DOCUMENT
16 JUNE 1914
37
dr
dl1
=
V
[4]
oder,
mit
y
=
r
x
=
U
Anfangsbedingungen:
für
x
=
0
"2
+
5y2y'2y" + 4yy'4
=

Jy2x2
y
= a
(Drahtradius)
ƒ
=
b
(wegen
V0
=
const.)
y"
=
f(a,
b)
( dV
(wegen
dF0
=
K
Hierbei ist
am
Draht senkrechter Austritt
der
Teilchen
angenommen
(S
=
0).
So kann aber auch
Ç
resp.
U
=
x
beliebig
anders
vorgegeben
werden.
ALS.
[21
544].
At the foot
of
the document Einstein’s
secretary,
Ilse
Einstein,
has noted:
“Angekom
men
Mitte Februar 1919.” There
are perforations
for
a
looseleaf
binder at the left
margin
of
the
document.
Schottky’s
appended
calculations
are [21
545].
[1]Schottky
(18861976) was
Scientific
Director of
the Central
Laboratory
of
Siemens & Halske
in Berlin. He
probably
made Einstein’s
acquaintance
in the
Wednesday physics
colloquium
of
the
University
of
Berlin,
which
both
frequently
attended
(see, e.g.,
the
entry
of
20
May
1914 in Walter
Schottky Agenda
1914,
GyMDM, Schottky
Nachlaß).
Schottky
had
paid a
visit to
Einstein
(“Audienz
bei
Einstein”)
six
days
before he wrote this letter
(see
the
entry
of
19
June 1914 in Walter
Schottky
Agenda 1914,
GyMDM, Schottky Nachlaß).
It
was probably
his first
(see
the
entry
of
19 February
1915 in Walter
Schottky
Agenda 1915,
GyMDM, Schottky Nachlaß,
in which
Schottky
notes that
he
has
paid
Einstein
a
second
visit).
[2]Schottky
considers
an
axial filament
emitting
electrons
in
a
radial electric field and
an
axial
mag
netic field.
J
represents
the radial electron current
per
unit
of
length
in the axial direction.
In
a paper
received
on 10
April
(Schottky 1914),
the
author
reports
on
experiments
for
the
same
system
but without
a
magnetic
field. He found
a
Maxwellian
velocity
distribution for the emitted elec
trons.
[3]dU/dr
on
the lefthand side should be
(dU/dr)2.
As
a consequence,
the final
equation
below is
wrong.
The constant K is
equal
to
4c3J/H3r2
[4]dr/dU
should be
(dr/dU)2
and
a
factor
of
2c2/H2r
is
missing on
the
righthand
side. The
square
brack
ets
are
in the
original.