D O C U M E N T 1 1 5 S E P T E M B E R 1 9 2 3 183 Einladung erhalten. Indess m[u]ss ich eins bemerken. Genau genommen kann man nicht sagen, dass, wie Sommerfeld meint, Deutsche ausgeschlossen seien. In den Satzungen ist mit keinem Worte die Rede davon.[12] Ich könnte sagen, die Tür ist nicht geschlossen, sondern steht angelehnt und in Zukunft hoffen wir sie zu öffnen. In den nächsten Jahren wird das aber nicht gehen das wird auch Sommerfeld ver- stehen. Wir dürfen nicht vergessen, dass es sich hier um ein Institut handelt, das ge- rade in Belgien seinen Sitz hat, um die Schöpfung eines Mannes, der schwer unter den Ereignissen der Kriegsjahre gelitten hat.[13] Mit herzlichen Grüssen, auch von meiner Frau, treulich Ihr H. A. Lorentz ALS (NL-LeRM). Kox 2008, pp. 558–559. [16 556]. There are perforations for a loose-leaf binder at the left margin of the document. [1]Lorentz had turned seventy on 18 July. Herman Haga (1852–1936) was Professor Emeritus of Physics at the University of Groningen Pieter Zeeman (1865–1943) was Professor of Physics at the University of Amsterdam Paul Ehrenfest Willem de Sitter. [2]The daughters, Geertruida de Haas-Lorentz (1885–1973) and Johanna Leemhorst-Lorentz (1889–1980) the sons-in-law, Wander J. de Haas (1878–1960), Professor of Physics at the University of Groningen, and Hendrik Carel (Henri) Leemhorst (1884–1974), the son Rudolf Lorentz (1895– 1977) and the future daughter-in-law, Maria van Vollenhoven (1900–?). At the time, Lorentz actually had eight grandchildren: Albert (1911–1967), Aletta (1913–?), Johanna (1916–?), and Hendrik (1919–?) de Haas and Johann (1913–2000), Hendrik (1915–?), Johanna (1917–?), and Jan (1921–?) Leemhorst. [3]Lorentz’s Monday morning lectures on recent developments in physics, which he had been delivering since his move to Haarlem in 1912. [4]Doc. 78. [5]Lorentz and Einstein first met in February 1911, when Einstein visited Leyden to give a lecture (see Vol. 5, Calendar/Chronology). Einstein 1911h (Vol. 3, Doc. 23), which further elaborated on gravitational time dilation after Einstein’s original formulation of the equivalence principle in Einstein 1907j (Vol. 2, Doc. 47), was submitted on 21 June 1911. [6]Aletta Lorentz-Kaiser (1858–1931). [7]The second session of the International Committee on Intellectual Cooperation had taken place from 26 July to 2 August 1923. [8]Marie Curie-Sk¤odowska (1867–1934) was Professor of Physics at the Sorbonne. [9]George E. Hale (1868–1938) was honorary director of Mount Wilson Observatory. [10]Paul H. Périgord (1882–1959) was Professor of European History at the California Institute of Technology, Pasadena. Lorentz had spent the first months of 1922 at the California Institute of Tech- nology (see Paul Ehrenfest to Einstein, 4 February 1922 [Vol. 13, Doc. 45]). [11]Doc. 102. The fourth Solvay Congress was to be held in Brussels in April 1924. [12]Arnold Sommerfeld. According to article 9 of the Institute’s statutes, new members were to be appointed by the administrative committee on the basis of recommendations made by the scientific committee (see Solvay 1923, p. 5). [13]Ernest Solvay (1838–1922) was the co-founding gérant of Solvay & Cie. and founder of the Solvay Congresses. The German invasion and occupation of Belgium led to serious hardships for the Solvay chemical company. Solvay himself was involved in the establishment of a relief organization for the Belgian population (see Bertrams et al. 2013, pp. 151–158).