and Velocity of the Solar Motion . 231 
of which I have given catalogues * would amply furnish me 
with arguments. 
If a still more powerful but more diffused exertion of 
attraction should be required than what may be found in the 
union of clusters, we have hundreds of thousands of stars, 
not to say millions, contained in very compressed parts of the 
milky way, some of which have already been pointed out in 
a former Paper.-f Many of these immense regions may well 
occasion the sidereal motions we are required to account for ; 
and a similarity in the direction of these motions will want no 
illustration. 
With regard to the situation of the condensed parts of the 
milky way, and of the two clusters that have been mentioned, 
we must remark, that the seat of attraction may be in any 
part of the heavens whatsoever ; for when projectile motions 
are given to bodies that are retained by an attractive centre, 
they may have any direction, even that at right angles to its 
situation not excepted. 
It will give additional force to the arguments I have used 
for the admission of far distant centres of attraction, as well 
as projectile motions in the stars that are connected with 
them, when we take notice that, independent of the solar 
motion, and setting that intirely aside, the action of these 
causes will be equally required to explain the acknowledged 
proper motions of the stars. For if the sun be at rest, then 
Arcturus must actually change its place more than 2" a year, 
and consequently this and many other stars, which are well 
known to change their situation, must be supposed to have 
• Phil. Trans, for 1786, page 457 ; for 1789, page 212; for 1802, page 477, 
f Ibid, for 1802, page 495.. 
