372 Dr. Herschel’s Account of the Changes that have happened 
Times of the observations. 
Observed 
angles. 
Calculated 
angles. 
Differences. 
Feb. 16, 1782 
7° 37' ».f 
7° 
37' 
o° o' 
April 38, 1783 
5 24 nf 
6 
5 l 
— • 1 27 
Jan. 24, 1800 
3 16 s f 
4 
15 
— 0 59 
Feb. 19, 1800 
3 23 sf 
4 
18 
1 
0 
Or 
Ot j 
March 2 6, 1800 
3 47 rf 
4 
22 
^ 0 35 
Jan. 26, 1802 - 
6 4 sf 
5 
_35_ 
+ 0 29 
Feb. 10, 1803 
3 33 s f 
6 
16 
— 2 43 
March 22, 1803 
6 32 sf 
6 
20 
+ 012 
March 2 6 , 1803 - 
6 21 sf 
6 
21 
0 0 
The difference between the calculated and observed angles, 
contained in the 4th column of the preceding Table, is so little, 
that we may look upon the gradual change of these angles as 
established by observation ; and we may form a calculated esti- 
mate of the time which will be taken up by the mutual revo- 
lution of the two stars. The apparent places x x', being referred 
to their real ones, give the arch hh', which has been described 
in 21 years and 38 days ; and this arch, seen from the centre y, 
is about 6 ° 20' : it follows, that the length of a whole revolution 
of our small star round y Leonis, will be about 1200 years. 
e Bootis. 
This beautiful double star, on account of the different colours 
of the stars of which it is composed, has much the appearance 
of a planet and its satellite, both shining with innate but diffe- 
rently coloured light. 
There has been a very gradual change in the distance of the 
two stars ; and the result of more than 120 observations, with 
