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  LXXII. 
  On 
  the 
  Cliange 
  of 
  the 
  Electrical 
  Resistance 
  of 
  Metals 
  

   when 
  placed 
  in 
  a 
  Magnetic 
  Field. 
  By 
  J. 
  Patterson, 
  B.A. 
  

   (Toronto), 
  1851 
  Exhibition 
  Science 
  Scholar, 
  Emmanuel 
  

   College, 
  Cambridge 
  *. 
  

  

  THE 
  change 
  o£ 
  the 
  electrical 
  resistance 
  of 
  metals 
  when 
  

   placed 
  in 
  a 
  magnetic 
  field 
  was 
  first 
  observed 
  in 
  iron 
  

   and 
  nickel 
  by 
  Lord 
  Kelvin 
  f 
  in 
  1856. 
  He 
  found 
  that 
  the 
  

   electrical 
  resistance 
  of 
  these 
  metals 
  was 
  increased 
  when 
  mag- 
  

   netized 
  longitudinally, 
  and 
  diminished 
  when 
  magnetized 
  

   transversely 
  to 
  the 
  direction 
  of 
  the 
  current. 
  

  

  Tomlinson 
  % 
  showed 
  that 
  bismuth 
  had 
  its 
  resistance 
  increased 
  

   by 
  a 
  field 
  parallel 
  to 
  the 
  direction 
  of 
  the 
  current; 
  while 
  Righi 
  § 
  

   observed 
  that 
  its 
  resistance 
  was 
  also 
  increased 
  when 
  the 
  field 
  

   w 
  T 
  as 
  transverse 
  to 
  the 
  direction 
  of 
  the 
  current. 
  

  

  Goldhammer 
  || 
  made 
  more 
  accurate 
  experiments 
  on 
  bis- 
  

   muth 
  and 
  on 
  the 
  magnetic 
  metals 
  iron, 
  cobalt, 
  and 
  nickel, 
  

   He 
  also 
  found 
  that 
  antimony 
  and 
  tellurium 
  exhibited 
  this 
  

   phenomenon. 
  

  

  Recently 
  Lenard^f 
  made 
  very 
  careful 
  experiments 
  on 
  

   bismuth 
  with 
  both 
  steady 
  and 
  alternating 
  currents. 
  He 
  found 
  

   that 
  the 
  change 
  of 
  resistance 
  was 
  different 
  when 
  the 
  current 
  

   was 
  alternating 
  from 
  what 
  it 
  was 
  when 
  steady, 
  and 
  also 
  that 
  

   the 
  increase 
  of 
  resistance 
  for 
  a 
  longitudinal 
  field 
  was 
  less 
  than 
  

   for 
  a 
  transverse 
  one. 
  He 
  obtained 
  a 
  small 
  change 
  in 
  german- 
  

   silver 
  and 
  copper, 
  but 
  in 
  this 
  case 
  it 
  was 
  the 
  same 
  whether 
  

   the 
  current 
  was 
  steady 
  or 
  alternating. 
  

  

  This 
  phenomenon 
  has 
  recently 
  been 
  explained 
  by 
  Prof. 
  J. 
  

   J. 
  Thomson** 
  on 
  the 
  corpuscular 
  theory 
  of 
  electric 
  conduction 
  

   in 
  metals. 
  According 
  to 
  this 
  theory, 
  the 
  electric 
  currents 
  in 
  

   the 
  metals 
  are 
  carried 
  by 
  negatively-charged 
  corpuscles 
  moving 
  

   with 
  a 
  definite 
  velocity 
  under 
  an 
  applied 
  E.M.F. 
  These 
  cor- 
  

   puscles 
  are 
  considered 
  to 
  act 
  as 
  a 
  perfect 
  gas 
  : 
  consequently 
  

   they 
  have 
  a 
  mean 
  free 
  path 
  and 
  mean 
  velocity 
  and 
  exert 
  a 
  

   definite 
  pressure. 
  

  

  He 
  has 
  shown 
  that 
  if 
  the 
  corpuscles 
  be 
  moving 
  under 
  an 
  

   electric 
  force, 
  and 
  then 
  a 
  transverse 
  magnetic 
  force 
  be 
  applied, 
  

   the 
  particles 
  move 
  in 
  a 
  cycloid. 
  Their 
  path 
  is 
  thus 
  increased, 
  

   and 
  consequently 
  the 
  resistance 
  of 
  the 
  conductor 
  is 
  changed. 
  

  

  * 
  Communicated 
  by 
  Prof. 
  J. 
  J. 
  Thomson, 
  F.R.S. 
  

   f 
  Math. 
  & 
  Physical 
  Papers, 
  vol. 
  ii. 
  p. 
  307. 
  

   I 
  Phil. 
  Trans. 
  1883, 
  p. 
  1. 
  

  

  § 
  Journal 
  de 
  Physique, 
  ser. 
  2, 
  tome 
  iii. 
  p. 
  35-5 
  (1834). 
  

   || 
  Wied. 
  Annalen, 
  vol. 
  xxxi. 
  p. 
  360 
  (1887). 
  

   % 
  Wied. 
  Annalen, 
  vol. 
  xxxix. 
  p. 
  619 
  (1890). 
  

   ** 
  Rapports 
  presences 
  au 
  Conyres 
  International 
  de 
  Physique, 
  iii. 
  p. 
  138, 
  

   Paris, 
  1900. 
  

  

  