Nov., 1886.; 



1 



ELLIOTT 



SOCIETY 







127 



TaUe of Elements of Orbits of Comets of 1618, 1844, and 1886 j 



DATE, 



M. TIME 

 GEEEK- 

 WICH. 



PEEIH. 

 EOX. 



PERTH. 



' INCLN 



DisT. : 



ascend'g 



NODE ECC'tEY CALCUEAT'e 

 EOXG. 1 1 



1678, Aug. 18 

 1844, Sep. 2 

 1886, Nov. 22 



7^ hours 



lU " 



17i " 



322^48' 

 342^31' 

 347°50' 



1.1453 

 1.1864 

 1.2240 



2° 52' 

 2° 55' 

 3^23' 



163" 20' 

 63' 49' 

 48° 36' 



0.62697 

 0.61765 

 Sot given 



LeYerrier. 

 Briinnow. 

 Holetschek 



Motion of each was Direct. 



It will be seeu from this Table that, the Node has been rapidly retrograding, 

 nearly 3° at each revolution, the Perihelion advancing at a nearly uniform rate 

 of 40' at each revolution, that the PeriheHon Distance and Inclination are 

 slowly increasing, and that the Eccentricity is diminishing. Until some change 

 in the character of the pertiu'bations takes jjlace it vnil become less and less 

 conspicuous at each observed return. The Aphelion Distance Ls not explicitlj' 

 given by the calculators, but can easily be obtained from the Table, does not 

 differ much from 5, and ap^jears to be nearly the same in 1 844 that it was in 

 1678, so that the major axis has increased by nearly the amount of increase of 

 the perihelion distance ; the periodic time must therefore be slowly increasing. 

 The orbit therefore lies whoUy within the orbit of Jupiter, and their aphelia he 

 not far from each other. 



The similarity of the orbit-elements of this Comet to those of the Comet of 

 1678, has of course been perceived by others as well as myself, and LeYerrier 

 made them the subject of special investigation in his researches on peiiodic 

 Comets, and he gave, in the Coniptes Bendus of 20th Dec, 1847, as the result 

 of his studies, this conclusion : " that as far as can be judged, the Comets of 

 1678 and 1844 are identical." It is doubtful whether any stronger affirmation 

 than this can ever be given, as LaHire's observations lack precision ; they seem 

 not to be the result of measurements, but of eye-estimates of the Comet's po- 

 sition among the neighboring stars. See Lemoimier, Histoire Celeste, p. 238, 

 and Pingi-e', CometograpMe, ii. p. 24. The elements of the elhptic orbit of 

 the Comet of 1678, \\ith a periodic time of 5| years, as calculated by LeYenier, 

 we give in the adjacent Table for comparison with those of the Comet of 1844. 

 The differences between the corresponding pau'S of elements, according to the 

 calculations of LeYerrier. are caused by the attraction of the planet Jupiter. 



With a period so short as 5t years, there must have been numerous returns, 

 between these three recorded appearances. If we assume 8 periods in the in- 

 terval 1844 — 1886, which is 42,2-9 years, we get an average period of 5.28 years; 

 and if we assume 32 periods in the interval 1678—1844, which is 166, 1-24 years, 

 we get an average period of 5.19 years; which results agi'ee with the increase 

 in length of period already remarked. If we assume 33 periods, we would uot 

 an average })eriod of 5.00 years. I have not lieard th;ii it has ever been oLser- 



