﻿252 
  Mr. 
  B. 
  Hodgson 
  on 
  the 
  Conductivity 
  of 
  

  

  if 
  we 
  screen 
  off 
  the 
  other 
  bright 
  fringes, 
  passing 
  the 
  waves 
  in 
  

   the 
  one 
  through 
  a 
  slit, 
  the 
  slit 
  width 
  necessary 
  turns 
  out 
  to 
  

   be 
  just 
  what 
  is 
  needed 
  to 
  prevent 
  resolution. 
  

  

  In 
  the 
  region 
  between 
  the 
  sources 
  we 
  must 
  regard 
  the 
  

   same 
  thing 
  as 
  going 
  on, 
  the 
  only 
  difference 
  being 
  that 
  here 
  

   the 
  incidence 
  is 
  more 
  nearly 
  normal. 
  The 
  waves 
  are 
  stationary 
  

   on 
  the 
  line 
  joining 
  the 
  sources, 
  but 
  as 
  soon 
  as 
  we 
  get 
  off 
  this 
  

   line 
  we 
  must 
  regard 
  the 
  stationary 
  waves 
  as 
  oozing 
  out 
  in 
  all 
  

   directions, 
  the 
  velocity 
  of 
  the 
  oozing 
  increasing 
  with 
  the 
  

   distance 
  from 
  the 
  line. 
  

  

  I 
  realize 
  that 
  the 
  language 
  which 
  I 
  have 
  used 
  here 
  is 
  not 
  

   very 
  exact, 
  but 
  it 
  is 
  not 
  easy 
  to 
  visualize 
  exactly 
  what 
  is 
  

   going 
  on, 
  and 
  still 
  harder 
  to 
  put 
  it 
  into 
  words. 
  If 
  this 
  note 
  

   serves 
  to 
  direct 
  attention 
  to 
  a 
  new 
  view-point 
  of 
  a 
  well-known 
  

   phenomenon, 
  it 
  will 
  have 
  accomplished 
  all 
  that 
  I 
  had 
  intended 
  

   it 
  to 
  do. 
  

  

  XXXI. 
  The 
  Conductivity 
  of 
  Dielectrics 
  under 
  the 
  Action 
  of 
  

   Radium 
  Rays. 
  By 
  B. 
  Hodgson^ 
  B.Sc, 
  Prize 
  Demonstrator 
  

   in 
  Physics, 
  Armstrong 
  College, 
  Newcastle-on-Tyne* 
  , 
  

  

  A 
  STUDY 
  of 
  the 
  conductivity 
  of 
  dielectrics 
  under 
  the 
  

   action 
  of 
  radium 
  rays 
  is 
  extremely 
  important 
  in 
  view 
  

   of 
  the 
  fact 
  that 
  the 
  work 
  already 
  done 
  on 
  tbis 
  problem 
  is 
  

   throwing 
  light 
  on 
  the 
  nature 
  of 
  dielectric 
  conductivity 
  itself, 
  

   and 
  perhaps 
  also 
  on 
  the 
  nature 
  of 
  polarization 
  in 
  dielectrics. 
  

  

  The 
  early 
  investigators 
  f 
  were 
  inclined 
  to 
  look 
  upon 
  

   dielectric 
  conductivity 
  as 
  electrolytic 
  in 
  action, 
  but 
  recent 
  

   work 
  seems 
  to 
  point 
  to 
  a 
  conduction 
  similar 
  to 
  that 
  occurring 
  

   in 
  a 
  dense 
  gas. 
  

  

  The 
  conductivity 
  acquired 
  under 
  the 
  action 
  of 
  radium 
  rays 
  

   was 
  demonstrated 
  by 
  P. 
  Curie, 
  Becquerel, 
  and 
  Becker, 
  and 
  

   recently 
  the 
  phenomena 
  have 
  been 
  studied 
  in 
  great 
  thorough- 
  

   ness 
  by 
  Jaffe 
  J. 
  

  

  Curie 
  §, 
  Becquerel 
  ||, 
  and 
  Becker^ 
  showed 
  that 
  dielectrics 
  

   under 
  the 
  action 
  of 
  radium 
  rays 
  increase 
  in 
  conductivity, 
  and 
  

   noticed 
  some 
  departure 
  from 
  Ohm's 
  law. 
  

  

  Jaffe 
  divided 
  the 
  current 
  into 
  two 
  parts 
  : 
  

  

  (1) 
  obeying 
  Ohm's 
  law, 
  

  

  (2) 
  an 
  ionization 
  current. 
  

  

  * 
  Communicated 
  by 
  Prof. 
  H. 
  Stroud. 
  

  

  t 
  Von 
  Schweidler, 
  Ann. 
  d. 
  Thys. 
  xxiv. 
  p. 
  711 
  (1907). 
  

  

  \ 
  Jafe6, 
  Ann. 
  d. 
  Phys. 
  xxv. 
  p. 
  257 
  (1908). 
  

  

  § 
  Curie, 
  Cwnp. 
  Rend, 
  cxxxiv. 
  p. 
  420 
  (1902). 
  

  

  II 
  Becquerel, 
  Comp. 
  Rend, 
  cxxxvi. 
  p. 
  1173 
  (1904). 
  

  

  «f] 
  Becker, 
  An7i. 
  d. 
  Phys. 
  xiii. 
  p. 
  394 
  (1904). 
  

  

  