84
DOCUMENT
48 JANUARY 1915
für
berechtigte
Transformationen nicht
gemacht
habe
(sonst
wäre mein
geliebtes
Kartenhaus
rettungslos
verloren).
Es
grüsst
Sie
herzlich Ihr
Einstein
Beste Grüsse
an
Ihre Frau
Gemahlin,
Ehrenfest
und
Kamerlingh-Onnes.[11]
ALS
(NeHR,
Archief
H. A.
Lorentz).
[16 436].
There
are perforations
for
a
loose-leaf
binder at the
left
margin
of
the document.
[1]See
Doc. 43
for
a
draft of
Lorentz’s letter.
[2]Wander de Haas
was
married to Lorentz’s
daughter
Geertruida Luberta
(1885-1973).
He collab-
orated with Einstein
on
the
experimental
confirmation
of
Ampère’s theory
of
molecular currents
(see
Doc.
39,
note
2).
[3]In
the
original
version
of
the
Einstein-De Haas
experiment,
an
iron
cylinder
hangs
inside
a coil,
through
which
an alternating
current
runs,
the magnetic field
of
which
induces
torsional oscillations
in the bar. The modification Einstein refers
to
is
perhaps
De Haas’s idea
of
winding
the coil
directly
around the
cylinder
in
order
to eliminate
disturbing
effects due to the
interaction of
the horizontal
components
of
the
magnetic
field
of
the coil and the induced
magnetization
in the
cylinder.
The
method
was
not
employed
in
Berlin,
but De
Haas used
it when
repeating
the
experiment
later in the
year
at
Teyler’s
Institute,
Haarlem
(see
Doc.
122).
[4]Here
and in
the
following paragraphs,
the
section,
page,
and
equation
numbers
refer
to Einstein
1914o
(Vol.
6,
Doc.
9).
See Doc.
43,
note
2,
for
a
discussion
of
the contents
of
§12.
[5]“Justified” transformations
are
transformations between
“adapted”
coordinate
systems
(see
Doc.
18,
note
5,
for
the definition
of
these
notions).
[6]This
is
probably
the
reasoning
behind Einstein’s claim in Docs.
5
and
14,
and, more
explicitly,
in Einstein to Michele
Besso, ca.
10
March 1914
(Vol.
5,
Doc.
514),
that the “Entwurf”
theory
holds
in
“adapted”
coordinate
systems corresponding
to frames
of
reference in
arbitrary
states
of
motion.
[7]See
the first paragraph
of
Einstein
1905r
(Vol. 2,
Doc.
23).
[8]The
following argument
also
occurs
in Einstein
1914i
(Vol. 4,
Doc.
31),
which
was published
on
1
May
1914.
[9]See
Einstein
1915a,
1915b
(Vol. 4,
Docs. 20 and
21),
the second
of
which Lorentz had criticized
in Doc. 43.
[10]Emil Warburg
(1846-1931)
was
editor
of
the
physics
volume
of
the “Kultur
der
Gegenwart”
series and
President of
the
Physikalisch-Technische
Reichsanstalt in Berlin.
[11]Heike
Kamerlingh
Onnes (1853-1926)
was
Professor of
Experimental Physics
at the Univer-
sity
of
Leyden
and
Director of
its Institute
of
Experimental Physics.
48. To
Hans Albert Einstein
[Berlin,]
25. Januar 1915.
Mein lieber Albert!
Durch Hans Wohlwend[1] und die Tante
in
Luzern[2]
höre
ich,
dass
es
Dir und
Tete
gut geht,
und
dass Ihr
am Zürichberg
eine hübsche
Wohnung
habt.[3]
Auch
weiss
ich,
dass Du
Dir
die
Lenkvorrichtung an
Deinen Schlitten
hast
machen lassen