﻿Periodicity of Electrical Waves on Iran Wires. 4U 



I wish to express my great obligation to Prof. John Trow- 

 bridge for the encouragement and suggestions that I have 

 received from him. 



Conclusions, 



1. The self-induction of iron circuits is greater than that 

 of similar copper circuits under very rapid electric oscillations 

 (115 x 10 6 reversals per second). The change in self-induction 

 varies from 3*4 to 4*3 per cent, in the present investigation 

 and increases with decreasing diameters. 



2. The increase in self-induction produces greater damping, 

 and a shortening of the wave-length of 1*5 to 2 per cent. 



3. The permeability ft of annealed iron wire under this rate 

 of alternation is about 385. 



4. For oscillations of the same period, the wave-length 

 along parallel copper wires varies directly with the diameter 

 of the wires. (Range of wires used 0'03915 centim. to 0*1201 

 centim.) The maximum decrease observed is 5 per cent. 



Jefferson Physical Laboratorv, 

 July 24, 1894. 



LIII. Change of Period of Electrical Waves on Iron Wires. 

 By John Trowbridge*. 



IN an investigation upon the damping of electrical waves 

 on iron wires |, I endeavoured to detect a change of 

 periodicity as well as a damping of these waves. On account, 

 however, of the strong damping effect exerted by the magnetic 

 nature of the conductors, not a sufficient number of oscilla- 

 tions could be set up in them to enable one to make conclusive 

 measurements. AVith more powerful means of experimenting 

 I returned to the subject, and I have detected a marked change 

 in the period of electrical waves which is produced by the 

 magnetic nature of the wire. At the same time Mr. Charles 

 E. St. John, working in the Jefferson Physical Laboratory, 

 by an entirely different method, has shown a change in wave- 

 length on iron wire even for the very rapid period of the 

 Hertz vibrator. It will be remembered that Hertz believed 

 that iron wires behaved like copper wires when transmitting 

 very rapid electrical oscillations. Stefan % in a recent paper 

 gives an analysis of electrical oscillations, in which he proves 

 that rapid electrical waves on iron-wire circuits have the same 

 wave-length as those on copper circuits of the same geome- 



* Communicated bv the Author. 



t Phil. Blag. Dec. 1891. 



| Wied. Ann. xli. 1890, p. 422. 



Phil. Mag. S. 5. Vol. 38. No. 234. Nov. 1601. 2 II 



