﻿the 
  Uranium 
  Dis'mtegration 
  Series. 
  817 
  

  

  Therefore 
  any 
  line 
  in 
  the 
  spectrum 
  obtained, 
  other 
  than 
  those 
  

   due 
  to 
  calcium 
  or 
  uranium, 
  mioht 
  possibly 
  belong 
  to 
  a 
  final 
  

   product. 
  To 
  simplify 
  the 
  examination, 
  a 
  comparison 
  was 
  

   made 
  with 
  a 
  carefully 
  purified 
  specimen 
  of 
  uranium 
  oxide. 
  

   To 
  obtain 
  wave-lengths, 
  an 
  iron 
  reference-spectrum 
  was 
  

   used. 
  The 
  arc 
  with 
  carbon 
  poles 
  was 
  used 
  to 
  burn 
  the 
  

   substances. 
  As 
  the 
  mineral 
  did 
  not 
  burn 
  very 
  well, 
  calcium 
  

   chloride 
  was 
  used 
  as 
  a 
  flux. 
  The 
  three 
  spectra 
  were 
  obtained 
  

   on 
  the 
  photographic 
  plate, 
  one 
  above 
  the 
  other, 
  that 
  of 
  the 
  

   mineral 
  being 
  in 
  the 
  centre. 
  In 
  this 
  way 
  we 
  could 
  see 
  what 
  

   lines 
  were 
  in 
  the 
  mineral 
  spectrum 
  and 
  not 
  in 
  the 
  uranium, 
  

   and 
  by 
  means 
  of 
  the 
  iron 
  spectrum 
  find 
  the 
  wave-lengths 
  of 
  

   such 
  lines. 
  In 
  this 
  way 
  it 
  was 
  found 
  that 
  the 
  only 
  lines 
  in 
  

   the 
  spectrum 
  of 
  the 
  mineral 
  not 
  belonging 
  to 
  calcium 
  or 
  

   uranium 
  belonged 
  to 
  iron, 
  lead, 
  barium, 
  and 
  strontium. 
  

   Barium 
  and 
  strontium 
  may 
  certainly 
  be 
  discarded 
  as 
  most 
  

   calcium 
  salts 
  contain 
  a 
  little 
  of 
  them. 
  Iron 
  is 
  an 
  almost 
  

   universal 
  constituent 
  of 
  minerals, 
  being 
  present 
  even 
  in 
  clear 
  

   white 
  salt 
  and 
  Iceland 
  spar 
  : 
  thus 
  not 
  much 
  weight 
  can 
  be 
  laid 
  

   on 
  its 
  appearance. 
  Other 
  analyses 
  carried 
  out 
  on 
  (1) 
  another 
  

   specimen 
  of 
  autunite, 
  locality 
  not 
  knowm, 
  (2) 
  torbernite 
  from 
  

   Cornwall, 
  the 
  double 
  phosphate 
  of 
  copper 
  and 
  uranium 
  

   {Cu(U02)oPoOs 
  + 
  8HoO}. 
  

  

  Except 
  that 
  in 
  the 
  first 
  of 
  these 
  there 
  was 
  more 
  barium 
  

   and 
  in 
  the 
  second 
  that 
  the 
  calcium 
  was 
  replaced 
  by 
  copper, 
  

   the 
  analyses 
  give 
  the 
  same 
  result. 
  

  

  We 
  see, 
  therefore, 
  by 
  the 
  analyses 
  of 
  three 
  minerals 
  from 
  

   different 
  localities, 
  that 
  lead 
  is 
  the 
  only 
  substance 
  not 
  

   accounted 
  for. 
  We 
  all 
  know 
  that 
  if 
  the 
  final 
  product 
  is 
  

   metallic 
  and 
  the 
  mineral 
  old 
  enough, 
  lines 
  belonging 
  to 
  that 
  

   product 
  ought 
  to 
  appear 
  in 
  the 
  spectrum. 
  The 
  spectroscopic 
  

   analysis 
  of 
  these 
  minerals 
  therefore 
  strongly 
  points 
  to 
  lead 
  

   being 
  the 
  ultimate 
  product 
  of 
  the 
  uranium 
  series. 
  

  

  Certain 
  phosphatized 
  bones 
  have 
  been 
  shown 
  by 
  Strutt 
  (Proc. 
  

   Roy. 
  Soc. 
  Aug. 
  1908) 
  to 
  be 
  moderately 
  rich 
  in 
  radioactive 
  con- 
  

   stituents. 
  It 
  was 
  thought 
  worth 
  while 
  to 
  test 
  these 
  for 
  lead. 
  

   The 
  result 
  was 
  positive. 
  No 
  connexion 
  could^ 
  however, 
  be 
  

   traced 
  between 
  the 
  geological 
  age 
  of 
  the 
  specimens 
  and 
  the 
  

   quantity 
  of 
  lead. 
  It 
  must 
  be 
  supposed 
  that 
  here 
  the 
  lead 
  is 
  

   not 
  wholly 
  of 
  radioactive 
  origin. 
  

  

  Summing 
  up, 
  we 
  find 
  that 
  lead 
  is 
  the 
  only 
  substance 
  which 
  

   by 
  spectroscopic 
  analysis 
  can 
  be 
  considered 
  as 
  the 
  ultimate 
  

   product 
  of 
  the 
  uranium 
  series. 
  It 
  has 
  often 
  been 
  pointed 
  out 
  

   on 
  theoretic 
  grounds 
  that 
  lead 
  was 
  probably 
  the 
  ultimate 
  

   product. 
  Boltw^ood's 
  experiments 
  lead 
  to 
  the 
  same 
  conclusion. 
  

   A 
  rough 
  estimate 
  was 
  made 
  of 
  the 
  amount 
  of 
  lead 
  in 
  the 
  

   FUl. 
  Mag. 
  S. 
  6. 
  Vol. 
  18. 
  No. 
  107. 
  A'oi-. 
  1909. 
  3 
  I 
  

  

  