ST. JOHN. WAVE LENGTHS OF ELECTRICITY. 219 



This anomalous result was referred by Professor Henry to an action of 

 the discharge of a Leydeii jar never before recognized. He here first 

 describes the oscillating character of such a discharge as follows : — 



" The discharge, whatever may be its nature, is not correctly rep- 

 resented (employing for simplicity the theory of Franklin) by the 

 single transfer of an imponderable fluid from one side of the jar to 

 the other ; the phenomena require us to admit the existence of a 

 principal discharge in one direction, and then several reflex actions 

 backward and forward, each more feeble than the preceding, until 

 equilibrium is obtained. All the facts are shown to be in accordance 

 with this hypothesis, and a ready explanation is afforded by it of a 

 number of phenomena which are found in the older works on elec- 

 tricity, but which have until this time remained unexplained." 



The ap[)arent change in the direction of the induced currents with a 

 change in distance between the primary and secondary circuit, as 

 indicated by a change in the direction of the magnetization of the 

 needle, was shown to be due to the fact that the discharge of the 

 Leyden jar does not produce an induced current in a single direction, 

 but several successive currents in opposite directions. 



There can be no doubt that these discharges were oscillatory in 

 character, and that steel needles and bars were magnetized by them, 

 sometimes by the direct discharge, sometimes by the current induced 

 in a neighboring circuit, sometimes by the first impulse, sometimes by 

 the second or return impulse. 



Feddersen * was of the opinion that iron might show some devia- 

 tion from the behavior of copper and lead ; of the last two he says, 

 that the time between two consecutive like-directed current maxima 

 is independent of the cross section and the specific conducting power 

 of the wires forming the circuit, and also of the density of the accu- 

 mulated electricity. And in regard to iron he adds the following note : 

 " Beim Eisen konnte in Folge der Magnetisirungen eine Abweichung 

 hervortreten: indess zeigt der Versuch dass dieselbe keinenfalls be- 

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

 Electricitat beim Eisen ein grosseres Hinderniss fande als bei den 

 iihrigen Metallen." 



Tlie rate of oscillation obtained by Feddersen was one million per 

 second. 



The late Professor Hertz f gives in his first paper some experi- 

 ments that bear upon this subject. He was of the opinion that an 



* Poggenaorff, Annalen, CVIII. 499. 1859. t Ibid., XXXI. 429. 1887. 



