THE ORIGIN OF WORLDS. y 



ing if the planes in which they moved differed one degree in their incli- 

 nations to the ecliptic. A slight difference in the size or in the shape 

 of their orbits would also be an unsurmountable barrier to their union. 

 If a collision should occur between two asteroids, they would be only 

 shattered into fragments, and a coalescence into one mass would be 

 rendered more hopeless. But on the extreme verge of a solar system 

 the numerous meteors consigned to large circular orbits lying in the 

 same plane would have very nearly the same velocity in contiguous zones, 

 and would be ready for the work of aggregation when their numbers 

 were sufficiently increased by a long-continued electro-magnetic action. 



In such an innumerable group of small and light bodies in symmet- 

 rical array, a large meteorite or the nucleus of a comet might become 

 the embryo of a future world which may require many thousand years 

 to attain the mass of one of the average asteroids. But its attraction 

 after a time must become powerful enough to clear a large tract of 

 space of matter, and thus to divide into two zones the great ultra-plane- 

 tary ring of floating matter, while it must gradually make the paths of 

 the small bodies deviate from true circles. From the outer zone it re- 

 ceives the meteors, which are in the perihelia of their orbits, and have 

 their velocity most rapid ; but the meteoric bodies from the internal 

 zone unite with the growing mass near the points at which their motion 

 is reduced to the lowest rate. Accordingly, the rotation of the new 

 world must be in the same direction in which the constituents of the 

 great ring were moving, and in which the parent orbs moved around 

 their common center of gravity. The same direction of motion would 

 also be exhibited by meteors which, instead of incorporating at once 

 with the growing world, only described ellipses around it in accordance 

 with the law of gravity. 



In this early stage of its existence a world would be able to acquire 

 a large train of meteors revolving permanently around it chiefly in con- 

 sequence of two circumstances : The rapid increase in the mass and the 

 attraction of the growing planet will make the velocity gained by bodies 

 in approaching it always less than that lost while they are retiring ; 

 and orbits, even when slightly hyperbolic, would be changed into el- 

 lipses. Besides this, the va^t atmosphere of nebulous matter around 

 the new-born sphere would be more effective for the same end, as it 

 would check the velocity of the passing meteors and cause them to re- 

 volve around the growing mass long before they incorporate with it. It 

 is in consequence of these meteoric falls, and not the mere process of 

 cooling, that the abundance of cometary and nebulous matter surround- 

 ing a young world is brought into a more dense condition. A planetary 

 atmosphere of oxygen and hydrogen would maintain a gaseous form in 

 spite of the refrigerating influence of many ages ; but it would be 

 quickly converted into aqueous vapor by the chemical forces awakened 

 on the fall of a meteoric stone, and in the course of time might become 

 liquid or solid as it parted with heat. 



