D O C U M E N T 1 4 8 J U N E 1 9 2 1 1 9 1
2. Empfehle ihn, bitte, in meinem Namen an den jungen
Bragg[13]
und—falls es
sein kann—an
Rutherford.[14]
Nämlich: Es ist für ihn—in Verband mit geplanten
(sehr witzigen) Arbeiten von ihm sehr wichtig für ihn diese beiden ruhig sprechen
zu können. N. B. mit Dolmetscher weil er zwar sehr gut deutsch aber fast gar nicht
englisch sprechen kann. Joffe hat absolut nichts nöthig außer Gedankenaustausch!
Lieber, lieber Einstein—sei lieb zu Joffe—seit 1905 will er Dich kennen lernen
immer misslang es. Du wirst sehr viel
Freude[15]
an ihm haben—sowohl an dem
Physiker als an dem Menschen. Lass mir durch Deine Frau Schreiben—zwei Wor-
te—Van
Aardenne[16]
und ich warten ungeduldig auf Nachricht wann Du durch
Holland kommst— Dein
P. Ehrenfest.
ALS. [9 559]. Written on letterhead “Laboratorium voor Natuurkunde en Electrotechniek.” Wander
de Haas’s greeting is omitted.
[1]Abram F. Ioffe. See also Doc. 71, note 1.
[2]Square brackets are in the original.
[3]Hendrik A. Lorentz; Heike Kamerlingh Onnes.
[4]Dmitry S. Rozhdestvensky.
[5]James Franck.
[6]Wilhelm C. von Röntgen (1845–1923) was Professor Emeritus of Physics at the University of
Munich. Ioffe had been his Assistent there from 1905 until 1913.
[7]For example, it was found that the conductivity of quartz increased upon irradiation with X-rays,
but that the conductivity of rock salt grew only moderately upon irradiation with X-rays when kept in
a dark environment. However, its conductivity would be considerably increased when subsequently
exposed to daylight. The behavior of quartz after long periods of irradiation further suggested that
conduction was due to impurities in the crystal (Röntgen 1913 and 1921; Ioffe 1923 [for the publica-
tion history of this work, see its p. 461]).
[8]Square brackets are in the original.
[9]In 1919, Ioffe, together with Melitina V. Kirpicheva, had found that, when compressed, a crystal
of NaCl breaks up into crystals of smaller size and same structure that slide along the plane of the
rhombic dodecahedron and rotate at the same time through different angles. They had further devel-
oped a method to determine the constants of elasticity, in the case of elastic strains, for one small sam-
ple of a crystal (see Ioffe and Kirpicheva 1922).
[10]A reference to work done on the Einstein-De Haas effect in collaboration with Pëtr L. Kapitsa
(see Paul Ehrenfest to Einstein, 2 September 1920 [Vol. 10, Doc. 127], note 10). For the Einstein-
De Haas effect, see Einstein and De Haas 1915a, 1915c (Vol. 6, Docs. 13, 14), and Docs. 57, 146.
[11]At the top of the page, Ehrenfest appended the following note: “Prof. Joffe bei Mr. D. Filitz
London W.C. 1. 133 High Holborn Museum Station. || Telegr. Adresse: Abahafil-Westcent London
[Telef. 67-29 Centrum].” Square brackets are in the original.
[12]Here Ehrenfest indicates a note that he appended at the top of the paragraph, with an arrow
pointing to it: “Adresse auf Briefchen an Deine Frau.”
[13]William L. Bragg (1890–1971) was Professor of Physics at the University of Manchester.
Ehrenfest also recommended Ioffe by letter to Bragg (see Paul Ehrenfest to Abram F. Ioffe, 14 June
1921 [Ehrenfest and Ioffe 1990, p. 147]).
[14]Ernest Rutherford (1871–1937) was Cavendish Professor of Physics at the University of Cam-
bridge.
[15]At this point Ehrenfest indicates a note that he appended at the left margin: “Dir gefielen alle
die ich Dir empfohlen habe!”
[16]Gijsbert van Aardenne.