255 
Motion of the Sun , and solar System, 
The sum of the real motions required, witli the apex of the 
solar motion above mentioned, is less in this Table than that 
in the former by o", 50343. 
In these calculations we have proceeded upon the principle 
of obtaining the least possible quantity of real motion, by way 
of coming at the most favourable situation of a solar apex, and 
have proved that the sum of the observed proper motions of 
the six principal stars, amounting to 5' ',353 4, may be the result 
of a composition of two other motions, and that the real motions 
of these stars, if they could be reduced to their smallest possible 
quantities, would not exceed o ",9559. 
But as I do not intend to assert that these real motions can 
be actually brought down to the low quantities that have been 
mentioned, it will be necessary to show that the validity of the 
arguments for establishing the method I have pursued will not 
be affected by that circumstance. In the first place then, we 
should consider that although the great proper motions of 
A returns, Procyon, and Sirius, are strong indications of their 
being affected by parallax, it does not follow, nor is it probable, 
that the apparent changes of the situation of these stars should 
be intirely owing to solar motion ; on the contrary, we may 
reasonably expect that their own real motions will have a 
great share in them. Next to this, it is evident that in the case 
of parallactic motions the distance of a star from the sun is of 
material consequence ; and as this cannot be assumed at plea- 
sure, we are consequently not at liberty to make the parallactic 
motion sp in Fig. 1, equal to the line sm of the same figure ; 
hence it follows, that the real motion of the star cannot be 
from m to a, as the foregoing calculations have supposed ; but 
will be from p to a. It is however very evident, that if ma be 
