MAGNETIC AND ELECTRIC CO-OPERATION. I 19 



While an electric current is transmitted through 

 the flexible strip of gold-leaf, it is 

 propelled forward or backward, 

 according to the direction of the 

 current up or down. This instru- 

 ment is one of the most available 

 tests of the slightest transmission 

 of an electric current. A glass 

 tube, T, protects it from agitation 

 by currents of air. 



The forcible action developed 

 between magnetic and electric cur- 

 rents is most strikingly manifested 

 by the apparatus of a wheel re- 

 volving between the two vertical 

 poles of a horse-shoe magnet ; as 

 in Fig. 38. By arranging connecting wires in the 

 base-board, the electric cur- 

 rent is made to descend from 

 the axis of the wheel into 

 conducting mercury in the 

 trough, to complete the cir- 

 cuit. A swift rotation of 

 the wheel is thus produced, 

 by the action and reaction de- 

 veloped by the co-operation 

 of magnetic and electric cur- 

 rents. The electro-mechan- 

 ical action is intensified, pro- 

 ducing very swift-revolving 



Fig. 38. 



