tuck. 



At the end of 12 observations, 



the instrument gave . . . 



Index error . ..... 



81 16 



CIRCLE. 509 



Tables for facilitating the Use of the Repeating Circle. Circle. 



TABLE I. Containing the change in the Altitude of the 

 Pole Star, for half an hour on each side of the Meridian. 



55".5 

 3.3 



81 

 360 



16 58.8 



Correctioa 



The first four observations give 



eight 



ten 



twelve . . . . 



12)441 16 58.8 



36 46 24.9 

 4.7 



36 46 20.2 



36 46 22.2 



36 46 19.6 



86 46 21.0 



. 36 46 20.2 



Example of the Use of the general Tables. 



1793.3 



1.292 



coi. D, coi. L ,, /cos. D, con. L\* _. _ 



F= : -rp: ;-r/= [ : =r ; I COt. D L 



sin. (D L) - \ sin. D L / 



Log. 1793.3=3.25358 

 Co. log. 12. =8.92082 

 Log. F =8.49337 



+4."65=0.66777 



Log. 1.2.92=0.11126 

 Co. log. 12=8.92082 

 Log./ =7.11313 



6.14521 



Tab. II. +4."65 

 III. O."00 



-J-4"65= correction, which 

 is very nearly the same as in the preceding example. 



N. B. In using the following Table for observations 

 above the Pole, we must multiply the correction found 

 by the Table by 0.95 ; and for observations below the 

 Pole by 0.88. 



