762 
OY ad 
Olson = — Sad JX, 
Ow, 
From (36), (14) and (37) we can infer what values must then be 
given to the quantities gq. We must put g-=0O and for a=-c’) 
Ja = Wa dee. 
For OL we must substitute the expression (cf. $ 6) 
dL Ge) | he 
ae Ed 
where the index w attached to the seeond derivative indicates that only 
the variability of the coefficients (depending on g,,) in the quadratic 
function L must be taken into consideration. The equation for the 
component A, which we finally find from (43) may be written in 
the forin 
jk OL SRT Fb 
ke = = = (B) git Se 
O2r¢ wb El 
where 
Relik SB) Wes Wien Oe 
and for bi=—c 
True (a) Was Weke tisk: Jat | 
Equations (44) correspond exactly to (24). The quantities 7’ have 
the same meaning as in these latter formulae and the influence of 
‘OL 
gravitation is determined by É - in the same way as it was 
: Oz 2 
DL 
formerly by ( ) : 
; ; Oar w 
We may remark here that the sum in (45) consists of three and 
that in (46) (on account of (39)) of two terms. 
Referring to (35), we find fi. from (45) 
Tiss = 5 CU st: Wss = WW, aa Wd; Per Wa Woo F W2W 9), 
while (46) gives. 
Ls = Ws W235 — Wiron 
The differential equations of the gravitation field. 
§ 13. The equations which, for a given material or electromagnetic 
system, determine the gravitation field caused by it can also be 
derived from a variation principle. Einstein has prepared the way 
') To understand this we must attend to equations (25 
