PROPOSED EXPLANATIONS OP THEM. 



terrestrial attraction exerted upon them predominating over 

 that of the moon, they may have either fallen down directly 

 upon the earth, or may have revolved round it in a curvilinear 

 orbit, with a motion constantly retarded by the earth's atmo- 

 sphere, the consequence of which would be that they would 

 continually approach the earth, and at length fall upon its 

 surface. We shall call this the lunar hypothesis. 



Fourthly. It has been supposed that meteo'rites are planetary 

 bodies ; that they revolve in orbits round the sun ; that these 

 orbits intersect the annual path of the earth ; that when the 

 earth passes through the point of intersection of its path with 

 their orbits they either encounter it directly, and fall upon its 

 surface, or entering its atmosphere, are rapidly retarded by the 

 resistance of that fluid, and are then drawn to the surface by the 

 terrestrial attraction. 



To render this supposition sufficient to explain the large 

 numbers of meteorites which sometimes appear simultaneously 

 and fall down upon the surface, it is assumed that these planetary 

 bodies circulate round the sun in groups consisting of numerous 

 individuals which move together with equal, or nearly equal, 

 velocities in parallel paths, thus maintaining for long periods 

 of time their relative position, and passing through the celestial 

 space like a flock of gregarious birds. Now, if we suppose the 

 parallel paths of a number of such bodies to be represented at 

 A A, (fig. 7), and that the earth's path, E E', passes across them, 



it is clear that it, while the earth is passing from e to e', these 

 bodies happen to be at that point of their orbit, an encounter 

 must ensue, and they must, in greater or less number, pass 



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