﻿132 
  

  

  Mr. 
  John 
  S. 
  Townsend 
  on 
  Electrical 
  

  

  at 
  which 
  the 
  cloud 
  falls 
  in 
  a 
  vessel. 
  The 
  velocity 
  of 
  the 
  drop 
  

   through 
  the 
  gas 
  was 
  obtained 
  by 
  taking 
  two 
  photographs 
  of 
  

   the 
  cloud, 
  allowing 
  some 
  minutes 
  to 
  elapse 
  between 
  the 
  two 
  

   exposures. 
  Fig. 
  3 
  represents 
  two 
  such 
  photographs 
  taken 
  

  

  Fi2. 
  '3. 
  

  

  B 
  

  

  A 
  

  

  

  

  

  <. 
  . 
  ; 
  

  

  : 
  160 
  S 
  

  

  

  

  ss®-§js§ 
  JK^itR 
  

  

  150-B 
  

  

  

  

  

  

  

  

  ,4C 
  H1 
  fl 
  R 
  «!5fB 
  

  

  I 
  140-j§ 
  

  

  

  

  ■ 
  B 
  'P 
  B 
  

  

  '30-3 
  

  

  

  

  

  

  

  

  uoH 
  ■ 
  » 
  ■ 
  

  

  120- 
  5 
  

  

  

  

  B 
  IB- 
  fl 
  

  

  t 
  .0 
  5? 
  

  

  

  

  ^B 
  Mm 
  ■ 
  

  

  >oo-J|l 
  

  

  

  

  

  90-f'r 
  

  

  

  

  B 
  •' 
  i 
  w& 
  

  

  $G-J§§ 
  

  

  

  IHV 
  v 
  

  

  wtt 
  i^F 
  ^mi 
  

  

  70-2 
  

   60-j§j 
  

  

  

  W& 
  

  

  

  

  

  9 
  

  

  .., 
  ; 
  jpj 
  s&l 
  

  

  ^jl 
  i 
  

  

  

  i 
  

  

  " 
  ■ 
  f 
  ' 
  ' 
  

  

  

  

  

  of 
  a 
  cloud 
  formed 
  by 
  bubbling 
  the 
  charged 
  oxygen 
  from 
  a 
  

   sulphuric-acid 
  electrolyte 
  through 
  water. 
  Three 
  minutes 
  

   were 
  allowed 
  to 
  elapse 
  between 
  the 
  two 
  exposures, 
  and 
  the 
  

   scale 
  shows 
  that 
  in 
  that 
  time 
  the 
  cloud 
  had 
  fallen 
  between 
  

   nine 
  and 
  ten 
  millimetres. 
  Similar 
  experiments 
  were 
  made 
  

   with 
  the 
  other 
  gases, 
  but 
  in 
  the 
  case 
  of 
  the 
  hydrogen 
  the 
  

   outline 
  of 
  the 
  cloud 
  never 
  became 
  so 
  distinct 
  as 
  it 
  did 
  in 
  the 
  

   oxygen. 
  

  

  The 
  sizes 
  of 
  the 
  drops 
  were 
  obtained 
  from 
  the 
  formula 
  

   mfiaY 
  = 
  %7ra*g 
  (Lamb, 
  'Motion 
  of 
  Fluids/ 
  p. 
  229). 
  

  

  This 
  gives 
  for 
  the 
  radios 
  of 
  the 
  drop 
  in 
  the 
  positive 
  oxygen 
  

   6*8 
  x 
  10 
  -5 
  , 
  the 
  rate 
  of 
  fall 
  being 
  ten 
  millimetres 
  in 
  three 
  

   minutes, 
  and 
  the 
  radius 
  of 
  the 
  drop 
  in 
  negative 
  oxygen 
  

   7 
  -9 
  x 
  10~ 
  5 
  > 
  the 
  rate 
  of 
  fall 
  being 
  eighteen 
  millimetres 
  in 
  four 
  

   minutes. 
  

  

  We 
  thus 
  know 
  the 
  weight 
  of 
  each 
  drop, 
  and 
  dividing 
  this 
  

  

  