AND ADDITIONS. 



The problem of the period of revolution of rj Corona; admits of two 

 solutions: of 42'5 and 66'3 years; but the late observations of Otto 

 Struve give the preference to the second. M. Yvon Villarceau finds the 

 semi-major axis, eccentricity, and period of revolution, in years : 



y Virginia 3"'446 0-8699 153787 

 I Cancri 0"'934 0'3G62 58-590 



a Centauri 12"'128 0'7187 78*486 



The occnltation of one fixed star by another, as was presented by Her- 

 culis, I have called apparent (p. 287). M. Faye shows that it is a con- 

 sequence of the spurious diameter of the stars (Cosmos, vol. iii. pp. 66 

 and 1 70,) seen in our telescopes. The parallax of 1830, Groombridge, 

 which I gave (p. 27) as 0"-226, is found by Schliiter and Wichmann, 

 0"-182, and by Otto Struve, 0"'034. 



