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Document number: 6465
Date: 20 Sep 1851
Recipient: TALBOT William Henry Fox
Author: PHILLIPS John
Collection: British Library, London, Manuscripts - Fox Talbot Collection
Collection number historic: Acc no 20487 (envelope only)
Last updated: 12th June 2015

[printed form with handwritten changes and insertions:]


October 10 , Sept 20 185 0 1


Having received no authentic abstract of your paper on M. Foucaults Pendulum Experiment <1> read at the Edinburgh Ipswich Meeting, I shall be obliged by your transmitting one to me without delay, as the Volume in which it should appear is now in the Press.

I have the honour to be, Yours very truly,
Assistant-General Secretary.

T. O

[on verso:]

I think it desirable to preserve the recommendation of the Point suspension & Bar, & for this purpose should wish to take a nearly full excerpt from the part headed A proposed New Experiment.

J. Phillips

[in WHFT's hand:} Profr. Phillips
Fox Talbot Esq
Lacock Abbey


1. WHFT's paper was never published in the BAAS Report. However, he had issued a pamphlet, Remarks on M. Foucault’s Pendulum Experiment by H.F. Talbot (London: privately printed by Cox and Wyman, 1851). In March 1851 Jean Bernard Léon Foucault (1819–1868), French physicist, suspended a metal ball, weighing 28 kg, in a wire from the dome of the Panthéon in Paris. The ball was set in a pendulous motion, and over a span of hours it would exhibit a slow rotation in the direction of the pendulous motion, but what seemed to be the gradual rotation of the direction of the pendulous motion would actually be the rotation of the earth in space. In his paper WHFT suggested a different experiment, in which a horizontal bar balancing on a vertical bar would have to revolve within the span of 24 hours if Foucault’s reasoning was true. WHFT was convinced that this experiment would fail and thereby prove Foucault wrong, and the experiment would have failed, but perhaps not for the reasons WHFT thought. WHFT’s experiment would fail because he operated with an object, which was at rest with respect to the earth, whereas Foucault operated with an object, or rather a movement, which was at rest with respect to the frame defined by the stars. In the defence of WHFT only the fewest contemporary observers perceived this difference, in 1851 neither did Powell. WHFT's did not attend the BAAS meeting at Ipswich, but his thinking on this was summarised by his friend, Sir David Brewster - see Doc. No: 06437, and Doc. No: 06438. See also Tobin, William, The Life and Science of Léon Foucault: the man who proved the earth rotates (Cambridge and New York: Cambridge University Press, 2003), pp. 133–172.].

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