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Document number: 3908
Date: 19 Jul 1839
Recipient: HERSCHEL John Frederick William
Author: TALBOT William Henry Fox
Collection: Royal Society, London
Collection number: HS 17:295
Last updated: 17th April 2010

Lacock Abbey
July 19. 1839

Dear Sir

I have received your two letters <1> giving a very interesting account of the Chemical effects of the spectrum; the specimen, tho’ unfixed, still retained the colours with sufficient distinctness. There are two main points to be made out concerning this phenomenon, (1) why the differently coloured rays act thus differently. (2) what is the state into which the silver is reduced? of how many states is it susceptible? and are these definite compounds, according to the atomic theory, or are they mixtures? or finally, does the silver pass from one state to another by a gradual change – gradual, as the change of refrangibility in the rays?

It is hard to believe that these are differently coloured oxides of silver, nor can they be metallic silver in a pulverulent form. Fixing destroys these faint colours as I have found. The transfer from an engraving which you sent, is very good: try some Rembrandt etching, perhaps it would come out as bold as the original.

I have got a piece of sensitive paper which manifests a curious property, I have 2 or 3 times blackened it a good deal in daylight, & it grows pale again during the night, I suppose this will not succeed beyond a limited number of times. Unluckily I have no memorandum how the paper was made: and it may depend upon some casual adjustment of proportion not to be readily obtained again. I am afraid our Birmingham meeting <2> will be greatly discouraged by these events, if indeed it takes place at all. A Chartist irruption into section A would put fly to all the sciences.

I find various obstacles to making good transfers of Camera Pictures; so that the final result hardly reaches one tenth of the perfection which the picture has when first taken out of the instrument. But the weather being now singularly gloomy, is partly the cause of it. I enclose <3> a little specimen however which might serve a traveller as a memento – This is taken on common paper, not very sensitive; the latter forms the pictures almost ten times quicker, but is less easy to fix.

Yours very truly
H. F. Talbot


1. See Doc. No: 03905 and Doc. No: 03906.

2. In spite of these concerns, WHFT took full advantage of the annual meeting of the British Association for the Advancement of Science, which met in Birmingham in August 1839. He exhibited 93 specimens of negatives and positives. They were listed in a pamphlet, A Brief Description of the Photogenic Drawings Exhibited at the Meeting of the British Association, at Birmingham, in August, 1839, by H. F. Talbot, Esq..

3. Enclosure not located.