D O C U M E N T 3 1 J A N U A R Y 1 9 2 1 5 7
Arthur Ehrenfest (b.1862). The other brothers were Emil (b. 1865), Hugo (b. 1870), and Otto (b.
Docs. 16 and 24.
For Einstein’s contribution to the Zeeman Fund, see Doc. 24.
In Doc. 24, Einstein had proposed to incorporate his written remarks into Wander de Haas’s lec-
ture to the Solvay Congress.
See Doc. 24 for Einstein’s remarks on the Hall effect.
In Doc. 24, Einstein briefly described his intention to detect a Stark effect induced in atoms by
the electric field of thermal radiation.
Gijsbert van Aardenne (1888–1983), a student who rented a room in Ehrenfest’s home.
Ehrenfest did not have Dutch citizenship yet. See his letter to Abram F. Ioffe, 28 March 1921
(Ehrenfest and Ioffe 1990, p. 144), and Klein, M. 1970a, p. 298.
Hugo Ehrenfest (1870–1942).
Ehrenfest’s older daughter, Tatiana.
Abram F. Ioffe (1880–1960).
Dmitry S. Rozhdestvensky.
See Doc. 21.
Aleksei N. Krylov (1863–1945); Melitina V. Kirpicheva (1887–1923); Anna B. Feringer; Petr
L. Kapitsa (1894–1984).
Square brackets are in the original.
In late December 1920, Hendrik A. Lorentz informed Ehrenfest that he had requested entry
visas into Holland for the five Russians from the Inspector of the Marechaussee in the Hague (see H.
A. Lorentz to Paul Ehrenfest, 29 December 1920 [NeLR]).
The sentence is placed in a box. For such a letter of support by Einstein to the Berlin Police
Headquarters, see 25 January 1921 in Calendar.
At this point in the original text, Ehrenfest indicates a note that he has appended at the top of
the page with an arrow pointing toward it: “ist aber als Lector excellent.— Nur im Einzelgespräch ist
er sprunghaft und unklar weil er es geschmacklos findet alles nöthige aufzuzählen.”
Harm (1893–1985), Menso Kamerlingh Onnes’s daughter Jenneke (1894–?), and Elisabeth
Maria (1897–?) Kamerlingh Onnes.
Niels Bohr had fallen ill (see Ehrenfest to Abram F. Ioffe, 28 March 1921 [Ehrenfest and Ioffe
1990, p. 145], and Bohr 1923, p. 228. For Lorentz’s request, see H. A. Lorentz to Paul Ehrenfest, 17
December 1920 [NeLR]).
31. From George B. Jeffery
365, Pinner Road, Harrow. Middlesex. 23:1:21
Dear Prof. Einstein,
I was very glad to have your very friendly letter and to receive the copy of Das
Relativitätsprinzip which you so kindly sent
I join with you most heartily in
the hope of the resumption of friendly relations between the scientific workers in
our respective countries. During the war I was in prison as a pacifist and “consci-
entious” objector to military service and it is a great encouragment to find that there
were those in Germany who also stood for peace and
I am glad to say
that in England the war-feeling is rapidly and unmistakably dying out. It is impos-
sible for any length of time to spend half ones lectures in expounding the work of