Electric Resonators 345 
celebrated experiments of Hertz, which in turn have 
formed the point of departure for wireless telegraphy. 
It is known also that such an electric resonator has 
been rightly compared to a vibrating dynamic system, to 
a pendulum which has an oscillation time of its own, to a 
sounding chord which the smallest impulses having the 
same frequence as itself can set in vibration, even in 
strong vibration. What happens in it is a continual 
periodic transformation of energy. At the instant when 
the sinusoidal alternating current reaches its maximum 
intensity, one has the maximum of actual energy, while 
the condenser, on the other hand, possesses then no 
potential energy whatever. At the instant when the in- 
tensity of the current drops to nothing, the condenser 
shows the greatest deformation of the respective di- 
electric, and possesses thus a potential energy fully equal 
to the actual energy possessed by the discharge at the 
moment of its greatest intensity, the process being thus 
exactly the same as in a pendulum in which potential 
energy is transformed continually into actual and vice 
versa. 
Tt will be sufficient here, for the purpose of a remote 
comparison, to note the fact just indicated that a sinu- 
soidal alternating electro-motive force induced in such an 
electric resonator, which need amount only to a very few 
volts, provided that it be of the same frequency as the 
oscillating discharge, will be able to induce in A and B 
differences of tension which may amount to many volts. 
For if we assume in the current so oscillating the faculty 
of depositing in each of the armatures of the condenser 
infinitely small particles of substance in series one after 
the other, so long as the total of their mass and the con- 
sequent electro-motor force does not surpass the electro- 
