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Document number: 1386
Date: 27 Feb 1826
Recipient: HERSCHEL John Frederick William
Author: TALBOT William Henry Fox
Collection: Royal Society, London
Collection number: HS 17:259
Last updated: 30th April 2012


27th Feb. 1826
Dear Sir,

I requested Fraunhofer <1> to send the articles you mentioned thro’ the agency of Messrs Tanner & Co of Hamburg & B. Richards & Co of London <2> which I believe is as good a channel of transmission as can be obtained. Have you read a remarkably interesting paper by Struve in No 77 of Astronomische Nachrichten <3> in which he gives a list of 113 new double stars discovered by him with the Great Achromatic in a space where only 40 were known before; and hazards the bold idea that the orbits of the Binary stars have their planes nearly in the plane of the Milky Way. He seems to establish the excellence of the telescope, having observed a double star that is closer than 0.″5 I am glad that so fine an instrument is in such able hands, it appears that he had only had it 3 or 4 months at the date of the above paper; he must therefore have observed every fine night, to have discovered so much, I doubt whether, if it had been at Greenwich, we should have had so many observations.

I have remarked that Friar’s Balsam <4> is a good instance of a Red Liquid, this is green when sufficiently thin. I have not had opportunity to try the other liquids you mention as having that property. I have made several attempts to convert the brilliant light of ignited lime to some use, but I find that tho’ its quality is very good, it is generally deficient in quantity, and [illegible deletion] the illuminating power of a wax candle is the utmost that I have in general obtained (using only atmospheric air to feed the Blowpipe). <5> If hydrogen or oxygen is used I have no doubt a great effect might be obtained, but my object was to see if an Economical bright light could be obtained. Compressed Oil Gas appears to me the most likely to succeed; I have not at present the means of trying. When the light of Lime is compared with a wax candle by observing the two shadows of any object, the shadows are coloured: the candle throws a blue shadow & the lime a yellow one. I am afraid that if the ball of St Paul’s were lit with lime, we should only have a star of the first magnitude– Can you give me a letter to any of the savans of Geneva, I should be much obliged to you, as I mean to stop there a little while, on my journey.

I remain Dear sir Yours most truly
H. F. Talbot

I shall be glad to hear your opinion of Ramage’s Telescope, <6> & whether he said what price he meant to ask for it. Do you wish to send anything to Amici <7> of Modena, as I pass there. I forget whether he is a friend of yours. In the Bibliotheque Universelle de Genèva <8> for Dec. 1825 you will find p. 465 an explicit statement of the difference found by Fraunhofer between Electrical & Common Light in the Refrangibility of Rays of the same colour. I am nevertheless very sceptical on this point & should be very glad if you would take an opportunity of observing a strong electrical light, in order to determine a point of such fundamental importance to optical science. I mentioned to you the other day a curious theorem in the Annales des Mathematiques <9>– I find it susceptible of a rather simpler form, which is the following. Given a,b,c 3 radii vectors of a Conic Section issuing from the Focus, and also given A,B,C the angles respectively [illustration] opposite to them; to find an expression for the Latus Rectum

mathematical equation

This is a remarkable instance of the advantage of the symmetrical forms to which the French Mathematicians generally endeavour to bring their calculations. I deduce the following Corollary– let A = B = C = 120o

mathematical equation

ab + bc + ca ¼ + 1/6 + ½

T. on Council of Astronl

J.F.W. Herschel, Esq.
56 Devonshire Street


1. Joseph von Fraunhofer (1787–1826), optician, Munich.

2. Tanner & Brock Co. and Bingham Richards & Company, London.

3. Friedrich Georg Wilhelm Struve (1793–1864), astronomer.

4. A compound containing benzoic acid, used for treating a variety of ailments.

5. The oxyhydrogen blowpipe, invented in 1801 by Robert Hare (1781–1858), enabled a person to create a hot, bright flame with oxyhydrogen gas obtained by the electrolysis of water.

6. Probably the giant telescope of John Ramage (1783–1835), erected at Greenwich in 1825.

7. Prof Giovanni Battista Amici (1786–1868), Italian optician & man of science.

8. Bibliothèque universelle de Genève formerly Bibliothèque universelle des sciences, belles-lettres, et arts. See Doc. No: 01348, for more comments on Fraunhofer’s theories.

9. Annales de Mathématiques Pures et Appliquées, edited by Joseph Diez Gergonne (1771–1859), French mathematician.

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