be seen to advantage atcertain angles.

The sulphuretted paper may be rendered sensitive, in the samemanner as the plates, by exposure to the vapour of iodine. I, however,prefer drawing the paper over a solution thus formed:—A saturatedsolution of any hydriodic salt is made to dissolve as much iodine aspossible, and of this liquid two drachms are mingled with four ouncesof water. Care is required that ono side only of the paper is wetted,which is by no means difficult to effect, the fluid is so greedily absorbedby it; all that is necessary being a broad shallow vessel to allow of thepaper touching the fluid to its full width, and that it be drawn over itwith a slow steady movement. When thus wetted, it is to be quicklydried by a warm, but not too bright fire; of course daylight must becarefully excluded. Papers thus iodidated do not lose their sensitivenessfor many days, if carefully kept from light

On examining the sheet, after the Daguerreotype processes in thecamera, and of mercurialization have been completed, a vory perfectpicture is found upon it: but it is still capable of vast improvement,which is, by the following simplo plan, accomplished in a way which isat once magical and beautiful.

Dip one of the Daguerreotype pictures, formed on the sulphurettedpaper, into a solution of corrosivo sublimate: tlio drawing instantlydisappears, but, after a few minutes, it is seen unfolding itself, andgradually becoming far more distinct than it was before; delicatelines, before invisible, or barely seen, are now distinctly marked,and a rare and singular perfection of detail given to the drawing. Itmay appear, at first sight, that tho bichloride of mercury dissolves offthe metal, and again deposits it in the form of chloride (calomel). Butthis does not account for the fact, that if the paper has been preparedwith the nitrate of silver, the mercury disappears, and the drawingvanishes, the deposit taking place only on those parts upon wliich lighthas acted but feebly; as, for instance, on the venations of leaves, leavingthose portions of surface which wero exposed to full luminous influence,without a particle of quicksilver. When the paper has been either a