EINSTEIN

IN

COLLABORATION

WITH GROSSMANN

301

satisfaction derived

from his

conviction that

the

transformations allowed

by

the

theory

include

numerous

kinds of transformations

to

accelerated frames of

reference, in

par-

ticular

to

rotating

frames,

so

that the

equivalence principle

seemed

to be

surprisingly

well

realized

by

the

"Entwurf"

theory

after

all.[37]

The collaboration with Grossmann ended when Einstein

departed

for Berlin

in the

spring

of

1914

and Einstein and Grossmann 1914b

appeared

only

after

he had

already

taken

up

his

new

position

at the

Prussian

Academy

of Sciences. Einstein's

hopes

that

the

riddle of

gravitation

had

found

a

satisfactory

solution turned

out to be

frail,

and

the eventual

discovery

that

the

"Entwurf"

field

equations actually

do not

hold

in

a

uniformly rotating system

did much

to

shatter

his

confidence

in the

theory.[38]

Nev-

ertheless,

in

more

than

one respect

the

collaboration

with

Grossmann

had

prepared

the

ground

for

the

general theory

of

relativity.

[37]See

Einstein and Grossmann

1914b,

p.

216;

Einstein

to

Michele

Besso,

ca.

10

March

1914 (Vol.

5,

Doc.

514);

and Einstein

to

Paul

Ehrenfest,

before

10

March

1914

(Vol.

5, Doc.

512).

[38]See

Einstein

to

Arnold

Sommerfeld, 28

November

1915; see

also Einstein

and

Besso's

manuscript

on

the motion of the

perihelion

of

Mercury (Doc. 14),

note 185.

For historical

discussions of

the

further

developments,

see

Stachel

1989 and

Norton

1984.