﻿104 
  H. 
  A. 
  Bumstead 
  — 
  Velocities 
  of 
  Delta 
  Bays. 
  

  

  near 
  to 
  the 
  gauze 
  ; 
  thus 
  at 
  any 
  given 
  voltage, 
  the 
  electrons 
  

   improperly 
  captured 
  must 
  lie 
  between 
  narrow 
  limits 
  of 
  velocity 
  

   and 
  would 
  form 
  a 
  small 
  fraction 
  of 
  the 
  total 
  not 
  returned 
  to 
  

   the 
  electrode. 
  Moreover, 
  since 
  the 
  shape 
  of 
  the 
  lines 
  of 
  force 
  

   near 
  the 
  gauze 
  remains 
  the 
  same, 
  this 
  fraction 
  would 
  not 
  vary 
  

   much 
  for 
  different 
  potentials. 
  The 
  principal 
  effect, 
  therefore, 
  

   of 
  this 
  error 
  would 
  be 
  to 
  increase 
  each 
  ordinate 
  of 
  the 
  curve 
  in 
  

   nearly 
  the 
  same 
  proportion, 
  which 
  would 
  not 
  seriously 
  affect 
  

   its 
  accuracy. 
  

  

  2. 
  Some 
  of 
  the 
  tertiary 
  electrons, 
  set 
  free 
  by 
  the 
  S-rays 
  

   which 
  strike 
  the 
  gauze, 
  may 
  be 
  returned 
  to 
  the 
  electrode. 
  In 
  

   a 
  preceding 
  section 
  reasons 
  have 
  been 
  given 
  for 
  supposing 
  that 
  

   these 
  will 
  form 
  a 
  nearly 
  constant 
  fraction 
  of 
  all 
  the 
  tertiary 
  

   electrons 
  from 
  both 
  gauze 
  and 
  case. 
  If 
  this 
  is 
  so, 
  Curve 
  I 
  lies 
  

   below 
  its 
  true 
  position, 
  each 
  ordinate 
  having 
  subtracted 
  from 
  

   it 
  a 
  fraction 
  of 
  the 
  corresponding 
  ordinate 
  of 
  II. 
  This 
  would 
  

   alter 
  the 
  course 
  of 
  1, 
  depressing 
  it 
  most 
  between 
  100 
  and 
  200 
  

   volts, 
  and 
  less 
  at 
  higher 
  potentials. 
  This 
  correction, 
  however, 
  

   cannot 
  be 
  large. 
  The 
  wires 
  of 
  the 
  gauze 
  occupy 
  only 
  IT 
  per 
  

   cent 
  of 
  its 
  total 
  area, 
  and 
  certainly 
  most 
  of 
  the 
  tertiary 
  elec- 
  

   trons 
  which 
  originate 
  upon 
  it 
  must 
  be 
  captured 
  by 
  the 
  auxiliary 
  

   field. 
  It 
  is 
  quite 
  improbable 
  that 
  this 
  correction 
  can 
  amount 
  

   to 
  more 
  than 
  1 
  or 
  2 
  per 
  cent 
  of 
  the 
  ordinates 
  of 
  Curve 
  II. 
  

  

  3. 
  Some 
  of 
  the 
  S-rays 
  originating 
  upon 
  the 
  sides 
  of 
  the 
  

   box-source 
  will 
  cross 
  its 
  opening 
  obliquely, 
  and 
  will 
  be 
  

   deflected, 
  so 
  as 
  to 
  strike 
  the 
  box, 
  by 
  fields 
  too 
  small 
  to 
  stop 
  

   them. 
  Thus 
  at 
  any 
  given 
  potential, 
  some 
  electrons 
  which 
  

   should 
  get 
  away 
  will 
  not 
  do 
  so, 
  and 
  the 
  ordinates 
  of 
  Curve 
  I 
  

   will 
  be 
  thereby 
  diminished. 
  But 
  the 
  number 
  thus 
  improperly 
  

   stopped 
  at 
  any 
  voltage 
  must 
  be 
  a 
  nearly, 
  or 
  quite, 
  constant 
  

   fraction 
  of 
  those 
  which 
  should 
  escape, 
  so 
  that 
  the 
  effect 
  would 
  

   be 
  merely 
  to 
  change 
  the 
  scale 
  of 
  the 
  curve. 
  

  

  We 
  may 
  reasonably 
  conclude, 
  I 
  think, 
  that 
  the 
  measure- 
  

   ments 
  given 
  represent 
  a 
  fair 
  first 
  approximation 
  to 
  the 
  distri- 
  

   bution 
  in 
  velocity 
  of 
  the 
  swifter 
  S-rays. 
  It 
  will 
  probably 
  be 
  

   possible 
  to 
  improve 
  the 
  accuracy 
  of 
  the 
  determination 
  by 
  using 
  

   a 
  more 
  intense 
  source 
  of 
  a-rays 
  and 
  receiving 
  a 
  restricted 
  beam 
  

   of 
  S-rays 
  in 
  a 
  Faraday 
  cylinder. 
  A 
  suitable 
  source 
  of 
  a-rays 
  

   for 
  this 
  method 
  is 
  not 
  at 
  present 
  at 
  my 
  disposal. 
  

  

  §6. 
  

  

  The 
  preceding 
  measurements 
  have 
  had 
  to 
  do 
  only 
  with 
  

   S-rays 
  whose 
  velocities 
  exceeded 
  20 
  volts. 
  By 
  reducing 
  the 
  

   sensitiveness 
  of 
  the 
  electroscope 
  to 
  somewhat 
  less 
  than 
  one- 
  

   eighth 
  of 
  its 
  former 
  value, 
  measurements 
  could 
  be 
  taken 
  with 
  

   smaller 
  negative 
  potentials 
  on 
  the 
  gauze 
  cage. 
  A 
  series 
  of 
  

  

  