147 



the effect the parallel wires were replaced by an induction 

 coil as shown in Fig. 51. M is the microphone which is 

 placed in series with a cell and with P, the primary of the 

 induction coil. The secondary of this coil is placed in 

 series with the arc. 



Braun, in the same year, 1 stated that the larger the cur- 

 rent flowing through the arc, the greater the change in the 

 amount of energy of the arc, when a small E.M.F. is in- 



duced in the arc circuit. This would be true if the current 

 in the arc obeyed Ohm's law, but since it does not, we can 

 not find from theory the best conditions for large changes 

 in the energy of the arc. 



Several methods have been used in connecting the micro- 

 phone in the circuit. 2 A very common one is that shown 

 in Fig. 52, where the microphone M is in shunt with an 

 inductive resistance /, so that each change in the resistance 



1 Wied. Ann., 65, 358; 1898. 



2 Ruhmer, Elektrot. ZS., 22, 197; 1901, and 23, 859; 1902. 

 Simon, Elektrot, ZS., 22, 510; 1901. 



Duddell, Lond. Elec., 46, 269; 1900. 



