FLUXES OF ENERGY IN THE ELECTROMAGNETIC FIELD. 
441 
There is also waste of energy (in conductors, namely) at the rates 
Q 1 = EC, Q 3 = HK,.(83) 
where the fluxes C and K are also linear functions of E and H respectively ; thus 
C = A-E, K = r/H,.(84) 
where, when the force is parallel to the flux, and l is scalar, it is the electric conduc¬ 
tivity. Its magnetic analogue is g, the magnetic conductivity. That is, a magnetic 
conductor is a (fictitious) body which cannot support magnetic force without con¬ 
tinuously dissipating energy. 
Electrification is the divergence of the displacement, and its analogue, magnetifica- 
tion, is the divergence of the induction ; thus 
p = div D, <j = div B.(85) 
are their volume densities. The quantity cr is probably quite fictitious, like K. 
According to Maxwell’s doctrine, the true electric current is always circuital, and 
is the sum of the conduction current and the current of displacement, which is the 
time rate of increase of the displacement. But, to preserve circuitality, we must add 
the convection current when electrification is moving, so that the true current 
becomes 
J — C T I) -)- q/>,. (86) 
where q is the velocity of the electrification p. Similarly 
G = K + B + q*.(87) 
should be the corresponding magnetic current. 
§ 15. Maxwell’s equation of electric current in terms of magnetic force in a 
medium at rest, say, 
curl H[ = C + D, 
where H 1 is the force of the field, should be made, using H instead, 
curl (H — h 0 ) = C + D + q />, 
and here h 0 will be the force of intrinsic magnetisation, such that gh 0 is the intensity 
of intrinsic magnetisation. But I have shown that when there is motion, another 
impressed term is required, viz., the motional magnetic force 
MDCCCXCII.—A. 
h = VDq, 
3 L 
(88) 
