﻿in 
  Iron 
  by 
  Rapidly 
  Oscillating 
  Current-fields. 
  505 
  

  

  5. 
  As 
  stated 
  in 
  § 
  2, 
  we 
  wish 
  to 
  determine 
  (1) 
  the 
  deflexion 
  

   due 
  to 
  the 
  maximum 
  of 
  the 
  magnetizing 
  current, 
  and 
  (2) 
  that 
  

   due 
  to 
  the 
  magnetization 
  induced 
  by 
  the 
  same 
  in 
  the 
  bundle 
  

   of 
  iron 
  wires 
  under 
  consideration. 
  For 
  this 
  purpose, 
  the 
  two 
  

   coils 
  L 
  2 
  and 
  L 
  3 
  were 
  first 
  connected 
  up 
  so 
  as 
  to 
  act 
  in 
  the 
  

   same 
  sense 
  on 
  the 
  cathode-rays, 
  and 
  the 
  iron 
  was 
  placed 
  in 
  

   the 
  distant 
  solenoid 
  L 
  x 
  . 
  The 
  deflexion 
  obtained 
  on 
  closing 
  

   the 
  primary 
  circuit 
  of 
  the 
  induction-coil, 
  after 
  connecting 
  

   up 
  the 
  required 
  self-induction 
  and 
  capacity 
  in 
  the 
  secondary 
  

   circuit, 
  was 
  that 
  due 
  to 
  the 
  maximum 
  of 
  the 
  magnetizing 
  

   current 
  — 
  which 
  for 
  shortness 
  we 
  shall 
  call 
  simply 
  the 
  

   " 
  current." 
  The 
  direction 
  of 
  the 
  current 
  through 
  L 
  3 
  was 
  

   now 
  reversed, 
  so 
  that 
  the 
  cathode-rays 
  were 
  undetected, 
  and 
  

   the 
  spot 
  in 
  its 
  position 
  of 
  rest, 
  the 
  iron 
  brought 
  from 
  the 
  

   solenoid 
  L 
  x 
  and 
  placed 
  in 
  L 
  2 
  . 
  The 
  deflexion 
  now 
  obtained 
  

   was 
  due 
  only 
  to 
  the 
  magnetization 
  induced 
  in 
  the 
  iron 
  by 
  the 
  

   current 
  just 
  determined. 
  The 
  experiments 
  were 
  repeated 
  

   after 
  suitably 
  altering 
  the 
  values 
  of 
  the 
  self-induction 
  and 
  

   capacity 
  in 
  circuit. 
  

  

  In 
  order 
  that 
  the 
  " 
  current 
  " 
  and 
  frequency 
  may 
  remain 
  

   unaltered, 
  the 
  iron 
  must 
  occupy 
  the 
  same 
  relative 
  position 
  in 
  

   the 
  solenoids 
  L 
  ± 
  and 
  L 
  2 
  , 
  and 
  must 
  in 
  fact 
  be 
  placed 
  in 
  the 
  

   same 
  positions 
  throughout 
  a 
  series 
  of 
  measurements. 
  

  

  The 
  value 
  of 
  the 
  " 
  current" 
  was 
  determined 
  by 
  calibrating 
  

   the 
  tube 
  by 
  means 
  of 
  direct 
  current 
  deflexions, 
  the 
  currents 
  

   being 
  measured 
  directly 
  by 
  a 
  Weston 
  ammeter. 
  The 
  mag- 
  

   netizations 
  induced 
  in 
  the 
  iron 
  by 
  the 
  oscillatory 
  currents 
  

   were 
  similarly 
  compared 
  with 
  those 
  induced 
  by 
  direct 
  currents 
  

   of 
  the 
  same 
  strength. 
  Measurements 
  showed 
  that 
  when 
  the 
  

   self-induction 
  and 
  spark-gap 
  were 
  kept 
  constant, 
  the 
  deflexions 
  

   due 
  to 
  the 
  oscillatory 
  currents 
  were 
  proportional 
  to 
  the 
  square 
  

   root 
  of 
  the 
  capacity 
  in 
  circuit, 
  proving 
  that 
  for 
  the 
  frequencies 
  

   used 
  the 
  cathode-rays 
  possessed 
  no 
  detectable 
  inertia. 
  In 
  

   order 
  to 
  be 
  able 
  to 
  vary 
  the 
  frequency 
  within 
  wider 
  limits, 
  

   two 
  sets 
  of 
  coils 
  were 
  used, 
  the 
  coils 
  of 
  each 
  set 
  having 
  re- 
  

   spectively 
  645 
  and 
  140 
  turns. 
  It 
  is 
  easy 
  to 
  see 
  that 
  by 
  the 
  

   substitution 
  of 
  one 
  set 
  of 
  solenoids 
  for 
  the 
  other 
  in 
  the 
  

   secondary 
  circuit, 
  other 
  self-inductions 
  being 
  absent, 
  and 
  

   the 
  capacity 
  and 
  sparking 
  potential 
  remaining 
  the 
  same, 
  

   the 
  magnetizing 
  force 
  inside 
  the 
  solenoids 
  will 
  remain 
  prac- 
  

   tically 
  unaltered, 
  as 
  also 
  the 
  " 
  current 
  " 
  deflexions, 
  thus 
  

   affording 
  an 
  excellent 
  means 
  of 
  obtaining 
  wide 
  variations 
  in 
  

   the 
  frequency 
  of 
  oscillation 
  for 
  our 
  purpose. 
  The 
  more 
  exact 
  

   comparison 
  or 
  reduction 
  of 
  the 
  measurements 
  was 
  carried 
  out 
  

   in 
  the 
  following 
  manner 
  : 
  — 
  

  

  For 
  the 
  first 
  systems 
  of 
  solenoids 
  let 
  lSJ^ai', 
  and 
  

  

  