Oxford
July 8
Dear Sir
I beg to thank you for a copy of your pamphlet <1> on M. Foucaults experiment which has been so much discussed. At the British Assoc. <2> the substance of your remarks was given to the Section A. by Sir D Brewster <3> – In some conversation I afterwards had with one or two Members, there seemed to be an opinion that the experiment you propose would succeed if friction could be suffly got rid of, & that this would most likely be secured by a delicate suspension by Silk fibres instead of the upright pivot. At all events it would be a very delicate expt to perform.
I remain Very truly yours
B Powell
[envelope:]
H. Fox Talbot Esqr
Athenæum
London
Notes:
1. Remarks on M. Foucault’s Pendulum Experiment by H.F. Talbot, privately printed by Cox and Wyman, London, 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. [See Doc. No: 06438, and Doc. No: 06564; 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.].
2. The British Association for the Advancement of Science.
3. Sir David Brewster (1781–1868), Scottish scientist & journalist.