210 Dr. Herschel on the Quantity 
trary change from 0,53 to 0,86 and to i",i8. We may also 
notice that Capella and Aldebaran, which have a negative 
sign prefixed to their real motions when the solar motion is 
i",o are affected differently from Arcturus, Sirius, and Pro- 
cyon, which have a positive sign ; and that even the motions 
of the two last become negative when the solar motion is 
increased beyond a certain point. It may be easily understood 
that the motion of Arcturus itself would become negative 
were we to increase the solar motion till the parallactic mo- 
tion of this star should exceed its apparent motion. 
From these considerations it appears, that a certain equa- 
lization, or approach to equality may be obtained between the 
motions of the stars, or between that of the sun and any one 
of them selected for the purpose ; for instance, the motions 
of Arcturus and Aldebaran being contrary to each other, may 
be made perfectly equal by supposing the sun's annual 
motion to be 1 ",85925. For then we shall have the real 
annual motion of Arcturus towards the parallactic centre 
i",°9i, and that of Aldebaran towards the opposite part of 
the heavens, in which the solar apex is placed, will be i",o9i 
likewise ; the first in a direction 55 0 29' 39" south-preceding, 
the latter 88 e 16' 31" north-following their respective parallels ; 
and a composition of these motions with the parallactic ones 
arising from the given solar motion, will produce the appa- 
rent motions of these stars which have been established by 
observation. But since Arcturus, by the hypothesis which 
has been adopted in Table VIII. is a nearer star than Alde- 
baran, the velocities of the real motions, describing these 
equal arches will be 1309109 in the former and 1527780 in 
the latter. And it is not the arches but these velocities that 
