﻿Velocities 
  of 
  Delta 
  Rays. 
  241 
  

  

  that 
  we 
  have 
  here 
  the 
  resultant 
  of 
  two 
  effects, 
  the 
  first 
  inde- 
  

   pendent 
  of 
  the 
  time 
  since 
  the 
  vacuum 
  was 
  made, 
  and 
  depending 
  

   upon 
  the 
  applied 
  potential, 
  while 
  the 
  second 
  is 
  independent 
  

   of 
  the 
  potential, 
  but 
  does 
  vary 
  greatly 
  with 
  the 
  time. 
  The 
  

  

  

  

  

  

  

  

  

  Fig. 
  

  

  3. 
  

  

  

  

  

  

  

  

  + 
  n 
  

  

  

  

  

  

  

  

  

  

  

  

  

  1 
  

  

  B 
  

  

  

  

  

  

  

  

  

  

  

  

  

  1 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  \ 
  

  

  

  

  

  

  

  "■*" 
  -i 
  

  

  r™ 
  — 
  « 
  

  

  ez: 
  

   ill 
  

  

  H 
  

  

  4C 
  

  

  

  

  

  

  

  

  

  

  — 
  

  

  

  M 
  

  

  

  "^^^ 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  - 
  * 
  ' 
  

  

  — 
  * 
  

  

  

  

  X 
  

  

  first 
  effect 
  is 
  plainly 
  due 
  (at 
  least 
  in 
  great 
  part) 
  to 
  the 
  escape 
  

   from 
  the 
  source, 
  B. 
  of 
  the 
  swifter 
  §-rays, 
  thus 
  giving 
  it 
  

   a 
  positive 
  charge, 
  which 
  is 
  decreased 
  as 
  larger 
  opposing 
  

   potentials 
  are 
  applied 
  to 
  the 
  gauze. 
  The 
  "second 
  phe- 
  

   nomenon 
  causes 
  the 
  source 
  to 
  gain 
  negative, 
  or 
  to 
  lo>e 
  

   positive, 
  electricity 
  at 
  a 
  rate 
  which 
  is 
  independent 
  of 
  the 
  

   potential 
  beyond 
  40 
  volts; 
  and 
  its 
  variation 
  with 
  the 
  time 
  

   -hows 
  that 
  it 
  must 
  be 
  due 
  to 
  residual 
  gas 
  — 
  either 
  that 
  which 
  

   occupies 
  the 
  volume 
  of 
  the 
  chamber, 
  or 
  that 
  which 
  is 
  con- 
  

   1 
  upon 
  its 
  walls 
  and 
  on 
  the 
  electrode. 
  

   It 
  seemed 
  desirable 
  first 
  to 
  investigate 
  the 
  nature 
  and 
  canse 
  

   of 
  the 
  >eeond 
  effect. 
  When 
  the 
  apparatus 
  was 
  in 
  the 
  condition 
  

   which 
  gave 
  the 
  upper 
  curve 
  (IV) 
  in 
  fig. 
  3, 
  the 
  liquid 
  air 
  was 
  

   removed 
  from 
  the 
  charcoal, 
  and 
  a 
  small 
  quantity 
  of 
  air 
  

   admitted 
  to 
  the 
  chamber 
  so 
  that 
  the 
  pressure 
  rose 
  to 
  0'2 
  mm. 
  

   This 
  was 
  allowed 
  to 
  remain 
  for 
  about 
  15 
  minutes, 
  when 
  

   exhaustion 
  was 
  recommenced, 
  while 
  the 
  charcoal 
  bulb 
  was 
  

   heated 
  in 
  the 
  usual 
  manner. 
  When 
  the 
  pressure 
  had 
  fallen 
  

   :'» 
  mm., 
  the 
  liquid 
  air 
  was 
  again 
  applied. 
  Three 
  hour- 
  

   later 
  a 
  series 
  of 
  measurement- 
  was 
  taken, 
  the 
  results 
  of 
  which 
  

   between 
  those 
  represented 
  in 
  Curves 
  H 
  and 
  IJJ, 
  fig. 
  3. 
  

  

  