532

DOCS.

511,

512 APRIL

1918

an

equatorially

distributed

fluid.

But

your

calculation[5]

immediately yields

the

following

asymmetrical case,

which

I

show

with

a figure:[6]

void

fluid

of

constant

density

The

relevant

formulas

are:

mass-point

for

I:

1/h2

=

1

- A/6r2

for II:

1/h2

=

1+2M/r-2u0+A/6r2.

The

boundary

condition

M=~r~

is

exactly

the

same as

in

your case,

whereas M

is

the

mass

of

a

real

point mass.[7]

Evidently,

for

this

M,

one can

also

substitute

an

extended

homogeneous

fluid.

It thus

seems

that

no

grounds

are

provided

for

space possessing

the

connec-

tivity properties

of

elliptic

geometry.

With

cordial

regards,

I

am

yours very truly,

A.

Einstein.

I

hope you

have received

my

postcard,[8]

in which

I reported to

you

more

exactly

the

objection bothering

me

with

regard

to

your

new

theory. (Objective meaning

for

ds,

not

just

for

the ratios of different ds’s

originating

from

one

point.)

512. To

Hermann

Weyl

[Berlin,]

19 April 1918

Dear

Colleague,

Another letter from

that

Einstein! This time

I

must

give a

complete

report

on

the

submission of

your

article;[1]

for

a

difficulty

has arisen which

I

have unfor-

tunately

not been able to master

until

now.

A

week

ago

yesterday

I

presented

the

paper

at the

class

meeting.[2]

I

sketched

the

train of

thought,

first from

a purely geometrical

point

of

view,

and

then

its

application

to

the

theory

of

relativity.

At

the

end

I

also described

my

objection

to it,

which

you already

know.

(In

my view,

ds

itself

has

physical

meaning.)[3]