coil or transformer, a current of low pressure is transformed into a current of high pressure, but of low frequency, and this high-pressure current is utilized to charge the Leyden jars.
When the Leyden jars are fully charged (which action takes place almost instantaneously), the resistance of the spark-gap is “broken down,” and the oscillatory discharge takes place between the points of the spark-gap.
11. The Inductance
In order to successfully utilize the high-frequency oscillations due to the discharge of the Leyden jars across the spark-gap, a controlling device is necessary which shall vary the electrical inertia of the circuit into which these oscillations are to be delivered.
Adjustment is obtained by varying the number of turns of wire in the oscillating circuit. In Fig. 7 the inductance is represented by the spirals in the connecting wire between the Leyden jars and the spark-gap. In practice the inductance usually consists of a dozen or so turns of copper wire, about ⅛ inch in diameter, wound spirally around a wooden frame. In Fig. 6 the inductance is shown placed around the spark-gap; this, however, is simply a matter of design.
Referring again to Fig. 7, one side of the inductance is permanently connected to the ground. There are two other wires flexibly connected to the inductance,