300 PHILOSOPHICAL TRANSACTIONS, [aNNO 1773. 



ence of declination being 3° 1' 2&".g. On the 24th and 26th of May, and 5th 

 of June, 1768, the difference of right ascension between the same stars observed 

 at Oxford was 24^" 44^58 of sidereal time, = 6° W g"A, the difference of de- 

 clination being 2° 58' 24".2. In 1768, the difference of right ascension should 

 have been 2^7 greater, = 6° 9' 3A".g; and the difference of declination l' 3l".7 

 less, = 3° O' 57".2, But they were observed to be 6° 1 1' Q"A, and 2° 58' 24".2. 

 Arcturus therefore in 73.978 years has, by a comparison with this star, moved 

 1' 34".2 westward, and 2' 33".0 southward. 



Again, the difference of declination between Arcturus and tt Bootis was ob- 

 served to be 3° 2' 33".9 on the ]4th of February, 1690, when the difference of 

 right ascension between these two stars was not observed by Mr. Flamsteed. It 

 appears by computation, that the difference of variation in declination between 

 the times of observation was l' 34".5, by which quantity the difference of decli- 

 nation was diminished, and should therefore in 1768 have been 3° o' 59''.4. 

 But it was 2° 58' 24*.2 by actual observation. Arcturus therefore by this obser- 

 vation has moved southward 2' 35".2 in 78.256 years. 



By the foregoing comparisons Arcturus appears to have moved as in the fol- 

 lowing table. 



Years. Westward. Southward. 



By the small star Feb. 1 4, 1690, in 77.237. ... . . 1' 5 \".S5 2' 35".0 



» Bootis Feb. 14, 1690, in 78.257. .Utelj-.'i . 1 18 .8 2 6 .3 



B Bootis April 5, 1691, in 77.120 1 31 .5 2 5 .3 



>i Bootis May 4, I691, in 77.<>71 131.8.. ..2 JO. 3 



1 Bootis May 27, 1692, in 75.1)78 1 28 .4 2 9 .3 



By » Bootis May 27, l6'9?, in 75.978 1 34 .2 2 33 .0 



sr Bootis Feb. 14, 1690, in 78.257 not obs 2 35 .2 



As the quantity of the motion of Arcturus southward in declination, as de- 

 duced from a comparison with » Bootis, differs considerably from the quantities 

 given by the small star and tt Bootis, which agree very nearly together, Mr. H. 

 compared « Bootis with some of the neighbouring stars, as that star, though of 

 the 3d magnitude only, may have a small motion of its own. On the 14th of 

 Feb. 1690, the difference of declination between n and -n- Bootis was observed by 

 Mr. Flamsteed to be = 2° ll'47'''.8. By computation, that difference in 1768 

 should have been 2"" 43^9 less, = 2° 9' 3".g: but it was actually observed to be 

 2° 8' 34 ".3 only The star n Bootis therefore appears by this comparison to 

 have moved southward 29*.6 in 78.257 years. 



On the 27th of May, 1692, » Bootis was observed by Mr. Flamsteed to be 

 1° \\' ZT'.& to the north of tt Bootis, which quantity should by computation be 

 2' 39".l less in 1768, or 2° 8' 58".7- But it was found to be 2° 8' 34'''.3. The 

 star n therefore appears to have moved southward 24'''.4 in 75-978 years. 



On the 2Sth of April, 1693, n Bootis was observed to be 40' 20'''.8 to the 

 .south of f Bootis, a star of the 6th magnitude; and by Mr. H. that difference 



