MISCELLANEOUS PROCESSES.

1.—On the Application of tiie Daguerreotype to Paper .

The expense and inconvenience of metallic tablets rendered it in thehighest degree desirable that paper might be employed in their place.A very extensive series of experiments at length led to the pleasingconclusion, of being enabled to prepare a paper, which answered in everyrospect as well as the silver plates, and in many much better.

This discovery formed the subject of a communication to the Royal Society , which that learned body did me the honour to print in theirTransactions. My memoir is entitled,—“ On the Influence of Iodine inrendering several Argentine Compounds, spread on Paper , sensitive toLight , and on a new method of producing, with greater distinctness, thePhotographic Image'’ This paper contains the substance of the follow-ing remarks; but since the publication of the Transactions, I have beensuccessful in simplifying the process of preparation.

My experiments established, in the most satisfactory manner, thateven on the silver tablets a semi-oxidized surfaco was presented to theiodine. They also proved that perfectly pure untarnished silver was byno means readily acted on by the iodine. From this I was led to pre-pare oxides of silver in many different ways, which enabled me tospread them over paper, and the result was instructive. Any of theordinary photographic papers allowed to darken to a full brown, whichis a stago of inducod oxidation, become, by long exposure to iodino,of a steel-blue or violet colour. If oxposcd in this stato to sunshine fora long period, their colour changes from grey to a clear olive. Now,exposure to sunshine for a minuto, or to diffused day light for fiveminutes, produces no apparent change; but mercurial vapour speedilyattacks the portions which havo been exposed to light, and a faithfulpicture is given of whatever may have been superposed. Thero is,however, a want of sufficient contrast between the lights and shadows.By allowing the first darkening to proceed until the paper acquires theolive colour which indicates the formation of a true oxide of silver, itwill be found, although it is not more speedily acted on by the iodino,that it is more sensitive, and that a better picture is formed. Thekind of photographic preparations used appears to have but little influ-ence on the results,—a chloride, iodide, or bromide of silver, allowedto darken, answers equally well.

There aro many things, unfortunately, which prevent our availing