﻿190 
  On 
  the 
  Source 
  of 
  the 
  x-Rays. 
  

  

  was 
  produced 
  both 
  when 
  the 
  wire 
  was 
  the 
  cathode 
  and 
  when 
  

   it 
  was 
  the 
  anode. 
  It 
  can 
  he 
  explained 
  on 
  the 
  hypothesis 
  that 
  

   a 
  layer 
  of 
  electrified 
  particles 
  is 
  held 
  by 
  a 
  condenser-action 
  on 
  

   the 
  wall 
  of 
  the 
  tube, 
  and 
  that 
  the 
  fresh- 
  coming 
  particles 
  are 
  

   strongly 
  repelled 
  by 
  those 
  that 
  have 
  accumulated 
  at 
  the 
  

   spot. 
  

  

  The 
  behaviour 
  of 
  aluminium 
  toward 
  the 
  ^-rays 
  is 
  so 
  re- 
  

   markable 
  that 
  it 
  merits 
  especial 
  investigation. 
  Can 
  it 
  be 
  

   that 
  it 
  manifests 
  a 
  remarkable 
  condenser 
  action 
  toward 
  the 
  

   high 
  electromotive 
  forces 
  which 
  produce 
  the 
  a?-rays, 
  similar 
  

   to 
  the 
  action 
  which 
  has 
  been 
  observed 
  at 
  lower 
  voltages 
  ? 
  * 
  

  

  We 
  connected 
  to 
  the 
  air-pump 
  at 
  the 
  same 
  time 
  two 
  

   exactly 
  similar 
  tubes, 
  one 
  of 
  which 
  had 
  two 
  pointed 
  terminals 
  

   of 
  platinum, 
  the 
  other 
  two 
  pointed 
  terminals 
  also 
  ; 
  but 
  one 
  

   consisted 
  of 
  aluminium 
  and 
  the 
  other 
  of 
  platinum. 
  The 
  

   discharge 
  from 
  a 
  Ruhmkorf 
  coil 
  w 
  r 
  as 
  sent 
  through 
  these 
  tubes, 
  

   which 
  were 
  in 
  multiple 
  circuit. 
  At 
  a 
  certain 
  stage 
  of 
  the 
  

   exhaustion 
  it 
  was 
  seen 
  that 
  the 
  discharge 
  passed 
  more 
  easily 
  

   when 
  the 
  aluminium 
  wire 
  was 
  made 
  a 
  cathode 
  than 
  when 
  it 
  

   constituted 
  the 
  anode. 
  When 
  the 
  wire 
  terminals 
  in 
  both 
  

   tubes 
  were 
  made 
  of 
  thin 
  disks 
  the 
  difference 
  was 
  less 
  marked. 
  

   This 
  might 
  have 
  been 
  surmised 
  from 
  previous 
  investigations 
  

   on 
  the 
  effect 
  of 
  form 
  of 
  electrodes 
  on 
  resulting 
  polarization 
  f. 
  

   It 
  may 
  be 
  that 
  the 
  anomalous 
  action 
  of 
  aluminium 
  in 
  respect 
  

   to 
  the 
  #-rays 
  is 
  due 
  to 
  a 
  species 
  of 
  dielectric 
  polarization 
  on 
  

   the 
  surface 
  of 
  the 
  platinum, 
  and 
  that 
  thus 
  the 
  surface 
  becomes 
  

   a 
  new 
  source 
  of 
  electrostatic 
  stress 
  similar 
  to 
  that 
  which 
  was 
  

   observed 
  by 
  connecting 
  a 
  bit 
  of 
  tinfoil 
  and 
  a 
  capacity 
  to 
  the 
  

   tube. 
  Since 
  we 
  are 
  dealing 
  with 
  very 
  high 
  differences 
  of 
  

   potential, 
  and 
  with 
  high 
  charges 
  on 
  the 
  ions, 
  the 
  instantaneous 
  

   exhibition 
  of 
  electrical 
  energy 
  is 
  very 
  great, 
  and 
  might 
  

   probably 
  explain 
  the 
  diffusion 
  of 
  this 
  energy 
  through 
  the 
  air. 
  

   According 
  to 
  this 
  hypothesis 
  the 
  light 
  manifestations 
  of 
  the 
  

   a?-rays 
  arise 
  only 
  at 
  the 
  fluorescent 
  screens, 
  or 
  at 
  other 
  

   suitable 
  surfaces. 
  

  

  Conclusions. 
  

  

  1. 
  A 
  Crookes 
  tube 
  enclosing 
  a 
  continuous 
  conductor 
  is 
  well 
  

   suited, 
  with 
  the 
  employment 
  of 
  high 
  electromotive 
  force, 
  for 
  

   the 
  study 
  of 
  electric 
  lines 
  of 
  induction. 
  

  

  2. 
  The 
  direction 
  of 
  the 
  so-called 
  sc-rajs 
  and 
  cathode-rays 
  

   can 
  be 
  changed 
  by 
  electric 
  induction. 
  

  

  3. 
  The 
  so-called 
  #-ray 
  burn 
  can 
  be 
  produced 
  by 
  an 
  intense 
  

   state 
  of 
  electrification. 
  

  

  * 
  L. 
  Graetz, 
  Wied. 
  Ann. 
  No. 
  10, 
  1897, 
  p. 
  323. 
  

   t 
  Karl 
  Robert 
  Klein, 
  ibid. 
  p. 
  259. 
  

  

  