C 99 ] 
as determined by Mr. Fiamfteed, on the 4th of May, 
is manifeftly erroneous. 
On the 27th of May, 1692, ^ Bootis preceded 
Arfturus in right afcen non by 21' 3 2 /7 , 5 of mean 
folar time, — 5 0 24' io",i, the difference of decli- 
nation being 50 ' 50" ,6. In 75,9 7 B years the 
difference of right afcen lion fhould have been 
5 0 23' ii",8 and 51' 58", o in declination; but 
thofe differences were obferved to be 5 0 2i / 43 // ,4 
and 49 / 48 // ,7 < Ardturus therefore has moved 1/28M4 
weft ward, and 2 / 09'', 3 fouthward. 
On the 27th of May, 1692, Ardlurus preceded 
<tt Bootis in right afcenfion by 24' 3 5 // , 5 of mean 
folar time, — 6° 9' 32", 2, when an allowance is 
made for the going of the clock and the error of the 
plane of the inftrument, the difference of declination, 
being 3° 2' 28''', 9. On the 24th and 26th of May, 
and 5th of June, 1768, the difference of right afcen- 
fion between the fame ftars obferved at Oxford was 
24' 44 // ,5 8 of ftdereal time, —6° ii / 9 / ',i, the 
difference of declination being 2 0 58' 24 / ,2„ In 
1768, the difference of right afcenfion fhould have 
been 2 f, ,‘] greater, —6° 9' 34", 9 ; and the differ- 
ence of declination 1' 31", 7 lefs, = 3 0 o' 57", 2. 
But they were obferved to be 6 3 11' 9", r, and 
2 0 58' 24 // ,2. Ardturus therefore in 75, 978 years 
has, by a companion with this ftar, moved i' 3 4", 2 
weft ward, and 2' 33A0 fouthward. 
Again, the difference of declination between Arc- 
turus and tt Bootis was obferved to be 3° 2' 3 3 /7 ,9 
on the 14th of February, 1690, when the difference 
of right afcenfion between thefe two ftars was not 
obferved by Mr. Flamfteed. It appears by compu- 
O 2 tation, 
