DOCUMENT 309 NOVEMBER 1911 353 Nehmen Sie noch meinen innigsten Dank entgegen dafür, dass Sie sich meinetwegen in so prekäre Unternehmungen gestürzt haben, und seien Sie herzlich gegrüsst von Ihrem Einstein Freundliche Grüsse von Haus zu Haus. ALS (Estate of Heinrich Zangger, Zurich). [39 639], The year is provided by the reference to the possibility of an ETH appointment. Objections to Einstein's appointment at the ETH (see Doc. 305, note 2) had been over- come. Einstein's response to Marcel Grossmann is made in the preceding document. His col- league at the ETH, Pierre Weiss, solicited letters of recommendation for an Einstein appoint- ment, one of which was written by Henri Poincare, ca. November 1911, the other by Marie Curie, 17 November 1911 (see SzZE Schulratsarchiv 1911, Akten for substantial excerpts from both letters, see Seelig 1954, pp. 162-163). The meeting of the Swiss School Council, of which Robert Gnehm was President, took place twelve days later (see the minutes of 2 December 1911, in SzZE Schulratsarchiv 1911, Protokoll des Schweizerischen Schulrates, no. 117). For Gnehm's overture, see Doc. 317. Fritz Haber (1868-1934) was Director of the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry. The relation expresses the assumption that atoms and electrons perform harmonic oscil- lations characterized by the same force-constant (see Haber 1911b). See Haber 1911b, p. 1119, for Haber's hypothesis that the heat produced in a chemical reaction is equal to the difference of the energy needed to remove all electrons from the atoms that undergo the reaction, and the energy needed to remove all electrons from the atoms of the end product. The energies are expressed as E hvi, with vi the frequencies of the electrons. Friedrich Krüger. See Krüger 1911. Emil Warburg attended the Solvay Congress at the beginning of the month. See Warburg 1907, 1909. published as Einstein 1912b (Vol. 4, Doc. 2). In the paper Einstein states that Warburg's papers (see the preceding note) had instigated his work on photochemical decomposition (p. 834). See Docs. 182 and 187 for evidence of Einstein's earlier interest in photochemical phenomena. See also Vol. 4, the editorial note, "Einstein on the Law of Photochemical Equiv- alence," for a discussion. 309. To Heinrich Zangger [Prague, 20 November 1911] Habe Grossmann zugesagt trotzdem Paris fahren herzlichen Gruss Einstein TGM (Estate of Heinrich Zangger, Zurich). [39 641]. The telegram is addressed to "Zangger Stadthausquai Zuerich" and was received at 12:45 p.m. Einstein indicated his willingness to accept a position at the ETH to Marcel Grossmann in Doc. 307.