of Shooting Stats and Aerolites. 3 



earth. Why then may we not suppose them to he satellites^ 

 revolving rapidly round the earth in orhits more or less ec- 

 centric, and occasionally plunging into the upper regions of 

 the atmosphere? It does not follow because these bodies 

 move with " planetary velocity," that they must therefore be 

 planets. The satellites nearest to the bodies of Jupiter and 

 Saturn revolve round those planets with a velocity of about 

 ten miles per second, which is not very greatly inferior to that 

 assigned to some shooting stars; and as the velocities of sa- 

 tellites increase with their proximities, we may well suppose 

 that satellites revolving within 150 miles of their primary 

 would have very high velocities. The alleged velocities of 

 shooting stars accord sufficiently well (allowing for the per- 

 turbations to which the proximity of the earth may give rise) 

 with Kepler's law, that the squares of the times are propor- 

 tionate to the cubes of the distances. By applying this law 

 to the known velocity of the moon, it results that a satellite 

 revolving round our earth at 5000 miles from the centre, or 

 about 1000 miles from the surface, would have a velocity of 

 about 40 miles per second, which is even greater than that 

 hitherto assigned to shooting stars. 



We may surely then conceive these bodies to be of the 

 nature of satellites, having all their elements so adjusted as to 

 ensure a perpetual revolution round the earth, into whose at- 

 mosphere they occasionally dip and undergo a momentary 

 ignition. 



It appears moreover difficult to conceive, that if the motion 

 of meteors is of a planetary nature, such small bodies could 

 pass within a few miles of the earth, and then proceed on their 

 course round the sun, comparatively uninfluenced by the ter- 

 restrial attraction. The perturbation produced by the earth's 

 mass on a planet of only a few hundred feet in diameter pass- 

 ing within 100 or 150 miles' distance, would surely be so 

 enormous as wholly to destroy the original orbit of the minor 

 body, and the most probable effect would be to convert it into' 

 a satellite and to retain it permanently within the earth's at- 

 traction. So that even admitting that these asteroids may 

 have once been in the condition of planets, and that many 

 such bodies may still, unknown to us, be revolving in circum- 

 solar orbits, we must yet regard all the shooting stars which 

 ordinarily make their appearance within our atmosphere, as 

 being at present in the condition of satellites. 



The main objection, and it is certainly a very important 

 one, to the satellitary theory of shooting stars, is founded on 

 the fact of the nearly (though not quite regular) periodical 

 recurrence of an increased number of these meteors at certain 



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