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  812 
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  LXXXV. 
  On 
  the 
  Radium 
  Content 
  of 
  certain 
  Igneous 
  Hocks 
  

   from 
  the 
  Sub- 
  Antarctic 
  Islands 
  of 
  New 
  Zealand. 
  By 
  

   C. 
  Coleridge 
  Faer, 
  D.Sc, 
  and 
  D. 
  C. 
  H. 
  Florance, 
  

   M.A., 
  M.Sc.^ 
  

  

  RUTHERFORD 
  (' 
  Radioactive 
  Transformations 
  ') 
  has 
  cal- 
  

   culated 
  that 
  4' 
  6 
  X 
  10""^* 
  gramme 
  of 
  radium 
  per 
  unit 
  

   mass 
  of 
  the 
  Earth 
  would 
  generate 
  an 
  amount 
  of 
  heat 
  equal 
  

   to 
  that 
  lost 
  by 
  the 
  Earth 
  by 
  conduction 
  through 
  its 
  crust. 
  

   Strutt 
  (Proc. 
  Roy. 
  Soc. 
  1907) 
  has 
  examined 
  the 
  radium 
  

   content 
  of 
  a 
  number 
  of 
  igneous 
  and 
  sedimentary 
  rocks, 
  and 
  

   his 
  results, 
  corrected 
  by 
  Eve 
  and 
  Mcintosh 
  for 
  an 
  error 
  of 
  

   standardization, 
  give 
  for 
  mean 
  values 
  

  

  Igneous 
  rocks 
  1*7 
  x 
  10~^^ 
  gramme 
  radium 
  

  

  Sedimentary 
  rocks... 
  1*1x10"^^ 
  „ 
  „ 
  

  

  a 
  result 
  which 
  is 
  about 
  28 
  times 
  as 
  large 
  as 
  the 
  theoretical 
  

   quantity. 
  Eve 
  and 
  Mcintosh 
  (Phil. 
  Mag. 
  Aug. 
  1907) 
  find 
  a 
  

   mean 
  for 
  Igneous 
  and 
  Sedimentary 
  rocks 
  of 
  1*1 
  x 
  10~^^ 
  per 
  

   gramme 
  of 
  rock. 
  Joly 
  (' 
  Nature,^ 
  Sept. 
  1908) 
  finds 
  values 
  

   much 
  higher 
  than 
  these, 
  his 
  mean 
  for 
  igneous 
  rocks 
  being 
  

   6*1 
  X 
  10~^^, 
  whilst 
  the 
  mean 
  content 
  of 
  the 
  Basalts 
  examined 
  

   by 
  him 
  was 
  5*0 
  X 
  10~^^, 
  which 
  is 
  much 
  higher 
  than 
  the 
  

   value 
  found 
  by 
  other 
  investigators 
  for 
  similar 
  rocks. 
  

  

  Method 
  of 
  Testing, 
  — 
  The 
  rocks 
  examined 
  by 
  us 
  were 
  ground 
  

   to 
  a 
  very 
  fine 
  powder, 
  and 
  20 
  grammes 
  were 
  fused 
  in 
  a 
  

   platinum 
  crucible 
  with 
  ordinary 
  fusion 
  mixture, 
  one 
  gramme 
  

   of 
  the 
  powdered 
  rock 
  being 
  mixed 
  with 
  six 
  grammes 
  of 
  the 
  

   mixed 
  carbonates 
  w^hich 
  had 
  been 
  previously 
  tested 
  for 
  

   radium. 
  The 
  fused 
  mass 
  was 
  dissolved 
  partly 
  in 
  distilled 
  

   water 
  and 
  partly 
  in 
  HCl, 
  both 
  of 
  which 
  were 
  separately 
  

   examined. 
  The 
  acid 
  and 
  alkaline 
  solutions 
  were 
  then 
  sepa- 
  

   rately 
  corked 
  with 
  glass 
  tubes 
  and 
  clipped 
  rubber 
  connexions 
  

   in 
  position, 
  and 
  the 
  cork 
  coated 
  with 
  sealing-wax 
  to 
  prevent 
  

   possible 
  leakage 
  of 
  the 
  emanation, 
  and 
  the 
  flasks 
  were 
  then 
  

   set 
  aside 
  for 
  three 
  weeks 
  to 
  mature. 
  The 
  apparatus 
  was 
  

   similar 
  to 
  that 
  described 
  by 
  Strutt 
  (loc. 
  cit.). 
  The 
  solution 
  

   was 
  boiled 
  for 
  one 
  hour, 
  the 
  steam 
  being 
  condensed 
  in 
  a 
  

   Liebig 
  condenser 
  and 
  the 
  gases 
  evolved 
  being 
  collected 
  over 
  

   fresh 
  distilled 
  water. 
  Before 
  the 
  boiling 
  was 
  stopped, 
  the 
  

   water 
  in 
  the 
  jacket 
  of 
  the 
  condenser 
  was 
  run 
  off 
  and 
  steam 
  

   was 
  passed 
  through 
  as 
  far 
  as 
  the 
  collecting 
  vessel 
  to 
  drive 
  

   over 
  the 
  last 
  traces 
  of 
  emanation. 
  The 
  electroscope 
  was 
  

   similar 
  to 
  that 
  used 
  by 
  Boltwood 
  (Amer. 
  Journal 
  of 
  Science, 
  

  

  * 
  Communicated 
  by 
  Professor 
  E. 
  Rutherford, 
  F.R.S. 
  

  

  