1 2 4 D O C U M E N T 6 8 S E P T E M B E R 1 9 2 5 nachdem ich einigermassen mein Herz gelüftet hatte. Aber leider habe ich in der Zwischenzeit aus ABSOLUT verlässlichen Daten entnehmen können, dass er aus dem Wunsche Direktor des Utrechter Laborat. zu werden (als Nachfolger von[16] Julius) [Er[17] hat dieses Laborat. total reorganisiert!! und zur Blühte gebracht!][18] und seinen Schüler Burger[19] die Professur für theoret. Physik zu verschaffen (statt Kramers!)—doch wieder merkwürdig kräftige (internationale) Mittel benützt. Ob Ornstein die Experimental-Professur bekommen soll, entzieht sich ganz meiner Be- urtheilung. Dass aber Burger die Theoret. Professur erhalten soll, wenn Kramers[20] zu haben ist finde ich lächerlich. Herzl. Grüße Dir, Deiner Frau Ilse u. Margot! Dein P. Ehrenfest TLS. [10 110]. There are perforations for a loose-leaf binder at the left margin of the document. [1]Niels Bohr and Margrethe Bohr-Nørlund (1890–1984). [2]Hendrik A. Lorentz. [3]The celebration of the fiftieth anniversary of Hendrik A. Lorentz’s doctorate on 11 December. Einstein had announced his intention to attend in Doc. 49. [4]Corrected in Ehrenfest’s hand. [5]Underlined in red pencil in Ehrenfest’s hand. A large “1)” and a short vertical line, both in red pencil, are added at the left margin. [6]See their exchange in 1921–1922 on the topic (Einstein to Ehrenfest, 20 January 1921 and Ehrenfest to Einstein, 22 January 1921 [Vol. 12, Docs. 24 and 30]), as well as Einstein 1922a (Vol. 7, Doc. 68) and the manuscript “On an Experiment Whose Result Is Incompatible with the Undulatory Theory” (Vol. 13, Doc. 29). [7]Ehrenfest 1925a. [8]See, e.g., Ehrenfest’s notebook ENB:1, 29 (NL-LeRM, Ehrenfest Archive), entries 6164 (“Dia- magnetismus in Bi-fest,” 10–16 August 1925) and 6176 (“Deutung des hohen Atomdiamagnetismus in festem Bi: Zwei Möglichkeiten,” 16–30 August 1925). A short publication on the subject followed later that year in the special issue of the journal Physica dedicated to Hendrik Lorentz at the fiftieth anniversary of his doctorate (Ehrenfest 1925b). [9]Marcel Minnaert (1873–1970) was observator at the astronomical observatory of the University of Utrecht. [10]Einstein was planning to write an obituary for Willem Julius. [11]Underlined in red pencil in Ehrenfest’s hand. A large “2)” in red pencil is added at the left margin. [12]Geertruida de Haas-Lorentz (1885–1973). [13]Dayton C. Miller was repeating the Michelson-Morley experiment at Mount Wilson (see, e.g., Doc. 12). [14]Underlined in red pencil in Ehrenfest’s hand. A large “l” in red pencil is added at the left margin. [15]Leonard Ornstein. [16]The remainder of the text is in Ehrenfest’s hand. It starts at the foot of the page, continues at the left margin, then upside down above the current paragraph, and ends at the right margin. [17]Ehrenfest has drawn an arrow from “Er” to “Ornstein” in the same paragraph. [18]The square brackets are in the original. [19]Herman Carel Burger (1893–1965), lecturer in physics at the University of Utrecht. [20]Hendrik Kramers.