Memoir on the approaching Return of Hallei/s Comet. 4-9 



However doubtful it may remain whether it will be possible 

 to see the comet before its conjunction, yet an attempt to find 

 it may be easily made; and even an unsuccessful result will 

 afford some information with respect to the proportion it 

 bears to the comet of 1811. With a view to afford all pos- 

 sible facility to the discovery, I subjoin a double ephemeris of 

 Halley's comet. By the first I find the 1st of November, and 

 by the second the 11th, to be the day on which it will pass 

 its perihelion. Most probably the passage of the perihelion 

 will take place between these two days. The following ele- 

 ments are taken from Pontecoulant : 



Eccentricity ()-9675212 



Longitude of perihelion 304°3r43" 



8 55 30 



Inclination of the orbit 17 44- 24* 



Greater semiaxis J7*99711 



Mean daily motion 46"-475058 



M. Pontecoulant makes the greater semiaxis = 1 7*98705, 

 and the mean daily motion = 46"*5 12265. But a slight over- 

 sight has been committed with respect to this last quantity. 

 Pontecoulant has added the integral o^ dn for 1682 = 0*373945 

 instead o{ fdn for 1759 = 0*3367382 to N^ and thus brings 

 out W = 46*512265 instead of N" = 46*475058; and from 

 this incorrect value of N^^ he has deduced the greater semi- 

 axis. The following are the places of the comet for mean 

 midnight at Berlin : 



Perihelion Passage, November 1*5, 1835. 



gravity less capable of reflecting the sun's light; and that as the distance 

 of the comet from the sun becomes greater, its volume is again contracted, 

 and its dispersed constituent particles re- united. 



Third Series. Vol.6. No. 31. Jan. I S3 5. H 



