﻿240 
  

  

  Prof. 
  H. 
  A. 
  Bumstead 
  on 
  the 
  

  

  §*• 
  

  

  With 
  the 
  case 
  grounded 
  and 
  with 
  various 
  negative 
  potentials 
  

   on 
  the 
  gauze 
  cage, 
  readings 
  of 
  the 
  electroscope 
  gave 
  the 
  

   charge 
  acquired 
  by 
  the 
  source 
  in 
  a 
  given 
  time, 
  usually 
  one 
  

   minute. 
  It 
  was 
  soon 
  evident 
  that 
  the 
  readings 
  thus 
  obtained 
  

   varied 
  greatly 
  with 
  the 
  time 
  which 
  had 
  elapsed 
  since 
  the 
  

   production 
  of 
  the 
  vacuum. 
  Three 
  hours 
  after 
  the 
  liquid 
  air 
  

   had 
  been 
  applied 
  to 
  the 
  charcoal 
  bulb, 
  a 
  negative 
  potential 
  

   of 
  40 
  volts 
  on 
  the 
  gauze 
  was 
  sufficient 
  to 
  give 
  a 
  slight 
  negative 
  

   charge 
  to 
  the 
  electrode 
  (the 
  source 
  of 
  S-rays, 
  B, 
  rig. 
  2); 
  and 
  

   larger 
  negative 
  potentials 
  caused 
  a 
  marked 
  increase 
  in 
  this 
  

   negative 
  current. 
  (See 
  Curve 
  I, 
  fig. 
  3.) 
  As 
  time 
  went 
  on, 
  

   however, 
  these 
  effects 
  were 
  much 
  altered 
  ; 
  positive 
  currents 
  

   were 
  observed 
  with 
  negative 
  potentials 
  on 
  the 
  gauze 
  greater 
  

   than 
  300 
  volts, 
  and 
  the 
  negative 
  currents 
  at 
  the 
  higher 
  

   potential 
  were 
  much 
  diminished 
  in 
  magnitude. 
  The 
  results 
  

   of 
  four 
  series 
  of 
  observations 
  are 
  given 
  in 
  Table 
  I., 
  and 
  shown 
  

   graphically 
  in 
  fig. 
  3. 
  

  

  Table 
  I. 
  

  

  Volts. 
  

  

  I(3hrs.). 
  

  

  II(22brs.). 
  

  

  III 
  (46 
  brs.). 
  

  

  IV 
  ( 
  66 
  hrs.). 
  

  

  II-I. 
  

  

  III-I. 
  

  

  IV-I. 
  

  

  76-3 
  

  

  - 
  40 
  

  

  - 
  0-3 
  

  

  +63-6 
  

  

  +72-7 
  

  

  4-76- 
  

  

  63-9 
  

  

  73- 
  

  

  - 
  80 
  

  

  —39-7 
  

  

  4-21-5 
  

  

  +33- 
  

  

  + 
  34-5 
  

  

  61-2 
  

  

  72-7 
  

  

  74-2 
  

  

  -120 
  

  

  -51-7 
  

  

  4- 
  8-3 
  

  

  -is- 
  

  

  +205 
  

  

  63-0 
  

  

  727 
  

  

  75-2 
  

  

  -160 
  

  

  -61-3 
  

  

  + 
  1-4 
  

  

  +10- 
  

  

  + 
  13-5 
  

  

  62-7 
  

  

  71-3 
  

  

  74-8 
  

  

  -200 
  

  

  -67-5 
  

  

  - 
  35 
  

  

  + 
  6- 
  

  

  + 
  9- 
  

  

  64-0 
  

  

  735 
  

  

  76-5 
  

  

  -240 
  

  

  -70- 
  

  

  - 
  6-2 
  

  

  + 
  1-7 
  

  

  4- 
  5-5 
  

  

  63-8 
  

  

  71-7 
  

  

  75-5 
  

  

  -280 
  

  

  

  -10- 
  

  

  - 
  1-0 
  

  

  4- 
  2-8 
  

  

  

  

  

  -320 
  

  

  -74- 
  

  

  -10-7 
  

  

  - 
  2-8 
  

  

  o- 
  

  

  63-3 
  

  

  71-2 
  

  

  74- 
  

  

  -360 
  

  

  

  -13-4 
  

  

  

  - 
  1- 
  

  

  

  

  

  —400 
  

  

  -78-4 
  

  

  -14-5 
  

  

  — 
  7" 
  

  

  - 
  3- 
  

  

  639 
  

  

  71-4 
  

  

  75-4 
  

  

  -440 
  

  

  

  -16- 
  

  

  

  - 
  4- 
  

  

  

  

  

  -480 
  

  

  -82-2 
  

  

  -17-8 
  

  

  - 
  9- 
  

  

  - 
  6- 
  

  

  64-4 
  

  

  71-2 
  

  

  76-2 
  

  

  -520 
  

  

  -79-7 
  

  

  -19-6 
  

  

  

  - 
  7- 
  

  

  601 
  

  

  

  72-7 
  

  

  -560 
  

  

  

  -21-4 
  

  

  -ii- 
  

  

  - 
  8- 
  

  

  

  

  

  -600 
  

  

  

  — 
  22-2 
  

  

  

  - 
  9- 
  

  

  

  

  

  -640 
  

  

  -85- 
  

  

  -21-5 
  

  

  -13-2 
  

  

  -10-5 
  

  

  635 
  

  

  71-8 
  

  

  74-5 
  

  

  In 
  the 
  table 
  the 
  first 
  column 
  gives 
  the 
  negative 
  potentials 
  

   applied 
  to 
  the 
  gauze 
  cage; 
  the 
  second, 
  third, 
  fourth, 
  and 
  fifth 
  

   give 
  the 
  currents 
  (in 
  arbitrary 
  units) 
  observed 
  at 
  3, 
  22, 
  46, 
  

   and 
  66 
  hours, 
  respectively, 
  after 
  the 
  application 
  of 
  the 
  liquid 
  

   air; 
  the 
  remaining 
  columns 
  give 
  the 
  differences 
  between 
  these 
  

   currents. 
  

  

  It 
  will 
  be 
  observed 
  that 
  these 
  differences 
  are 
  constant, 
  and 
  

   that 
  the 
  four 
  curves 
  of 
  fig. 
  3 
  have 
  the 
  same 
  form 
  and 
  are 
  

   merely 
  shifted 
  vertically 
  on 
  the 
  diagram. 
  It 
  is 
  quite 
  clear 
  

  

  