﻿tliroufjli 
  the 
  Gases 
  HCL 
  HBr, 
  and 
  HI. 
  481 
  

  

  The 
  only 
  experiment 
  Avhich 
  in 
  the 
  case 
  of 
  ordinary 
  dis- 
  

   charge 
  should 
  indicate 
  an 
  influence 
  of 
  the 
  substance 
  of 
  the 
  

   tube, 
  is 
  that 
  a 
  tube 
  of 
  lead-glass 
  under 
  equal 
  conditions 
  gave 
  

   10 
  per 
  cent, 
  less 
  absorption 
  than 
  a 
  similar 
  one 
  of 
  soda-glass. 
  

   But 
  this 
  may 
  equally 
  ^vell 
  be 
  explained 
  by 
  differences 
  in 
  

   the 
  size 
  of 
  the 
  cathode 
  surfaces. 
  Silvering 
  the 
  inside, 
  but 
  

   keeping 
  electrodes 
  unaltered, 
  gave 
  no 
  change 
  in 
  absorption. 
  

  

  Some 
  of 
  his 
  experiments, 
  for 
  which 
  he 
  has 
  not 
  been 
  able 
  

   to 
  give 
  any 
  satisfactory 
  explanation, 
  are 
  easily 
  explained 
  by 
  

   the 
  assumed 
  connexion 
  between 
  cathode 
  fall 
  and 
  absorption. 
  

  

  With 
  a 
  tube 
  ^^here 
  one 
  electrode 
  was 
  a 
  small 
  rod, 
  the 
  

   other 
  a 
  cylindrical 
  vessel 
  surrounding 
  the 
  first 
  one, 
  the 
  ab- 
  

   sorption 
  for 
  the 
  current 
  used 
  (10c> 
  . 
  10~^} 
  was 
  exceedingly 
  

   small 
  when 
  the 
  cylinder 
  was 
  made 
  a 
  cathode, 
  but 
  had 
  the 
  

   usual 
  large 
  value 
  when 
  it 
  was 
  made 
  an 
  anode. 
  This 
  is 
  

   immediately 
  explained 
  by 
  the 
  difference 
  that 
  must 
  exist 
  

   between 
  the 
  cathode 
  falls 
  for 
  the 
  two 
  directions. 
  Another 
  

   experiment 
  (loc. 
  cit. 
  fig. 
  7), 
  where 
  he 
  also 
  used 
  electrodes 
  of 
  

   different 
  size, 
  is 
  explained 
  in 
  the 
  same 
  way. 
  In 
  an 
  experi- 
  

   ment 
  where 
  there 
  was 
  dissymmetry 
  with 
  regard 
  to 
  tube, 
  but 
  

   symmetry 
  as 
  regards 
  electrodes, 
  a 
  reversion 
  of 
  current 
  pro- 
  

   duced 
  no 
  change 
  in 
  absorption. 
  

  

  From 
  this 
  it 
  seems 
  beyond 
  doubt 
  that 
  the 
  cathode 
  fall 
  is 
  

   the 
  essential 
  property 
  for 
  the 
  absorption. 
  The 
  next 
  question 
  

   will 
  be 
  in 
  what 
  way 
  the 
  cathode 
  fall 
  is 
  able 
  to 
  produce 
  

   absorption. 
  The 
  assumption 
  that 
  almost 
  forces 
  itself 
  upon 
  

   us 
  is 
  that 
  the 
  absorption 
  is 
  carried 
  out 
  by 
  the 
  ions 
  which 
  by 
  

   the 
  large 
  cathode 
  fall 
  are 
  given 
  such 
  velocities 
  as 
  to 
  be 
  shot 
  

   as 
  it 
  were 
  into 
  the 
  solid 
  matter. 
  This 
  is 
  in 
  agreement 
  with 
  

   the 
  fact 
  that 
  the 
  maximum 
  absorption 
  is 
  of 
  the 
  same 
  order 
  

   as 
  the 
  electrochemical 
  equivalent. 
  

  

  From 
  the 
  view 
  we 
  have 
  at 
  present 
  as 
  to 
  the 
  mechanism 
  of 
  

   the 
  discharge, 
  it 
  is 
  further 
  most 
  likely 
  that 
  the 
  greatest 
  

   absorption 
  effect 
  is 
  produced 
  by 
  the 
  positive 
  ions 
  falling 
  into 
  

   the 
  cathode. 
  AVe 
  must 
  remember 
  that 
  the 
  essential 
  thing- 
  

   is 
  not 
  that 
  the 
  ions 
  acquire 
  a 
  certain 
  velocity, 
  but 
  that 
  

   they 
  have 
  it 
  the 
  moment 
  they 
  strike 
  the 
  solid 
  matter. 
  Sow 
  

   the 
  positive 
  ions 
  get 
  their 
  maximum 
  velocity 
  just 
  when 
  they 
  

   strike 
  the 
  cathode. 
  The 
  negative 
  electricity 
  will 
  within 
  the 
  

   space 
  of 
  the 
  cathode 
  fall 
  mostly 
  exist 
  as 
  corpuscles. 
  Some 
  

   of 
  these 
  may 
  pass 
  through 
  the 
  gas 
  without 
  collision, 
  in 
  

   which 
  case 
  they 
  can 
  produce 
  no 
  aljsorption, 
  some 
  will 
  stick 
  

   to 
  molecules 
  and 
  communicate 
  to 
  them 
  their 
  kinetic 
  energy 
  

   acquired 
  at 
  the 
  cathode 
  fail 
  ; 
  but 
  these 
  molecules 
  may 
  now 
  

   make 
  collisions, 
  and 
  thus 
  gradually 
  lose 
  kinetic 
  energy. 
  

   Thus 
  it 
  should 
  at 
  least 
  onlv 
  be 
  a 
  small 
  fraction 
  of 
  the 
  neoative 
  

  

  