﻿H. 
  D. 
  Day 
  — 
  Magnetic 
  Increment 
  of 
  Rigidity, 
  etc. 
  449 
  

  

  Akt. 
  XLYI. 
  — 
  The 
  Magnetic 
  Increment 
  of 
  Rigidity 
  in 
  Strong 
  

   Fields 
  ; 
  by 
  Howabd 
  D. 
  Day. 
  

  

  In 
  the 
  endeavor 
  to 
  study 
  the 
  magnetic 
  rigidity 
  of 
  filamentary 
  

   wires 
  in 
  its 
  variation 
  with 
  the 
  thickness 
  of 
  the 
  wire, 
  it 
  seemed 
  

   desirable 
  to 
  preface 
  the 
  work 
  in 
  question 
  by 
  extending 
  the 
  

   experiments 
  throughout 
  much 
  stronger 
  magnetic 
  fields 
  than 
  has 
  

   hitherto 
  been 
  done. 
  The 
  present 
  paper, 
  therefore, 
  treats 
  of 
  

   the 
  increase 
  of 
  resistance 
  to 
  torque 
  produced 
  by 
  the 
  magnetiza- 
  

   tion 
  of 
  twisted 
  wires 
  of 
  various 
  diameters, 
  when 
  the 
  magnetic 
  

   field 
  increases 
  to 
  many 
  times 
  the 
  amount 
  needed 
  to 
  bring 
  out 
  

   the 
  ordinary 
  magnetic 
  saturation. 
  

  

  The 
  object 
  of 
  the 
  research 
  is 
  to 
  make 
  a 
  clear 
  comparison 
  

   between 
  the 
  phenomenon 
  of 
  magnetization 
  or 
  magnetic 
  inten- 
  

   sity 
  on 
  the 
  one 
  hand 
  and 
  the 
  phenomena 
  of 
  magnetic 
  rigidity 
  

   on 
  the 
  other; 
  to 
  show 
  that 
  the 
  two 
  are 
  quite 
  distinct 
  in 
  charac- 
  

   ter*, 
  — 
  that 
  the 
  former 
  practically 
  subsides 
  in 
  relatively 
  weak 
  

   fields, 
  whereas 
  the 
  latter 
  are 
  not 
  as 
  fully 
  complete 
  even 
  in 
  the 
  

   highest 
  fields 
  applied. 
  It 
  thus 
  appears 
  that 
  the 
  manifestation 
  

   of 
  magnetic 
  saturation 
  is 
  but 
  one 
  phase 
  of 
  a 
  magnetic 
  phenom- 
  

   enon 
  of 
  a 
  far 
  wider 
  range. 
  In 
  other 
  words, 
  if 
  the 
  magnetic 
  

   qualities 
  of 
  iron 
  be 
  expressed 
  in 
  some 
  way 
  not 
  involving 
  direct 
  

   or 
  indirect 
  reference 
  to 
  the 
  magnetic 
  moment, 
  then 
  the 
  mag- 
  

   netic 
  relations 
  of 
  the 
  iron 
  to 
  the 
  field 
  will 
  appear 
  in 
  quite 
  a 
  

   different 
  light 
  ; 
  for 
  the 
  influence 
  of 
  the 
  increasing 
  field 
  on 
  the 
  

   iron 
  will 
  be 
  found 
  to 
  continue 
  with 
  but 
  slowly 
  decreasing 
  mag- 
  

   netic 
  effects 
  up 
  to 
  the 
  limits 
  of 
  observation. 
  

  

  Work 
  on 
  somewhat 
  similar 
  lines 
  has 
  recently 
  been 
  published 
  

   by 
  Bid 
  well 
  : 
  but 
  the 
  Joule 
  effect 
  as 
  studied 
  by 
  Bid 
  well 
  is 
  

   apparently 
  distorted 
  from 
  its 
  true 
  nature 
  by 
  the 
  occurrence 
  of 
  

   molecular 
  rotation. 
  The 
  Wiedemann 
  effect 
  investigated 
  in 
  the 
  

   present 
  paper 
  shows 
  no 
  apparent 
  relation 
  to 
  the 
  magnetic 
  

   saturation 
  of 
  iron 
  whatsoever, 
  or, 
  at 
  least, 
  is 
  free 
  from 
  any 
  con- 
  

   temporaneous 
  distortion. 
  Hence 
  this 
  effect 
  is 
  peculiarly 
  

   adapted 
  for 
  expressing 
  the 
  magnetic 
  qualities 
  of 
  iron 
  through- 
  

   out 
  the 
  wide 
  range 
  under 
  which 
  they 
  continue 
  with 
  but 
  mod- 
  

   erately 
  diminished 
  sensitiveness. 
  

  

  The 
  method 
  and 
  apparatus 
  employed 
  in 
  this 
  investigation 
  

   are 
  adaptations 
  of 
  that 
  used 
  by 
  Barus 
  in 
  his 
  researchesf 
  wherein 
  

   one 
  of 
  two 
  countertwisted 
  wires 
  similar 
  in 
  all 
  respects 
  is 
  mag- 
  

   netized, 
  and 
  the 
  resulting 
  difference 
  in 
  rigidity 
  of 
  the 
  two 
  

   wires 
  observed. 
  The 
  rigidity 
  of 
  a 
  wire 
  of 
  length 
  I 
  and 
  radius 
  

   r, 
  twisted 
  by 
  torque 
  t 
  through 
  an 
  angle 
  0, 
  is 
  given 
  by 
  

  

  On 
  — 
  2W/7rr 
  4 
  

  

  * 
  Barus 
  : 
  this 
  Journal, 
  (3) 
  vol. 
  xxxiv, 
  p. 
  181, 
  1887. 
  

   f 
  Barus 
  : 
  Bull. 
  U. 
  S. 
  Geol. 
  Sur., 
  No. 
  73. 
  1891. 
  

  

  