670 



Proceedings of the Royal Irish Academy. 



four have been found to have a parallax greater than one-tenth of a 

 second, viz, : 



7] Cassiopese, 



0-154, 



. 0. Struve, . . 



1856 



a Canis Majoris, 



0-389, 



. Gill and Elkin, 



1884 





0-273, 



. Abbe, . . . 



1868 





0-193, 



. Gvlden, . . . 



1864 



a Centauri, . . 



0-741, 



. Gill and Elkin, 



1884 





0-512, 



. Elkin, . . . 



1880 





0-88, 



. Moesta, . . . 



1868 





0-976, 



. C. A. E. Peters, 



1852 





0-919, 



. Maclear, , . 



1851 



iQp Ophiuchi, . 



0-162, 



. Krueger, . . 



1863 



•while -with regard to the fifth, y Coronae Australis, I am not aware 

 of any measures having been made with the view of determining its 

 parallax. The value 1-224 for 11 Fshows, however, that either it has 

 a sensible parallax, or that in the year 1 880 its motion in the line of 

 sight was more than twelve miles a second. The quantity 11 /^attains 

 a second maximum in June of this year, reaching the value 0-857 : so 

 that, if the parallax should prove to be very small, we might expect to 

 see some displacement of the lines in the spectrum which would enable 

 us to obtain a measure of its amount. As the distance will be then 

 1"*5, and the components are equal in magnitude, the circumstances 

 are rather favourable for the detection of such a displacement. 



The system 40 or 02 Eridani is composed of three stars. The pri- 

 mary {A), of 4-4 magnitude, and a companion double star {B, C), of 

 magnitudes 9^ and 10^ respectively, distant 82" from A. That they 

 belong to one system seems certain, from the fact that they all have a 

 common proper motion amounting to no less than 4"- 10 annually. The 

 elements of the pair £, C have been computed by Mr. Gore, and pub- 

 lished in the Monthly Notices of the Royal Astronomical Society, for 

 March of this year. From these elements I find that 11 F is equal 

 to 0-886. This, taken in connexion with Dr. Gill's determination of its 

 parallax, which he finds to be 0"-166, shows that this is a slowly-mov- 

 ing pair, as its velocity in the line of sight can never exceed five and 

 a-half miles per second. If, however, at any time the orbit of the 

 companion pair around the primary should be found capable of com- 

 putation, we might reasonably expect that with such an apparent 

 distance as 82" the linear relative velocity would become measurable 

 with the spectroscope. 



