which form Binary Systems. 91 



Q^Q years a complete revolution will have been performed. 

 It appears from late observations in 1825, that the small star 

 B has continued its motion, and apparently with an accelerated 

 velocity. 



In 1825 we have 



A, B, Position 64^21' sf. Dist. ^529. 



A, C, Position 35 21 np. Dist. 9'a84. 



S. Castor, R. Asc. 7'^ 23'. Decl. N. 32°ir. 



This star is double, and the two are of the third and 

 fourth magnitudes. That it forms a binary system is fully 

 demonstrated. In consequence of an observation having been 

 made by Dr Bradley so long ago as 1759.8, we have till 

 1823.11, a period of no less than 63.3 years, during which the 

 angle of position varied 61 J°, or on an average 0*.971 annually. 

 The distance of the stars has during that period been un- 

 changed. This indicates a circular orbit at right angles to 

 the line of sight ; but it is most probable that this orbit is el- 

 liptical, and merely projected into a circle, for the observations 

 seem to show that the angular velocity is sensibly retarded, 

 having been 23*^.7 in the first twenty years, 2l°.4 in the next 

 twenty-three years, and only 16°.4 in the last twenty-one 

 years. 



In 1825, the position was 6° 42 sp, and the distance 4''. 77, 

 the angle having varied 1° 41', since 1823.11. 



4. 7 Lemis, R. Asc. 10^ 10'. Decl. N. 20^ 45'. 



This is a quadruple star, A and B, which are both reddish, 

 are close, and pretty unequal ; A and C are extremely un- 

 equal, and A, D excessively unequal. The mean annual mo- 

 tion of A, B, for position is about 0°.30 direct. From 

 1822.44 till 1825.3 the change in the angle of position has 

 been 2° 53', which indicates an acceleration in the motion. 



In 1825.3, the angle of position is 11° 17' sf and the dis- 

 tance 2".716. 



5. 1 Ursw Majoris R. A 11^ 9. Decl. N. 32° 33'. 

 This very remarkable star is double, and the two are of the 

 6th and 6j magnitude. These two stars, undoubtedly con- 



