2*78 On Encke's Comet. 



Instead of which, Professor Encke found diat die following 

 ellipUcal oi-bit would satisfy all the observations made in 1805. 



d. 

 Time of passing the perihelion 1805, Nov. 21.529. 

 Longitude of the perihelion - - 156° 47' 24" 



Longitude of the ascending node - - 334 20 10 



Inclination of the orbit - - - 13 33 30 



Eccentricity - - - 0.8461 



Mean distance fi'om the sun - - 2.2131 



In fift}^ observations of the right ascension and declination, 

 thirty-two are given, by these elements, to less than half a 

 minute, and the greatest error is 1' 39". 



The near agreement of these elements with those of the 

 comet of 1819 made Professor Encke feel confident that it 

 was the same comet. This discovery having been communi- 

 cated to Dr. Olbers, led him to a further investigation of the 

 subject ; and he, with his usual sagacity and promptness, im- 

 mediately perceived and gave the information to Professor 

 Bode, that it had also ajipeared in 1786 and in 1795. 



During its appearance in 1795, it was about three minutes 

 in diameter, not well defined, without any tail or nucleus, and 

 was first discovered near the constellation Cygnus. It was 

 found extremely difficult to make the observations at that 

 time correspond with a parabolic orbit, and the results of dif- 

 ferent astronomers were very discordant ; making the time of 

 passing the perihelion December 14th or 15th; longitude of 

 the perihelion 157° to 171°; the node 353° to 361°; inclina- 

 tion 10° to 24°; perihelion distance 0.212 to 0.258. After a 

 new reduction and computation of the observations. Professor 

 Encke found that the following elliptical elements would re- 

 present very well the observations made at that tune. 



Time of passing the perihelion 1795, Dec. 21.47. 

 Longitude of the perihelion - _ - 156° 41' 20" 



Longitude of the ascending node - - 334 39 22 



Inclination of the orbit - - - 13 42 30 



Eccentricity _ _ . 0.8489 



Mean distance from the sun - - 2.2131 



In 1 795 the comet was frequently observed in a part of the 

 heavens where there were no bright stars favourably situated 

 to compare with it ; and on this account the observations of 

 different astronomers sometimess varied considerably from 

 each other. However, out of thirty-eight observations of the 

 right ascension and declination, twenty-three were within one 

 minute, and but vei'y few of the observed places varied more 

 than two minutes from the calculations. 



On 



