5 0 4 D O C U M E N T 2 1 6 D E C E M B E R 1 9 2 0
“to detect this effect have not led to a decision whether it exists or not” (p. 397).
[4]Beck 1919b, which gives a brief summary of Beck 1919a (see note 6).
[5]Arvidsson 1920, received 22 October 1919 and published 15 February 1920, reported experi-
ments to determine the value of the specific charge e/m done at the University of Uppsala, where
Arvidsson had obtained values of between 3.35 ×
and 4.16 ×
emu/g, which is about
twice the value used in Einstein and De Haas 1915a (Vol. 6, Doc. 13), and also twice the modern
Beck 1919a, received 7 May 1919, reported values of (see note 1) that are lower
by almost a factor of ½ compared to the expected value of 1.13 ×
(in electromagnetic
units) and the value reported in Einstein and De Haas 1915a (Vol. 6, Doc. 13). Beck’s paper
acknowledges a conversation with Einstein (p. 144) and also discusses the papers by Barnett
and Stewart cited below.
[7]Stewart 1918, wich presented values for that differed from the theoretical expectation (see
notes 1 and 6) by a factor of 0.51 0.04 for iron and by a factor of 0.47 0.11 for nickel.
[8]Barnett 1917, where an investigation of the inverse effect, i.e., magnetization by rotation, is
reported with values of 2 between and , i.e., 0.72 respectively 0.92 times
the expected value, whereas earlier experiments had produced values that were off by a factor of 0.5
(see the following note). The results of Barnett 1917 were later retracted because of the discovery of
a systematic error (see Barnett 1921/1922, p. 248).
[9]Barnett 1915. The investigation of the inverse effect undertaken by Samuel J. Barnett in 1915
was acknowledged by Einstein and De Haas as a complementary investigation to their own work in
Einstein and De Haas 1915d (Vol. 6, Doc. 23), although they did not comment on the fact that
Barnett’s results disagreed by a factor of ½ with their own.
[10]Tolman and Stewart 1916, in which an experiment is reported that is similar to the first Maxwell
experiment described in note 2, i.e., the experiment where the electric pulse created by a rapid accel-
eration or deceleration of a rotating circular coil is measured. These experiments gave experimental
estimates of the specific charge or, equivalently, of the inertial mass of electrons in atomic units
that are close to but somewhat larger than today’s accepted values.
[11]Tolman and Stewart 1917, in which the investigations of the previous reference were extended
to silver and aluminum with similar results.
[12]De Haas 1915. Further experiments done by De Haas in Haarlem after moving from Berlin to
the Netherlands had confirmed the earlier results, i.e. the expected value of 1.13 ×
(in elec-
tromagnetic units) to within 15%.
[13]De Haas and De Haas 1915, which gives a theoretical analysis of the gyromagnetic effect.
216. To Hans Mühsam
[Berlin], den 1. XII. 20.
Sehr geehrter Herr Doktor!
Im Auftrage von Herrn Prof. Einstein sende ich Ihnen einliegend zu gunsten ei-
nes wohltätigen jüdischen Zweckes ein von Herrn Prof. Einstein eigenhändig ge-
schriebenes kurzes
Mit vorzüglicher Hochachtung
Die Sekretärin
Ilse Einstein.
e m
1 =
5.1 10–7 6.5 10–7
e m
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