. The cyclopaedia; or, Universal dictionary of arts, sciences, and literature. Encyclopedias and dictionaries. COMET. which he did not confid r, it will bring it very near to the timeunwhich it did pafs the penhelion, and prove h . ..ation of the effect of Jupiter have beei sccurace. If he mean the time when it would fir It appear, diction was very accurate, for it was firft fcen â iie 14_tli, 1758, and his computation of the effects of Jupiter will then be more accurate than could have been expected, confidering that he made his calcu- lations only by an indirect method, and in a manner p
. The cyclopaedia; or, Universal dictionary of arts, sciences, and literature. Encyclopedias and dictionaries. COMET. which he did not confid r, it will bring it very near to the timeunwhich it did pafs the penhelion, and prove h . ..ation of the effect of Jupiter have beei sccurace. If he mean the time when it would fir It appear, diction was very accurate, for it was firft fcen â iie 14_tli, 1758, and his computation of the effects of Jupiter will then be more accurate than could have been expected, confidering that he made his calcu- lations only by an indirect method, and in a manner profeffedly not very accurate. Dr. Halley, therefore, had the glory, full to foretel the return of a cornet, and the cent anfwered remarkably to his prediction. He fur- ther obferved, tint the action of Jupiter, in the defcent of the comet towards its perihelion in l6Sz. would to increafe the inclination of its o:bit ; and accordingly the inclination in 1682 was found to be 22' greater than in 1607. From the obfervations of M. Meffier upon a comet in 1770, M. Edric Profperin, member of the Royal Academies of Stockholm and Upfal, (hewed, that a para- bolic orbit would not anfwer to its motions, and he re- commended it to aftronomcrs to feek for the elliptic orbit. This laborious talk was undertaken by M. Lexell, who has (hewn that an ellipfe, in which the periodic time is about 5 years and 7 months, agrees very well with the obfervations. (See Phil. Tranf. for 1779-) As the ellipfes which the cornets defcribc are all very eccentric, aftronomcrs, for the eafe of calculation, fuppofe them to move in parabolic orbits for that part which lies within the reach of oblervation, by which they canvcry accurately find the place of the perihelion of a comet, its dillance from the fun, the inclination of the plane of its orbit to the ecliptic, and the place of the node. But before we can determine the orbit of a comet, from oblervation, it will be neceffary to premife fuch par- ticula
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