Contributions to Astro-Meteorology . 49 



The telescopic comet 1866 I. was discovered by Tempel on 

 the 19th of December 1865, and was visible about a month. 

 Its minimum distance from the earth's orbit was "00660, about 

 twice and a half the distance from the earth to the moon. 

 This distance for Turtle's comet is '00472, or about 430,000 

 miles. 



4. Age of the November Group of Shooting -stars. 



In the Paris Academy of Sciences, January 21, 1867, Le Ver- 

 rier spoke of the November meteors (Comptes Rendus, vol. lxiv. 

 p. 94). Inasmuch as the group is not a complete ring, he ar- 

 gues that it is of comparatively recent formation, having come 

 into the solar system and been turned into its present orbit 

 within a few centuries. 



Now a body coming from a great distance and so having a 

 great velocity in the vicinity of the earth, could not be thrown 

 into an orbit nearly circular by the feeble action of the lower 

 planets. Computation leads to this result, w r hich is fully con- 

 firmed by the fact that the swarm passes every 33 years near 

 the earth, and yet returns at regular intervals. 



Assuming, then, an orbit whose period is 33^ years, whose 

 perihelion distance is 0*989, viz. the earth's distance from the 

 sun on the 14th of November, and assuming the position of the 

 radiant to be long. 142°, N. lat. 8J°, he computes corresponding 

 elements. 



The group, when it came into the system, could not be thrown 

 into its present orbit except by a powerful perturbing cause, 

 as was the case with the comet of 1770. Moreover comets so 

 acted upon that the newly acquired orbit has a small perihelion 

 distance, return necessarily to the orbit of the disturbing body, 

 just as the comet of 1770 returned to Jupiter. We cannot help, 

 then, being struck with the circumstance that the November 

 group extends to the orbit of Uranus and a very little further, 

 and that these orbits intersect, very nearly, just after the group 

 passes its aphelion, and above the plane of the ecliptic. 



The question then arises whether the group and Uranus have 

 ever been together at this point. By calculation it is found 

 that no such meeting could have taken place since the year 126 

 of our era, and that by a change of the computed node for that 

 epoch of 1° 48', and by placing the perihelion 4° from the de- 

 scending node in November, the group would then actually 

 strike the planet Uranus. These two changes are not greater 

 than the possible errors of our observations. 



Le Verrier's researches further show that a globular group 

 one-third of the diameter of Uranus (more or less) might at that 

 time have been then thrown into a shape and an orbit which 



Phil. Mag. S. 4. Vol. 34. No. 227. July 1867. E 



