C 97 ] 
77/287 years. Therefore the right afcenfion of Ardtu- 
rus alters lefs than that of the fta rj and cotvfe- 
q'uently Ardturus Should in 1767 have followed the 
ftar by 42 \ 6 . But the ftir was obferved to follow 
Ardturus by 1 8 ' The right afcenfion there- 
fore of Ardturus has increafed lefs than that of rhe 
ftar, or Ardturus has moved wefiward 1' 51 v , 3 5 in 
77,287 years; and has gone fouthward 2' 3 5" in 
the fame time, fuppofing the fmall ftar not to have 
moved, which is highly probable. 
On the fame day the difference of right afcenfion 
in time between the ftar q Bootis and Ardturus was 
2 1' 32" of mean folar time,= 5 0 24' 02", 2, when a 
proper allowance is made for the going of .he clock, 
and for the error of the plane of the inftrument ; 
and the difference of declination was 50' 45", 6, 
when an allowance is made for refradtion. On the 
24th, 26th, and 29th of May, and the 9th of June, 
of the year 1768, I determined the difference in 
right afcenfion to be 2 1' 27" of fidereal time by the 
two former obfervations, and 21' 26!" by the two 
latter, the difference in declination being 49' 48 // ,7, 
by a mean of the obfervations in May, the extremes 
differing only four feconds. It appears from compu- 
tation, that between the times of obfervation the va- 
riation of v; Bootis in right afcenfion was 337i // >7> 
and 1417", 3, in declination; of Ardturus 33 1 i /r ,7 
in right afcenfion, and 1347", 9 in declination : The 
difference of variation in right afcenfion is 1' o " , 
and of declination 1' 9 // ,4 ; by the former the dif- 
ference in right afcenfion was diminished, and in de- 
clination increafed by the latter, agreeably to the places 
of the two Stars. The difference in right afcenfion 
Vol. LXIII. O there- 
