BiCKEETON. — On the Orirjiyi of the Solar System. l59 



Molecular exchange, resistance, and its collecting power, may have ren- 

 dered its orbit circular, and have brought it into the plane of the planet's 

 rotation. There seem no strong reasons, such as irregularity, etc., why 

 Proctor's theory might not account for the formation of the moons. Another 

 objection to this theory is the fact that there are comparatively few small 

 bodies still travelhng the system. There are, of course, a countless number 

 of such bodies, but not so many as might be expected. The nebula would 

 cause the bulk of the small bodies, except moons, to be absorbed into 

 the sun ; and the same action may have cleared the space about the 

 planets of all matter except the satellites. 



The motion of the sun and its system in space may be accounted for 

 in so many different ways, and does not appear to offer any difficulties to 

 any theory, that I shall not discuss it. 



Becapitulation. 



I recapitulate the more important of the points in what at present 

 seems the most probable origin of the solar system. 



Two rare bodies, moving with considerable velocity, rotating, and 

 having revolving around them in all planes a large number of bodies, some 

 of a large size, come within each others attraction, are brought together by 

 gravitation, and come into tangential collision. During the collision most 

 of the accompanying bodies fly off in directions which are approximately in 

 one plane ; the component of the motion not in the plane being due to 

 their original orbital rotation. The new orbit of all the bodies tends to be 

 highly eccentric, but the general mass expands, and by its agency the orbit 

 becomes nearly circular. Among the vast number of bodies thrown off 

 during impact, the larger gradually collect the lesser up, also much of the 

 matter that coalesces from the nebula, and many heavy molecules. "Where 

 this action is very considerable, the original mass forms so small a fraction 

 of the final planet, that its original irregular motion almost disappears, and 

 its axis is almost rendered perpendicular. The nebular resistance will tend 

 to lessen the distance of the smaller bodies, and convert them into zodiacal 

 light, or absorb them entirely into the sun, except the moons, which cannot 

 escape the planet's attraction. All the smaller planets and those nearer 

 the sun are robbed of their lighter molecules, and become very dense 

 compared to the general mass of the system, but, as the nebulae contract 

 within their orbit, they again pick up the lighter molecules which become 

 the atmosphere. 



