Places of the Comet of 1822. 



415 



In the determination of the degree of brightness, the unit is sup- 

 posed to be that which the comet exhibited the 5th January,! 8 19. 

 It then appeared in the field of the telescope at the same time with 

 a fine nebula in the head of Aquarius, n. 77 of Bode, or n. 2 of 

 the Connaissance des TemSy and was precisely of the same magni- 

 tude, form, and brightness. When the comet was first discovered, 

 on the 20th October, 1805, its brightness, in terms of this unit, 

 was 1.321, and it was then considered as equal to that of a star 

 of the fifth magnitude. In the beginning of July, 1822, there- 

 fore, it will be brighter than a star of the fourth magnitude. 



It appears from this ephemeris, that we shall not be able to see 

 the comet in Europe in the spring of 1822, because it will be too 

 faint in comparison with the evening twilight. Whether it may be 

 possible to discover it in December 1821, or Januarp 1822, with 

 very powerful telescopes, is very doubtful. But in southern lati- 

 tudes it will be easily discoverable as soon as the 9th or 10th of 

 June, 1822, since it will be sufficiently emerged from the solar 

 rays, and of the brightness of a star of the fifth magnitude. The 

 delay of nine days in the passage of the perihelium, from the ac- 

 tion of Jupiter, prevents the subsequent approach of the comet so 

 near to the earth, as Dr. Olbers had computed, on the hypothe- 

 sis of its arrival at the perihelium on the 15th or 16th of May. 



