BiOKEKTON. — Causes tending to alter Eccentricity of Planetary Orbits. 149 



Art. XIII, — On the Causes tending to alter the Eccentricity of 



Planetary Orbits. — By Professor A. W. Bickeeton. 



[Read before the Philosophical Institute of Canterbury, Qth May, 1880.] 



Plate I. 



In former papers it has been shown that the partial impact of cosmical 

 bodies may not unfrequently produce a central mass and attendant bodies, 

 which I have called respectively a sun or nebula, and planets. The sun is 

 at a high temperature and rotates. The planets, in a solid, liquid, or 

 gaseous state, revolve round in one general plane with orbits of varying area 

 and of high eccentricity. All the motions, whether of sun or planets, have 

 one common direction. Further it was shown that the planetary path 

 is due to a portion of the original proper motion escaping conversion into 

 heat at impact. For the same reason the temperatm-e of the planet is 

 lower than that of the sun, whose high molecular velocity, due to its tem- 

 perature and comparatively small mass, may cause it to expand into a 

 nebula. 



The present paper requires that the central mass shall become a nebula, 

 and shall expand beyond aphelion distance of the most'Uremote planet. The 

 forces acting on the planet will be the attraction of the nebula, gaseous 

 adhesion while traversing the nebula, and at the same time exchange of 

 molecules with those of the nebula. The heavier molecules will generally be 

 attracted to the planet, while the lighter ones will leave it. The probability 

 of such a system being formed, or the possibility of gaseous planets moving 

 in a nebul^ with its attendant effects on the size of the orbit and the change 

 of apsides, is not treated in this paper. It is solely occupied with the 

 change of eccentricity. 



The foUowing are five causes which are calculated to result in such a 

 change : — 



1st, An alteration in the amount of the attractive force exerted on the 

 planet by the nebula. 



2nd. The varying resistance and interchange of molecules incmTed by 

 the planet in its path. 



3rd. The gaseous adhesion to the planet revolving on its axis within 

 a nebula. 



4th. The accretion of some of the vast number of small bodies which 

 would exist in the nebula. 



5th. Some others wMeh are too dependent upon the special character 

 of the impact to be discussed at present. 



