﻿142 
  Mr. 
  John 
  S. 
  Townsend 
  on 
  Electrical 
  

  

  formula 
  — 
  — 
  -= 
  -7— 
  X 
  l 
  -^— 
  that 
  the 
  increase 
  in 
  the 
  charge 
  due 
  

   p 
  k 
  q 
  & 
  

  

  to 
  heating 
  the 
  cell 
  arises 
  from 
  an 
  increase 
  in 
  the 
  number 
  of 
  

  

  carriers 
  with 
  the 
  same 
  charge, 
  and 
  not 
  from 
  an 
  increase 
  of 
  

  

  the 
  charge 
  on 
  the 
  carriers 
  already 
  present 
  ; 
  for, 
  if 
  the 
  

  

  increase 
  in 
  density 
  were 
  due 
  to 
  an 
  increase 
  in 
  e, 
  we 
  should 
  

  

  have 
  found 
  — 
  — 
  - 
  to 
  be 
  proportional 
  to 
  the 
  square 
  of 
  p 
  . 
  

  

  18. 
  It 
  would 
  be 
  almost 
  impossible 
  to 
  arrange 
  to 
  pass 
  the 
  

   gas 
  along 
  a 
  tube 
  in 
  such 
  a 
  way 
  that 
  the 
  discharging-power 
  

   would 
  be 
  as 
  small 
  as 
  the 
  theoretical 
  value, 
  calculated 
  from 
  

   the 
  numbers 
  given 
  for 
  k 
  (Section 
  13). 
  Small 
  differences 
  in 
  

   temperature 
  between 
  the 
  gas 
  and 
  the 
  sides 
  of 
  the 
  tube, 
  and 
  

   other 
  effects 
  which 
  would 
  give 
  rise 
  to 
  currents 
  in 
  the 
  gas, 
  

   considerably 
  increase 
  the 
  discharging-power, 
  but 
  here 
  a 
  com- 
  

   paratively 
  small 
  effect 
  on 
  the 
  loss 
  of 
  charge 
  when 
  the 
  gas 
  is 
  

   allowed 
  to 
  stand 
  in 
  the 
  tube. 
  The 
  velocity 
  of 
  the 
  carrier 
  

   towards 
  the 
  sides 
  of 
  the 
  tube, 
  due 
  to 
  an 
  electromotive 
  force, 
  

   will 
  on 
  this 
  account 
  be 
  too 
  large 
  when 
  calculated 
  from 
  the 
  

  

  formula«= 
  4 
  -px^. 
  

  

  Thus, 
  when 
  we 
  substitute 
  the 
  values 
  given 
  in 
  Sections 
  15 
  

  

  16 
  for 
  — 
  — 
  - 
  and 
  p 
  0y 
  we 
  obtain 
  for 
  h 
  the 
  values 
  : 
  ^h 
  = 
  3^h 
  ? 
  and 
  

  

  r 
  

  

  k 
  =12e 
  . 
  

  

  Causes 
  which 
  Influence 
  the 
  Discharging 
  Power. 
  

  

  19. 
  In 
  the 
  above 
  experiments 
  the 
  gases 
  were 
  always 
  

   treated 
  in 
  the 
  same 
  way 
  before 
  entering 
  .the 
  tube 
  C, 
  being 
  

   bubbled 
  first 
  through 
  a 
  solution 
  of 
  potassium 
  iodide, 
  and 
  then 
  

   through 
  strong 
  sulphuric 
  acid. 
  When 
  the 
  gases 
  are 
  bubbled 
  

   through 
  water 
  instead 
  of 
  sulphuric 
  acid, 
  they 
  will 
  enter 
  C 
  

   carrying 
  with 
  them 
  a 
  cloud, 
  the 
  effect 
  of 
  gravity 
  upon 
  which 
  

   makes 
  itself 
  very 
  apparent 
  by 
  comparing 
  the 
  charges 
  acquired 
  

   per 
  minute 
  by 
  the 
  tube 
  when 
  in 
  the 
  vertical 
  and 
  horizontal 
  

   positions. 
  Thus 
  in 
  the 
  case 
  of 
  a 
  stream 
  of 
  highly 
  charged 
  

   hydrogen, 
  which 
  bubbled 
  through 
  water 
  before 
  entering 
  0, 
  

   it 
  was 
  found 
  that 
  the 
  charge 
  acquired 
  was 
  fourteen 
  scale- 
  

   divisions 
  per 
  minute 
  as 
  the 
  gas 
  passed 
  through 
  C 
  in 
  the 
  

   vertical 
  position 
  ; 
  and 
  forty-seven 
  divisions 
  per 
  minute 
  with 
  

   C 
  in 
  the 
  horizontal 
  position. 
  The 
  electric 
  capacity 
  of 
  the 
  

   conductor, 
  consisting 
  of 
  C 
  and 
  the 
  quadrants, 
  was 
  not 
  altered 
  

   by 
  more 
  than 
  three 
  per 
  cent, 
  by 
  turning 
  the 
  tube 
  round, 
  so 
  

   that 
  the 
  large 
  increase 
  in 
  the 
  discharging-power 
  must 
  have 
  

  

  