﻿Chemistry 
  and 
  Physics. 
  301 
  

  

  the 
  separate 
  components 
  of 
  the 
  hydrogen 
  lines 
  are 
  available. 
  — 
  

   Proc. 
  Boy. 
  Soc, 
  96A, 
  147, 
  1919. 
  ' 
  h. 
  s.u. 
  

  

  7. 
  Experiments 
  with 
  Perforated 
  Electrodes 
  on 
  the 
  Nature 
  of 
  

   the 
  Discharge 
  in 
  Gases 
  at 
  Low 
  Pressures. 
  — 
  Certain 
  more 
  or 
  less 
  

   preliminary 
  experiments 
  on 
  the 
  passage 
  of 
  electricity 
  through 
  

   rarefied 
  gases 
  have 
  been 
  performed 
  by 
  F. 
  W. 
  Aston 
  in 
  a 
  man- 
  

   ner 
  which 
  promises 
  to 
  appreciably 
  increase 
  our 
  knowledge 
  of 
  

   the 
  complex 
  phenomena 
  involved. 
  

  

  A 
  brief 
  description 
  of 
  the 
  discharge 
  vessel 
  will 
  now 
  be 
  given. 
  

   A 
  cylindrical 
  glass 
  shade, 
  with 
  a 
  plane 
  lower 
  edge 
  and 
  a 
  hemi- 
  

   spherical 
  top 
  (axis 
  of 
  revolution 
  vertical), 
  was 
  closed 
  at 
  the 
  

   bottom 
  by 
  a 
  disc 
  of 
  stout 
  plate 
  glass. 
  The 
  electrodes 
  were 
  circu- 
  

   lar 
  discs 
  of 
  zinc 
  having 
  a 
  diameter 
  (11-8 
  cm.) 
  slightly 
  less 
  than 
  

   that 
  of 
  the 
  inside 
  of 
  the 
  glass 
  cylinder. 
  When 
  used 
  as 
  cathode 
  

   material, 
  zinc 
  was 
  found 
  to 
  have 
  several 
  advantages 
  over 
  alumin- 
  

   ium 
  and 
  other 
  base 
  metals; 
  for 
  example, 
  — 
  it 
  gave 
  off 
  but 
  little 
  

   gas, 
  it 
  sputtered 
  inappreciably, 
  and 
  it 
  was 
  readily 
  worked 
  into 
  

   shape. 
  The 
  lower 
  disc 
  was 
  fixed 
  relative 
  to 
  the 
  containing 
  

   vessel, 
  while 
  the 
  upper 
  electrode 
  could 
  be 
  raised 
  or 
  lowered 
  by 
  

   means 
  of 
  a 
  vacuum-tight 
  winch. 
  The 
  lower 
  electrode 
  was 
  cut 
  

   through 
  by 
  a 
  diametral 
  slit 
  10- 
  cm. 
  long 
  and 
  0-0182 
  cm. 
  wide. 
  

   To 
  the 
  underside 
  of 
  this 
  electrode 
  a 
  Faraday 
  cylinder 
  was 
  

   fastened. 
  The 
  vertical 
  cross-section 
  of 
  this 
  cylinder 
  was 
  similar 
  

   in 
  outline 
  to 
  that 
  of 
  a 
  sector 
  of 
  a 
  circle, 
  having 
  an 
  obtuse 
  angle 
  

   at 
  the 
  vertex. 
  The 
  upper 
  chamfered 
  edges 
  of 
  the 
  Faraday 
  cyl- 
  

   inder 
  were 
  separated 
  from 
  each 
  other 
  just 
  enough 
  to 
  produce 
  

   a 
  slightly 
  wider 
  slit 
  than 
  the 
  opposing 
  one 
  in 
  the 
  lower 
  electrode. 
  

   The 
  distances 
  between 
  the 
  corresponding 
  edges 
  of 
  the 
  two 
  paral- 
  

   lel 
  slits 
  could 
  be 
  reduced 
  to 
  less 
  than 
  001 
  cm. 
  The 
  Faraday 
  

   cylinder 
  was 
  protected 
  by 
  an 
  appropriately 
  shaped 
  guard 
  cylin- 
  

   der. 
  A 
  description 
  of 
  the 
  auxiliary 
  apparatus 
  and 
  an 
  account 
  

   of 
  the 
  manner 
  of 
  making 
  observations 
  would 
  be 
  superfluous 
  in 
  

   this 
  place. 
  

  

  The 
  most 
  important 
  results 
  obtained 
  may 
  be 
  summarized 
  as 
  

   follows: 
  (a) 
  When 
  the 
  lower 
  disc 
  was 
  made 
  the 
  cathode, 
  and 
  

   was 
  maintained 
  at 
  the 
  same 
  potential 
  as 
  the 
  Faraday 
  cylinder, 
  

   the 
  experiments 
  showed 
  that 
  about 
  one 
  half 
  of 
  the 
  total 
  current 
  

   in 
  the 
  discharge 
  is 
  brought 
  up 
  to 
  the 
  cathode 
  by 
  positive 
  ions. 
  

   (b) 
  Owing 
  to 
  the 
  intense 
  ionization 
  in 
  the 
  neighborhood 
  of 
  the 
  

   slit 
  (and 
  to 
  other 
  possible 
  causes 
  discussed 
  in 
  the 
  paper) 
  all 
  

   attempts 
  to 
  determine 
  the 
  distribution 
  of 
  velocities 
  in 
  this 
  stream 
  

   failed 
  to 
  give 
  unambiguous 
  results, 
  (c) 
  When 
  the 
  perforated 
  

   disc 
  and 
  the 
  upper 
  electrode 
  were 
  made 
  respectively 
  the 
  anode 
  

   and 
  the 
  cathode, 
  while 
  the 
  total 
  current 
  was 
  kept 
  constant, 
  it 
  was 
  

   found 
  that 
  the 
  current 
  carried 
  into 
  the 
  Faraday 
  chamber 
  by 
  the 
  

   cathode 
  rays 
  decreased 
  in 
  geometrical 
  proportion 
  as 
  the 
  cathode 
  

   receded 
  in 
  arithmetical 
  progression, 
  (d) 
  The 
  effect 
  both 
  of 
  the 
  

   distance 
  apart 
  of 
  the 
  electrodes 
  and 
  of 
  the 
  total 
  current, 
  on 
  the 
  

  

  