188 
Here u is the mass of the centre of gravitation C’ 
Concerning the “space-coordinates” 7 (or @), 4, p‚ it is assumed 
that @ and w have the same values as would be ascribed to them 
by an observer who made his observations and calculations in the 
conviction that space is Euclidian; for the rest neither 7 nor o need 
be exactly equal to the distance R measured from C on Euclidian 
suppositions, but 7 and FR or @ and Z are supposed to be univalent 
Ss 
3 r J 3 : : 
functions of each other, so that — and = ditfer so little from 1 that, 
R R 
r 2 0 2 
at least for not too small values of &, (5) and (2) may be 
neglected relatively to unity. 
The units of length and time are assumed such that the light 
covers the unit of length in the unit of time, so that we may for 
1 
instance consider 1 km. and ST cee those units; finally the 
vu. 
mass u is expressed in gravitation-units. If e.g. we consider the 
centre of the sun to be the centre of gravitation, we have u= 1,47, 
L 
and already immediately outside the surface of the sun Ë will be 
very small; in the field outside the sun we may therefore, asa first 
approximation, neglect the second and higher powers of © and 
2 
replace (1’) by 
wl! 2 “) aw—(1 + haere (sin? B dy? + d6*)} . (2) 
e Q 
3. In the space (2) the propagation of light occurs along a 
minimum line, i.e. along a line for which 
ds: 
or for which 
(1 — Ee) dt? a sE “) {do* + 0° (sin? 6 dp + dé’)}; 
0 e 
as the nature of the field makes it at once clear that the path will 
lie in a “plane” through C, we may here put 6 = 47, so that for 
the path of the light we have: 
UN ze u : ans 
(15e =(14") a 0" dp Nvt reste 1008) 
oO 
N 
It is assumed that even now the path between 2 points A and B 
in three dimensional space may be found by making the condition 
that the first variation of the integral: 
