6th May 1855.
My dear Sir,
Two causes have prevented me from writing to you sooner. The first is that a wrong paper was in the first instance sent to me, and the correction of this mistake occasioned a delay of a couple of days. The second is that a bad head and many other engagements conspired to prevent me from making a few remarks on Mr Thomson’s memoranda1 – I will now swiftly refer to his notes taking them in the order in which they come.
It is perfectly certain that not only is another explanation conceivable but that such has been conceived and supported for years by writers on diamagnetism. Plücker himself made some experiments2 for the express purpose of proving the explanation referred to [as] false – but he now just as expressly admits the error of his experiments and the truth of mine. With regard to the question of priority mooted in the commencing paragraph a reference to both our papers will show what each has done – no doubt the superior repulsion of bismuth along the planes of cleavage was established before my results were published; but I think I did something to generalise this result. If Mr Thomson however thinks otherwise I am content.
The experiments of Joule3 and others on magnetic saturation are very familiar ones to me, but I leave you to judge whether the following fact does not justify the caution which I have observed. I have found many feeble diamagnetic bodies which, operated on by the self-same magnetic forces, do not follow the law of repulsion observed in the case of bismuth, but whose repulsion increases much less rapidly. This of course can only be explained by reference to the condition of the body operated on. The whole matter however affects the general aim of my paper so little that to avoid all discussion I will strike out the passage altogether.
A similar wish to remove all possible grounds of dispute induces me to strike out what has been said regarding places of stronger and weaker force. Its omission, though deprecated by some, does not affect the paper. At some future time4 I shall take occasion to say a few words upon the subject.
With regard to Mr Thomson’s views as to the influence of diamagnetic particles upon each other, I can only say that they do not coincide with mine. When I spoke of the ‘promised proof’ I was well acquainted with the paper in the British Association Report.5 But if you look at the paper I am sure you will agree with me that it does not go beyond simple affirmation without any proof what ever.
Not long ago I had a letter from Mr v. Feilitsch accompanying his paper6 and drawing my attention to his results. He is far from believing that his views originate in an obvious mistake. I hardly think the mistake was obvious until my paper proved it to be so. Even at the present moment there are experiments by v. Feilitsch which I know influence the minds of some who have though mostly deeply upon these matters and which still remain unanswered. In fact, however clear Mr Thomson’s views may be, this subject is really in a state of great confusion and if I have succeeded in stating the truth with clearness it is all that I desire.
From many of his published papers7 I should have inferred that Mr Thomson assumed the existence of diamagnetic polarity. Now even supposing this polarity never to have been doubted it is certainly worth while to convert the assumption into a fact and this I think has been done in the paper under consideration. But from what he mentioned to me himself in private, from his reply to me in Belfast,8 from Mr Faraday’s reference to his supposed refutation of the doctrine of diamagnetic polarity in the lecture upon education9 – from the recent repetition of Thomson’s argument10 that a perpetual motion must result if diamagnetic polarity be conceded, I think I was warranted in concluding that Mr Thomson had changed his views. I should be the last to endeavour to hold him to an opinion once expressed, but I should also like to show that in supposing him to be the opponent of diamagnetic polarity I had grounds for believing him to be more than ‘an imaginary adversary’. However all that involves his name in connexion with the question of polarity has been struck out and this makes an end of the discussion.
I am not aware that I have been anticipated by ‘various writers’ on the point referred to in Mr Thomson’s last paragraph,11 but am rather of opinion that I am the first who pointed it out. Nevertheless in this case also I have struck out the passages referred to.
I trust the paper in its present state will meet the wishes of all concerned. I have also attended to remarks of the second referee as far as my time permitted me.
The paper is now quite ready.
Believe me | Yours very truly | John Tyndall.
If you wish I will take the paper to the printers. I shall only add a short note or two which will bear the present date and which indeed contain nothing to contend about. I shall have to make some arrangement about the plates | J.T.
RI MS JT/1/4/1464–6
LT Typescript Only
Mr Thomson’s memoranda: Thomson’s letter to Stokes of 14[?] March 1855 included ‘some memoranda hastily put down in reading’ Tyndall’s RS paper ‘On the Nature of the Force by which Bodies Are Repelled from the Poles of a Magnet’ (RS RR 2/252; Thomson to Stokes, [14 March 1855], cited in letter 1076, n. 4.
Plücker himself made some experiments: Plücker published several papers on diamagnetic properties of crystals including ‘Ueber die Abstossung der Optischen Axen der Krystalle durch die Pole der Magnete’, Poggend. Annal., 72 (1847), pp. 315–43; ‘Ueber die Theorie des Diamagnetismus, die Erklärung des Ueberganges Magnetischen Verhaltens in Diamagnetisches und Mathematische Begründung der bei Krystallen beobachteten Erscheinungen’, Poggend. Annal., 86 (1852), pp. 1–34. After reading Tyndall’s Bakerian Lecture, Plücker expressed his annoyance to Faraday: see Faraday Correspondence, 5:3109.
The experiments of Joule: J. Joule, ‘Account of Experiments Demonstrating a Limit to the Magnetizability of Iron’, Phil. Mag., 2 (1851), pp. 306–15 and 447–56.
At some future time: Tyndall subsequently addressed this issue in his ‘On the Relation of Diamagnetic Polarity to Magnecrystallic Action’, Phil. Mag., 11 (1856), pp. 125–37.
the paper in the British Association Report: probably W. Thomson, ‘On the Equilibrium of Elongated Masses of Ferromagnetic Substance in Uniform and Varied Fields of Force’, Brit. Assoc. Rep. 1852, pp. 18–20.
a letter … accompanying his paper: letter missing. The paper was probably F. C. O. von Feilitzsch, ‘Erklärung der diamagnetischen Wirkungsweise durch die Ampère’sche Theorie’, Poggend. Annal., 92 (1854), pp. 366–401 and 536–76.
many of his published papers: see Jackson, pp. 453–5.
his reply to me in Belfast: presumably in the discussion at the BAAS meeting on 1 September 1852, following Thomson’s paper ‘On Certain Magnetic Curves’; see Jackson, p. 458.
Mr Faraday’s … upon education: Faraday used the following example to caution against drawing conclusions prematurely. To account for the diagmagnetic behaviour of bismuth or phosphorus between the poles of a strong magnet ‘I at one time suggested the idea that a polarity was induced in the phosphorus or bismuth the reverse of the polarity induced in iron, and that opinion is still sustained by eminent philosophers.’ Owing to contrary evidence, Faraday subsequently withheld judgment on that theory (‘Observations on Mental Education’, in M. Faraday, Experimental Researches in Chemistry and Physics (London: R. Taylor & W. Francis, 1859), pp. 453–91, on p. 482).
the recent repetition of Thomson’s argument: In a note to his Bakerian Lecture (Phil. Trans., 145 (1855), pp. 50–1), Tyndall drew attention to the report in the Athenæum of Thomson’s comments on a paper (‘On the Diamagnetic Force’) that Tyndall had delivered at the 1854 meeting of the BAAS. There Thomson had admitted ‘that he had not perfect confidence in the truth of the conclusion, as one of the assumptions on which the reasoning was founded admitted of doubt’ (Athenæum (7 October 1854), pp. 1203–4).
Mr Thomson’s last paragraph: The last paragraph of Thomson’s report held in the archive of the RS (RS RR 2/252) makes no mention of ‘various writers’.
Please cite as “Tyndall1082,” in Ɛpsilon: The John Tyndall Collection accessed on