V O L U M E 8 , D O C U M E N T 2 6 2 b 5 3
return address “Afzender. A. Einstein adres. b. Prof. Ehrenfest. Leiden.,” and postmarked “’s Graven-
hage Station H.IJ.S. 5.X.16. 2–3N[amiddag].”
Hendrik A. Lorentz.
Einstein had sent a card to the De Haases, announcing his arrival in Haarlem two days earlier
(see Einstein to Wander and Geertruida de Haas, 3 October 1916 [Vol. 8, Doc. 262]). Einstein had
collaborated with Lorentz’s son-in-law Wander de Haas in Berlin in spring 1915 and had developed
a friendship with the couple (see Einstein to Paul Ehrenfest, beginning of December 1914 [Vol. 8,
De Haas had recently been appointed conservator of the laboratory of the Teyler Foundation in
Haarlem (see Hendrik A. Lorentz to Einstein, 6 June 1916 [Vol. 8, Doc. 225]).
Einstein was possibly attending a meeting of the Central Organization for a Durable Peace,
which was headquartered in The Hague. He had been elected to its Great Council in fall 1915 (see
Einstein to Michele Besso, 30 November 1915 [Vol. 8, Doc. 155]). See also Vol. 8, Doc. 159a, note 2,
in the present volume.
See Kox 1992 for more on the reception of general relativity in the Netherlands.
To pay a visit to Paul Ehrenfest’s colleagues to discuss relativity (see the following document).
Ilse and Margot Einstein and Rudolf and Fanny Einstein.
Vol. 8, 262b. To Elsa Einstein
[Leyden,] Samstag. [7 October 1916]
In Eile diesen Gruss. Es kommen heute Abend die Groninger
zu uns, um über Relativität zu reden. Ich brauche also nicht nach Groningen zu fah-
Fett kann ich nicht besorgen. Ich habe mich an offizieller Stelle erkundigt.
Ihr müsst mich also Donnerstag fettlos aber doch freundlich
hier waren unvergesslich interessant und auch recht angenehm zu erleben. Meine
Theorie hat hier so recht ihre Heimat
Die persönliche Kultur der hie-
sigen Menschen . . . . . .
Aber ich freue mich deshalb nicht minder auf Dich und
unser ruhiges Leben. Gruss & Kuss von Deinem
AKS. [143 037]. The postcard is addressed “Frau Elsa Einstein Haberlandstr. 5 Berlin W.,” with re-
turn address “Afzender. A. Einstein adres. b. Prof. Ehrenfest Leiden.,” and postmarked “Leiden
One of the colleagues was presumably Jacobus Cornelius Kapteyn (1851–1922), Professor of
Astronomy and Theoretical Mechanics at the University of Groningen. Einstein cites an oral opinion
by Kapteyn at a commission meeting of the Prussian Academy in late October (see Einstein to Willem
de Sitter, before March 1917 [Vol. 8, Doc. 311], note 4). Another one might have been Frits Zernike
(1888–1966), Lecturer in Mathematical Physics and Kapteyn’s former assistant.
Einstein had expressed his intention of visiting Groningen two days earlier (see the preceding
Einstein had not yet looked into the question of obtaining cooking fat a week earlier (see Vol. 8,
Doc. 261c, in the present volume). Rationing of fat had been introduced in Germany in July 1916, and
by October an adult resident of Berlin could obtain only 72 grams of cooking fat per week, compared
with 84 grams in July 1916 and 60 grams at the end of the war (see Skalweit 1927, pp. 215–216).
See the preceding document for a similar statement.
Einstein had expressed similar favorable sentiments about the Dutch (as opposed to the Ger-
mans) ten days earlier (see Vol. 8, Doc. 261b, in the present volume).