﻿406 
  On 
  the 
  Radium- 
  Content 
  of 
  Sea 
  Water. 
  

  

  thousands 
  o£ 
  square 
  miles 
  into 
  the 
  equatorial 
  region 
  and 
  there 
  

   bring 
  it 
  to 
  the 
  surface 
  within 
  the 
  lapse 
  of 
  a 
  very 
  few 
  days, 
  

   the 
  view 
  that 
  the 
  emanation 
  is 
  for 
  the 
  larger 
  part 
  unattended 
  

   by 
  radium 
  seems 
  quite 
  untenable. 
  

  

  It 
  is 
  otherwise 
  if 
  we 
  assume 
  that 
  the 
  carriage 
  of 
  radium- 
  

   rich 
  water, 
  from 
  beneath 
  upwards, 
  takes 
  place. 
  The 
  time 
  

   element 
  does 
  not 
  then 
  enter 
  the 
  question. 
  It 
  may 
  well 
  be 
  the 
  

   case 
  that, 
  among 
  other 
  factors, 
  vertical 
  circulation 
  is 
  largely 
  

   concerned 
  in 
  the 
  distribution 
  of 
  the 
  surface 
  radioactivity 
  of 
  

   the 
  ocean. 
  Such 
  a 
  view 
  involves 
  no 
  dij0&culties 
  ; 
  but 
  in 
  

   waters 
  far 
  from 
  the 
  land 
  we 
  are 
  not 
  entitled 
  to 
  assume 
  the 
  

   absence 
  of 
  much 
  of 
  the 
  equivalent 
  radium 
  without 
  adequate 
  

   direct 
  evidence 
  to 
  support 
  such 
  a 
  difficult 
  view. 
  

  

  There 
  are 
  many 
  features 
  of 
  interest 
  in 
  these 
  recent 
  obser- 
  

   vations. 
  The 
  fact 
  of 
  a 
  very 
  wide 
  range 
  of 
  radioactivity 
  is 
  

   strikingly 
  brought 
  out. 
  It 
  must 
  be 
  remembered, 
  however, 
  

   that 
  a 
  null 
  result 
  such 
  as 
  appears 
  among 
  Knoche^s 
  obser- 
  

   vations 
  may 
  be 
  due 
  to 
  temporary 
  de-emanation 
  where 
  the 
  

   quantity 
  of 
  radium 
  is 
  small. 
  Allowing 
  that 
  some 
  part 
  of 
  the 
  

   emanation 
  may 
  be 
  free 
  or 
  exotic, 
  the 
  higher 
  values 
  are 
  in 
  

   fair 
  agreement 
  with 
  my 
  higher 
  readings, 
  but 
  somewhat 
  in 
  

   excess. 
  The 
  mean 
  is 
  a 
  little 
  above 
  the 
  mean 
  which, 
  on 
  

   the 
  strength 
  of 
  a 
  couple 
  of 
  high 
  oceanic 
  readings, 
  I 
  thought 
  

   most 
  probable 
  when 
  writing 
  my 
  Address 
  to 
  Section 
  C, 
  A 
  

   comparison 
  of 
  the 
  results 
  given 
  in 
  the 
  earlier 
  part 
  of 
  this 
  

   paper 
  with 
  the 
  radium-equivalent 
  of 
  the 
  emanation 
  measured 
  

   by 
  Knoche 
  shows 
  many 
  points 
  of 
  resemblance. 
  Knoche's 
  

   determinations 
  show 
  a 
  very 
  decid-ed 
  maximum 
  about 
  the 
  

   Equator. 
  The 
  one 
  observation 
  which 
  I 
  was 
  able 
  to 
  make 
  on 
  

   these 
  waters 
  is 
  in 
  good 
  agreement. 
  Going 
  south 
  the 
  radio- 
  

   activity 
  diminishes 
  and 
  Knoche's 
  lowest 
  results 
  are 
  from 
  

   waters 
  between 
  12° 
  and 
  30° 
  S. 
  Correspondingly 
  one 
  of 
  the 
  

   lowest 
  readings 
  obtained 
  by 
  me 
  was 
  from 
  the 
  sample 
  taken 
  

   in 
  latitude 
  17° 
  S. 
  The 
  waters 
  examined 
  by 
  me 
  were 
  taken 
  

   in 
  the 
  same 
  year, 
  1908, 
  but 
  at 
  a 
  different 
  season 
  — 
  February. 
  

  

  I 
  see 
  no 
  reason 
  to 
  ascribe 
  these 
  coincidences 
  to 
  chance. 
  

   The 
  vertical 
  circulation 
  beneath 
  the 
  Equator, 
  which 
  so 
  many 
  

   facts 
  go 
  to 
  support, 
  is 
  probably 
  responsible 
  for 
  the 
  main 
  

   features 
  of 
  the 
  Atlantic 
  observations. 
  On 
  this 
  view 
  exami- 
  

   nation 
  of 
  the 
  bottom 
  waters 
  should 
  reveal 
  a 
  radioactivity 
  

   generally 
  in 
  excess 
  of 
  that 
  which 
  has 
  been 
  observed 
  at 
  the 
  

   surface 
  of 
  the 
  more 
  northern 
  parts 
  of 
  the 
  ocean. 
  

  

  Considerations 
  arising 
  from 
  the 
  denudative 
  history 
  of 
  the 
  

   continents 
  show 
  that 
  vast 
  quantities 
  of 
  uranium 
  have 
  entered 
  

   the 
  ocean 
  in 
  the 
  course 
  of 
  geological 
  time 
  and 
  have 
  subse- 
  

   quently 
  been 
  removed 
  into 
  the 
  sediments. 
  On 
  an 
  evaluation 
  

  

  