Notice of the Periodical Comet of 1S\^. ^75 



make knoAvn what M. Damoiseau has added in the memoir 

 we have submitted to your examination. ^ 



The first part of this memoir was presented to the acade- 

 my the 16th of February last, and the second part the 26th 

 of April. In the first part, M. Damoiseau, speaking of the 

 elliptic elements calculated by M. Encke for the epoch of 

 1819, determines the perturbations which they have under- 

 gone from that epoch to 1822. The elements which he has 

 deduced for this last epoch differ but little from those of M. 

 Encke, which we have already cited ; and it could not be 

 otherwise, because, having both adopted the same data, the 

 difference in their results must be owing to the difference 

 in the methods they pursued. The duration of the anoma- 

 listic revolution of 1819 and 1822 being nevertheless known 

 ■by observation, M. Damoiseau has made use of it in order to 

 rectify the daily motion of 1819, of which he had already 

 availed himself. He decided at the same time the mean daily 

 motion of 1822, which was necessary to enable him to calcu- 

 late the perturbations of the comet, from its first appearance 

 to its next return to its perihelion. In this new calculation, 

 M. Damoiseau makes use of the elements of 1822, deduced 

 from the observations at Paramatta. The perturbations of 

 this revolution are much less considerable than those that hap^ 

 |)ened before, and the duration between two consecutive pas- 

 sages through its perihelion will be about 1212 days like the 

 preceding. M. Damoiseau fixes the next return of the comet 

 to its perihehon on September 17, 1825. He gives for that 

 epoch its elliptic elements, and he assigns the places which it 

 will occupy in the heavens during the time of its appearance ; 

 but thinking that it will then be too near the sun to admit of 

 observations being taken, he has proposed to calculate the 

 epoch of its following return, and its ephemeris for that epoch. 

 These calculations are the subject of M. Damoiseau's second 

 memoir. The second return to the perihelion which he has 

 determined will take place January 10, 1829 ; and the author 

 announces that the comet, according to his ephemeris, will be 

 visible in every part of Europe. The time between this pas- 

 sage through the perihelion and that of 1825 will be very 

 nearly 1211 days, or only one day less than the period of the 

 preceding revolution. 



