164
DOC.
4
THEORY
OF STATIC GRAVITATIONAL
FIELD
[29]See
Abraham
1912a,
p.
4.
This remark alludes
to
a
problem
mentioned
by
Abraham
on
p.
3,
which
was
first
pointed
out in
Maxwell
1865
(pp.
492-493):
In
a
field
theory
of
gravitation
the
field
energy
will
turn out to
be
negative
if
one
imposes
the condition that the
energy
is
zero
for
vanishing gravitational
force. For
a
contemporary
discussion of this
problem, see
Zenneck
1903,
§34.
[30]See
Planck
1906a,
1907.
[31]Hamilton's
principle
is
the
starting point
for the
gravitational theory presented
in
Einstein
and Grossmann
1913
(Doc. 13).
For further
discussion,
see
the editorial
note,
"Einstein's
Research Notes
on a
Generalized
Theory
of
Relativity,"
pp.
193-194.