90 Messrs Herschel and South on the Double Stars 



logy. Truth, however, had in this case thrown her shadow 

 before, and what she then dimly unveiled to our fancy, she has 

 now displayed before our judgment with all the fulness of de- 

 monstration. From observations separated by an interval of 

 twenty-five years. Sir W. Herschel discovered in more than 

 fifty double stars a change both of position and of distance. 

 In Castor, s Bootis, 5 Serpentis, and y Virginis the angle of 

 position, (or the angle which the line joining the two stars 

 forms with the direction of their daily motion,) had suffered a 

 very great change, while the distances of the stars remained 

 the same ; and in ^ Hercules, the two stars had approached so 

 near to each other, that five-eighths of the apparent diameter 

 of the small star were actually eclipsed hy the larger (me. 



These curious results have been confirmed and extended by 

 subsequent astronomers, and the tabulated observations of Mr 

 South, upon no fewer than 838 double stars, enable us to ar- 

 range into classes the various systems which they present to 

 our notice. 



In the present communication, we shall confine ourselves to 

 the description of the Binary Systems which are considered by 

 Messrs Herschel and South as perfectly determined. 



1. n CassiopeicB, R. A. Asc. 0° 38'. Decl. N. BQ"" 51. 



This star is double. The largest is red, and the smallest 

 green, and they are of the 6th and 9th magnitude. 



In 1782.4, Sir W. Herschel found the angle of position of 

 this star to be 29* 9° nf, and the distance of the stars ll".l. 



In 1825.78, Mr South found the angle of position to be 

 6® 55, and the distance 9". 9. A connection between these 

 stars cannot be doubted, as they have a common proper mo- 

 tion of nearly 2" per annum. The apparent orbit is evidently 

 elliptic, and the period is probably 700 years. 



2. 12 Lyncis, R. Asc. Q^ SO'. Decl. N. 59* 37. 



This star is a triple one, the three stars A, B and C being of 

 the 7th, 1\, and 9th magnitudes, and C being of a blue co- 

 lour. The motion of B in 40.81 years is no less than 22°. 74 ; 

 and should this continue uniform, the lapse of fifty-seven 

 years will bring the three stars into one straight line, and in 



