Munich
2d June 1842
My Dear Sir
I find, from a conversation with Dr Steinheil, <1> who very obligingly related his experiments to me, that he has recently written to you respecting his proposed method of constructing Reflecting Telescopes. I therefore beg to put you in possession of some facts regarding the priority of this discovery, for, as I observed to Mr S. himself today, Science is now cultivated by so many, that it is impossible that cases of simultaneous invention should not frequently arise. About a year ago Mr Wheatstone <2> & myself independently arrived at the idea or invention, of constructing telescope mirrors by taking electrotype copies from an original mirror – Mr W. proposed to make the copy of platina or other white metal; but he did not put the invention in practice; altho’ both he & I were of opinion it would be of great importance to Science. My invention, which was quite independent, consisted in making the electrotype copy of Copper and then whitening that copper by exposing it to the vapour of hydrosulphuret of ammonia, or some other analogous vapour. – A friend was obliging enough to make me a few electrotype copper mirrors which I treated as aforementioned and (altho’ they are now a year old) I do not find any difference whatever in their appearance, from what they were at first. – The action of the vapour does not affect the polish but (since it transforms the copper into sulphuret of copper) the mirror cannot oxydate, because sulphuret of copper is a stronger chemical affinity than oxide of copper. These 2 last points are what appeared to me of chief [illegible deletion] importance – I took out a patent for the invention, or rather I included it in a patent for other things, of which the specification was published before I left England. <3> My chief object in so including it, was to establish my claim to the invention, altho’ I was not aware that it had occurred to anyone else but Mr Wheatstone.
Dr Steinheil’s procedure is a good deal different, as he preciptes gold first & then copper – The plan which I had formed for using the mirrors if we could copy the Earl of Rosse’s <4> large one, for example, closely resembles Dr Steinheil’s, indeed that method of mounting a telescope occurred to me from 10 to 20 years ago, as being the only one which we could have recourse to, if our reflecting telescopes grew much larger – I have been often on the point of describing it in the Phil. Mag. <5> but have always forgotten to do so, so I suppose I must be content to forego this part of the thing – So far from following Horace’s precept of keeping things back for nine years & then reconsidering them, as to whether they deserve publication. I think that in the present universal impetus for discovery a delay of nine days is unadvisable, nine months very hazardous, nine years assuredly fatal to any claim of discovery – The weather here is hot and bright beyond belief, equal to the Cape I should think; I don’t think I ever saw it equalled in England, much less a long continuance of the same.
Believe me, yours ever
H. F. Talbot
Sir J. Herschel Bart
Collingwood
Hawkhurst
Kent
England
Notes:
1. Carl August von Steinheil (1801–1870), astronomer, physicist and optician, wrote to Herschel on 13 May, describing his process for plating gold on mirrors. See Herschel letters at the Royal Society Library, RS:HS 17.4.
2. Sir Charles Wheatstone (1802–1875), scientist.
3. This was WHFT’s patent No. 9167, Coating and Coloring Metallic Surfaces, filed 9 December 1841 and enrolled on 18 May 1842. In his research notebook P on 30 January 1840, WHFT recorded his idea for a “Voltaic copy of Telescope Specula”. WHFT published his procedures in, ‘On the Improvement of the Telescope’, Report of the British Association for the Advancement of Science, 1842, part 2, pp.16–17.
4. William Parsons, 3rd Earl of Rosse (1800–1867), astronomer & MP.
5. Philosophical Magazine.