208
DOC. 288 SEPTEMBER
1911
288. To Willem
Julius
Prague,
22
September 1911
Highly
esteemed
Colleague:
The renewed
inquiry
regarding
the
chair
in
Utrecht
surprised[1]
and
pleased
me so
much
that
I
am
now
thinking
quite seriously
of
accepting an
offer from
your
university,
if it
came
to
that. For
you
can
hardly imagine
how
enchanted
I
was by
the
circle
of
people
whose
acquaintance
I
had the
pleasure
of
making
last
year
in
Leiden[2]
even
without
including your
incomparable
H. A.
Lorentz.
For
that
reason
I
must ask
you
for
some
additional information.
Since I
am
not well-
to-do,
I
must
ask
you
whether
you
have
some
kind
of
old-age
and widow
pensions, and,
further,
whether the
moving expenses
are
reimbursed. When
is
the
job
to
be
started?
I
would
prefer
it if this would not be
during
this
semester,[3]
so
that
I would not have
to
behave
much
too
ungraciously
vis-ä-vis
the
authorities and
my colleagues
here,
and
so
that
the
students
would not be
hurt
by
the
change.
There
is
one
more
thing
I
must
tell
you.
Before
I
left
my
hometown of
Zurich
for
Prague,
I
promised
in
private
in
Zurich that
I would advise
them before
accepting
another
offer
from somewhere
else,[4]
so
that
the
administration of the
Polytechnikum
can
also
make
me an
offer if
they
find it fit to do
so.-
And
now
to
our sun.
I have
read
your
papers[5]
for the
most part,
and I like
them
very
much.
I
like
your
theory
of
sunspots[6]
very
much,
and not
less
so
the
beautiful
experiments
you
have
done
in
connection
with
it.[7]
I
am
not
conversant
enough
with
the
details
of the
phenomenon to
be able to
judge
whether the
dependence
of
the
phenomenon
on
the
visual
angle[8]
fits
your
theory.
Also,
the
introduction of
dispersion
as a cause
of
apparent absorption
and
apparent displacement
toward
the
red[9]
is
so
natural that
one
must
wonder
why none
of the
sun
folks hit
upon
this
idea before. Of
course,
one
does
not
hit
so
easily
upon
the idea that the
irregular
local
density
fluctuations
can cause
a
regular displacement
of
the
lines.[10]
As
far
as
my
theory is
concerned, it
leads
to
a
constant
displacement
of about
0.01
Angstrom,[11]
independently
of the
position on
the sun's
surface.
By
no
means can one
say
that it
could
explain
the
entire
phenomenon;
all
one can
say
is
that
my
theory
may
not be
compatible
with
the
already
existing
observations.
What
is
especially
apt
to
arouse
suspicion
is
that the
measurements
by
Hale
and
Adams[12]
that
you
have
mentioned
have
shown that,
on
the
average,
the
lines
of the
chromosphere
must
display
such
a
small
displacement (0.002
A!) as
compared
with
the terrestrial lines-a
thing
that
casts
doubt
on
my conception.
If these
lines
are
very fine,
then
I believe
that
my
theory is
refuted
by
these
observations.
I would be
very
pleased
if
you
told
me
candidly
your opinion
about
this
matter.
After
all,
I know
very
well
that
my
theory
rests
on a shaky
foundation.
What
attracts
me
to
it
is
the fact
that
it leads to
consequences
that
seem
to be accessible
to
experiment
(mainly
the refraction of
light rays
by
the
gravitational
field),
and
that
it