﻿560 
  Williams 
  — 
  Twist 
  in 
  Steel 
  and 
  Nickel 
  Rods. 
  

  

  heat 
  treatments. 
  Once 
  the 
  rods 
  were 
  annealed 
  it 
  would 
  be 
  

   impossible 
  to 
  come 
  back 
  to 
  the 
  condition 
  they 
  are 
  now 
  in 
  and 
  

   which 
  from 
  a 
  magnetic 
  standpoint 
  is 
  exceedingly 
  interesting. 
  

   I 
  want 
  a 
  series 
  of 
  comparative 
  studies 
  on 
  them 
  in 
  their 
  present 
  

   state. 
  

  

  In 
  the 
  graphs 
  I 
  have 
  indicated 
  the 
  direction 
  of 
  the 
  motion 
  

   of 
  the 
  films 
  by 
  a 
  long 
  arrow 
  and 
  the 
  twist 
  is 
  marked 
  by 
  R 
  and 
  

   L 
  to 
  indicate 
  whether 
  the 
  lower 
  end 
  of 
  the 
  rod 
  when 
  viewed 
  

   from 
  above 
  twisted 
  clockwise 
  or. 
  counter 
  clockwise. 
  The 
  

   photos 
  are 
  shown 
  as 
  though 
  one 
  stood 
  behind 
  a 
  transparent 
  

   screen 
  and 
  viewed 
  the 
  deflections 
  in 
  that 
  way. 
  The 
  graphs 
  

   are 
  numbered 
  along 
  the 
  left 
  hand 
  margin 
  of 
  the 
  photos 
  and 
  

   the 
  letters 
  T„ 
  T 
  2 
  , 
  T 
  3 
  , 
  etc., 
  refer 
  to 
  the 
  way 
  in 
  which 
  the 
  films 
  

   were 
  catalogued 
  in 
  my 
  collection 
  of 
  films. 
  

  

  Discussion 
  of 
  Results. 
  

  

  I 
  have 
  spoken 
  of 
  having 
  demagnetized 
  the 
  rods 
  by 
  a 
  decreas- 
  

   ing 
  A. 
  C. 
  sent 
  through 
  the 
  solenoid. 
  It 
  was 
  found 
  that 
  no 
  

   matter 
  which 
  end 
  of 
  the 
  rod 
  was 
  up 
  the 
  rod 
  always 
  showed 
  

   permanent 
  magnetization 
  downwards 
  after 
  each 
  demagnetiza- 
  

   tion. 
  Not 
  only 
  was 
  this 
  permanent 
  magnetization 
  independent 
  

   of 
  the 
  end 
  which 
  was 
  up 
  but 
  also 
  it 
  was 
  independent 
  of 
  the 
  

   direction 
  of 
  the 
  previous 
  magnetic 
  field. 
  In 
  every 
  case 
  the 
  

   remanent 
  magnetism 
  was 
  directed 
  downwards. 
  If 
  a 
  steel 
  rod 
  

   is 
  held 
  parallel 
  to 
  the 
  earth's 
  field 
  and 
  tapped 
  with 
  a 
  hammer 
  

   it 
  will 
  be 
  found 
  to 
  possess 
  a 
  polarity 
  corresponding 
  to 
  the 
  

   direction 
  of 
  the 
  earth's 
  field. 
  In 
  the 
  shaking 
  up 
  of 
  the 
  ele- 
  

   mentary 
  magnets, 
  thev 
  have 
  settled 
  into 
  alignment 
  under 
  the 
  

   influence 
  of 
  the 
  earth's 
  field. 
  It 
  would 
  seem 
  that 
  here 
  a 
  

   similar 
  effect 
  occurred 
  when 
  the 
  elementary 
  magnets 
  were 
  dis- 
  

   turbed 
  by 
  the 
  field 
  due 
  to 
  the 
  decreasing 
  alternating 
  current. 
  

   The 
  effect 
  of 
  this 
  permanent 
  magnetization 
  was 
  eliminated 
  in 
  

   the 
  final 
  results 
  by 
  taking 
  the 
  mean 
  of 
  the 
  reversed 
  readings. 
  

  

  That 
  the 
  permanent 
  magnetization 
  has 
  much 
  to 
  do 
  with 
  this 
  

   effect 
  is 
  shown 
  by 
  a 
  comparison 
  of 
  the 
  curves 
  marked 
  IT 
  and 
  D 
  

   for 
  both 
  of 
  the 
  nickel 
  rods, 
  figs. 
  3 
  and 
  4. 
  The 
  rods 
  not 
  demag- 
  

   netized, 
  (U),.show 
  a 
  much 
  larger 
  twist 
  than 
  those, 
  (D), 
  from 
  

   which 
  at 
  least 
  a 
  part 
  of 
  the 
  permanent 
  magnetization 
  has 
  been 
  

   removed. 
  This 
  leads 
  to 
  another 
  point, 
  which, 
  so 
  far 
  as 
  I 
  know, 
  

   is 
  new, 
  viz., 
  that 
  in 
  the 
  magnetostrictive 
  effects 
  we 
  have 
  the 
  

   analogue 
  of 
  the 
  Yon 
  Waltenhofen* 
  phenomenon. 
  

  

  A 
  close 
  inspection 
  of 
  the 
  rods 
  indicated 
  that 
  in 
  the 
  process 
  

   of 
  drawing 
  they 
  had 
  been 
  given 
  a 
  permanent 
  torsional 
  set 
  and 
  

   in 
  the 
  case 
  of 
  the 
  nickel 
  rods 
  this 
  was 
  a 
  right-handed 
  twist. 
  

  

  * 
  The 
  data 
  have 
  been 
  collected 
  on 
  this 
  subject 
  and 
  will 
  be 
  presented 
  at 
  a 
  

   later 
  date. 
  

  

  