382 Astrommical and Nautical Collections. 



vi. Elliptic Elements of Pons' s Comet 0/ 1 8 1 9. In a Letter from 

 Dr. Olbers. 



The year 1819 will always be memorable in the history of 

 comets. It is singular that the small comet discovered by 

 Pons, which appeared in June and July in the Lion, describes 

 an ellipsis, and has a very short period of revolution. From 

 the observations made at Marseilles in June only. Professor 

 Encke found, as you may already have learned from the Berlin 

 Almanac of 1822, or from Zach's Correspondence, that the 

 orbit was in all probability very remarkably elliptic. The ob- 

 servations made at Milan in July, published in the Ephemeris 

 for 1820, have now established this fact beyond all doubt. 

 Professor Encke's elements are these : 



Passage of the perihelium, 1819, July 18, 93002 M. T. at 

 Seeberg. 

 Longitude of the gj 113" 10' 45",8^From the mean equi- 



Perihelium 274 40 51,2 J nox, 1 July, 1819. 

 Inclination 10 42 47,6 



Eccentricity .75519035 



Logarithm of the M. distance .4997096 

 Period 2051.93 days, or 5yrs. 7 months. 



By means of these elements the whole of the observations, 

 which Carlini found irreconcilable with any parabola, are repre- 

 sented with wonderful accuracy. Even a difference of half a 

 a year more or less in the period introduces very improbable 

 errors into the observations. A greater degree of accuracy is 

 scarcely to be expected, since we have, unfortunately, been 

 able to find no evidence of an earlier appearance of this comet. 

 One is, however, involuntarily reminded by it of the comet of 

 1770, which may, perhaps, have had the elements of its orbit 

 very materially altered by the effect of the attraction of Jupiter. 



Breme7i, 28 May, 1820. 



The Translation of Dr. Olbers's Essay on Comets will be conti- 

 nued in our next Number. 



