230 



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

 witli 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 



SECOND OBSERVATION. 



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



„ north pole, . 82 15, „ = 17 20 



Bar removed, . 47 35, mean = 16 58 



In the preceding observations a telescope of low power 

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



