em 
895 
first part of which vanishes because of the undestructibleness of 
the charge Ee 
| Ov guy 
NEEN gei from (C) 
dah 
v/a) ge Ode; 
oe Voy” = 
dap day 
Here the last term is equal to 0. 
We thus substitute in (3) 
ie OV guy?! dei 
— (wg,) = ——— 
dws On? 
Then (3) becomes 
es lee and ‘ | 
Oay, (Vg Wei Whi ) = dz, (u qi) ie 
this must be equal to 
OL Wo OL Wg OL aq OL. g 
VOA LRE ker En PR Eeen EST EA Sive 
| V9 | Ox, ( Otte A Ox, ( Oa Jl : 
ÒL; Vg ae: 
Here ———- means the increase of the quantity Lig in the 
Ue. 
case of a displacement in the direction w‚. Our variation is however 
such that after it only the gs and ws have a value as before at a point 
at a distance — dz, further in the direction of «.. That is why the 
OLiVg . : 
terms occur, which represent the increase of Lig only 
ve w‚g 5 
caused by the variation of the gp, while a and q are kept constant. 
Taking into consideration (II) and (II), and equalizing the two 
last expressions, we obtain 
aL.Va 0 prs b 
KeV9 + | |) =P bi — Oe W™ Pn) 
wq 
Ox, Oa'p | 
b ; 
Hered, 1 ror 0: according vas 6 = c wr 6 ==: 
_ Thus we have as energy tensor 
Re = V9 (YW Pa — + Jc EN Pete (EE) 
Neglecting the gravitation we may use a system of coordinates 
where the g,, have their normal values and the intensities of the field 
may be determined by means of the equations : 
K, = — o(dx + vy h, — v, hy) ete. 
By means of the scheme 
