37 4 * Z)/\ Herschel’s Account of the Changes 
system, it follows, that the parallax arising from this principle, 
cannot account for the motion, of both the sets of double stars: 
it may explain the change of the preceding, but not of the fol- 
lowing one. The situation of both, however, is in a part of the 
heavens which is so rich in scattered small stars, that a variety 
of casual, and merely apparent combinations may be expected. 
p Serpentarii FI. 70. II, 4. 
The alteration of the angle of position, that has taken place in 
the situation of this double star, is very remarkable. Oct. 7, 
1779, the stars were exactly in the parallel, the preceding star 
being- the largest ; the position therefore was o° o' following.* 
Sept. 24, 1781, it was 9 0 14' north-following; and, May 29, 
1804, it was 48° 1 7 north-preceding; which gives a change of 
1 3 1 ° 59 r > in 24 years and 234 days. This cannot be owing to 
the effect of systematical parallax, which could never bring the 
small star to the preceding side of the large one. 
x Ophiuchi . I, 83. 
The position, March 9, 1783, was 14 0 30' north-following. 
May 20, 1802, it was 20° 41'. The difference, in 19 years and 
72 days, is 6'° 11 7 . March 9, 1783, the distance, with 460, was 
|or| diameter of the small star. May 1 and 2, 1802, I could 
not perceive the small star, though the last of the two evenings 
was very fine. May 20, 1802, with 327 , 1 saw it very well, but 
* The first position was not given in my Catalogue, as I had no reason to suppose, 
at the time of its publication, that the positions of the stars were liable to any pro- 
gressive change. It may be remembered, that my principal aim was, if possible, to 
find out some small annual variation, or libration of position, which might lead to a 
discovery of the parallax of the fixed stars. 
