236 Dr. Herschel on the Quantity 
the form of “ Thoughts"' on the subject;* but I believe, 
from what has been said in this Paper, it will now be found 
that we are within the reach of a link of the chain which 
connects the principles of the solar and sidereal motions with 
those that are the cause of orbitual ones. 
A discovery of so many hitherto concealed motions, pre- 
sents us with an interesting view of the construction of that 
part of the heavens which is immediately around us. The 
similarity of the directions of the sidereal motions is a strong 
indication that the stars, having such motions, as well as the 
sun, are acted upon by some connecting cause, which can 
only be attraction ; and as it has been proved that attraction 
will not explain the observed phenomena without the ex- 
istence of projectile motions, it must be allowed to be a 
necessary inference, that the motions of the stars we have 
examined are governed by the same two ruling principles 
which regulate the orbitual motions of the bodies of the solar 
system. It will also be admitted that we may justly invert 
the inference, and from the operation of these causes in our 
system, conclude that their influence upon the sidereal mo- 
tions will tend to produce a similar effect ; by which means 
the probable motion of the sun, and of the stars in orbits, 
becomes a subject that may receive the assistance of argu- 
ments supported by observation. 
What has been said in a paragraph of a former Paper, 
where the sun is placed among the insulated stars,' f does 
not contradict the present idea of its. making one of a very 
extensive system. On the contrary, a connection of this na- 
'* See the note Phil. Trans, for 1783, page 283. f Ibid, for 1802, page 478. 
