﻿Magnetization 
  on 
  the 
  Resistance 
  of 
  Graphite, 
  161 
  

  

  (ef. 
  fig. 
  3). 
  On 
  the 
  other 
  hand, 
  Koenigsberger 
  and 
  Reichen- 
  

   heim 
  * 
  found 
  a 
  decrease 
  o£ 
  resistance 
  of 
  one 
  half 
  by 
  a 
  rise 
  of 
  

   temperature 
  from 
  —185° 
  to 
  -+- 
  191°. 
  According 
  to 
  Clay 
  t, 
  

   the 
  resistance 
  of 
  a 
  glow-lamp 
  filament 
  decreases 
  by 
  24 
  per 
  cent, 
  

   on 
  heating 
  it 
  from 
  —255° 
  to 
  0°. 
  The 
  specific 
  resistance 
  of 
  

   amorphous 
  carbon 
  has 
  always 
  been 
  found 
  to 
  be 
  much 
  greater 
  

   and 
  a 
  decrease 
  accompanies 
  increase 
  of 
  temperature 
  ; 
  the 
  

   temperature 
  coefficient 
  becomes 
  numerically 
  smaller 
  as 
  the 
  

   change 
  into 
  the 
  graphite 
  modification 
  proceeds, 
  but 
  no 
  

   change 
  in 
  sign 
  has 
  previously 
  been 
  noticed 
  J. 
  Such 
  a 
  

   phenomenon 
  has 
  recently 
  been 
  observed 
  by 
  von 
  Pirani 
  § 
  in 
  the 
  

   case 
  of 
  the 
  so-called 
  metallized 
  filaments. 
  Thick 
  filaments, 
  

   free 
  from 
  ash, 
  carbonized 
  twice 
  above 
  2500°, 
  showed 
  

   finally 
  the 
  smallest 
  specific 
  resistance 
  and 
  a 
  small 
  positive 
  

   temperature 
  coefficient 
  +0*00007, 
  which 
  is 
  exceeded 
  by 
  the 
  

   above 
  (variety 
  G 
  I.) 
  thirty-five 
  times. 
  From 
  this 
  it 
  appears 
  

   possible 
  to 
  obtain 
  preparations, 
  having 
  a 
  vanishingly 
  small 
  

   temperature 
  coefficient, 
  which 
  could 
  be 
  used 
  as 
  standard 
  

   resistances 
  ||. 
  

  

  The 
  effect 
  of 
  magnetization 
  on 
  the 
  resistance 
  of 
  graphite 
  

   was 
  investigated 
  by 
  Patterson 
  (loc. 
  cit.\ 
  who 
  found 
  the 
  

   resistance 
  of 
  a 
  glow-lamp 
  filament 
  increased 
  by 
  0*027 
  per 
  

   cent, 
  in 
  a 
  transverse 
  field 
  of 
  25 
  kgss. 
  Laws 
  ^[ 
  has 
  also 
  

   investigated 
  the 
  effect 
  for 
  glow-lamp 
  filaments, 
  pencils, 
  and 
  

   for 
  graphite, 
  without, 
  however, 
  finding 
  it 
  to 
  be 
  of 
  an 
  

   exceptionally 
  high 
  order. 
  At 
  ordinary 
  temperatures 
  he 
  

   found 
  the 
  increase 
  of 
  resistance 
  of 
  graphite 
  in 
  a 
  transverse 
  

   field 
  of 
  11 
  kgss. 
  to 
  be 
  only 
  1 
  per 
  cent, 
  of 
  the 
  resistance 
  

   outside 
  the 
  field, 
  while 
  at 
  the 
  temperature 
  of 
  liquid 
  air 
  the 
  

   effect 
  appeared 
  to 
  be 
  increased 
  threefold. 
  Within 
  the 
  small 
  

   limits 
  of 
  his 
  field 
  it 
  was 
  found 
  that 
  the 
  increase 
  of 
  resistance 
  

   was 
  proportional 
  to 
  the 
  square 
  of 
  the 
  field, 
  and 
  between 
  the 
  

   temperatures 
  —186° 
  and 
  +18°, 
  inversely 
  proportional 
  to 
  the 
  

   absolute 
  temperature. 
  From 
  what 
  follows 
  it 
  will 
  be 
  seen 
  

  

  * 
  J. 
  Koeniirsberger 
  and 
  O. 
  Reichenheim, 
  Physik. 
  Zeitsch. 
  vii. 
  p. 
  575 
  

   (1906). 
  

  

  t 
  J. 
  Clay, 
  Inaurj.-Diss., 
  Leiden, 
  1908. 
  

  

  7 
  Cf. 
  llandb. 
  d. 
  Phys. 
  iv. 
  p. 
  380 
  (1905) 
  ; 
  G. 
  Wiedemann, 
  Eleldrizitiit, 
  

   i. 
  p. 
  539 
  (1882). 
  

  

  § 
  Unpublished 
  communication, 
  from 
  Dr. 
  Bi. 
  v. 
  Pirani 
  to 
  Prof. 
  Koem':_ 
  r 
  -- 
  

   berger, 
  and 
  kindly 
  sent 
  to 
  me 
  by 
  the 
  latter. 
  

  

  Since 
  my 
  first 
  communication, 
  Versl. 
  Kon. 
  Ahad. 
  Wet. 
  Amst. 
  xxi. 
  

   p. 
  221 
  (1912), 
  this 
  suggestion 
  has 
  been 
  made 
  by 
  IT. 
  Kost, 
  Phi/sik. 
  

   Zeit 
  <chr. 
  xiii. 
  p. 
  896(1912). 
  

  

  % 
  S. 
  C. 
  Laws, 
  Phil. 
  Map:. 
  [6] 
  xix. 
  p. 
  694 
  (1910). 
  He 
  investigated 
  

   graphite 
  from 
  the 
  Morgan 
  Crucible 
  Co., 
  London. 
  

  

  Phil. 
  Mag. 
  8. 
  6. 
  Vol. 
  26. 
  No. 
  151. 
  July 
  1913 
  M 
  

  

  