2 College, Glasgow | Sep 10, 18511
Dear Sir
I enclose a short testimonial, according to your request, and I shall be very glad if you find it in any degree useful in promoting your present object. I see your letter is dated Sep. 1, and I regret the delay I have made in answering it which arose from my having been at a considerable distance from home when it was forwarded to me and only having returned today.2
I enclose also copies of some short papers on Electricity and Magnetism;3 and by the same, or nearly the same post, you ought to receive some more extended papers on Magnetism, and on the Dynamical Theory of Heat,4 all of which I shall be glad if you will accept.
If you read § 21 of my paper5 (enclosed) entitled ‘Remarks on the Forces &c.’ you will perceive that the experiments described in the first part of your paper of this month6 are particularly satisfactory to me. Indeed I have always felt very much inclined to believe that Plücker’s ‘loi générale’ about magnetism decreasing less rapidly than diamagnetism was entirely a delusion, and I am still so inclined after reading your two last papers. Your experiments on the attraction of soft iron balls make it I think very improbable that Plücker has really observed the phenomenon indicated in § 23 of my ‘Remarks &c’.7
I am very glad to see that, by your experiments8 on the differences of force experienced by crystals of calcareous spar and other substances according to the directions in which they are turned with reference to the lines of force in a magnetic field, you have so amply confirmed the theory of magne-crystallic induction as suggested by Poisson, and by Faraday (2588), and verified experimentally by Faraday (2841)9 for the single case of bismuth.
The only difference of opinion regarding the theory of magnetic induction which I am now aware to exist between us is regarding ‘the influence of proximity’ of which you speak.10 Ever since May 1847 (See Cambridge & Dublin Mathl Journal Vol II p. 235 § 12;11 or British Association Report Swansea 1848 Physical Section p. 912) I have been prepared to demonstrate that the effect of proximity among the particles of a diamagnetic powder is the reverse of what you assume it to be, but that it is so small as to be insensible in actual experiments. I think the very important experiments you describe in pages 19, 20, 21 of your last paper13 demonstrate that the effects of compression which you observe are due to a molecular alteration of the substances, and they fully confirm the second of the conjectures which I threw out at Edinburgh14 last year. I am quite ready to give up the first conjecture, the objection to it stated in p. 17 of your paper having occurred to myself as probably fatal to it, and your measurements (foot of p. 18)15 being very decisive against it.
I hope before long to be able to write a short paper for the Philosophical Magazine,16 explaining my views regarding form and proximity as affecting the bearing of single bodies or of groups, in a magnetic field.
I remain, Dear Sir, | Yours very faithfully | William Thomson
John Tyndall Esq
RI MS JT/1/T/10
Sep 10, 1851: Tyndall received this letter, along with letters from Francis and Dove (both missing), on 13 September (Journal, JT/2/13b/549).
your request ...returned today: see letter 0519, n. 1.
some short papers on Electricity and Magnetism: only one of these papers can be identified with certainty, as it is mentioned below (n. 5). Thomson may also have sent a copy of his, ‘On the Theory of Magnetic Induction in Crystalline and Non-Crystalline substances’, Phil. Mag., 1:2 (March 1851), pp. 177–86.
more extended papers … Theory of Heat: Thomson sent the magnetism papers that Tyndall told him he had not seen (letter 0519, n. 4). We have not identified the paper on the dynamical theory of heat.
my paper: Thomson, ‘Remarks on the Forces experienced by inductively Magnetized Ferromagnetic or Diamagnetic Non-crystalline Substances’, Phil. Mag., 37:250 (October 1850), pp. 241–53. Thomson refers to pp. 250–2.
your paper of this month: Thompson alluded to Tyndall’s paper ‘On Diamagnetism’ (cited 0498, n. 6), which Tyndall had sent him 10 days earlier (letter 0519, 1 Sept 1851), and which he had heard at the BA meeting. Tyndall discussed, and refuted, the general law that Thompson referred to here on pp. 165–7.
the phenomena … my ‘Remarks &c.’: see n. 5; § 23 is on p. 253.
by your experiments: reported in ‘On Diamagnetism’ (see n. 6). Although there is no reference to Poisson in that paper, the detailed references to Faraday match Thomson’s comments here.
Faraday (2588), ... (2841): the numbers refer to paragraphs in Faraday’s ongoing ‘Experimental Researches in Electricity’: ‘ERE 22 (continued)’, p. 31 (§ 2588) ; ‘ERE 26’, p. 41 (§ 2841).
difference of opinion …of which you speak: in letter 0520 Tyndall told Thomson he had expected an ‘onset’ from him in response to his BAAS paper. Tyndall posits and provides evidence for ‘the influence of proximity’ on pp. 180–6 of his paper ‘On Diamagnetism’ (n. 6 above); Thompson quotes from p. 185.
Cambridge … 12: Thomson, ‘On the forces experienced by small spheres under magnetic influence; and on some of the phenomena presented by diamagnetic substances’, Cambridge and Dublin Mathematical Journal, 2, 1847, pp. 230-5.
British Association … p. 9: Thomson, ‘On the Equilibrium of Magnetic or Diamagnetic Bodies of any Form, under the Influence of the Terrestrial Magnetic Force’, Brit. Assoc. Rep., 1848, pp. 8–9.
pages 19, 20, 21: pages 183–5 of ‘On Diamagnetism’ as published in the Phil. Mag. (cited letter 0499, n. 6).
Edinburgh: at the Edinburgh BA meeting. Thomson gave a paper ‘On the Theory of Magnetic Induction in Crystalline Substances’ (Brit. Assoc. Rep., 1850, p. 23) in which he ‘stated two principles, involving no physical hypothesis regarding the ultimate nature of magnetization’. The abstract only explains one – ‘the superposition of magnetic inductions’ – which ‘cannot be considered as fully established by experiment’. (The Report also noted that Thomson had discussed his research with Tyndall while at the meeting.) The paper was subsequently published in full in the Phil. Mag. (see n. 3).
the objection to it stated in p. 17 … (foot of p. 18): ‘On Diamagnetism’, pp. 181 and 182 as published in the Phil. Mag. Tyndall quoted from, and replied to, Thomson on p. 181.
short paper for the Philosophical Magazine: this does not seem to have happened.
Please cite as “Tyndall0528,” in Ɛpsilon: The John Tyndall Collection accessed on 27 April 2024, https://epsilon.ac.uk/view/tyndall/letters/Tyndall0528