﻿818 
  Notices 
  respecting 
  New 
  Books. 
  

  

  first 
  specimen 
  o£ 
  autunite, 
  and 
  from 
  that 
  a 
  determination 
  of 
  

   its 
  age. 
  A 
  tenth 
  of 
  a 
  gramme 
  of 
  autunite 
  was 
  burnt 
  in 
  the 
  

   arc 
  with 
  a 
  little 
  calcium 
  chloride, 
  the 
  image 
  of 
  the 
  arc 
  being 
  

   exposed 
  on 
  the 
  slit 
  for 
  two 
  minutes, 
  which 
  was 
  practically 
  

   sufiicient 
  to 
  burn 
  the 
  lead 
  out. 
  The 
  same 
  thing 
  was 
  done 
  for 
  

   similar 
  amounts 
  of 
  two 
  specimens 
  of 
  calcium 
  chloride, 
  the 
  

   first 
  containing 
  - 
  ^ 
  ^^ 
  gramme 
  of 
  lead 
  per 
  gramme, 
  the 
  

   second 
  "^ooo 
  g^^"^™© 
  of 
  lead. 
  There 
  was 
  less 
  lead 
  in 
  

   the 
  mineral 
  than 
  in 
  the 
  first 
  specimen 
  of 
  calcium 
  chloride 
  

   and 
  more 
  than 
  in 
  the 
  second. 
  It 
  was 
  judged 
  that 
  the 
  

   mineral 
  contained 
  — 
  '^ 
  — 
  p-ramme 
  of 
  lead 
  per 
  gramme. 
  As 
  

  

  20^000 
  ^ 
  1 
  . 
  1 
  P 
  

  

  it 
  contams 
  50 
  per 
  cent, 
  uranium, 
  this 
  means 
  that 
  for 
  one 
  

   o;ramme 
  of 
  uranium 
  the 
  autunite 
  contains 
  - 
  — 
  ^- 
  o-ramme 
  

   of 
  lead. 
  In 
  radioactive 
  equilibrium, 
  in 
  one 
  gramme 
  of 
  

   uranium 
  there 
  is 
  3*8 
  X 
  10"'^ 
  gramme 
  of 
  radium. 
  Taking 
  the 
  

   period 
  of 
  radium 
  as 
  2500 
  years, 
  the 
  fraction 
  of 
  radium 
  under- 
  

   going 
  transformation 
  per 
  year 
  is 
  2'S 
  x 
  10~*. 
  This 
  means 
  

  

  207 
  

   that 
  3-8 
  X 
  10-^ 
  X 
  2-8 
  x 
  10-^ 
  x 
  ^ 
  gramme 
  of 
  lead 
  or 
  9 
  x 
  10"^ 
  

  

  would 
  be 
  formed 
  per 
  year 
  for 
  one 
  gramme 
  of 
  uranium 
  in 
  radio- 
  

   active 
  equilibrium. 
  Therefore 
  the 
  time 
  taken 
  for 
  10~^gramme 
  

  

  of 
  lead 
  to 
  form 
  would 
  be 
  ^ 
  — 
  — 
  —^ 
  years, 
  or 
  about 
  a 
  million 
  

   years*. 
  _ 
  _ 
  9 
  x 
  10-" 
  ■' 
  

  

  In 
  conclusion, 
  I 
  wish 
  to 
  record 
  my 
  thanks 
  to 
  Professor 
  

   Strutt, 
  who 
  suggested 
  these 
  experiments, 
  for 
  his 
  interest 
  and 
  

   help 
  throughout, 
  and 
  also 
  to 
  Professor 
  Fowler 
  for 
  his 
  help 
  

   in 
  overcoming 
  the 
  difficulties 
  of 
  spectrum 
  analysis. 
  . 
  

  

  LXXXVII. 
  Notices 
  resjjecting 
  Neio 
  Books. 
  

  

  Report 
  of 
  a 
  Magnetic 
  Survey 
  of 
  South 
  Africa. 
  By 
  J. 
  C. 
  Beattie, 
  D.Sc. 
  

   Published 
  for 
  the 
  Eoyal 
  Society 
  and 
  Sold 
  by 
  the 
  Cambridge 
  

   University 
  Press. 
  I*oudon, 
  1909. 
  20s. 
  net. 
  4to., 
  pp. 
  x 
  + 
  126, 
  

   with 
  six 
  Appendices, 
  pp. 
  1-235, 
  and 
  nine 
  Charts 
  at 
  the 
  end. 
  

  

  ^pmS 
  voluiue 
  deals 
  with 
  observations 
  made 
  at 
  fully 
  400 
  places 
  

   ■•*- 
  in 
  S. 
  Africa, 
  ranging 
  from 
  the 
  extreme 
  South 
  of 
  Cape 
  Colony 
  

   to 
  Victoria 
  Palls 
  in 
  the 
  North. 
  The 
  stations 
  are 
  mostly 
  in 
  British 
  

   territory, 
  hut 
  a 
  few 
  are 
  in 
  Portuguese 
  East 
  Africa. 
  The 
  observations 
  

   were 
  made 
  by 
  Prof. 
  Beattie 
  with 
  the 
  assistance 
  of 
  some 
  friends, 
  

   especially 
  Prof. 
  J. 
  T. 
  Morrison, 
  between 
  1898 
  and 
  1906. 
  The 
  

  

  * 
  On 
  p. 
  204 
  of 
  his 
  book, 
  ^ 
  The 
  Interpretation 
  of 
  Radimn,' 
  Soddy 
  

   mentions 
  that 
  autunite 
  contains 
  no 
  detectable 
  quantity 
  of 
  lead. 
  This 
  is 
  

   probably 
  due 
  to 
  the 
  small 
  amount 
  of 
  lead, 
  which 
  would 
  be 
  very 
  hard 
  to 
  

   detect 
  by 
  ordinary 
  chemical 
  methods, 
  and 
  which 
  would 
  also 
  depend 
  on 
  

   the 
  ao-e 
  of 
  the 
  mineral. 
  

  

  