Introduction. 



XXV 



If n he tlie number of scale di-visions from the zero or reading for u = 90°, when 

 i/ = vdt:^, N the number from the zero, for the same force, if v had its normal 

 value, then 



sm V — smv cos v 



N = TTt— — =fc n 



a. cos V cos V' 



or adapting the first constant to logarithmic computation, 



2 sin I 



cos 



a COS V 



= A + w B. 



(-0 



W- I + w 



COS® + /3 



COS V 



jS is considered negative when v is diminished, and n is negative when the reading 

 is below the zero. 



The following are the values of /3, A, and B, used in reducing the extra obser- 

 vations : — 



Table 9. — Constants for the Reduction of Observations after altering the reading 



of the Torsion Circle. 



Periods to which the quantities 

 apply. 



Angle V. 



/3. 



A. 



B. 





1841. 



(I. h. m. d. h. m. 



o , 



Q ' 







Sept. 



7 23 0—30 5 



65 2 



+ 50 



+ 43-8 



0-969 



Sept. 



25 4 0—25 5 20 



65 52 



+ 60 



+ 282-4 



0-761 





25 5 20—25 5 25 



65 52 



+ 40 



+ 196-8 



0-842 





25 5 25—25 5 40 



65 52 



+ 30 



+ 150-8 



0-882 





25 5 40—25 5 50 



65 52 



+ 50 



+ 240-7 



0-802 





25 5 50—25 6 25 



65 52 



+ 30 



+ 150-8 



0-882 





25 6 25—25 7 



65 52 



+ 20 



+ 102-6 



0-921 



Oct. 



6 20 0—19 20 

 1842. 



69 6 



- 50 



- 45-3 



1-038 



July 



2 10 16— 2 13 



69 6 



- 2 22-5 



- 133-7 



1-108 



Adjustments. 



29. The scale of the collimator contains 280 divisions with the graduation at 300. 

 Determination of the angular value of 1 scale division : — 



MAG. AND met. OBS., VOL. I. 



