of the Sun and Solar Syftem . 2 j : 
With refpedt to the change of declination I would obferve, 
that the point of A Hercuiis, which m fg. 4, is afTumedasthe 
Apex * of the folar motion is not perhaps the heft felected. A 
fomewhat more northern fituation may agree better with the 
changes of declination of Ardturus and Sirius, which capital 
ilars may perhaps be the moil proper to lead us in this hypo- 
thecs ; but as we fhould be guided by facts in refearches of this 
nature, it may be as well to expedt the afliftance of future ob- 
iervations before we are too particular in determining this 
point -f . 
It may be expedted I fhould alfo mention fomething concern- 
ing the quantity of the folar motion ; but here I can onlv offer 
a few diftant hints. From the annual parallax of the fixed 
liars, which, from my own obfervations, I find much lefs than 
it ha-s hitherto been proved to be, we may certainly admit 
(without entering into a fubjedt which I referve for a future 
opportunity) that the diameter of the earth’s orbit, at the 
difhance of Sirius or Ardturus, would not nearly fubtend an 
angle of onefecond; but the apparent motion of Ardturus, if 
owing to a tranflation of the folar fvfiem, amounts to no lefs 
than 2 ;/ ,7 a year, as will appear if we compound the two mo- 
tions of 1' 1 1" in right afcenfion, and i' 55" in declination, 
into one lingle motion, and reduce it to an annual quantity. 
* I ufe the terra Apex here to denote that point of fig. 4. wherein all great 
circles, drawn through the fuppofed direction of the motion of the folar fyfiem, 
interfett, and which, in other ftereographic proje&ions, is generally a pole, either 
of the ecliptic or equator. As this point is in the northern or elevated hemi- 
1 pi 1 ere, the fun, by tending to it, may be f.iid to afeehd, and the term Apex may 
perhaps not be an improper one. 
f From the additional teftimony of other capital fiars confidered in the poft- 
feript it now appears, that the point of * Hercuiis is probably as well choien as 
apy we can fix upon in that part of the heavens. 
\ O o z 
Hence 
