[ 10 + 1 
putation.the variation in the difference of right af- 
eenffoiv was i6'' / ,o,by which the afcenfional differ- 
ence fhould'have been diminiihed, and — 5°2 2 / 09 ",0. 
But by obfervation it was found — 5 0 21' 43", 4: 
Ar&urus therefore by this laft oblervation appears to 
have gone 25,6/' weffward. 
Bv the observations therefore at Shirburn Caftle 
Arcturus appears to have gone weffward as in the 
following table ; in the laft column of which are 
contained the quantities refulting from the obferva- ' 
tions of each year, reduced to 78 years. 
/ // 
/ // 
1741 
0 35>° 
I 41,11 
1744 
0 28,3 
1 3 1 =97 
1746 
0 26,1 
1 3 2 >59 
1 747 
0 25,6 
1 34,90 
Mean 1 35,14 
The mean of all the obfervations, when reduced 
to an interval of 78 years, is T 35 // , 1 4> which dif- 
fers only 1 ",17 from the mean of the other com- 
parifons. 
As then the proper motions of Ardturus weffward 
in right afcenfion =z i / 33 // ,974> and 2' 36", 81 in de- 
clination fouthward, feem well eftablifhed; the real 
motion of Ardturusis inclined in an angle of 30° 56' 
to the weft of the meridian or horary circle, and to be 
in that direction 3' 2", 81 in 78 years, or at the 
rate of 2", 343 in a year. As this dire&ion of its 
motion is nearly perpendicular to the plane of the 
ecliptic, the latitude of Ar&urus muft diminilh yearly 
aim oft in the fame proportion j and its longitude will 
alter lefs than that of other ftars, though not fo con- 
fiderably as its right afcenfion. 
The 
