(ovt) 
3rd, A force 
k 1 dr 17 
V2 P 4 PC ’ ( ) 
parallel to the velocity p. 
4th A force 
1 
DAGO EN we Oar eg es Ce wy QOD 
V2 2 
in the direction of r. 
Of these, (15) and (16) depend only on the common velocity p, 
(17) and (18) on the contrary, on p and w conjointly. 
It is further to be remarked that the additional forees (15)—(18) 
are all of the second order with respect to the small quantities 
ee and = y 
V V 
In so far, the law expressed by the above formulae presents a 
certain analogy with the laws proposed by WEBER, RIEMANN and 
Cuaustius for the electromagnetic actions, and applied by some astro- 
nomers to the motions of the planets. Like the formulae of CLAUSIUS, 
our equations contain the absolute velocities, 1, e. the velocities, rela- 
tively to the aether. 
There is no doubt but that, in the present state of science, if we 
wish to try for gravitation a similar law as for electromagnetic forces, 
the law contained in (15)—(18) is to be preferred to the three other 
just mentioned laws. 
§ 9. The forces (15)—(18) will give rise to small inequalities in the 
elements of a planetary orbit; in computing these, we have to take 
for p the velocity of the Sun’s motion through space. I have calcu- 
lated the secular variations, using the formulae communicated by 
TISSERAND in his Mécanique céleste. 
Let a be the mean distance to the sun, 
e the eccentricity, 
p the inclination to the ecliptic, 
0 the longitude of the ascending node, 
@ the longitude of perihelion, 
# the mean anomaly at time = 0, in this sense that, if x 
