140 G. Hinrichs on Planetology. 
The same principles will apply to the satellites; but we 
too few data to make a comparison of this principle with 
vation profitable. 
§ 11. The periodic time of the Planets ; Kepler's third law. . 
Since every particle in the same shell revolves around th 
under the influence of a force R proportional to the distance 
from the axis (§ 9), we know from mechanics that the p 
time T of such a particle is 
T Qn 
ay, 8 ts 
oa (24) 
whole nebula had the same density throughout it would 
like one solid. But if the density be different in different p 
some shells will rotate faster than others (§ 12). 
Eliminating 9 by means of (18) we get 
T2 —— 4! a’ 7} 
=u 
og agement 
‘ 3 Ji P12 (14-22) tans 
We know that the ellipticity of the nebula is determ! 
the centrifugal force, and the latter by the state of cont 
tion (§ 8); and even in case an ellipsoid becomes imposs! 
can not but conclude that the figure continues to be dete 
inthe same manner. But the condensation continues 
crease of the centrifugal force depending thereon will a! 
tinue and produce a series of rings in a certain successi0 
at = constant; ° . . . * : = 
