24th March 1826
The Courier Contini has obligingly offered to take this – I sent your book to Professor Gautier <1> from Lyons by the diligence as I received information just before I left Town that the steamboat for Corfu would leave Ancona on the 25th which obliged me to take a more direct line, than the road thro’ Geneva. The steamer is not yet however come into port. I had a remarkably pleasant journey from London hither of 13 days, stopping at an inn every evening. I made some observations on the purity of the air on Mt Cenis – I found that it was sufficient to hinder the sun with the tip of the finger, in order entirely to obliterate his light, as the finger did not appear surrounded by a halo, but by dark blue sky. This would be the atmosphere to repeat Dr Wollaston’s expts on the appearance of Venus when in conjunction with the Sun. <2> I also repeated an observation which I have made before in the Alps, on the effect of sunrise from behind a distant pine-wood. The road lay at the foot of a cliff 2000 or more feet in height, & fringed with pines. When the Sun, hid behind this cliff, was about to emerge, every branch of the these pines took the appearance of fire, which was strongly set off by the blue sky behind. I observed with a telescope, with which the effect was very beautiful. I cannot explain this exactly by the theory of the diffraction of light; – I called on Amici <3> at Modena: he is coming to England next year about this time. He seemed much pleased with a compliment you paid to his telescopes in the Astron. Nachrichten <4> & asserts them to be superior to Struve’s <5> at Dorpat. <6> His 11 inch Reflectors cost £240. I should be glad to know whether in your opinion that is reasonably cheap: & whether they are equal in effect to 11 inch reflectors of 15 or 20 feet focus. He is much concerned at a new microscope produced in London by one Cuthbert <7> which he says is precisely the same as his own. Amici says he has discovered
an a method of dividing instruments without Error: & that he will publish it. In fact he shewed me some instruments that were very nicely divided.
Believe me Dear Sir Yours very faithfully
H. F. Talbot
Ansd May 22. 1826. <8>
J. F. W. Herschel Esqre
56 Devonshire Street
1. Emile Gautier, Professor of Astronomy.
2. Rev Francis Wollaston, ‘Observations of the Transit of Venus over the Sun, on June 3, 1769; and the Eclipse of the Sun next Morning; made at East Derham, in Norfolk’, Philosophical Transactions of the Royal Society of London, no. 59, 1769, pp. 407–413.
3. Prof Giovanni Battista Amici (1786–1868), Italian optician & man of science.
4. The well-circulated Astronomische Nachrichten.
5. Friedrich Georg Wilhelm Struve (1793–1864), astronomer.
6. City in Eastern Estonia on the Ema river, now called ‘Tartu’.
7. Amici was concerned that John Cuthbert, a London optician, was manufacturing reflecting microscopes and claiming the invention as his own.