170
DOCS. 239-241 DECEMBER
1910
molecules from
the radiation
formula.
The
thing
is
quite
simple
but,
of
course,
somewhat
problematic.
I
wish
you
a
very
pleasant
remainder of
the vacation. With
best
regards
to
you as
well
as
your
parents,[7]
I
remain
yours,
A.
Einstein
My
wife also
sends her
regards
and thanks.
Happy
New Year!
240. To
Edgar
Meyer
[Zurich,
27
December
1910]
Congratulations
on your professorship[1]
&
Happy
New
Year
and
a
pleasant
vacation.
Yours,
Einstein
241. To
Jakob
Laub
[Zurich,
28
December
1910][1]
I
still have
not
received
an
appointment
(to
Prague)
....[2]
Soon
I
will send
you a
few
shorter
papers
from
the
Annalen. The
one on
elasticity
&
specific
heat[3] is
the
most
interesting among
them. Also
interesting
is
the
following.
Six
years ago
I
deduced: If
small
spheres
are
suspended
in
a
liquid,
and
the total
volume
of the
spheres per
unit
volume
is
p,
then
7]
=
tj0(1
+
p)
if
r]
denotes the
viscosity
coeff. of
the
mixture,
and
tj
that of
the
suspension medium.[4]
Perrin
arranged
to have
experiments
done
in his
laboratory
using
mastic emulsions
with
different
particle
sizes,
but
he
found[5]
7]
=
7j0(l
+ 3.8
q)
My
first
thought
was
that
my
calculation
might
have
been
wrong,
but
even
the
most
careful
checking
of
my
calculations
(to
be
found
in the Annalen in
1906,
in
the
paper
"A
New Determination of Molecular
Dimensions")[6]
did not
reveal
any error.
But
either