﻿898 
  Mr. 
  T. 
  Royd.s 
  on 
  the 
  Boppler 
  Effect 
  

  

  and 
  for 
  the 
  cathode 
  with 
  holes 
  by 
  Stark 
  * 
  and 
  Trowbridge 
  f. 
  

   In 
  tl^e 
  latter 
  cases 
  the 
  Doppler 
  effect 
  is 
  chiefly 
  due 
  to 
  the 
  canal 
  

   rays 
  behind 
  the 
  cathode 
  which 
  are 
  seen 
  through 
  the 
  holes. 
  

  

  It 
  is 
  o£ 
  interest 
  to 
  note 
  that 
  the 
  general 
  appearance 
  of 
  the 
  

   Doppler 
  effect 
  in 
  front 
  of 
  the 
  cathode 
  is 
  similar 
  to 
  that 
  

   observed 
  in 
  the 
  canal 
  rays 
  behind 
  the 
  cathode 
  in 
  that 
  with 
  

   values 
  of 
  the 
  cathode 
  fall 
  between 
  certain 
  limits 
  it 
  consists 
  

   of 
  two 
  strips. 
  The 
  extreme 
  edge 
  of 
  the 
  shifted 
  line 
  is 
  not 
  

   sharp 
  as 
  might 
  have 
  been 
  expected. 
  As 
  noted 
  by 
  Paschen, 
  

   the 
  shifted 
  line 
  lies 
  nearer 
  the 
  stationary 
  one 
  than 
  in 
  the 
  case 
  

   behind 
  the 
  cathode. 
  It 
  was 
  observed 
  by 
  Paschen 
  and 
  by 
  

   Trowbridge 
  that 
  there 
  is, 
  besides 
  the 
  Doppler 
  effect 
  of 
  rays 
  

   approaching 
  the 
  cathode, 
  also 
  one 
  on 
  the 
  opposite 
  side 
  of 
  the 
  

   stationary 
  line 
  denoting 
  a 
  motion 
  towards 
  the 
  anode. 
  Paschen 
  

   found 
  that 
  the 
  latter 
  effect 
  was 
  more 
  intense 
  than 
  the 
  former. 
  

   These 
  rays 
  probably 
  consist 
  of 
  the 
  particles 
  reflected 
  on 
  impact 
  

   at 
  the 
  cathode 
  surface, 
  for 
  when 
  a 
  holed 
  cathode 
  is 
  focussed 
  

   on 
  the 
  slit 
  the 
  Doppler 
  effect 
  of 
  rays 
  approaching 
  the 
  negative 
  

   glow 
  is 
  weaker 
  at 
  the 
  holes. 
  The 
  reflexion 
  is 
  probably 
  

   diffuse, 
  for 
  the 
  Doppler 
  effect 
  is 
  smaller 
  and 
  the 
  space 
  between 
  

   the 
  stationary 
  and 
  shifted 
  lines 
  is 
  not 
  so 
  dark 
  ; 
  this 
  effect 
  

   may 
  also 
  be 
  due 
  to 
  light 
  reflected 
  diffusely 
  at 
  the 
  mattened 
  

   surface 
  of 
  the 
  cathode. 
  

  

  On 
  account 
  of 
  the 
  feebleness 
  of 
  the 
  light 
  in 
  front 
  of 
  the 
  

   cathode, 
  experiments 
  were 
  only 
  made 
  with 
  high 
  potentials 
  

   and 
  as 
  strong 
  a 
  current 
  as 
  consistent 
  with 
  the 
  safety 
  of 
  the 
  

   discharge-tube. 
  With 
  a 
  cathode 
  fall 
  of 
  2650 
  volts 
  an 
  

   exposure 
  of 
  10 
  hours 
  was 
  found 
  necessary 
  to 
  avoid 
  under- 
  

   exposure^ 
  which 
  would 
  cause 
  the 
  measurement 
  of 
  tlie 
  minimum 
  

   Doppler 
  effect 
  to 
  be 
  too 
  large. 
  

  

  The 
  photographs 
  were 
  measured 
  by 
  means 
  of 
  a 
  Zeiss 
  

   comparator. 
  The 
  cross-wires 
  were 
  set 
  upon 
  the 
  edge 
  of 
  the 
  

   stationary 
  and 
  shifted 
  lines 
  by 
  eye. 
  The 
  densest 
  portion 
  was 
  

   estimated 
  photometrically 
  with 
  the 
  arrangement 
  described 
  by 
  

   Paschen 
  J. 
  Although 
  it 
  does 
  not 
  follow 
  that 
  the 
  homo- 
  

   geneity 
  of 
  the 
  light 
  in 
  the 
  canal 
  rays 
  is 
  the 
  same 
  as 
  that 
  in 
  

   the 
  stationary 
  line, 
  the 
  minimum 
  Doppler 
  effect 
  was 
  measured 
  

   from 
  the 
  farther 
  edge 
  of 
  the 
  stationary 
  line, 
  since 
  the 
  spectral 
  

   width 
  of 
  the 
  latter 
  was 
  small 
  compared 
  with 
  the 
  width 
  of 
  tie 
  

   slit-image. 
  Even 
  when 
  the 
  minimum 
  was 
  measured 
  from 
  

   the 
  centre 
  of 
  the 
  stationary 
  line 
  the 
  relative 
  differences 
  in 
  

  

  * 
  Stark, 
  Phys. 
  Zeits. 
  vii. 
  747 
  Anm. 
  (1906). 
  

   t 
  Trowbridge, 
  Phil- 
  Mag-, 
  xvii. 
  250 
  (1909). 
  

   X 
  Paschen, 
  Ann. 
  d. 
  Fhys. 
  xxiii. 
  247 
  (1907). 
  

  

  