Xll 



HUMBOLDT S CORRECTIONS AND ADDITIONS. 



said The time which elapses between the moment in which the plane 

 tary secondary star is nearest to the Earth, and that in w'hich it is mos 

 distant from it, is always longer when the star passes from the point of 

 greatest proximity to that of greatest elongation, than in the converse, 

 ♦vhen it returns from the point of greatest elongation to that of greatest 

 proximity. 



Page 213, line 1. 



In the French translation of the astronomical volume of the Cosmo*^ 

 which to my great gratification, M. H. Faye has again undertaken, this 

 learned astronomer has much enriched, the section upon double stars 

 I had myself neglected to make use of the important treatises of M. 

 Yvon Villarceau, which were read at the Institute in the course of the 

 year 1849. (See ConTiaissance des Temps pour Van 1832, p. 3-128.) 

 I quote here from the table by M. Faye, of the orbital elements of eight 

 double stars, the first four stars, which he considers to be the most cer 

 tainly determined : 



Elements of the Orbits of Double Stars. 



The problem of the period of revolution of rj Coronse 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 f.emi-major axis, eccentricity, and periods of revolution in yeans 



3"-446 0-8699 153-787 



y Virgmis 

 ^ Cancri 

 a Ceutauri 



0"-934 

 12"-128 



0-3662 

 0-7187 



58-590 

 78-486 



The occultation of onej^:re^ s^ar 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., p. 66 

 snd 170) seen in our telescopes. The parallax cf 1830, Groombridge, 

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

 0"-ie2, and by Otto Struve, 0"i>U. 



