163 
for this in his last paper by introducing a quantity which he calls 
H and which is a funetion of the quantities y,, and their derivatives, 
without further containing anything that is connected with the 
material or the electromagnetic system. All we have to do now is 
to add to the left hand side of equation (12) a term depending on 
that quantity M. We shall write for it the variation of 
se Gea 
QS, 
x 
where x is a universal constant, while Q is what EINsTeiN calls 
that 
a l 7 . 
sf LdS + - sf Qds +{ = (a) Regis sd Ol, Ce Se 
2 
not only for the variations considered above but also for variations 
of the gravitation field defined by dus, if these too vanish at the 
limits of the field of integration. 
To obtain now 
1 
JL-+ — dQ + (a) Koda 
x 
we have to add to the right hand side of (17) or (40), first the change 
of L caused by the variation of the quantities y, viz. 
de DE 
(ab) : SJabs 
Jab 
Ae Lazen 
and secondly the change of Q multiplied by — This latter change is 
4 
_—= 9Q dQ 
(ab) — doa + 3B (abe) — dg ate: 
dab 00a be 
ë 5 8 ‘ Odab 
where goe has been written for the derivative ——. 
Jab, ee 
As 
Òdgar 
Ogabe = vl 
we may replace the last term by 
pb. 00 df "DQ 
(abe) Ox dg : ‘ Sad — 2 (ab ¢) 3 da ; daan. 
$ 14. As we have to proceed now in the same way in the case 
1) I have not yet made out which sign must be taken to get a perfect conform: 
ity to EiNsreiN’s formulae. 
