gap of an induction coil, on the other and free end of which were soldered a couple of sheets of copper. (See the accompanying picture.)
He also devised a simple apparatus to detect the presence of these waves—that is, to receive them, which he called a
resonator, and this was a cut wire ring with a little brass ball on each of its ends as shown in the following diagram. Now when Hertz set his induction coil going, streams of sparks were set up in the spark-gap of the oscillator and
electric oscillations, or high-frequency currents, surged from one of the copper plates to the other and back again, and
