Damping of Electrical Oscillations on Iron Wires. 505 



stored up in the dielectric, which would not be the case if it 

 were copper."* 



" In the experiments on alternative path," as described by 

 Dr. Lodge, " the main result is very briefly summed up by 

 saying that, where a sudden discharge had to pass through a 

 conductor, it was found that iron and copper acted about 

 equally well, and indeed iron sometimes exhibited a little 

 superiority, and that the thickness of the conductor and its 

 ordinary conductivity mattered very little indeed. In the 

 case of enormously rapid oscillations the value of the impul- 

 sive impedance varies in simple proportion to the frequency 

 of the oscillations, and depends on the form and size of the 

 circuit, but not at all on its specific resistance, magnetic per- 

 meability, or diameter For discharges of a million per 



second and upwards, such as occur in jar-discharges and per- 

 haps in lightning, the impedance of all reasonably conduct- 

 ing circuits is the same, and independent of conductivity and 

 permeability, and hardly affected by enormous changes in 

 diameter" t- 



Turning now to the observations of Hertz, we find it stated 

 that the material, resistance, and diameter of the wire of 

 the micrometer-circuit employed by him have very little 

 influence on the result. The rate of propagation of an elec- 

 trical disturbance along a conductor depends mainly on its 

 capacity and coefficient of self-induction, and only to a small 

 extent on its resistance. Hertz concludes that, owing to the 

 great rapidity of the alternations, the magnetism of the iron is 

 unable to follow them and therefore has no effect on the self- 

 induction. When a portion of the micrometer-circuit em- 

 ployed by Hertz was surrounded by an iron tube, or replaced 

 by an iron wire, no perceptible effect was obtained; and thus 

 the result was apparently confirmed that the magnetism of 

 the iron is unable to follow such rapid oscillations and there- 

 fore exerts no appreciable effect. The velocity of propagation 

 in a wire has a definite value independent of its dimensions 

 and material. Even iron wires offer no exception to this, 

 showing that the magnetic susceptibility of iron does not play 

 any part in the case of such rapid motions J. 



* Fleming's 'The Induction of Electric Currents,' p. 398. The author 

 describes in full Dr. Lodge's experiments to prove the nonmagnetizability 

 of iron by sudden discharges. 



t Fleming, 'The Induction of Electric Currents,' p. 411. 



\ " Ersetzen wir den bisherigen Kupferdraht durch einen dickeren 

 oder diinneren Kupferdraht oder durch einen Draht aus anderem Metall, 

 so behalten die Knoten-punkte ihre Lage bei. Die Fortpflanzungs- 

 geschwindigkeit in alien solchen Drahten ist daher gleich, und wir 

 sind berechtigt von derselben als einer bestiuimten Geschwindigkeit zu 



