DOCS.
281,
282
NOVEMBER-DECEMBER
1916 269
To
obtain
your
formula for
Tij,
one
must
thus
set
2£
=
M.
(8)
Then
your
formulas
agree
with those
by
Herglotz.[8]
From Hamilton’s
principle
it
can
be
deduced
that
the
first
expression
(6)
for
Tij
really
is
valid in
the
general
theory
of
relativity, by
designating
spatial
variations to the
mass-points, leaving
the
guv's
unchanged,
however.
From
ô ƒ
$
dx
dy
dz
dt
=
0,
the
differential
equation[9]
E
+
5
E
^
dg^
=
0
dxj
dx
i
is
thus
obtained,
which contains
nothing new,
of
course.-
I
hope you can
see
what
the
issue
is
from
this short
summary.
I
have
written
a
brief communication
about
it
and
am
going
to
publish
it here in
Holland.[10]
From inside
information,
I
gather
that the
following
four
persons
are being
considered
as
the
experts
solicited
for
opinions
on
the
filling
of
the
professorship
at
the
polytech[nic]:
two
Helsingfors professors
Sundell and
Melander, Bjerkén
at
the
Stockholm
Polytech.,
and Birkeland in
Norway[11]
I
hope
that
my
cousin Carl Hirn has
come
to
see you.
I
send
you
most cordial
greetings
and
hope
that
we
shall be
seeing
each
other
again
next
year. Yours,
Gunnar
Nordstrom.
282.
To Paul Ehrenfest
[Berlin,]
4
December
[1916]
Dear
Ehrenfest,
I
wrote to Knudsen
a
while
ago
and have received his consent in
reply.[1]
Un-
fortunately,
according
to Nordstrom’s
letter,
he
is apparently
not
being
asked.[2]
Should I write to
anyone
else
about the matter? Lorentz
has received
my
letter, I
hope.[3]
Has
Waldeyer
written
to
him?
He
had
definitely
promised to.[4]
I
recently
spoke
with
Miss
R.
Prisoners
are
not
permitted
to send
money
abroad
because
of
the
exchange
rate.[5]
Maybe
it
would be
best
if
you
wrote
concerning
Nordstr[om]