quantities. The six prineipal stars, whose intersecting arches have been given, when their proper motions in right ascension and polar distance are brought into one direction, will have the apparent motions contained in the following Table.
Names of the
Direction of the apparent
Quantities of the apparent
|Sirius –||68°||49'||40",7||south-preceding||1",11528||per year|
|Lyra – –||56||20||57,3||north-following||0,32435||————|
|Sum of the apparent motions||5",35337|
We must now recur to what has been said, when the construction of the triangle expressing the three motions of a star, that is not at rest, was explained; and, as we are to find out a solar motion which will require the least real motion in our six stars, an attention to this triangle will be of considerable use; for when the line p a, Fig. 1, which represents the real motion, is brought into the situation m a, where it is perpendicular to s p, the real motion which is required will then be a minimum. It also follows, from the construction of the same triangle, that if by the choice of an apex for the solar motion we can lessen the angle made at s by the lines s p and s a, we shall lessen the quantity of real motion required to bring the star from the parallactic line s p m to the observed position a.
It has already been shown, in the case of Sirius and Arcturus,