﻿502 
  Dr. 
  W. 
  Mansergh 
  Varley 
  on 
  Magnetism 
  induced 
  

   and 
  we 
  obtain 
  for 
  the 
  first 
  amplitude 
  

  

  ,e 
  22 
  V 
  L 
  

  

  -ma, 
  ^^ 
  

  

  which, 
  for 
  the 
  same 
  reason, 
  further 
  simplifies 
  to 
  

  

  i 
  _ 
  Q 
  

  

  •LC 
  

  

  Now 
  Q 
  = 
  VC, 
  where 
  V 
  is 
  the 
  potential-difference 
  between 
  

   the 
  plates 
  immediately 
  before 
  the 
  discharge, 
  so 
  that 
  

  

  -*V£ 
  

  

  We 
  can 
  utilize 
  the 
  two 
  equations 
  

  

  (i.)»=--^, 
  (ii.)w=Vg=m 
  

  

  (where 
  H 
  is 
  the 
  maximum 
  field 
  inside 
  a 
  solenoid 
  included 
  in 
  

   the 
  discharge 
  circuit) 
  for 
  the 
  purpose 
  of 
  the 
  present 
  problem, 
  

   For 
  if 
  we 
  wish 
  to 
  investigate 
  the 
  dependence 
  of 
  the 
  mag- 
  

   netization 
  (B) 
  on 
  the 
  frequency 
  (n) 
  alone, 
  we 
  need 
  only 
  alter 
  

  

  L 
  and 
  C, 
  keeping 
  the 
  ratio 
  -.- 
  unchanged; 
  while 
  to 
  investi- 
  

   gate 
  the 
  dependence 
  on 
  the 
  field-strength, 
  the 
  frequency 
  

   remaining 
  constant, 
  we 
  need 
  only 
  alter 
  L 
  and 
  0, 
  keeping 
  the 
  

   product 
  L 
  . 
  C 
  the 
  same. 
  

  

  In 
  practice 
  it 
  is 
  not 
  possible, 
  nor 
  indeed 
  necessary, 
  to 
  

   fulfil 
  these 
  conditions 
  exactly, 
  but 
  they 
  are 
  so 
  nearly 
  fulfilled 
  

   in 
  the 
  experiments 
  described, 
  that 
  only 
  the 
  simplest 
  inter- 
  

   polation 
  is 
  necessary 
  to 
  reduce 
  the 
  measurements 
  back 
  to 
  the 
  

   ideal 
  case. 
  

  

  In 
  order 
  to 
  determine 
  the 
  magnitude 
  of 
  the 
  maximum 
  

   current 
  (z 
  max 
  .) 
  and 
  the 
  magnetization 
  (B) 
  induced 
  in 
  the 
  iron 
  

   by 
  it, 
  use 
  was 
  made 
  of 
  the 
  deflexion 
  of 
  cathode-rays 
  after 
  

   the 
  method 
  of 
  Braun*. 
  The 
  experiments 
  were 
  so 
  arranged 
  

   that 
  at 
  one 
  time 
  the 
  deflexion 
  was 
  due 
  only 
  to 
  the 
  maximum 
  

   of 
  the 
  magnetizing 
  current, 
  and 
  at 
  another 
  time 
  due 
  only 
  to 
  

   the 
  magnetization 
  induced 
  by 
  the 
  same 
  in 
  the 
  iron. 
  The 
  

   frequency 
  was 
  calculated 
  from 
  the 
  self-induction 
  and 
  capacity 
  

   in 
  circuit. 
  A 
  more 
  detailed 
  description 
  of 
  the 
  method 
  of 
  

   experiment 
  is 
  given 
  in 
  the 
  following 
  paragraph. 
  

  

  3. 
  The 
  oscillatory 
  current 
  was 
  produced 
  by 
  allowing 
  the 
  

   condensers 
  C, 
  consisting 
  of 
  leyden-jars 
  specially 
  fitted 
  up 
  

   so 
  as 
  to 
  give 
  good 
  internal 
  and 
  external 
  contact, 
  to 
  discharge 
  

  

  * 
  F. 
  Braun, 
  Wied. 
  Ann. 
  lx. 
  p. 
  552 
  (1897). 
  

  

  