﻿162 
  Mr. 
  D. 
  E. 
  Roberts 
  on 
  the 
  Effect 
  of 
  Temperature 
  and 
  

  

  that 
  his 
  results 
  are 
  not 
  in 
  agreement 
  with 
  those 
  obtained 
  with 
  

   my 
  specimens. 
  

  

  Regarding 
  the 
  resistance 
  effect 
  in 
  tbe 
  case 
  of 
  crystallized 
  

   bismuth, 
  von 
  Everdingen 
  * 
  found 
  that 
  the 
  resistance 
  outside 
  

   the 
  field 
  could 
  be 
  represented 
  by 
  an 
  ellipsoid 
  of 
  conductivity, 
  

   the 
  axis 
  of 
  rotation 
  of 
  which 
  bore 
  to 
  the 
  rectangular 
  axes 
  the 
  

   relations 
  \/'d 
  : 
  \/l>. 
  If 
  the 
  crystalline 
  axis 
  was 
  placed 
  to 
  

   coincide 
  with 
  that 
  of 
  the 
  field, 
  an 
  ellipsoid 
  of 
  revolution 
  was 
  

   again 
  obtained 
  with 
  a 
  slightly 
  different 
  relation 
  between 
  the 
  

   axes. 
  If 
  the 
  crystalline 
  axis 
  was 
  placed 
  perpendicular 
  to 
  

   the 
  field, 
  the 
  ellipsoid 
  in 
  this 
  case 
  had 
  three 
  different 
  axes 
  

   with 
  marked 
  differences 
  in 
  their 
  relation 
  to 
  one 
  another 
  ; 
  for 
  

   inclined 
  positions 
  similar 
  results 
  hold 
  in 
  accordance 
  with 
  the 
  

   principle 
  of 
  superposition. 
  The 
  relation 
  between 
  the 
  trans- 
  

   verse 
  and 
  longitudinal 
  effect 
  hns 
  been 
  investigated 
  by 
  

   Lenard 
  f 
  for 
  a 
  "filament" 
  from 
  compressed 
  bismuth 
  con- 
  

   taining 
  zinc 
  and 
  iron; 
  the 
  resistance 
  for 
  an 
  alternating 
  

   current 
  was 
  measured 
  for 
  different 
  angles 
  ty 
  between 
  the 
  

   filament 
  (referred 
  to 
  the 
  direction 
  of 
  the 
  measuring 
  current) 
  

   and 
  the 
  field, 
  and 
  the 
  results 
  represented 
  by 
  the 
  purely 
  

   empirical 
  formula 
  

  

  ^-g^ 
  = 
  A 
  + 
  B 
  . 
  sin 
  2 
  i/r-C 
  sin 
  2 
  2^ 
  cos 
  2^. 
  

  

  The 
  influence 
  of 
  temperature 
  and 
  transverse 
  magnetization 
  

   on 
  the 
  resistance 
  (for 
  steady 
  currents) 
  of 
  pure 
  diamagnetic 
  

   electrolytic 
  bismuth 
  and 
  of 
  ferromagnetic 
  "pure 
  nickel" 
  

   (commercial) 
  was 
  investigated 
  in 
  detail 
  in 
  this 
  laboratory 
  by 
  

   Blake 
  ; 
  his 
  publication 
  contains 
  an 
  extensive 
  summary 
  of 
  the 
  

   new 
  literature 
  on 
  this 
  subject. 
  

  

  The 
  longitudinal 
  effect 
  in 
  nickel 
  was 
  investigated 
  simul- 
  

   taneously 
  by 
  du 
  Bois 
  J. 
  Quite 
  recently 
  Kamerlingh 
  Onnes 
  

   and 
  Beckmann 
  § 
  have 
  published 
  measurements 
  on 
  bismuth, 
  

   copper, 
  iron, 
  gold, 
  and 
  palladium 
  at 
  temperatures 
  below 
  

   -200°. 
  

  

  I. 
  Experimental 
  Arrangement. 
  

  

  The 
  specimens 
  most 
  used 
  in 
  the 
  investigation 
  were 
  prepared 
  

   from 
  the 
  same 
  commercial 
  Ceylon 
  graphite 
  (afterwards 
  

  

  * 
  E. 
  v. 
  Everdingen, 
  Arch, 
  neerl. 
  [2] 
  iv. 
  p. 
  462 
  (1901). 
  

  

  t 
  P. 
  L. 
  Lenard, 
  Wied. 
  Ann. 
  xxxix. 
  p. 
  646 
  (1890) 
  

  

  % 
  F. 
  C. 
  Blake, 
  Ann. 
  d. 
  Phys. 
  xxviii. 
  p. 
  449 
  (1909); 
  H. 
  du 
  Bois, 
  Verh. 
  

   Ned.nat. 
  Congress, 
  xii. 
  p. 
  128, 
  Utrecht 
  (1909); 
  cf. 
  E. 
  A. 
  Owen, 
  Phil. 
  

   Mag. 
  [6] 
  xxi. 
  p. 
  122.(1911) 
  ; 
  C. 
  W. 
  Heaps, 
  Phil.' 
  Mag. 
  [6] 
  xxii. 
  p. 
  900 
  

   (1911), 
  and 
  xxiv. 
  p. 
  813 
  ( 
  1912). 
  

  

  § 
  H. 
  Kamerlingh 
  Onnes 
  and 
  B. 
  Beckmann, 
  Versl. 
  Kon. 
  Akad. 
  Wet. 
  

   Amst. 
  xxi. 
  pp. 
  263, 
  478, 
  481, 
  881 
  (1912). 
  

  

  