﻿Williams 
  — 
  Twist 
  in 
  Steel 
  and 
  Nickel 
  Bods. 
  555 
  

  

  Aet. 
  XLIX. 
  — 
  Comparative 
  Studies 
  of 
  Magnetic 
  Phenomena. 
  

   IV. 
  Twist 
  in 
  Steel 
  and 
  Nickel 
  Rods 
  due 
  to 
  a 
  Longi- 
  

   tudinal 
  Magnetic 
  Field 
  /* 
  by 
  S. 
  R. 
  Williams. 
  

  

  It 
  is 
  a 
  well-known 
  fact 
  that 
  if 
  a 
  ferromagnetic 
  wire 
  or 
  rod 
  

   is 
  both 
  circularly 
  and 
  longitudinally 
  magnetized 
  it 
  will 
  suffer 
  

   a 
  twist 
  though 
  no 
  external 
  mechanical 
  force 
  is 
  used. 
  This 
  is 
  

   known 
  as 
  the 
  Wiedemann! 
  magnetostrictive 
  effect. 
  Wiede- 
  

   mann 
  also 
  found 
  that 
  if 
  an 
  iron 
  rod 
  was 
  first 
  twisted 
  mechani- 
  

   cally 
  and 
  then 
  subjected 
  to 
  a 
  longitudinal 
  magnetic 
  field 
  it 
  

   would 
  also 
  twist 
  mechanically 
  due 
  to 
  the 
  imposed 
  field. 
  This 
  

   last 
  effect 
  has 
  received 
  very 
  little 
  attention 
  since 
  Wiedemann 
  

   first 
  discovered 
  it 
  in 
  iron 
  and 
  so 
  far 
  as 
  the 
  author 
  knows 
  no 
  

   extension 
  of 
  the 
  work 
  has 
  been 
  done 
  on 
  nickel 
  and 
  cobalt. 
  

   The 
  method 
  used 
  in 
  a 
  former 
  work 
  J 
  for 
  photographically 
  

   registering 
  changes 
  in 
  length 
  and 
  twist 
  due 
  to 
  a 
  magnetic 
  Held 
  

   has 
  been 
  so 
  successful 
  in 
  picking 
  up 
  small 
  details 
  of 
  the 
  vari- 
  

   ation 
  that 
  it 
  seemed 
  worth 
  while 
  to 
  apply 
  it 
  to 
  this 
  effect, 
  

   particularly 
  as 
  this 
  special 
  effect 
  found 
  by 
  Wiedemann 
  is 
  

   superimposed 
  upon 
  the 
  regular 
  effect 
  known 
  as 
  the 
  "Wiede- 
  

   mann 
  effect" 
  and 
  it 
  should 
  be 
  sifted 
  out. 
  As 
  cobalt 
  rods 
  

   could 
  not 
  be 
  procured, 
  this 
  study 
  deals 
  with 
  an 
  investigation 
  

   of 
  a 
  dozen 
  steel 
  rods 
  and 
  two 
  nickel 
  rods. 
  Only 
  one 
  set 
  of 
  

   graphs 
  for 
  the 
  steel 
  rods 
  is 
  shown, 
  as 
  they 
  are 
  typical 
  of 
  the 
  rest. 
  

  

  The 
  literature 
  on 
  this 
  particular 
  subject 
  is 
  very 
  limited. 
  

   Smith§ 
  records 
  that 
  he 
  observed 
  in 
  the 
  case 
  of 
  one 
  iron 
  rod 
  a 
  

   tw 
  T 
  ist 
  due 
  to 
  a 
  longitudinal 
  magnetic 
  field, 
  but 
  he 
  merely 
  

   alludes 
  to 
  it 
  and 
  devotes 
  most 
  of 
  his 
  article 
  to 
  the 
  effect 
  of 
  

   magnetization 
  upon 
  steel 
  rods 
  possessing 
  " 
  permanent 
  torsional 
  

   set," 
  produced 
  at 
  the 
  time 
  the 
  rods 
  were 
  tested. 
  Grosser|| 
  

   also 
  found 
  that 
  under 
  certain 
  conditions 
  twists 
  in 
  steel 
  rods 
  

   occurred 
  due 
  to 
  a 
  longitudinal 
  field. 
  His 
  method 
  consisted 
  in 
  

   setting 
  the 
  rod 
  into 
  torsional 
  vibration 
  and 
  taking 
  the 
  means 
  

   of 
  a 
  series 
  of 
  amplitudes. 
  From 
  these 
  results 
  he 
  found 
  that 
  

   the 
  zero 
  points 
  were 
  shifted 
  as 
  the 
  field 
  strength 
  was 
  increased. 
  

   It 
  is 
  evident 
  from 
  the 
  accompanying 
  graphs, 
  figs. 
  1 
  and 
  2, 
  that 
  

   a 
  nickel 
  or 
  steel 
  rod 
  which 
  one 
  procures 
  from 
  the 
  open 
  market 
  

   may 
  show 
  a 
  twist, 
  when 
  magnetized 
  longitudinally. 
  

  

  In 
  a 
  former 
  paper,T~ 
  I 
  have 
  pointed 
  out 
  that 
  under 
  certain 
  

   conditions 
  one 
  should 
  expect, 
  from 
  the 
  planetesimal 
  theory 
  of 
  

   magnetism, 
  a 
  twist 
  due 
  to 
  a 
  longitudinal 
  field. 
  The 
  present 
  

   paper 
  deals 
  with 
  these 
  conditions 
  in 
  steel 
  and 
  nickel 
  rods 
  and 
  

   is 
  an 
  attempt 
  to 
  find 
  out 
  how 
  conditions 
  favorable 
  for 
  such 
  a 
  

   twist 
  are 
  brought 
  about. 
  

  

  *Read 
  by 
  title 
  before 
  the 
  Ohio 
  Academy 
  of 
  Science, 
  November, 
  1912. 
  

   fPogg. 
  Ann., 
  ciii, 
  571, 
  1858, 
  161, 
  1859. 
  Wiedemann's 
  Elektricitat. 
  

   JPhys. 
  Rev., 
  xxxiv, 
  258, 
  April, 
  1912. 
  §Phil. 
  Mag., 
  xxxii, 
  385, 
  1891. 
  

   || 
  Inaug. 
  Diss., 
  Rostock, 
  1896. 
  ^JPhys. 
  Rev., 
  abstract, 
  February, 
  1911. 
  

  

  