﻿Active 
  Deposit 
  of 
  Actinium 
  in 
  Electric 
  Fields. 
  397 
  

  

  contain 
  certain 
  quantities 
  of 
  suspended 
  microscopic 
  solid 
  

   matter, 
  which 
  it 
  retains 
  for 
  long 
  periods. 
  Suppose 
  now 
  we 
  

   have 
  emanation 
  transforming 
  in 
  the 
  presence 
  of 
  dust-laden 
  

   air, 
  what 
  effects 
  are 
  we 
  to 
  expect? 
  The 
  common 
  observa- 
  

   tion 
  that 
  radioactive 
  deposits 
  adhere 
  to 
  solid 
  surfaces, 
  seems 
  

  

  

  

  

  Fig 
  

  

  . 
  10. 
  

  

  

  

  

  16 
  

  

  1 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

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  at 
  a 
  

  

  TMOSPHEI 
  

  

  IIC 
  PRESS 
  

  

  JR£ 
  

  

  12 
  

  

  I 
  

  

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   2 
  

  

  

  

  

  

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  I 
  

   I 
  

  

  K/iTHODE 
  

  

  Anode 
  At 
  

  

  ICT/yiTY. 
  

  

  T/i/iry 
  

  

  

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  w 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  < 
  

  

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  0-5 
  

  

  1-5 
  

  

  Time 
  

  

  2-0 
  

  

  Ml 
  MUTES 
  

  

  to 
  indicate 
  that 
  the 
  " 
  rest-atoms 
  n 
  are 
  subjected 
  to 
  inter- 
  

   molecular 
  forces 
  of 
  a 
  cohesional 
  nature 
  in 
  the 
  presence 
  of 
  

   matter 
  in 
  the 
  solid 
  state, 
  irrespective 
  of 
  any 
  forces 
  developed 
  

   by 
  virtue 
  of 
  their 
  positive 
  charges. 
  We 
  should 
  expect, 
  

   therefore, 
  even 
  if 
  the 
  dust 
  were 
  uncharged, 
  that 
  it 
  would 
  

   receive 
  a 
  deposit 
  of 
  active 
  matter, 
  and 
  if 
  it 
  happened 
  to 
  

   possess 
  by 
  any 
  chance 
  a 
  negative 
  charge, 
  an 
  additional 
  

   attraction 
  for 
  the 
  active 
  deposit 
  would 
  be 
  furnished. 
  Hence 
  

   we 
  might 
  expect 
  active 
  matter 
  to 
  remain 
  suspended, 
  for 
  long- 
  

   periods, 
  in 
  dusty 
  air 
  near 
  radioactive 
  preparations. 
  

  

  This 
  was 
  long 
  ago 
  noticed 
  by 
  Miss 
  Brooks*. 
  She 
  found 
  

   that 
  if 
  air, 
  which 
  had 
  not 
  been 
  previously 
  rendered 
  free 
  

  

  * 
  Miss 
  Brooks, 
  Phil. 
  Mag. 
  viii. 
  p. 
  373 
  (1904). 
  

   Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  26. 
  No. 
  153. 
  Sept. 
  1913. 
  " 
  2 
  E 
  

  

  