OF ARTS AND SCIENCES. 115 



X. 



DAMPENING OF ELECTRICAL OSCILLATIONS ON 



IRON WIRES. 



By John Trowbuidge. 



Presented May 27, 1891. 



It has generally been assumed by those who have studied the subject 

 of very rapid oscillutious of electricity, such as occur in Leyden jar 

 discharges, that the magnetic character of the conductor has very 

 little influence upon the character of the discharge. Thus, in a note 

 to an article on electrical waves, W. Feddersen states that electrical 

 oscilhitions may suffer a slight weakening on iron ; but this diminu- 

 tion is very slight : — 



" Beim Eisen konnte in Folge der Magnetisirungen eine Abweichung 

 hervortreten ; in dess zeigt der Versuch, dass dieselbe keiuenfalls be- 

 deutend ist, iibrigens in dem Sinne erfolgen miisste, als wenn die 

 Elektiicitiit beim Eisen ein grossere Hinderniss fande, wie bei den 

 ubrigen Metallen."* 



In Dr. Lodge's treatise on Modern Views of Electricity (ed. 1889), 

 we find the following : — 



" But in the case of the discharge of a Leyden jar iron is of no 

 advantage. The current oscillates so quickly that any iron intro- 

 duced into its circuit, however subdivided into thin wires it may be, 

 is protected from magnetism by inverse currents induced in its outer 

 skin, and accordingly does not get magnetized ; and so far from in- 

 creasing the inductance of the discharge circuit, it positively diminishes 

 it by the reaction effect of these induced currents ; it acts, in fact, 

 much as a mass of copper might be expected to do." (p. 3Go.) 



Fleming writes as follows : — 



" With respect to the apparent superiority of iron it would natu- 

 rally be supposed that, since the magnetic permeability of iron bestows 

 upon it greater inductance, it would form a less suitable conductor for 

 discharging with great suddenness of electric energy. Owing to the 

 fact that the current only penetrates just into the skin of the conductor, 



* Annalen der Physik und Chemie, No. 108, 1859, p. 499. 



