TALBOT3932

Lacock Abbey
Sept. 12. 1839

Dear Sir

I am much obliged to you for the description of your new method of making a picture on glass. ¹ Do not publish it at present, for the following reason. Some one ² has lately taken out a patent for improvements in photogenic drawing; I am not acquainted sufficiently with the facts, to be able to judge whether he has any fair right to do so, i.e. whether he has himself invented anything new, or only intends to reap what others have sown; but having conversed with a lawyer on the subject I find there is nothing to prevent him from monopolizing the Daguerreotype (in England) if he is so disposed. Now, until he enrolls his specification, which he may delay 5 months longer, he is at liberty to claim as his own any improvement that you or I or any one else may publish, and prevent us from employing it without his permission. Those things only are safe, which were published previously to the date of the patent. ³

Such is the state of the law at present, and there is no help for it, that I know of, it behooves us therefore to describe no new process, applicable to the art, before next year.

Among various speculations which I had noted down in my journal, respecting the probable nature of the Daguerreotype I find one that came pretty near the mark: viz. to expose a silver plate to vapour of iodine (for this part of the process I have been acquainted with, more than a twelvemonth) and then, to make the photographic picture on this plate, and place it in a galvanic battery, so that it should be one of the poles of the battery. I then expected that if the electrolyte were a solution of silver, the metal would precipitate more abundantly on some parts of the plate than on others; & thus render the picture more visible, & also fix it; but I never had leisure to try this experiment. ⁴

I think it would be very desirable to transmit to M. Biot ⁵ for insertion in the Comptes Rendus, an account of your recent observations on the spectrum. Would you like me to draw it up & send it, along with some observations of my own? In that case, I should wish to have a correct account of the paper which you sent to the B. Assocⁿ at Birmingham ⁶ on the subject. It is one of the greatest interest & offers a wide field for speculation.

I have discovered a method of acting on glass, more convenient than fluoric acid, which if you like I will communicate. The fluoric vapours I believe are very noxious.

The whitening power of sunshine on iodized paper, has been published by M. Lassaigne (I think) at Paris, and D^r Fyfe ⁷ in Scotland. It is a most inconvenient property, for in consequence of it, it is difficult so to fix a photograph with iod. potass. as to resist prolonged exposure to light. If framed & glazed, on week’s exposure to daylight is injurious. Some indeed remain unaffected, but its difficult to say on what their permanence depends.

I have kept some photographs 4 or 5 months in a portfolio w^ch still retained a ground of the deepest black, yet one day’s exposure to light destroyed the blackness & reduced it to brown. The whitening power is not energetic enough to be employed directly to obtain the lights & shades in their proper place, in working [with?]⁸ the Camera Obscura.

I remain yours very truly
H. F. Talbot