SUMMARIES OF ETH
COURSES 625
of continua covered much of the
same
material
as
his
course on
advanced mechanics
three
years
earlier
(for
a
brief
description
of
this
course,
see
Vol.
3,
the editorial
note,
"Einstein's Lecture
Notes,"
pp.
3-10).
Einstein discussed the basics of
hydrodynam-
ics, including
the motion of frictionless
fluids,
Euler's
equations,
and
the
equation
of
continuity.
The
course
concluded
with
a
discussion of
wave
motion
and
of
vortex
flow.
Dällenbach's
notes
give
the
impression
that discussion of viscous
flow
was
deferred
to
the
physics
seminar
(see
below).
The
course
also
included
a
brief
expo-
sition of
the tensor
concept
and
an
explanation
of
the
notions of invariance
and
covari-
ance, topics
related
to
Einstein's
contemporary
collaboration with Marcel Grossmann
on
the
problem
of
gravitation
(see
the editorial
note,
"Einstein
on
Gravitation
and
Relativity:
The Collaboration
with
Marcel
Grossmann,"
pp.
294-301).
Dällenbach's
notes
end with
a
reference
to his
notebook
on
Einstein's
physics
seminar
(see
below).
b.
"Molekulartheorie der Wärme"
(2
hours)
Two
notebooks
are
available for
this
course:
the
first,
by
Eichelberg,
covers
the intro-
ductory part
on
the kinetic
theory
of
gases;
the
second,
by
Dällenbach,
covers
the
subsequent exposition
of statistical mechanics.
Eichelberg's
notes
cover
35
pages
of
a
notebook
(SzZE Bibliothek, Hs. 555:23),
whereas Dällenbach's
notes
comprise
102
manuscript pages
of
a
notebook entitled "Statistische Mechanik"
(SzZE Bibliothek,
Hs.
304:1224).
Einstein
closely
followed
the
notes he
had
prepared
for
a course on
this
subject
in
summer
semester 1910
(see
Vol.
3,
Doc.
4).
Dällenbach's
notes
on
statistical mechan-
ics,
however,
contain
a
number of remarkable
additions
reflecting
Einstein's interest
in
contemporary
successes
in this field. A
section
on
diatomic
molecules,
for
instance,
includes
a
reference
to
Eucken's
measurements
of
the
specific
heat
of
hydrogen
at
low
temperatures
(see
Eucken
1912,
and also
the editorial
note,
"Einstein
and
Stern
on
Zero-Point
Energy,"
pp.
xx-xx).
Another
example
is
Einstein's
discussion of the
theory
of
vapor pressure
by
his
collaborator Otto Stern
(also
discussed
in
his
Expert
Opinion
on
the Habilitation Petition of Otto
Stern, 15 July 1913
[Vol.
5,
Doc. 452]).
Dällenbach's
notes
also
provide
evidence for the
stronger emphasis
Einstein
laid
on
the
quantum theory compared
to his
earlier
course.
He
mentioned several of
his
own
contributions
to
the
quantum theory
of solids which
he
had summarized earlier
in
his
lecture
to the first
Solvay Congress
in
1911
(see
Einstein 1914a
[Vol. 3,
Doc.
26],
as
well
as
Debye's
recent
work
on
the
specific
heat of solids
[Debye 1912]).
c.
"Physikalisches
Seminar"
(2
hours)
The
part
of Dällenbach's notebook
(SzZE Bibliothek, Hs. 304:1222)
which
begins
on
manuscript page 71
and
ends
on
page
128
contains material
probably presented
in
Einstein's seminar of
summer
semester
1913, including
the
entropy
of
an
ideal
gas,
capillarity,
and
hydrodynamics,
which Einstein
may
have
presented
in
the seminar
or
in his
course
in
the
same
semester
on
the
mechanics of continua
(see
above).
The second
part
of Dällenbach's
notes
begins with
a
short section
on
the
theory
of
gases,
which
is
followed
by an
exposition
of
the basic
hypotheses
of Einstein's
deri–