in the relative Situation of double Stars. 383 
The position, Nov. 2, 1779, was 84° o' south-following.,* Oct. 
10, 1780, it was 86° 5'; and, Feb. 7, 1802, it was 89° 10'. The 
change, in 22 years and 97 days, is 5 0 10'. From the given right 
ascension and declination of the two stars, in Mayer’s Catalogue, 
we compute, that their position in 17 56 was 78 a 46' south- 
following; which gives a change of 5® 14', in 23 years and 306 
days, up to the time of my first observation. The two periods, 
which are nearly equal, give a change of io° 24', for 4 6 years 
and 38 days. A motion of y Arietis, arising from systematical 
parallax, by which we may admit the smallest of the two stars 
(on account of its supposed greater distance) not to be so much 
affected as the large one, will perfectly account for the change ; 
unless, hereafter, the proper motion of this star, when known,, 
should lead to a different conclusion. 
| Ur see. I, 2. 
This double star has undergone a very extraordinary change 
in the angle of position. Dec. 19, 1781, the smallest of the two 
stars was 53 0 47' south-following. Feb. 4, 1802, it was 7 0 31'; 
and, January 29, 1804, the position was only 2 0 38'. This gives 
a motion of 51 0 9', for 22 years 41 days, and amounts to 2 0 19'' 
per year. If an annual alteration to this amount should continue 
to take place for the future, a very few years would be sufficient 
to ascertain the cause of tills change, as no motion but a re- 
volving one could possibly explain the phenomenon. If, on the 
contrary, the parallactic motion of the largest star should have 
occasioned the change of situation, which is not impossible, it 
will soon be verified by an increased distance of the two stars, 
* This position, for reasons- explained in the note to p Serpentarii, page 374, has. 
not been given in my Catalogue, 
