TALBOT3839

Slough.
Mar 18/39

Dear Sir,

Many thanks for the specimens of your sensitive paper ¹ – It really deserves the name, and in fact so far surpasses my expectation from any trials I had made that I cannot help congratulating you on your hitting on so very valuable and curious a discovery.

I handed over all my best specimens of copies of engravings to the R.S. ² and owing to want of Sun yesterday or today I have none worthy of sending to Baron Humboldt. ³ but I thank you much for your offer.

In the last N^o of the Annales de Chimie there is a Chemical paper ⁴ which contains a hint which I think may turn out to be the key to Daguerre’s process. ⁵ The curious habitudes of Chlorine in relation to Carbon & hydrogen under the influence of Light have long been known – and in a note to the “Notice” I handed into the RS on Thursday, allusion is made to these reactions as a possible mode of “photogeny”– Well. Monssr Regnaults paper above alluded to mentions one reaction so marked & vivid [illegible deletion] not only under sunshine but in daylight that it seems hardly possible it should not become available some-how or other

The Experiment is this
Take of the oily liquid produced by action of Chlorine on Olefiant gas – quantum sufficiis ⁶ put it in a shallow dish & pour over it a stratum of water – Then place it in an atmosphere of Chlorine. This will be copiously absorbed and a liquid is produced which is permanent in the dark but decomposes as above described in the light. –
Now. NB. The “oily liquid” has also been called chloric ether and as you mentioned “muriatic ether” in a late letter as one of Daguerre’s re-agents this seems to strengthen the suspicion that we are to look in this direction for his process.–

Yours very truly
JFW Herschel

PS. I have laid my hands on a few specimens not of the best but passable, which perhaps you may think worth sending to H^{t 7} – The brown-looking one with the palm trees is not fixed – the others are. The Bas-relief is fixed with a solⁿ of Ferrocyanate of potash ⁸ containing 1/100 its weight of the salt and seems not disposed to fade.

H.F. Talbot Esq^r