﻿Stnatioiis 
  m 
  the 
  Electric 
  Discharge. 
  447 
  

  

  the 
  tube 
  as 
  determined 
  by 
  this 
  method 
  agreed 
  remarkably 
  

   well 
  with 
  that 
  determined 
  by 
  the 
  method 
  of 
  the 
  exploring^ 
  

   Avire. 
  When 
  the 
  discharge 
  was 
  striated 
  it 
  was 
  generally 
  

   found 
  that 
  where 
  the 
  cathode 
  rays 
  passed 
  underneath 
  a 
  

   striation, 
  i. 
  e. 
  on 
  the 
  cathode 
  side 
  of 
  the 
  bright 
  part 
  of 
  the 
  

   striation, 
  there 
  was 
  a 
  small 
  deflexion 
  of 
  the 
  cathode 
  rays 
  

   towards 
  the 
  cathode 
  of 
  the 
  discharge-tube, 
  showing 
  that 
  in 
  

   this 
  part 
  of 
  the 
  discharge 
  the 
  electric 
  force 
  is 
  negative^, 
  while 
  

   when 
  the 
  path 
  of 
  the 
  cathode 
  rays 
  passed 
  through 
  the 
  bright 
  

   part 
  of 
  a 
  striation 
  there 
  was 
  a 
  large 
  deflexion 
  of 
  the 
  cathode 
  

   rays 
  from 
  the 
  cathode 
  of 
  the 
  discharge-tube, 
  showing 
  that 
  in 
  

   this 
  part 
  of 
  the. 
  discharge 
  the 
  electric 
  force 
  was 
  strongly 
  

   positive. 
  The 
  change 
  from 
  the 
  small 
  negative 
  deflexion 
  to 
  

   the 
  strong 
  positive 
  one 
  w^as 
  exceedingly 
  abrupt, 
  so 
  much 
  so 
  

   that 
  when 
  the 
  anode 
  and 
  cathode 
  were 
  moving 
  downwards, 
  

   owing 
  to 
  the 
  sinking 
  of 
  the 
  float 
  supporting 
  them, 
  and 
  one 
  

   striation 
  after 
  another 
  was 
  thus 
  being 
  brought 
  across 
  the 
  

   path 
  of 
  the 
  cathode 
  rays, 
  the 
  phosphorescent 
  spot 
  moved 
  as 
  

   abruptly 
  as 
  if 
  it 
  had 
  been 
  struck 
  by 
  a 
  blow 
  when 
  the 
  bright 
  

   head 
  of 
  a 
  striation 
  crossed 
  its 
  path. 
  At 
  the 
  low 
  pressures 
  at 
  

   which 
  these 
  observations 
  are 
  made 
  the 
  potential-difference 
  

   between 
  the 
  electrodes 
  when 
  the 
  current 
  is 
  laroe 
  encuoh 
  to 
  

   produce 
  striations 
  is 
  exceedingly 
  small, 
  often 
  not 
  exceeding 
  

   60 
  or 
  70 
  volts. 
  Under 
  these 
  circumstances 
  the 
  negative 
  

   forces 
  although 
  unmistakable 
  are 
  small 
  : 
  when, 
  however, 
  the 
  

   current 
  through 
  the 
  tube 
  is 
  reduced 
  until 
  the 
  discharge 
  is 
  no 
  

   longer 
  striated, 
  the 
  potential-difference 
  betv,'een 
  the 
  electrodes 
  

   is 
  very 
  much 
  increased, 
  and 
  now 
  large 
  negative 
  forces 
  can 
  

   be 
  observefl 
  in 
  the 
  neighbourhood 
  of 
  the 
  anode. 
  Sometimes 
  

   the 
  region 
  in 
  which 
  tiie 
  force 
  is 
  negative 
  extends 
  a 
  con- 
  

   siderable 
  distance 
  from 
  the 
  anode: 
  in 
  one 
  case 
  I 
  observed 
  a 
  

   negative 
  force 
  for 
  two-thirds 
  of 
  the 
  distance 
  from 
  the 
  anode 
  

   to 
  the 
  cathode. 
  

  

  As 
  the 
  corpuscles 
  in 
  the 
  cathode 
  rays 
  have 
  an 
  exceedingly 
  

   small 
  mass 
  they 
  are 
  able 
  to 
  follow 
  very 
  rapid 
  variations 
  in 
  

   the 
  electric 
  field 
  ; 
  by 
  means 
  of 
  them 
  we 
  can 
  observe 
  the 
  

   gradual 
  establishment 
  of 
  the 
  steady 
  state 
  of 
  the 
  discharge 
  

   and 
  the 
  change 
  in 
  the 
  direction 
  of 
  the 
  electric 
  force 
  at 
  certain 
  

   places 
  from 
  positive 
  to 
  negative. 
  Thus 
  suppose 
  the 
  steady 
  

   current 
  through 
  the 
  tube 
  is 
  small 
  and 
  the 
  potential-difference 
  

   is 
  considerable, 
  and 
  that 
  the 
  pencil 
  of 
  cathode 
  rays 
  is 
  passing- 
  

   through 
  the 
  discharge 
  near 
  the 
  anode, 
  then 
  if 
  we 
  watch 
  

   the 
  behaviour 
  of 
  the 
  phosphorescent 
  spot 
  in 
  the 
  interval 
  

   immediately 
  following 
  the 
  application 
  of 
  the 
  potential- 
  

   difference 
  to 
  the 
  tube, 
  we 
  shall 
  find 
  that 
  when 
  the 
  current 
  first 
  

   starts 
  through 
  the 
  tube 
  the 
  spot 
  is 
  repelled 
  from 
  the 
  cathode. 
  

  

  