![Thumbnail: [Volume 27, 1894 page 496]](/journals/rsnz/images/rsnz_27/thumbnails/rsnz_27_00_0521_0496_ac_02.gif)
Plate XLIX., Fig. 12.
This experiment was arranged after the same method as Hertz's experiments. C and C′ were two conductors of small capacity attached to ends of circuit in order to give discharging circuit a sensible capacity; a b c d was the resonating circuit, m spark-gap in resonator.
When discharge passed across B oscillations were set up in the resonating circuit. The detector was placed in the side c a of the resonator, and when there were three turns of wire round detector deflection fell from 300 to 253.
It was not at all necessary that a spark should occur at m to get an effect on needle, the effect being still considerable when the knobs at m were 1ft. or more apart.
If one side of the rectangle was removed an effect was still observed, but not of such magnitude as when the circuit was in unison with the primary.
![Thumbnail: [Volume 27, 1894 page 497]](/journals/rsnz/images/rsnz_27/thumbnails/rsnz_27_00_0522_0497_ac_02.gif)
In rapidly oscillating fields, therefore, iron is magnetized in open circuit. The rapid surgings in a conductor are quite sufficient to demagnetize iron, and no complete circuit is required. The use of a sensitive detector as a means of investigating waves along wires will be discussed later.
It has been shown that iron still exhibits magnetic properties in fields of over 100,000,000 oscillations per second. A needle may be magnetized or demagnetized in open circuit by the oscillations set up in the wire.
More detailed experiments on the absorption of energy by iron cylinders and resistances of iron wires in rapidly-oscillating fields will now be entered upon.