348
PONDEROMOTIVE FORCES
[10]
where
we
have
put1
fIz
=
(13)
_
1(C2 +
&)
+
£ ®
+
15
®,
I
= S
V
+ j3
®
»
y X
y
Jx
y9
X
=
5
®
®
,
6X
=
•
Corresponding equations
hold for the other
two
components
of
the
ponderomotive
force.
By
integrating
(12)
over
the infinite
space,
one
obtains the
equation
[12]
(14)
Vr
=
1
IF
d&x
dr
TT
if the
field
vectors
vanish
at
infinity.
This equations states
that
on
introduction
of
the
electromagnetic
momentum
our
ponderomotive
forces
satisfy
the
law
of equality of
action
and
reaction.
Bern,
7
May
1908.
(Received
on
13
May
1908)
[11]
1Geheimrat
Wien kindly drew
our
attention
to
the fact that
H. A.
Lorentz
had
already presented
the
ponderomotive
forces for
nonmagnetizable
bodies in this
form.
Enzyklopädie
der
mathematischen
Wissenschaften 5, p.247.