356 D. Trowbridge on the Nebular Hypothesis. 
have coincided approximately with the plane of the equator. 
The first planetary ring abandoned would have an inclination 
to the boa. of the ecliptic nearly the same as that of the phn 
| ar m 
could not be ex aad when we reflect that the inclination of 
- the planes of the planetary orbits to the invariable plane, is con- 
ntly varying from planetary perturbations, and has been for 
immense ages.” 
25 an the same manner as that in which the first ie was 
separated at the same, or about the same time; and an investi- 
cae which will be given in a note, seems to strengthen the 
Opinion 
- «, History of Phys. Astron., p. 1 * Smithsonian Report for 1861, BS 210. 
*° I will make this prediction, it if more planets beyond Neptune be discov- 
ered, the inclination of their orbits will differ but little from that of the portale 
ane. 
* See this Journal, [2]. xxxviii, 5. The investigation referred to in the text, is 
as follows: The attraction of a homogeneous oblate sphervid on a particle withia 
its mass is, paralle Litsesst es y, and z, 
= a os 
2rz9) —z— sin-'e- — | t.vge0¢ (oappoes), 2reype, and 
= noe 
4rez| = 33 sin-! e b aeeeve, 
pr If u be the distance of the attracted particle from aie axis of rota- 
ie il be sez? + y?, and U=2reupe 
Wi ed eee jonas cu hha? to the axis of beads See Todhunters 
Analytical Statics, p. 265.) Call the centrifugal foree F = oye = angular ve 
___Tecity of rotation, Call the ratio of F to U, R, then R=y, = ne ae 
ae sre se hat Ris independent of, the datas from the axis of rotation, Hence 
