296 PROCEEDINGS OF THE AMERICAN ACADEMY 



Three Hundred and second Meeting. 



January 4, 1848. — Monthly Meeting. 



The President in the chair. 



Mr. Everett read a letter from M. Leverrier, acknowledging 

 his election as a Corresponding Member of the Academy. 



Mr. Everett also submitted to the Academy a paper received 

 from M. Leverrier, containing a succinct abstract of the first of 

 two memoirs lately read by him to the Academy of Sciences 

 at Paris, on the subject of periodical comets. It was the inten- 

 tion of M. Leverrier that this communication should reach 

 the Academy in advance of the publication of the Compte 

 Reiidii for the 25th of October, in which the abstract of the 

 first memoir appears in extenso. Owing to the great length 

 of the passage of the vessel by which M. Leverrier's com- 

 munication was transmitted, this expectation was disappointed. 

 As the Compte Rendu, however, of' course possesses but a 

 limited circulation in this country, a translation of this inter- 

 esting paper was read by Mr. Everett to the Academy. 



After alluding to the stability of the orbits of the planets, 

 caused by their moderate eccentricity, small inclination, and 

 the great preponderance of the central force, M. Leverrier ob- 

 serves, that 



" It is not so with respect to the comets. Those of them, which 

 move in planes but Uttle inclined to the ecliptic, cut very near the 

 orbits of one or more of the planets. It may accordingly happen, 

 that they will pass in the neighbourhood of the planets themselves, 

 and that the disturbing force, thus rendered preponderant, may turn 

 them from their course. Thus the comet, which, left to itself, would 

 have continued to move in a parabola, may by the action of Jupiter 

 be brought for ever, or only for a limited period, into an ellipse of 

 moderate extent. The same cause which shall have compelled the 

 comet to describe this ellipse may b^able hereafter again to control 

 its movement, and to force it for ever from our planetary system, by 

 throwing it into a hyperbolic curve." 



M. Leverrier then adverts to the discovery of a comet by 

 Messier in 1770, which was afterwards known as Lexell's, in 



