211 
and Velocity of the Solar Motion. 
must be equalized. Therefore, in order to have this required 
equality, let the solar motion be 1", 718865 then will a velocity 
of 1399478 in Arcturus, and 1399842 in Aldebaran, which 
are sufficiently equal, occasion such angular real motions in 
the two stars as will bring them, when compounded with 
their parallactic motions, to the apparent places in which we 
find them by observation. 
Before we proceed, it will be proper to obviate a remark 
that may be made against this way of equalization or approach 
to equality. We have said that the calculated velocities are 
such as would be true if the stars were at the assumed dis- 
tances, and if their real motions were performed in lines at 
right angles to the visual ray ; to which it may here be ob- 
jected that the last of these assumptions is so far from having 
any proof in its favour that even the highest probability is 
against it. We may admit the truth of what the objection 
states, without apprehending that any error could arise on 
that account, if the solar motion were determined by this 
method. For if the stars do not move at right angles to the 
visual ray, their real velocity will exceed the calculated one ; 
so that in the first place we should certainly have the mini- 
mum of their velocities : and if we were obliged, for want of 
data to leave the other limit of the motion unascertained, it 
must be allowed to be a considerable point gained if we could 
show what is likely to be the least velocity of the solar 
motion ; but a more satisfactory defence of the method is, 
that if we were to assume a mean of all the angular devia- 
tions from the perpendicular to the visual ray that may take 
place in the directions of the real motions of the stars, the 
only position we could fix upon as a mean would be an 
E e 2 
