DZ ON THE NEW PLANET CERES. 



occur; but it mud have happened on the 23d, as I calculate 

 from Von Zach's little ephemeris continued forwards ; viz. 

 when the geocentric plane was about 182°. The aftronomer 

 who has an obfervatory, and has noted the exacl time, will do 

 well to make the obfervation public. 

 Application to The mean time which elapfes between two fucceflive oppo- 

 the planet Ceres, fitions or conjunctions of a planet, as feen from the earth, is 

 called a fynodic revolution, and is determined by dividing 

 360° by the difference of the mean daily motions of the earth 

 and other planets. Thus : taking the mean daily motion of 

 Ceres at 770,7376", according to Gaufs, and of the earth at 

 5 S' 8,33". according to Lalande, we have _ T f£^_. =,466,6 

 days nearly for the whole fynodic period, on a luppofition that 

 the motions are both equable throughout their orbits; but their 

 refpective diitances from their aphelia at the time of oppofUion 

 mull be made the argument of a correction, either additive or 

 fubtraetive, as the cafe may be, to determine what a fynodic 

 period would be if both motions were equable. Now, if we 

 reverfe this procefs, we can juft as eafily gain the difference 

 of the daily motions between that of the earth and other pla- 

 nets, and confequently the whole period of the latter, from 

 having only the earth's daily motion, and ohferved Jj/nodic pe- 

 riod ; for 360°, divided by this period in days, gives the dif- 

 ference wanted at once, which, fubtracled from the daily mo- 

 tion of the earth, gives that of the other, if it be a fuperior 

 planet ; but if an inferior one, that difference muft be added ; 

 and the more nearly the tw r o daily motions approximate to 

 each other, the longer will be the refpective fynodic revolu- 

 tion. In the inftance before us, if we fuppofe the whole cor- 

 rected fynodic revolution of Ceres to be 466,6 days from ob- 

 fervation, we fhall have £gg£ = 2777,3924" for the difference 

 to be fubtracted from 3548,33" the earth's mean daily motion, 

 which will leave 770,7376" for the mean daily motion of 

 Ceres, as before ; by which if we divide 360°, we mail have 

 the wliole tropical period = 1681 a i2 h 8 m 49*. But it remains 

 to be obferved what a whole fynodic period of Ceres may 

 prove in reality, 



. . Suppolintr the epoch, or mean heliocentric longitude of 



Determination _, r , . « ..« „ r „ „ t 



or" the real pe- Ceres to have been 2 b. 1/36 34 on January 1, 1801, the 



iioH, &c. d 3 y of its difcovery, as is ilated by Gaufs, and the place of 



the aphelion 10 S. 26° 27' 38", the mean anomaly mud, on 



4 this 



