﻿Waves of Magnetic Flux alone/ Iron Wires. 437 



centre o£ the magnetizing solenoid ; while the other two, o£ 166 

 and 805 turns respectively, could be moved from point to 

 point along the rod, the one with the larger number of turns 

 being used for exploring the rod at points near its ends. 



During each series of experiments the magnetizing current 

 and the rate of alternation were kept as constant as possible, 

 and a continuous record was made by a chronograph of the 

 times taken for every 200 periods. 



The method of procedure in any one series of experiments 

 was as follows : — The speed of the rotary converter baying 

 been adjusted to the desired value by means of resistances in 

 the field circuit, or, if necessary, by changing the number of 

 storage-cells used on its direct-current side, the magnetizing 

 current drawn from its alternating side was adjusted by 

 means of resistances to the desired value, and allowed to run 

 until all conductors had attained a steady temperature. 



By means of the wave-tracer equi-spaced ordinates of the 

 magnetizing current wave sufficient in number to determine 

 it were now taken. Then the corresponding ordinates of the 

 flux-waA'es at the centre and at different points along the 

 rod were obtained, and finally the ordinates of the current 

 wave were redetermined to serve as a check on the constancy 

 of the mao-netizino- force during- the run. 



Each set of ordinates was now subjected to harmonic 

 analysis and the results affected by their proper factors * to 

 reduce them either to current or flux, as the case might be. 

 in absolute measure. 



Three frequencies were used with specimens A and C, and 

 two with specimen D, the central or initial flux being approxi- 

 mately the same for the different frequencies in any one 

 specimen. With A and D additional series were obtained at 

 one of the frequencies already used, but with different initial 

 fluxes. For each of the other specimens B, d?„ and d 2 , the 

 results of one series of experiments only are given below. 



For all the specimens but rfj and d 2 , by means of a ballistic 

 galvanometer, using the method of reversals, the fluxes at 

 different points along their lengths, due to a continuous mag- 

 netizing current in the central solenoid, were determined 

 when the continuous current was such as produced at the 

 centre a flux approximately equal to the amplitude of the 

 central alternating flux previously used. 



In addition the statical permeability of the material of each 

 of the specimens for different values of the flux density was 

 obtained by the method of reversals, a long solenoid being- 

 used to carry the magnetizing current. 



* T. R. Lvle, " Wave-Tracer and Analyser," Phil. Mac. vol. vi. p. o±9 

 (1903). 



