COMETS. 



perihelion in 1843 and its expected re-appearance in 1850-1, 

 subject to the disturbing action of the planets, and he predicted its 

 succeeding perihelion for the 3rd of April, 1851. 



Aided by the formula) of M. Le Terrier, Lieutenant Stratford 

 calculated a provisional ephemeris in 1850, by which observers 

 might be enabled mor easily to detect the comet, which was the 

 more necessary as the object is extremely faint and small, and not 

 capable of being seen except by means of the most perfect tele- 

 scopes. By means of this ephemeris, Professor Challis, of Cam- 

 bridge, found the comet on the night of the 28th November very 

 nearly in the place assigned to it in the tables. Two observations 

 only were then made upon it, which, however, were sufficient to 

 enable M. Le Verrier to give still greater precision to his formula?, 

 by assigning a definite numerical value to a small quantity which 

 before was left indeterminate. Lieutenant Stratford, with the 

 formula thus corrected, calculated a more extensive and exact 

 ephemeris, extending to the last day of March, and published it 

 in January, 1851, in the Nautical Almanack. 



The comet, though extremely faint and small, and consequently 

 difficult of observation, continued to be observed by Professor 

 Challis, with the great Northumberland telescope, at Cambridge, 

 and by M. Struve at Pultowa, and it was found to move in exact 

 accordance with the predictions. 



32. On the 22nd August, 1844, M. de Yico, of the Roman 

 Observatory, discovered a comet whose orbit was soon afterwards 

 proved by M. Faye to be an ellipse of moderate eccentricity, with 

 a period of about 5| years. It arrived at its perihelion on the 

 2nd of September, and continued to be observed until the 7th 

 of December. 



33. On the 26th of February, 1846, M. Brorsen, of Kiel, dis- 

 covered a faint comet, which was soon found to move in an elliptic 

 orbit, with a period of about 5 years. Its position in the heavens 

 not being favourable, the observations upon it were few, and the 

 resulting elements, consequently, not ascertained with all the pre- 

 cision that might be desired. Its re-appearance on its approach 

 to the succeeding perihelion, was expected from September to 

 November, 1851. It escaped observation, however, owing to its 

 unfavourable position in relation to the sun. Its next perihelion 

 passage will take place in 1857. 



34. On the 27th of June, 1851, Dr. d' Arrest, of the Leipsic 

 Observatory, discovered a faint comet, which M. Yillarceaux 

 proved to move in an elliptic orbit, with a period of about 6| 

 years. The next perihelion passage of this comet will take place 

 in the end of 1857, or the beginning of 1858. 



35. A revision of the recorded observations of former comets by 

 166 



