I. 
[ . 98 ] 
therefore in 1768, if neither of the ffcars had moved, 
ihould have been ~ 5 0 23' o2 // ,2, and 51' 55" in 
declination; but they were obferved to be 5 0 21' 
43", 4, and 49' 48 /; ,7. Ardturus therefore by this 
observation has in 78,257 years gone i 7 1 8 /r , 8 to the 
weft, and 2 7 o6 // ,3 to the fouth, fuppofing y Bootis not 
to have any proper motion. 
On the 5th of April, 1691, the difference in right 
afcenfion between q Bootis and Ardturus was 
21' 33" of mean folar time, = 5 0 24' i4 77 ,o; and 
the difference of declination 50' 45", 6, as in the 
preceding example. The difference of variation in 
right afcenfion is 59", 1, and in declination i 7 8' 7 ,4» 
The difference of right afcenfion therefore at the lat- 
ter end of May, i768,fhould have been 5 0 23' 14^, 9, 
and 51'' 54 // ,o in declination ; but, according to 
obfervation, they were 5 0 21' 43^,4, and 49' 48", 7. 
Ardturus therefore, according to this obfervation, has 
moved i 7 3 1 /x , 5 to the weft, and 2' 05 77 , 3 to the 
fouth in 77,120 years. 
On the 4th of May, 1691, the difference of right 
afcenfion between v\ Bootis and Ardturus was 2i / 33 // 
of mean folar time, = 5 0 24' 1 4 7/ ,3 when allow- 
ance is made for the going of the clock and the er- 
ror of the plane of the inftrument, and the difference 
of declination on the 3d of May = 50' 50", 6. 
According to computation, thofe differences fhould 
have been 5 0 23' 15", 2 and 51 7 59^,0 refpedt- 
ively; but they were obferved to be 5 0 21 7 43", 4,. 
and 4p ; 4 8 // ,7. Ardturus therefore in 77,071 years 
has moved i 7 3 1 8 weft ward, and 2' io 77 ,3 
fouthward. N. B. The zenith- diftance of Ardturus, 
as 
7 
