WITH MAGNETISM AND ELECTRICITY. 



191 



rent^ an ordinary compass is placed at a proper distance from 

 the spiral of the electro-diamagnet, so that the deflection pro- 

 duced by the current passing through the spiral may be conve- 

 niently measured. The experiments were carried out as fol- 

 lows : — 1. The direction of the current being normal, the com- 

 mutator was caused to rotate, and the bar of bismuth at the same 

 time set in motion to and fro within the induction-spiral. At 

 each elongation of the galvanometric needle, the observer changed 

 the subsidiary commutator, until the arc of oscillation thus mul- 

 tiplied approached its limit-value ; 2nd, the same series of experi- 

 ments was then made with the direction of the current reversed; 

 3rd, with the current again in the normal direction ; 4th, with 

 the reversed current ; and finally, 5th, once more with the nor- 

 mal current ; 6th, the bismuth bar w as exchanged for a thin bar 

 of iron, and its induction measured in the same manner, with the 

 current normally directed. 



