230 



able scale, reflected by the mirror, was brought to coincide 

 with the fixed wire of the telescope. The differences be- 

 tween each of these readings, and the similar reading when 

 the bar is removed, are double the deflections corresponding 

 to the two positions of the bar ; and, when they are nearly 

 equal, the mean of these deflections may be taken as that due 

 to the induced force. 



FIRST OBSERVATION. 



Acting end of bar a south pole, reading = 14° 8', deflection = 17° 0' 

 north pole, . 82 51, „ = 17 22 



Bar removed, • 48 7, mean = 17 11 



Inclination 



^■ 



Reading Angular 



u 



u 





to vertical. 



of Scale. Differences. 



Observed. 



Calculated. 





+ 14° 30' 



33° 40' 



2-2 



-1°56'.2 



15°14'-8 



13° 14'-5 



+ 0'-3 



+ 10 



29 10 



13-2 



-1 12-4 



15 58-6 



13 37-2 



+ 1-4 



+ 50 



24 10 



23-1 



- 33-0 



16 38-0 



16 37-8 



+ 0-2 







19 10 



31-4 



0-0 



17 11-0 







-30 



14 10 



37-5 



+ 24-3 



17 35-3 



17 36-7 



- 1-4 



- 10 



9 10 



42-8 



+ 45-4 



17 56-4 



17 54-7 



+ 17 



-13 30 



5 40 



45-8 



+ 57-3 



18 8-3 



18 2-7 



+ 5-6 



SECOND OBSERVATION. 



Acting end of bar a south pole, reading = 14° 23', deflections: 16° 36' 



„ north pole, . 82 13, „ = 17 20 



Bar removed, . 47 33, mean = 16 38 



Inclination 



'A- 



Reading 



Angular u 



« 





to vertical. 



of Scale. 



Differences. Observed. 



Calculated. 





+ 15° 0' 34° 10' 



2-6 



- 2° l'-8 



14° 56'-2 



14°57'-8 



- l'-6 



+ 10 



29 10 



14-4 



- 1 14-8 



15 43-2 



15 45-0 



- 1-8 



+ 50 



24 10 



24-8 



- 33-4 



16 24-6 



16 25-2 



- 0-6 







19 10 



33-2 



0.0 



16 58-0 







- 5 



14 10 



40-0 



+ 27-1 



17 25-1 



17 23-3 



+ 1-8 



In the preceding observations a telescope of low power 

 was employed, and the arc-value of a single division of the 



