﻿264 
  Prof. 
  More 
  and 
  Mr. 
  Mauchly: 
  Action 
  of 
  a 
  Magnetic 
  

  

  bright 
  and 
  dark 
  bands, 
  and 
  the 
  bright 
  bands 
  were 
  crossed 
  by- 
  

   fine 
  bright 
  and 
  dark 
  spaces. 
  

  

  Investigators 
  in 
  this 
  subject 
  soon 
  become 
  acquainted 
  with 
  

   the 
  instability 
  of 
  the 
  discharge 
  when 
  affected 
  by 
  the 
  magnetic 
  

   field. 
  Frequently 
  the 
  glow 
  flashes 
  and 
  then 
  stops. 
  This 
  

   succession 
  of 
  appearance 
  and 
  disappearance 
  was 
  very 
  erratic 
  

   with 
  a 
  high 
  potential 
  cold 
  cathode. 
  But 
  this 
  intermittent 
  

   ray 
  may 
  be 
  made 
  quite 
  regular 
  with 
  the 
  Wehnelt 
  cathode. 
  

   To 
  produce 
  this 
  regular 
  intermittency, 
  the 
  cathode 
  platinum 
  

   strip 
  is 
  heated 
  sufficiently 
  to 
  give 
  off 
  electrons, 
  but 
  not 
  hot 
  

   enough 
  to 
  produce 
  a 
  continuous 
  discharge. 
  By 
  regulating 
  

   the 
  pressure 
  of 
  the 
  gas, 
  the 
  potential, 
  and 
  the 
  strength 
  of 
  

   the 
  magnetic 
  field, 
  the 
  period 
  between 
  successive 
  flashes 
  

   could 
  be 
  changed 
  from 
  several 
  minutes 
  to 
  a 
  fraction 
  of 
  a 
  

   second. 
  In 
  fact, 
  the 
  succession 
  of 
  flashes 
  may 
  be 
  made 
  too 
  

   rapid 
  to 
  count. 
  This 
  intermittency 
  was 
  exceedingly 
  sensitive 
  

   to 
  the 
  temperature 
  of 
  the 
  cathode 
  ; 
  small 
  variations 
  in 
  the 
  

   heating 
  current 
  being 
  sufficient 
  to 
  alter 
  its 
  character 
  and 
  

   period 
  markedly. 
  

  

  The 
  explanation 
  of 
  this 
  intermittent 
  action 
  is 
  simple. 
  

   With 
  a 
  Wehnelt 
  cathode 
  we 
  have 
  an 
  abundant 
  and 
  steady 
  

   supply 
  of 
  electrons 
  near 
  the 
  cathode 
  and 
  a 
  great 
  lowering 
  of 
  

   the 
  potential 
  fall 
  necessary 
  to 
  produce 
  a 
  current. 
  But 
  if 
  we 
  

   cool 
  the 
  platinum 
  strip 
  to 
  a 
  dull 
  red, 
  and 
  at 
  the 
  same 
  time 
  

   reduce 
  the 
  power 
  of 
  the 
  other 
  factors 
  which 
  tend 
  to 
  produce 
  

   the 
  luminous 
  discharge, 
  we 
  still 
  have 
  many 
  electrons 
  pro- 
  

   duced 
  at 
  the 
  cathode, 
  but 
  not 
  sufficient 
  to 
  maintain 
  a 
  steady 
  

   current. 
  The 
  electrons 
  accumulate 
  until 
  a 
  critical 
  value 
  is 
  

   reached, 
  the 
  flash 
  of 
  light 
  occurs 
  in 
  the 
  tube 
  and 
  then 
  goes 
  

   out 
  because 
  of 
  the 
  insufficient 
  rate 
  of 
  supply 
  of 
  electrons. 
  

   The 
  phenomenon 
  is 
  accordingly 
  repeated 
  only 
  intermittently. 
  

   This 
  explanation 
  is 
  clearly 
  supported 
  by 
  the 
  way 
  the 
  negative 
  

   glow 
  on 
  the 
  anode 
  side 
  of 
  the 
  cathode 
  creeps 
  toward 
  the 
  

   cathode 
  until, 
  when 
  this 
  is 
  almost 
  reached 
  the 
  luminous 
  

   discharge 
  takes 
  place 
  ; 
  the 
  cessation 
  of 
  the 
  discharge 
  is 
  

   accompanied 
  by 
  the 
  jumping 
  of 
  the 
  negative 
  glow 
  away 
  

   from 
  the 
  cathode. 
  

  

  The 
  high 
  frequency 
  of 
  the 
  induced 
  column 
  which 
  

   Professor 
  Bighi 
  takes 
  to 
  be 
  the 
  criterion 
  of 
  magnetic 
  rays 
  

   is 
  in 
  all 
  probability 
  to 
  be 
  explained 
  in 
  a 
  similar 
  way. 
  It 
  is 
  

   almost 
  possible 
  to 
  make 
  the 
  intermittent 
  discharge 
  pass 
  into 
  

   a 
  high 
  frequency 
  induced 
  column. 
  An 
  intermediate 
  step 
  

   exists, 
  when 
  the 
  column 
  is 
  not 
  slowly 
  intermittent, 
  and, 
  on 
  

   the 
  other 
  hand, 
  does 
  not 
  give 
  the 
  tone 
  denoting 
  high 
  

   frequency, 
  but 
  is 
  striated 
  *. 
  Whether 
  this 
  explanation 
  is 
  

  

  * 
  Note: 
  During 
  - 
  long 
  period 
  flashes, 
  rapid 
  periodicity 
  was 
  often 
  noted. 
  

  

  