﻿Radium- 
  Content 
  of 
  Sea 
  Water. 
  403 
  

  

  and, 
  without 
  any 
  appearance 
  to 
  suggest 
  concealment, 
  can 
  

   retain 
  its 
  emanation 
  ; 
  or 
  that 
  the 
  higher-reading 
  water 
  picked 
  

   up 
  its 
  radium 
  from 
  the 
  bottle. 
  It 
  is 
  true 
  that 
  I 
  have 
  found 
  

   salt 
  water 
  to 
  be 
  a 
  considerably 
  more 
  active 
  solvent 
  of 
  silicates 
  

   than 
  fresh 
  water 
  *, 
  but 
  in 
  this 
  present 
  case 
  we 
  must 
  suppose 
  

   a 
  large 
  quantity 
  — 
  some 
  grams 
  — 
  of 
  glass 
  brought 
  into 
  solution 
  

   from 
  the 
  one 
  bottle 
  and 
  practically 
  none 
  from 
  the 
  other. 
  

   Again 
  the 
  results 
  of 
  (15) 
  and 
  (16) 
  find 
  support 
  in 
  quite 
  

   unconnected 
  exp(;riments 
  recorded 
  from 
  other 
  localities 
  and 
  

   from 
  some 
  in 
  the 
  same 
  localities, 
  but 
  carried 
  out 
  in 
  a 
  different 
  

   manner, 
  as 
  will 
  presently 
  be 
  seen. 
  

  

  Referrinor 
  to 
  the 
  o-eneral 
  considerations 
  which 
  Eve 
  has 
  

   frequently 
  and 
  so 
  effectively 
  raised, 
  might 
  we 
  not 
  regard 
  

   this 
  subject 
  from 
  another 
  aspect 
  and 
  gather 
  support 
  for 
  the 
  

   considerable 
  radioactivity 
  of 
  sea 
  water 
  from 
  the 
  ionization 
  and. 
  

   penetrating 
  radiation 
  observed 
  in 
  the 
  overlying 
  atmosphere 
  ? 
  

   It 
  does 
  not 
  seem 
  probable 
  that 
  thorium 
  will 
  prove 
  responsible 
  

   for 
  any 
  very 
  large 
  part 
  of 
  these 
  effects. 
  From 
  a 
  single 
  deter- 
  

   mination 
  of 
  the 
  thorium-content 
  of 
  water 
  from 
  the 
  Indian 
  

   Ocean 
  (20) 
  ante^ 
  I 
  measured, 
  the 
  quantity 
  as 
  0*9 
  X 
  10~^ 
  gram 
  

   per 
  litre. 
  Taking 
  the 
  radium 
  as 
  3*6, 
  the 
  uranium 
  equivalent 
  

   of 
  this 
  will 
  be 
  about 
  the 
  same 
  in 
  mass 
  as 
  the 
  thorium. 
  This 
  

   is 
  inferred, 
  indeed, 
  from 
  one 
  measurement 
  only 
  ; 
  but 
  three 
  

   other 
  observations, 
  on 
  lesser 
  quantities 
  of 
  water, 
  seemed 
  to 
  

   show 
  a 
  major 
  limit 
  but 
  little 
  above 
  the 
  quantity 
  of 
  thorium 
  

   found 
  in 
  the 
  water 
  from 
  the 
  Indian 
  Ocean 
  (Phil. 
  Mag. 
  

   July 
  1909). 
  

  

  It 
  remains 
  to 
  notice 
  a 
  recent 
  and 
  important 
  contribution 
  to 
  

   the 
  subject 
  of 
  oceanic 
  radioactivity. 
  In 
  the 
  course 
  of 
  a 
  voyage 
  

   across 
  the 
  Atlantic 
  and 
  through 
  the 
  Straits 
  of 
  Magellan 
  to 
  

   Chili, 
  W. 
  Knoche 
  {Phys. 
  Zeit. 
  March 
  1909) 
  in 
  twelve 
  experi- 
  

   ments 
  measured 
  the 
  emanation 
  content 
  of 
  sea 
  water. 
  He 
  

   used 
  the 
  Engler 
  and 
  Sieveking 
  apparatus 
  as 
  modified 
  by 
  

   Kohlrausch 
  and 
  Lowenthal. 
  Eight 
  of 
  the 
  observations 
  are 
  

   on 
  Atlantic 
  water, 
  from 
  12° 
  2^' 
  N. 
  to 
  12° 
  12' 
  S. 
  In 
  these 
  

   experiments 
  a 
  litre 
  of 
  the 
  sea 
  water 
  is 
  shaken 
  violently 
  with 
  

   air 
  in 
  a 
  closed 
  vessel 
  for 
  two 
  minutes, 
  and 
  the 
  air 
  then 
  

   immediately 
  introduced 
  into 
  the 
  electroscope. 
  Expressed 
  in 
  

   electrostatic 
  units 
  the 
  current 
  established 
  in 
  the 
  electroscope, 
  

   as 
  obtained 
  from 
  observation 
  of 
  the 
  fall 
  of 
  potential 
  during 
  

   the 
  first 
  thirtv 
  minutes, 
  ranges 
  in 
  the 
  several 
  experiments 
  

   from 
  0-00000 
  "to 
  0-00029. 
  This 
  current 
  is 
  due 
  to 
  the 
  eman- 
  

   ation 
  ; 
  the 
  normal 
  current, 
  estimated 
  over 
  the 
  previous 
  thirty 
  

   minutes, 
  being 
  deducted 
  from 
  the 
  reading. 
  The 
  mean 
  

   of 
  the 
  twelve 
  measurements 
  is 
  0*00012. 
  After 
  remarkino^ 
  

   * 
  Proc. 
  Royal 
  Irish 
  Academy, 
  xxiv. 
  A. 
  p. 
  21. 
  

  

  