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.