1109 
Now if ds? has the form 
d. 2 B 2 3 B #2 8 2 irre 3 2 
o> Erik, — |dt?—dl* =| 1— — | dl — | 14 — ]dr*—9’ sin? Odp*—r* dh, (2) 
r r 
than (1) can be replaced by 
BAC Ole 
mof DDO 0 
ORO IE 
In this equation the second term and the two last terms only 
then can be neglected with respect to the other terms, when id 
~ 
9 
diN® a 
and consequently (5) is of order —. Then the equation changes 
Pe 
fen EN en a A80 Dn, O68 
But this is the equation of classical mechanics in a threedimensional 
into 
space with the linear element d/ and a potential function U = 5 . (4) is 
ae 
equivalent to 
0U da” Av | de) dev 
ed : 
Oana | uw | de dt 
dl\? a 
If = and consequently 1 is of order —, which in particular 
r ip 
holds for the linear element of ScawarzscHiLD, for which B—a, the 
reduction to a threedimensional problem is not possible, at least 
not in this way *). 
Now we will demonstrate, that in the threedimensional problem 
1) Hence the equations derived Proc. Kon. Akad. XXI 1918, 1176—1183 on 
p. 1178—1180 hold only for velocities of order bef 
r 
