EINSTEIN'S

LECTURE NOTES

7

cut

choice between

1910

and

1912 cannot be

made

on

the basis of the available

material,

the notebook

is assigned

the earlier

date,

that

is,

the

summer

semester

of

1910.[24]

It

seems

that

Einstein found lectures

on

the

theory

of

heat to be

the

most

interesting

ones

to

prepare. A

course on

the molecular

theory

of heat

given

in 1908

was

his first

course

and

was

subsequently repeated

three

times.

His interest

in

kinetic

theory

and

statistical

physics

reveals

itself also

in the

character

of his

notes,

which

clearly

show

the

course

to be

the

most

original

of

his

lecture

courses.

The material

presented

in

the

notebook

can

be divided into

two

parts.

The

first

part

gives a simplified

but

compre-

hensive

account

of

the

kinetic

theory

of

gases.[25]

Einstein

here

follows

Boltzmann's

Vorlesungen

über Gastheorie

(Boltzmann 1896, 1898),

which

at

the time

was a

standard

reference

on

this

topic

and which Einstein had studied

during

his

student

years.[26]

He

also includes detailed discussions of

contemporary

and

ongoing research,

such

as

the

investigations by

Knudsen mentioned above. Einstein then

leaves

the

general

theme

of the kinetic

theory

of

gases

and

starts

an

altogether

new

section

under the

title

"Molecular Processes and

Probability" ("Molekulare Vorgänge

und Wahrscheinlich-

keit").

Similar

to

the

approach adopted

in

the mechanics

notebooks,

this section

starts

with

an

elaborate and careful discussion of

the

fundamental

concepts-in this

case,

of

the

concept

of

probability

and the

principles

of statistical mechanics. Einstein's

treat-

ment

is

based

on

his

early

work

on

statistical

physics,

but

also

clearly

shows

that

by

this time he had read Gibbs's book

on

statistical mechanics.

After

having

laid

the

foundations, he turns to

applications

and

more specific

issues

such

as

the

problem

of

specific

heats,

Brownian

motion,

and also

to

Langevin's

and

Weiss's

theories of

paramagnetism

and

ferromagnetism.

After

his

move

to

Berlin

in 1914

Einstein continued

to

give

lectures

on

statistical

mechanics.[27]

Student

notes

of

courses given

in

1917-1918 and

1918,

respectively,[28]

show

that

Einstein used

his notes

on

kinetic

theory

of heat for these lectures

as

well.

[24]This

particular course

was

taken

by

fourteen students and

eight

auditors

(Kontrollbücher

über die

Honorargebühren, S.S.

1910,

SzZU, Kassa-Archiv).

[25]A

similar, though less

technical

exposition

of much of the material

in

the

first

part

of the

notebook is

given

in

Einstein

1915a.

For Einstein's

general views

on

kinetic

theory, see

also

his

obituaries of Smoluchowski

(Einstein 1917)

and

Warburg

(Einstein 1922).

[26]See,

e.g.,

Einstein

to

Mileva

Maric, 13 September

1900

(Vol.

1,

Doc.

75),

for Einstein's

earlier

use

of Boltzmann's lectures and

his

enthusiasm about them. Both volumes

are

in

Einstein's

personal library.

Evidence for Einstein's

use

of Boltzmann

in

preparing

his

lectures

is

found

in

two

letters

to

Conrad Habicht

in

which

he

asks Habicht

to

bring

him "the Boltzmann"

because

he

needs it

for

his

lectures

(Einstein

to

Conrad

Habicht,

14

December

1909

and

4

March

1910).

He

is

also

likely

to

have consulted such textbooks

as Meyer, O.

E.

1899, a

copy

of which he had ordered

in 1908

(see

Einstein

to

Mileva

Einstein-Maric, 17 April

1908),

Kirchhoff 1894,

and

Clausius

1879-1891. For

a

further discussion of Einstein's

acquaintance

with relevant

sources,

see

Vol.

2,

the editorial

note,

"Einstein

on

the Foundations of Statistical

Physics," pp.

41-55.

[27]See Appendix B,

"Einstein's Academic

Courses," pp.

598-600.

[28]Notes

by

Walter Zabel and Werner

Bloch

of the

1917/18 course

have been

preserved,

as

have

notes by

Hans Reichenbach of

the 1918

course.