TALBOT8683

Sir,

M^r Niepce de Saint Victor, ¹ one of our most renowned scientific men, has told me that, through your researches for the improvement of photography you have discovered a peculiar property to both gum and gelatin, when one of these substances is combined with the bichromate of potassa. ² In that state and used as a kind of coat, the substance thus mixed, if dried and exposed to light should become insoluble in water, but might swell if getting humid.

Some years ago, I have lost the use of my eyes, and I try to get perfect a writing process, approved by the Institute of France, and I thought, Sir, of making out the best of your discovery, for an invention of mine, namely: a relievo-writing process for the use of the blind. ³ But M^r Niepce de Saint Victor not having been able to give me the exact proportions of the mixture of gum and potassa, I feel so confident, Sir, in your kindness, that I make myself certain of your cooperation in the philanthropic end which I aim, and I grant you, Sir, a thousand thanks for the answer, so precious for me, you will make to my queries.

I am, Sir, with gratitude, your most humble and obliged servant,
E. Duvignan

rue de la Bourse, 6, Paris.
Paris,
April 10, 1863.