22

DOC.

31

JULY

1905

31.

Expert Opinion

by

Alfred

Kleiner and Heinrich

Burkhardt

on

Einstein's

Dissertation[1]

[Zurich,

22-23

July

1905][2]

Institute of

Physics

University

of Zurich

Rämistr.

69

Prof. Dr. A.

Kleiner

Expert Opinion

on

Mr.

Einstein's

application

for the

conferment of

a

doctoral

degree.

Mr.

Einstein, who has

become

well known

on

account of

several

noteworthy papers

in the

area

of mathematical

physics (spec.,

molecular

theoret.),[3]

has

submitted

a

dissertation under the

title

"A New

Determination of

Molecular Dimensions."[4]

He

seeks

to

solve

the

problem,

which he

selected

and

posed

to

himself,

by calculating

observable

physical

constants

from the

immediate

properties

of

molecules,

their

dimensions,

and their numbers

per

unit

volume.

Among

the

physical

constants

of

this

kind,

he finds

the

viscosity

of

undissociated solutions and

the

diffusion coefficients to be

suitable

for

his

purpose,

since

these

two

depend

in

a

different

way on

the

dimensions

and the

number of the

dissolved

molecules,

so

that

it becomes

possible

to

determine

both

of

these

two

quantities separately

on

the

basis

of observational data.

The main

problem

that had

to

be solved

was

the

mathematical determination of

the

difference

between

the

viscosity

of

a

solution

and

that of

the

solvent; to

make

the

calculation

possible,

it

is

necessary

to

make

a

few artificial

assumptions

(spherical shape

of

the

molecule)

that

may

seem

admissible,

since it

is

only

the order of

magnitude

of

the

dimensions

sought

that

can possibly

be

determined. The

arguments

and

calculations

to

be carried

out

are

among

the

more

difficult

ones

in

hydrodynamics,

and

only

a

person

possessing perspicacity

and

training

in the

handling

of

mathematical and

physical

problems

could

dare

to

tackle them, and it

seems

to

me

that

Mr.

Einstein

has

proved

that

he

is

capable

of

working successfully on

scientific

problems;

I

would

therefore

recommend that the dissertation

be

accepted.

Since

the

main

achievement of

Einstein's

thesis consists

in

the

handling

of

differential

equations,

and

hence

is

mathematical

in

character

and

belongs

in

the domain

of

analytical

mechanics,

I would like to ask the

dean

also

to

approach

my colleague,

Professor

Burkhardt,

for

an

expert

opinion.

A.

Kleiner

At

the

request

of

my

colleague,

Professor

Kleiner, I

reviewed

the

dissertation

of

Mr.

Einstein,

and checked the

most

important part

of

his

calculations,

that

is,

all

of

the

places

indicated

by

Professor

Kleiner.

What

I

checked,

I found

to

be correct

without