distances and positions of 380 double and triple stars , &c. 251 
cr Coronae continued. 
circumstances for its measurement. Indeed the distance 
of the centres is less in <r than in a mean of 12 capital 
observations having given us i".455 for the former distance 
on the 5th of June, 1823, while??, on the same extraordinary 
night, measured T.577 ; hut the greater inequality of the 
stars of o- favours their separation. 
To explain these phoenomena we may suppose, first, that 
the orbit is elliptic, and the star approaching its perihelion. 
But this would require a much greater variation of distance 
than appears to have taken place, to produce the effect, 
without the assistance of a second supposition, viz. that of 
the motion being performed in a plane passing nearly through 
the eye. Without therefore going into the minutise of an 
elliptic orbit, let us conceive the small star to describe a cir- 
cle about the large one, in a plane 30° inclined to the visual 
line, and intersecting the plane of projection in the line S A 
which joined the two stars at the moment of the first 
observation. Taking the mean motion in the orbit at 2°.i3 
per annum, after the lapse of any number t of years from 
1781.79, the angle apparently described from A, or the 
angle ASP will be had by the trigonometrical theorem 
tan. ASP — sin 30°. tan ( t x 2°-i3 ). 
And the angle of position/ S P will = 102° 28' — ASP. If 
then we calculate the apparent places by this formula for 
all the times of observation, we get as follows .— 
