864 
If now we write 
EO 5 Was) =0, (14.3) 
this must be an identity in virtue of (14.1). 
The Muinkowskian force acting on a moving charge e has the 
covariant components: 
fa =e = oe = 1 fat 
These equations are supposed to hold within the finest structure 
of matter. 
To obtain the equations of matter in bulk, we take the mean 
over a small region, containing a great many atoms. We define 
S fas Vg det). ded pas IFS Vg ded dls) 
SWVgded..de® ”  fYgdelt).. dal)’ 
It is readily seen that still 1 SS EH) GFE GE Ng: 
The mean of the convection current gv’, as produced by the 
bound electrons, we have just found, and so the equations for non- 
conducting matter are: 
== 
0 
ag Va PO: (14.41) 
In conducting matter, the current from the conduction electrons 
Vgl* must be added in the right hand member. 
The other equations oo. 
0 
=) Veh = =O. | 
> (6) en Wa Fy) =0 (14.42) 
Now, we could try a solution #«’— 7, and add a solution 
E of the equations 
Ore “Va Fat) — 0 (14.51) 
and 
=O, CARENS = (0) "Wa T,"), (14.52) 
By’ and 7,°° being the conjugate tensors a Ee and Tet. Then 
Fab Tab 4 Fab 
is a solution of equations (14.41) and (14.42). We shall call 7% 
the internal, and Ze the external field. 
Separation of the Polarization and the Magnetization Tensor. 
15.1. It has been remarked, that in our tensor Vg 7 the 
