62 



NOMOS. 



passage of a current. The experiment is simple 

 and familiar. The instrument by which it is made 



Fig. 14. 



consists of two parts the moveable spiral conductor, 

 and an appropriate wooden stand. The moveable 

 conductor is a coil of insulated copper-wire, with 

 the ends arranged as in the figure. The stand is 

 furnished with two concentric troughs (each of 

 which is in connexion with a binding screw) and a 

 central pivot. When in position the moveable 

 spiral conductor is balanced horizontally upon the 

 pivot, with the free ends hanging down, one into 

 one trough, and the other into the other. In pre- 

 paring for action the troughs are filled with mer- 

 cury, and the electrodes of a battery are connected 

 with the binding screws ; and when this is done, the 

 moveable conductor becomes part of the circuit, the 

 current entering and leaving it by the ends which 

 dip into the mercury contained in the troughs. 



