26 Investigation of the Correctiuns 



K. The effect of the diurnal aberration is simply to cause 

 every object to approach in a minute degree toward the eastern 

 point of the horizon, the maximum, which occurs on the me- 

 ridian, being ",313; so that a transit instrument, exactly 

 perpendicular to its axis, would leave the circumpolar stars a 

 little longer to the east than to the west, and their culmination 

 above the pole would be a little too late, and their inferior 

 transit too early : but the difference can scarcely ever become 

 sensible. 



L. The value of the solar and lunar nutation becomes, ac- 

 cording to the computations of Lindenau and Bessel, neglecting 

 the thousandths of a second, 



a.' — uzz — 15',40 sin. ^ 



— ( 8",98 COS. Q cos.a + G^GS sin. Q sin. a) tang. S 



+ ",09 cos. 2 g^ COS. « tang, i 



— 1",14 sin. 2 O 



— ( 0",58 COS. 2 O COS. » + ',50 sin. 2 © sin. «) 



tang. ^ 



— ',18 sin. 2 < 



— ( ",09 COS. 2 ( cos. a. + ',08 sin. 2 ( sin. *) 



tang. ^ 

 J' — J = 8 ",98 cos. a sin. « — 6 ",68 sin. Q cos. « 



— ",09 cos. 2 gj sin. a 

 + ',58 cos. 2 O sin. a — ',50 sin. 2 © cos. « 

 + ',09 cos. 2 i sin. a — '",08 sin. 2 ( cos. «. 



It is obvious that if we wish to take account of every 

 hundredth of a second, it is quite necessary to introduce all 

 these terms into the computation ; but it can only be for the 

 most refined researches of philosophical astronomy that any 

 thing like such a degree of accuracy can be at all required ; 

 much less can it be worth our while to pay the least attention 

 to the terms of the higher orders, and the effects of the nuta- 

 tion on the aberration, with which Professor Bessel has found 

 it agreeable to amuse himself. He has given an example of the 

 results of the whole calculation, in a table for finding the true 

 place of the pole star, adapted to its situation at the begin- 



