240 RELATIVITY, THE GENERAL THEORYthe ETH shows that he had acted as Korreferent* for four theses, all in experi-
mental physics, but had not taken on PhD students in theoretical physics.
Encouraged by Einstein's response, Planck, Nernst, Rubens, and Warburg
joined in signing a formal laudatio, the statement supporting a proposal for mem-
bership, which was presented to the academy on June 12, 1913 [Kl]. On July 3,
the physics-mathematics section voted on the proposal. The result was twenty-
one for, one against [K2]. A number of arrangements remained to be worked out,
but already in July 1913 Einstein wrote to a friend that he was going to be in
Berlin by the spring of 1914 [E2]. In August he wrote to Lorentz, 'My cordial
thanks for your friendly congratulations concerning the new position. I could not
resist the temptation to accept a position which frees me of all obligations so that
I can devote myself freely to thinking' (Griibelei) [E3]. To similar good wishes by
Ehrenfest, he replied that he 'accepted this odd sinecure because it got on my
nerves to give courses, whereas there [in Berlin] I do not have to lecture' [E4]. To
Zangger he mentioned that contact with the colleagues in Berlin might be stim-
ulating. 'In particular, the astronomers are important to me (at this time)' [E5].
This was in obvious reference to his current interest in the red shift and the bend-
ing of light.
In a letter [K3] sent to the academy on December 7, 1913, Einstein formally
accepted membership and declared that he wished to begin his new position in
April 1914. On February 9, 1914, he gave a farewell talk before the Physical
Society of Zurich, in which he noted that 'we have progressed as little in the theory
of gravitation as the physicists of the eighteenth century when they knew only
Coulomb's law' [E6]. He mentioned the Nordstrom and the Einstein-Grossmann
theories, remarked that the former is simpler and more plausible but does not shed
any light on the relativity of nonuniform motion, and expressed the hope that the
bending of light (present in the Einstein-Grossmann theory, absent in the Nord-
strom theory) would soon lead to an experimental choice between these two
possibilities.
The Einsteins left Zurich in late March 1914. Einstein went for a brief visit to
Leiden and from there to Berlin, which was to be his home until December 1932.
His wife and children went for a few weeks to Locarno [E7] and then joined him
in Berlin, but not for long. Soon after Mileva's arrival, the Einsteins separated.
I do not know what precipitated this course of events at that particular moment.
But the marriage had been an unhappy one. Einstein never put all the blame for
that on Mileva. With inner resistance, he had entered an undertaking which even-
tually went beyond his strength [E7a]. Now Mileva and the boys were to return
to Zurich. Einstein saw them off at the station. 'Weinend ist er vom Bahnhof
zuriickgegangen'.** His love for his boys endured. For many years he would reg-
*The acceptance of an ETH thesis required formal approval by both a principal examiner (Refer-
ent) and a coexaminer (Korreferent). Einstein acted in the latter capacity for the theses of Karl
Renger, Hans Renker, Elsa Frenkel, and August Piccard.
**'He wept as he returned from the railway station.' (H. Dukas, private communication).