De. 
Instead of introducing two pairs of vectors (6, )) and (>', 5), 
both of which come into play in the electromagnetic actions, as 
well as in the phenomenon of gravitation, we might have assumed 
one pair for the electromagnetic field and one for universal attraction. 
For these latter vectors, say >, 9, we should then have established 
the equations (I), v being the density of ponderable matter, and 
for the force acting on unit mass, we should have put 
(570 ) 
—nf4nV2>+4[0. $]}, 
where 7 is a certain positive coefficient. 
§ 8. Every theory of gravitation has to deal with the problem 
of the influence, exerted on this force by the motion of the heavenly 
bodies. The solution is easily deduced from our equations; it takes 
the same form as the corresponding solution for the electromagnetic 
actions between charged particles !). 
I shall only treat the case of a body A, revolving around a cen- 
tral body J, this latter having a given constant velocity p. Let 
r be the line MA, taken in the direction from M towards 4, @, y, 2 
the relative coordinates of A with respect to M, w the velocity of 
A’s motion relatively to M, # the angle between w and p, finally 
pr the component of p in the direction of r. 
Then, besides the attraction 
ES AAE el ee ee 
r2 
which would exist if the bodies were both at rest, A will be sub- 
ject to the following actions. 
ist, A force 
(15) 
in the direction of r, 
2nd, A force whose components are 
ne) Sage a 
TS t 2V*0y\ 7 : 2V2de\r ij 
') See the second of the above cited papers. 
