D O C U M E N T 1 7 A P R I L 1 9 2 3 3 9 tivity Committee of the American Section of the International Astronomical Union Kasner was its chairman (see Stebbins 1922, p. 99). Astronomer Royal Frank Dyson (1868–1939). For the 1919 eclipse expeditions, see Vol. 9, Introduction, sec. III, and Crelinsten 2006, chaps. 5 and 6. The experiment referred to here was first proposed in Michelson 1904 and further worked out in Silberstein 1921. It was meant to test for (partial) dragging of the ether due to the rotation of the Earth. In the experiment, the two components of a split beam of light would run in opposite directions along an equilaterally shaped closed path before recombining and producing interference fringes. In the case of full dragging, ether theory predicts the same value for the phase difference between the beams as does the theory of relativity if the ether is only partially dragged by the Earth, a fraction of this difference is expected, in which case relativity would be “irremediably disproved” (Silberstein 1921, p. 306). Michelson had started preparing the experiment in 1921 at the insistence of Silberstein, who kept Einstein informed (see their correspondence in Vol. 12 see also Einstein to Ludwik Silberstein, 21 May 1921 [Vol. 12, Doc. 136], for Einstein’s comments on the experiment, and Swenson 1972, chaps. 10 and 11, for historical background). Yerkes Observatory in Williams Bay, Wisconsin, operated by the University of Chicago. In May 1921, when Silberstein was attending Einstein’s lectures at Princeton University. In the New York Times, 24 March 1923, it was reported that “a new and greater discovery of his [Einstein’s] was soon to be announced—something about the relation between the earth’s attraction and terrestrial magnetism.” See also Docs. 5 and 16 for a discussion of the article. Silberstein 1924. On p. 465, Einstein 1923e (Vol. 13, Doc. 425), Einstein 1923h, and Einstein 1923n (Docs. 13 and 52) are briefly mentioned. 17. From Gilbert Murray Yatscombe, Boar’s Hill, Oxford, April 20, 1923. CONFIDENTIAL. Dear Dr. Einstein, I saw some time ago the report in the newspapers of your letter to the C. I. C., and have just had a copy sent me officially from Geneva. I fully understand your action, and even feel the strongest sympathy with it, but I hope and believe that you are wrong. I am sure that the vast majority of the dele- gates present at the Assembly have the good-will that is necessary. One cannot attend a meeting of the Assembly, or spend a few days at the Secretariat, without being convinced of this. But of course the power is another matter. We are faced in Europe with a military supremacy in the hands of one nation about as great as Napoleon’s at the height of his power, and that makes all progress towards interna- tional justice extremely slow and difficult. Even those, who like myself, are deeply committed to the League, sometimes find it difficult to keep our patience.