Pole of a Magnet upon t^ on-magnetic Bodies. 129 



Distance of the 



position of rest 



from 0. 



Observed repul- 

 sion. 



Divisions 

 of scale. 



millims. 



Divisions 



of scale. 



B. 



millims 

 A. 



Distance of the pole of 



the magnet from the 



central point of action 



in the ball. 



Millims. 



Time of 

 vibra- 

 tion. 



Seconds. 



Repulsive force, 

 milligram. 



Observed. Calculated. 



10-488 

 69-250 

 43-670 

 21-205 



1-2223 



8-0889 

 5-1010 

 2-4769 





 58-762 

 33-182 

 10-717 





 6-8666 

 3-8787 

 1-2546 



x-\- 8-0889 

 .r+151010 

 .r+32-4769 



350-5 

 280-8 

 307-4 

 3337 





 009038 

 0-04260 

 0-01169 





 009038 

 0-04084 

 001042 



The last column i.s calculated upon the assumption that x, 

 i. e. the distance of the pole of the magnet when close to the 

 case from the central point of action in the ball, is 1504' mil- 

 limetres for the position of the torsion-rod at 0, and that the 

 repulsive force acts in an inverse ratio to the third power of 

 the distance. The differences do not exceed the possible 

 error of observation. 



At the distance of 15 millimetres from the surface of the 

 case, and with the position of the rod at of the scale, scarcely 

 the surface of the ball is attained, which would show that the 

 principal action is upon the nearest surface of the ball. 



A second observation gave the following measures of re- 

 pulsion : — Millims. 

 For the magnet close to the case . . . 7*388 

 At a distance of 10 millims. from the case 4*365 

 20 ... 2-64.1 

 30 ... 1*628 

 40 ... 0*856 



Since, however, the corresponding periods of vibration were 

 not observed, the repulsive force exerted in each instance can- 

 not be calculated from them. That the effect was found to be 

 greater on this occasion, is explained by the circumstance of 

 the position of rest of the rod, with the magnet removed, being 

 on an average at 0*994 of the scale instead of, as in the first 

 series of experiments, at 10*488 divisions, so that consequently 

 the distances vvere less than in the first observation. 



A third series of experiments were undertaken after the ball 

 of bismuth had been suspended from the north end of the rod. 

 In this instance it approached less close to the case than pre- 

 viously on the south side, as will be seen in the followuig tiom 

 the determination of :r. 



The direct observations gave — 



Position of rest in 

 divisions of the scale 



With the magnet removed . 72*6229 



Magnet close to the case . 33*2583 



At 10 millims. distance . . 50*1167 



At 20 ... distance . . 58*46875 



At 30 ... distance . . 63*73125 

 PhiL Mag. S. 3. Vol. 34. No. 227. Feb. 1849. 



Duration of vibra- 

 tion in seconds. 

 349*46 

 301*59 

 323*75 

 336-56 

 342*44 

 K 



