HUBERT ANSON NEWTON. 



275 



examine whether the fifth period, viz. that of 33'25 years, would give 

 a motion of the node in accordance with the observed value. As 

 this period gives a very long ellipse for the orbit, extending a little 

 beyond the orbit of Uranus, it was necessary to take account of the 

 perturbations due to that planet and to Saturn. Professor Adams 

 found 28' for the motion of the node. As this value must be regarded 

 as sensibly identical with Professor Newton's 29' of observed motion, 

 no doubt was left in regard to the period of revolution or the orbit of 

 the meteoroids.* 



About this time, M. Schiaparelli was led by a course of reasoning 

 similar to Professor Newton's to the same conclusion, that the mean 

 velocity of the meteoroids is not very different from that due to 

 parabolic orbits. In the course of his speculations in regard to the 

 manner in which such bodies might enter the solar system, the 

 questions suggested themselves : whether meteoroids and comets may 

 not have a similar origin ; whether, in case a swarm of meteoroids 

 should include a body of sufficient size, this would not appear as a 

 comet ; and whether some of the known comets may not belong to 

 streams of meteoroids. Calculating the orbit of the Perseids, or 

 August meteoroids, from the radiant point, with the assumption of a 

 nearly parabolic velocity, he found an orbit very similar to that of 

 the great comet of 1862, which may therefore be considered as one 

 of the Perseids, probably the largest of them all.t 



At that time no known cometic orbit agreed with that of the 

 Leonids, but a few months later, as soon as the definitive elements of 

 the orbit of the first comet of 1866 were published, their resemblance 

 to those of the Leonids, as calculated for the period of 33'25 years, 

 which had been proved to be the correct value, was strikingly 

 manifested, attracting at once the notice of several astronomers. 



Other relations of the same kind have been discovered later, of 

 which that of Biela's comet and the Andromeds is the most interesting, 

 as we have seen the comet breaking up under the influence of the 

 sun ; but in no case is the coincidence so striking as in that of 

 the Leonids, since in no other case is the orbit of the meteoroids 

 completely known, independently of that of the comet, and without 

 any arbitrary assumption in regard to their periodic time. 



The first comet of 1866 is probably not the only one belonging to 

 the Leonid stream of meteoroids. Professor Newton has remarked 

 that the Chinese annals mention two comets which passed rapidly in 

 succession across the sky in 1366, a few days after the passage of the 

 earth through the node of the Leonid stream, which was marked in 

 Europe by one of the most remarkable star-showers on record. The 



Monthly Notices Roy. Ast. Soc., vol. xxvii, p. 247. 

 G. II. S 2 



t Etdwurf, etc. , pp. 49-54. 



