ASTRONOMY. 95 



The place of the apsides thus found, may be correct- 

 ed, on the principle, that the axis is the only line 

 drawn through the focus of an ellipse, which bi- 

 sects its area. The time, therefore, from the sun's 

 being in one apsis, to his being 180 farther ad- 

 vanced, is precisely half a year. When, therefore, 

 two points are found in the sun's orbit, 180 or 6 

 signs distant from one another, and such, that the 

 sun takes precisely half a year to pass from the 

 one to the other ; they are the Higher and the 

 Lower Apsis. LA CAILLE, Mem. de I'Acad. des 

 Sciences, 1742. Also his Astronomic, p. 78. 

 WOODHOUSE, Astron. p. 210. 



Thus the longitude of the aphelion, for the year 1 780, 

 was determined by DE LAMBRE, from Dr MASKE- 

 LYNE'S observations, to be 99 8' 19".9, or 9 8' 

 19".9 advanced into the sign Cancer. The sun 

 passed through this point 4m past noon on the 

 3 1st of June, according to the time at Greenwich. 

 BIOT, Astron. vol. I. p. 220. 



The eccentricity of the sun's orbit was found, in 



(5 97.) = - x a. A method of finding - more ac- 

 m m 



curately than can be done merely by the observa- 

 tions of the sun's diameter will be immediately 

 explained. When so determined, it is found 

 = .016814, the mean distance being 1. In the 

 following propositions, the mean distance = a, 

 and the eccentricity == e. 



99. The 



