584

APPENDIX

A

In the second notebook the discussion of

electrodynamics

continues

with the in-

clusion of

ponderomotive

forces and

a

derivation of

equations

of motion. As

an

il-

lustration,

the motion of

an

electron

in

a

combined electric

and

magnetic

field

is

dis-

cussed

in

connection with the

experiments

on

the

determination of

the specific

charge

of the electron

(the

results of which

are

cited

in

support

of

special relativity).

The

next

topics

are

mass-energy equivalence

and the

law

of

energy-momentum

conserva-

tion. The notebook ends with

an

application

of

the

foregoing

considerations

to

fluid

motion.

2. Winter Semester 1917/1918

“Statistische Mechanik und Quantentheorie"

(2

hours)

Einstein’s

course on

statistical mechanics and

quantum theory

was

attended

by

Wern-

er

Bloch

as

well

as

by

Walter

Zabel,

and

notes

by

both have been

preserved.

Neither

set

of

notes

covers

the

complete course,

however: both end with the lecture of

20

De-

cember

1917.

Zabel’s

notes

are

contained

in

a

notebook

[80

018]

of

90

pages (in

the

possession

of Peter

Damerow,

Berlin).

The first

part

is

carefully

worked

out;

of the

last

two

lectures

(of

13

December and 20 December

1917)

only

shorthand

notes

are

preserved.

Bloch’s

notes

are

contained in

two

notebooks

[3

023]

and

[3

024]

of 64

and

47

pages, respectively.

The first

one

contains

worked-up

notes

for all lectures

ex-

cept

the last

two;

the second notebook contains what

seem

to

be Bloch’s unedited

class

notes.

All

notes

concern

statistical

mechanics;

no

notes

on quantum

theory

have

been

preserved

in

either notebook.

Presumably

this

topic

was

covered in the lectures

that

were

given

in the

first

months of

1918.

The

course

begins

with

a

discussion of

mechanics, in

particular Lagrange’s equa-

tions and variational

principles.

The

theory

of the

gyrocompass

is

developed

as an

illustration,

a

topic

that

was

of

personal

interest

to

Einstein

in

connection with his

role

as

technical witness

in

a

patent

dispute (see

Docs.

12

and

17).

The

discussion of

statistical

mechanics which follows

begins

with the introduction of

the

concept

of

phase

space

and

probability.

A

derivation of Liouville’s theorem

precedes

the intro-

duction of the canonical ensemble. Much

care

is

given

to

establishing

that the de-

nominator in the

exponential

of

the

canonical distribution function

can

be identified

with the

temperature.

This

is

done from

a

consideration of

two

systems,

a

small

one

and

a

large one,

in thermal

equilibrium

with each

other. As

applications,

the Maxwell

velocity

distribution

is

derived and the

specific

heat

is

calculated. Another

applica-

tion is

a

gas

under the influence of

gravity.

Next the

Langevin

formula for the

mag-

netization of

a

paramagnetic gas

is derived,

followed

by a

discussion of

Weiss’s

the-

ory

of

ferromagnetism.

The

following

lectures

are

devoted

to

Brownian motion.

First,

a

gas

in

equilibrium

under

the influence of

gravity

is studied,

and from the

stationarity

of

its

density

dis-

tribution

an

expression

for the

mean

square displacement

of the Brownian motion is