452 THE POPULAR SCIENCE MONTHLY. 



its inclined position it does not intersect the path of any of the inter- 

 mediate planets Saturn, Jupiter, and Mars. M. Le Verrier also calcu- 

 lated hack the epochs at which the planet and the meteors were at the 

 point of intersection, and found that early in the year a. d. 126 they 

 were both at that spot, but that this has not happened since. Taking 

 this in conjunction with what Signor Schiapparelli pointed out, we seem 

 to have a clew to a truly wonderful past history. All would be ex- 

 plained if we may suppose that, before the year 126, the meteors have 

 been moving beyond the solar system ; and that in that year they 

 chanced to cross the path of the planet Uranus, traveling along some 

 such path as that represented in the diagram. Had it not been for 

 the planet, they would have kept on the course marked out with a 

 dotted line, and, after having passed the sun, would have withdrawn 

 on the other side into the depths of space, to the same measureless dis- 

 tance from which they had originally come. But their stumbling on 

 the planet changed their whole destiny. Even so great a planet would 

 not sensibly affect them until they got within a distance which would 

 look very short indeed upon our diagram. But they seem to have 

 almost grazed his surface, and, while they were very close to such a 

 planet, he would be able to drag them quite out of their former course. 

 This the planet Uranus seems to have done, and when, pursuing his 

 own course, he again got too far off to influence them sensibly, they 

 found themselves moving slowly backward, and slowly inward ; and 

 accordingly began the new orbit round the sun, which corresponds to 

 the situation into which they had been brought, and the direction and 

 moderate speed of their new motion. 



They seem to have passed Uranus while they were still a small, 

 compact cluster. Nevertheless those members of the group which 

 happened to be next the planet as they swept past, would be attracted 

 with somewhat more force than the rest, the farthest members of the 

 group with the least. The result of this must inevitably have been 

 that, when the group were soon after abandoned to themselves, they 

 did not find themselves so closely compacted as before, nor moving 

 with an absolutely identical motion, but with motions which differed, 

 although perhaps very little, from one another. These are conditions 

 which would have started them in those slightly different orbits round 

 the sun, which, as we have seen, would cause them, as time wore on, 

 to be drawn out into the long stream in which we now, after seventeen 

 centuries, find them. 



What is here certain is, that there was a definite time when the 

 meteors entered upon the path they are now pursuing ; that this time 

 was the end of February or beginning of March in the year 126 is still 

 a matter of probability only. It is, however, highly probable, because 

 it explains all the phenomena at present known ; but astronomers are 

 not yet in a position to assert that it is ascertained, since one link in 

 the complete chain of proof is wanting. We who live now should be 



