272
DOCS.
368,
369
MARCH
1912
as
you
arrive.
But inform
me
immediately
of
the time
of
your
arrival.[5]
Do
you
have
lodgings?
Or
may
I find
you
some?
Unfortunately,
we are
not
yet
in
our
permanent
apartment,[6]
otherwise
I would insist
that
you stay
with
us.
With cordial
greetings,
yours
in
friendship,
Haber
369. To
Paul Ehrenfest
[Prague,
10
March
1912][1]
Dear
Mr.
Ehrenfest:
Shortly
after
your departure
I wrote to
Weiss,
asking
him to do
everything
he
deems
opportune
in
the interest of
your
Habilitation in
Zurich.[2]
I do not
think that
you
will
meet with
any
serious
difficulties there,
even
though
I know that, like
everywhere
else,
the older
gentlemen
are a
priori not
especially
fond
of habilitations.-[3]
I do not
doubt Joffe's
ability.
But do
you
take
me
for
the Grand
Mogul
of Zurich
who
pulls
all
the
strings?[4]
If
Debije leaves,[5]
his
opinion
will
be
sought
first,
and
even
his influence will be limited
because the
"natives" will not want
to
let the reins
slip
out
of their
hands.
On
top
of
that,
the
university
is
doubly
peeved at
me.[6]
I
already
knew
what
you are telling me
about the
properties
of
Röntgen
rays.
But
what
I
don't
know,
and would find
very
interesting, is
the
answer
to
the
following
question.
If
A, B,
&
C
are
three metals
in
a
series
of
decreasing proper frequencies
(atomic
weights),
then
C
cathode
rays can
be
produced
by
A
Röntgen
rays as
well
as
by
B
Röntgen
rays.
Do
the
C
cathode
rays
have
a
greater
velocity
in
the
first
case
than
in
the
second case? In
my
opinion
it should be
so.
This amounts
to
the
more
general
question,
whether the
frequency
of
the
exciting
radiation
or
that of
the excited
structure
determines the converted
hv.[7]
I
am
glad
that
you
are wrestling
with
the
fluctuations.
I
believe
you
will
totally
independently
come
to
conclusions similar to mine.
The
Biscuit led
me
to
curious
considerations. About
this in
person,
because
the
pen
demurs. I finished
the
investiga-
tions
on
the
statics
of
gravitation
(point
mechanics
electromagnetics
gravitostatics)[8]
and
am
very
satisfied with them. I
really
believe
that
I
discovered
a
piece
of truth.
Now I
ponder
the
dynamic
case,
going again
from
the
more
special
to
the
more
general.
With
kindest
regards
to
you, your
wife,
and
your
little
ones,[9]
also from
my family,
I
remain
yours,
A.
Einstein