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  Mr. 
  John 
  S. 
  Townsend 
  on 
  Electrical 
  

  

  calculate 
  as 
  being 
  the 
  atomic 
  charge, 
  on 
  the 
  supposition 
  that 
  

   at 
  ordinary 
  temperature 
  and 
  pressure 
  there 
  are 
  10 
  20 
  mole- 
  

   cules 
  in 
  each 
  cubic 
  centimetre 
  of 
  a 
  gas. 
  The 
  experiments 
  

   giving 
  the 
  weight 
  of 
  the 
  cloud 
  corresponding 
  to 
  the 
  charge 
  

   being 
  of 
  importance 
  were 
  repeated 
  by 
  the 
  following 
  method, 
  

   which 
  gave 
  the 
  same 
  proportionalities, 
  in 
  the 
  different 
  gases, 
  

   between 
  the 
  charge 
  per 
  c.c. 
  and 
  weight 
  of 
  cloud 
  per 
  c.c. 
  as 
  

   were 
  previously 
  obtained. 
  

  

  3. 
  The 
  apparatus 
  which 
  was 
  used 
  is 
  shown 
  in 
  fig. 
  1. 
  The 
  

   positively-charged 
  oxygen 
  and 
  hydrogen 
  given 
  off 
  from 
  a 
  

  

  Fig. 
  1. 
  

  

  dilute 
  sulphuric-acid 
  cell 
  were 
  first 
  bubbled 
  through 
  a 
  solution 
  

   of 
  potassium 
  iodide 
  in 
  the 
  small 
  flask 
  A, 
  and 
  then 
  through 
  

   distilled 
  water 
  in 
  B. 
  Both 
  A 
  and 
  B 
  were 
  immersed 
  in 
  a 
  

   trough 
  of 
  water 
  C, 
  so 
  that 
  they 
  should 
  remain 
  at 
  a 
  fixed 
  

   temperature 
  while 
  an 
  experiment 
  was 
  being 
  conducted. 
  The 
  

   charged 
  gas 
  thus 
  formed 
  a 
  cloud 
  and 
  carried 
  it 
  along 
  the 
  

   delivery-tube 
  D, 
  which 
  led 
  into 
  the 
  paraffin 
  block 
  P 
  inside 
  a 
  

   large 
  metallic 
  screen 
  S. 
  The 
  block 
  P 
  was 
  arranged 
  as 
  shown 
  

   in 
  the 
  figure, 
  in 
  order 
  that 
  the 
  moisture 
  should 
  not 
  break 
  

   down 
  the 
  insulation 
  by 
  settling 
  on 
  the 
  paraffin. 
  By 
  this 
  

   means 
  the 
  moist 
  gas 
  entered 
  the 
  larger 
  tube 
  T 
  connected 
  to 
  

   three 
  sulphuric- 
  acid 
  bulbs, 
  F, 
  set 
  up 
  between 
  the 
  two 
  paraffin 
  

   tunnels 
  P 
  and 
  Q. 
  After 
  the 
  gas 
  had 
  bubbled 
  through 
  the 
  

   acid 
  it 
  was 
  not 
  only 
  cleared 
  of 
  the 
  moisture 
  which 
  under 
  

   ordinary 
  conditions 
  it 
  would 
  have 
  carried 
  from 
  B, 
  but 
  the 
  

   cloud 
  was 
  also 
  completely 
  removed. 
  The 
  increase 
  of 
  weight 
  

  

  