Slough.
Sep 10/39

My dear Sir/

I have just rec^d your very pretty specimens of Magnified Lace ^<1> which are highly interesting in point of their object & principle & very fine in point of execution. – Daguerre ^<2> neither shewed me or alluded to any thing of the kind as having been done by him, though of course the “Daguerrotype” is applicable to that purpose. ^<3>

I have not tried Daguerre’s process – But I yesterday succeeded in producing a photograph on glass ^<4> having very much the character of his results – being Dark on a bright ground as in nature, and right not reversed as to right & left, and having much the appearance of a being done on polished Silver. The process is delicate & very liable to accident in the manipulations, as it consists in depositing on the glass a perfectly uniform film of Muriate of Silver – dry (by subsidence from water) – drying it – then washing it with Nitrate to render it sensitive (which it does, NB) To do this without injuring the film requires great precaution. When placed glass foremost in the focus of a Camera This takes the image with much greater sharpness than paper. – It fixes with a wash of hypo sulphite of Soda poured over it, quite easily & completely. The whole of the unreduced muriate is carried cleanly away and the reduced silver forms a brilliant metallic film on the glass which adheres firmly & will bear considerable friction.– The glass being then smoked or black varnished the effect is as described. –

But if the varnish be omitted there seems no reason why impressions should not be taken from it ad infinitum provided the film can be got thick enough.– And for this I propose to connect the Silvered Surface with a the pole of a Galvanic pile under solution of silver so as to cause more metal to be precipitated on it & thereby thicken it.– Probably also the silver film may defend the glass from the corrosion of fluoric acid gas – in which case an actual etching on glass would be the result.–

The Sun has been so dreadfully niggard of his beams that I have been unable duly to follow up the very curious train of enquiry about the peculiar effects of the spectrum-rays. – The White spot corresponds strictly to the extreme red. And the whitening power is transmitted through Cobalt blue glass.– But the most curious thing is the effect on paper already deeply tinted by a pure Violet ray. – On such paper the extreme rays develope a red of a surprising richness & intensity of which I enclose you a specimen. I should observe that the prism used for the enclosed is a Water prism.

I remain My dear Sir Yours very truly
JFW Herschel

PS– The Yellow metallic film which marks the full effect of sunshine on your paper – is produced by the blue rays & not so far as I can see by the yellow or green. PS.– I have found that a paper whose basis is acetate of lead possesses the property you allude to in yours of July 19 ^<5> in some degree. – When kept in an atmosphere of vapour of Oil of turpentine it recovers (very slowly) its whiteness & is afterwards again susceptible to of being darkened afresh by exposure. I have also observed that a drawin[g]^<6> overfixed by Hydriodate of Potash which slowly whitens in the dark – whitens with great rapidity in a bright sunshine. – I have specimens by me of paper so treated in which a portion exposed to light is discoloured while the rest remains dark.

H.F. Talbot Esq^r
Lacock Abbey
near Chippenham Wilts

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Notes:

1. Three negatives of magnified lace, all dated 1839 in WHFT’s hand, were owned by Herschel and are now held in the National Media Museum, Bradford, England. Schaaf 2250, 2274 and 2775. There is one print of magnified lace, also dated 1839 in WHFT’s hand, in the Herschel collection at Oxford History of Science Museum, Schaaf 3767.

2. Louis Jacques Mandé Daguerre (1787–1851), French artist, showman & inventor.

3. Herschel had been to Paris in May and had met with Daguerre, who showed him specimens of the daguerreotype.

4. Herschel made several circular negatives on glass depicting the forty-foot telescope shortly before it was dismantled at the end of 1839. They are housed in the collection of the National Media Museum, Bradford, England. Herschel may have tried this experiment after viewing a negative on glass at Daguerre’s studio. See Doc. No: 03875.

5. See Doc. No: 03908.

6. This word partly cut away under seal.