Falmouth
August 9th 1842
Sir,
the only knowledge I have ever obtained relative to your Patent, <1> was the mere fact, that such a patent was granted, from a list of patents I somewhere met with – and its application to Portraiture from the Advertisements of Mr Collen <2> – The Specification has never fallen in my way, consequently if I had sinned against it, I should have sinned in innocent ignorance – It would certainly be desirable to take views as well as portraits. You may remember that Sir John Herschel <3> sometime since, from the peculiar character of the spectrum impressed on Tartrate of Silver, came to the conclusion that the rays coming from the edge of the Sun, were changed in their character from the absorptive influence of the Sun’s atmosphere through a greater depth of which they, of course, passed. At the same time the same peculiarity was observed by myself on Spectra impressed on Daguerreotype plates. I was inclined to look on those rays as peculiar, quite independent of the absorptive influence – I have within the last few days observed some remarkable characteristics connected with these rays which go to confirm my former opinion – The Spectrum on the iodized paper washed with Ferro prussiate of potash is first rapidly impressed with the complementary colours of the rays, commencing at the red end of and proceeding regularly to the most refrangible rays and surrounded with a band, which is darker than any other part – The continued action of light bleaches the paper – rapidly at the red end, but gradually over every part of the spectrum except the dark band which is now quite protected even from the bleaching influence of the dispersed light – This remarkable energy in one case, and retarding power in another is exceedingly curious – and I should be glad to hear the opinion of so distinguished an experimentalist as yourself
I am Sir Yours Most respectfully
Robert Hunt
x The bleaching proceeds by impressing the natural colours of the rays –
Hy Fox Talbot Esqr
Notes:
1. The patent for the calotype process.
2. Henry Collen (1800–1879), miniature painter, calotypist & spiritualist, London. In August 1842, Collen became the first person licensed to practice calotype portraiture.
3. Sir John Frederick William Herschel (1792–1871), astronomer & scientist.