EVOLUTION OF THE SOLAR SYSTEM. 
523 
Main (with ellipticities 1/10’2, 1/11(1), 1/9-227 respectively) are 79", 82", and 94" 
respectively. * 
The period of rotation is 10 h 29^ m or ‘437 m.s. day. 
Assuming (as with the sun) that the surface density is infinitely small compared 
with the mean density, we have (7=-261497m 3 . I find then that these three values 
give respectively, 
703,000 
~ 497,000 . 535,000 
On —— . and tut and 
10 10 
10 10 
10 10 
The masses of the satellites are unknown, but Herschel thinks that Titan is nearly 
as large as Mercury. 
If we take its mass as - 06 in terms of the earth’s mass, its distance as 1 76"'755 at 
the planet’s mean distance from the sun, and its periodic time as 15 - 95 m.s. days, we 
find the orbital momentum to be 16,000/10 10 . The whole orbital momentum of the 
satellites and the ring is likely to be greater than this, for the ring has been variously 
estimated to have a mass equal to -xdyjth t° iryoth of the planet. 
It is probable therefore that orbital momentum of the system is /- 0 -th> or there¬ 
abouts, of the rotational momentum of the planet. 
Nothing is known concerning the rotation of Uranus and Neptune, and but little of 
their satellites. 
The results of this numerical survey of the planets are collected in the following 
table. 
Table II, 
Planet. 
i. 
Rotational 
momentum of 
planet x 10 10 . 
ii. 
Orbital 
momentum of 
satellites x 10 10 . 
iii. 
Ratio of ii. to i. 
iv. 
Total momentum 
of each planet’s 
system x 10 10 . 
Mercury . 
Venus 
Earth.... 
Mars .... 
Jupiter . 
Saturn 
•34 ? 
28-6 ? 
37-88 
1-08 
2,594,000 
f 500,000 ] 
i t0 r 
L 700,000 J 
181 
very small 
20,000 
f 16,000 
\ or more 
4-78 
very small 
i 
130 
* 1 
or more J 
•34 ? 
28-6 ? 
216 
1-08 
2,614,000 
f 520,000 ] 
1 v t0 f 
L 720,000 J 
The numbers marked with queries are open to much doubt. 
If the numbers given in column iv. of this table be compared with those given in 
Table I., it will be seen that the total internal momentum of each of the planetary 
* Deduced from values of the equatorial diameter found by these observers, referred to the planet’s 
mean distance from the sun, as given by Ball. 
3 Y 
MDCCCLXXXI. 
