274 SHOOTING STARS. 



assumption would be absurd. They would appear to be of 

 celestial nature because they recur at the same time of each year, 

 and thus depend for visibility upon the earth's position in space. 

 They cannot exist within the limits of the atmosphere because the 

 radiant could not, if they did, maintain a fixed position amongst the 

 stars while the earth rotated on her axis and revolved in her orbit. 

 The radiant point would undergo sensible and rapid change amongst 

 the stars, making a complete circuit of the heavens in one day, and 

 moreover, the radiant point of a shower would, as observed at two 

 very distant stations, give a sensible parallax or displacement, 

 whereas we know from contemporaneous observations of great 

 showers, and by observations of many minor systems, that the 

 same exact radiants have been manifested at the same time. But 

 by belonging to the earth, I mean that they must travel with her 

 in her orbit, and perhaps play the part of miniature satellites, having a 

 revolution around her with a period of three months which 

 corresponds to the observed re-appearances of the showers. It is 

 impossible to conceive of a cometary meteor stream having so vast 

 a width that the earth is occupied three months in completely 

 passing through it, and we know that it could not account for the 

 second outbursts, but must give one continuous feeble shower. 

 Nor can it be assumed that we pass a second time through the 

 same system, because the radiant points would be quite different 

 on the two occasions. The difficulty in accounting for these 

 alleged re-appearing meteor showers is very great, and we are driven 

 inevitably to the assumption that they are earth-revolving meteors 

 as before mentioned, or at any rate members of a system remain- 

 ing for a long while in the vicinity of the earth. There are, 

 however, some objections to this explanation, and it appears to me 

 that that theory is best, which shall give a terrestrial connection 

 with meteors dependent upon or resulting from a celestial nature 

 or origin. We know that the planets have a great influence over 

 comets in disturbing their orbits. The light, flexible, and 

 scattered nature of comets render them easily liable to perturbation 



