﻿626 
  Prof. 
  A. 
  S. 
  Eve 
  on 
  the 
  Amount 
  of 
  Radium 
  

  

  at 
  the 
  end 
  of 
  an 
  experiment 
  may 
  have 
  travelled 
  1300 
  miles 
  

   since 
  the 
  experiment 
  began 
  : 
  and 
  some 
  of 
  the 
  emanation 
  

   may 
  have 
  left 
  the 
  radium 
  in 
  the 
  ground, 
  or 
  sea, 
  any 
  time 
  

   during 
  about 
  a 
  month 
  previous, 
  although 
  the 
  greater 
  pro- 
  

   portion 
  must 
  have 
  been 
  of 
  much 
  more 
  recent 
  origin. 
  It 
  is 
  

   therefore 
  possible 
  to 
  connect 
  only 
  the 
  most 
  strongly 
  marked 
  

   differences, 
  in 
  excess 
  or 
  defect, 
  of 
  the 
  amount 
  of 
  emanation 
  

   present, 
  with 
  very 
  clearly 
  defined 
  weather 
  conditions. 
  More- 
  

   over, 
  the 
  amount 
  of 
  emanation 
  collected 
  is 
  so 
  small 
  that 
  the 
  

   effect 
  even 
  in 
  a 
  good 
  electroscope 
  is 
  less 
  than 
  the 
  natural 
  

   leak, 
  so 
  that 
  too 
  much 
  importance 
  must 
  not 
  be 
  attached 
  to 
  

   any 
  one 
  reading. 
  

  

  The 
  results 
  obtained 
  are 
  given 
  in 
  the 
  Table 
  which 
  follows 
  

   (pp. 
  628-9) 
  and 
  they 
  may 
  be 
  divided 
  into 
  two 
  series, 
  separated 
  

   by 
  a 
  double 
  line. 
  For, 
  on 
  the 
  12th 
  November, 
  1907, 
  there 
  was 
  

   an 
  abrupt 
  breakdown 
  in 
  the 
  electroscope 
  due 
  to 
  a 
  thin 
  deposit 
  

   of 
  black 
  dust 
  on 
  the 
  sulphur 
  bead 
  insulation, 
  possibly 
  due 
  to 
  

   smoke 
  or 
  very 
  fine 
  dust 
  from 
  the 
  charcoal. 
  The 
  whole 
  

   apparatus 
  was 
  reconstructed 
  of 
  fresh 
  material 
  after 
  this 
  

   accident, 
  and 
  the 
  natural 
  leak 
  and 
  calibration 
  of 
  the 
  electro- 
  

   scope 
  were 
  therefore 
  altered. 
  The 
  two 
  series 
  give 
  results 
  in 
  

   satisfactory 
  agreement. 
  In 
  the 
  second 
  column 
  of 
  the 
  table 
  

   is 
  given 
  the 
  sum 
  of 
  the 
  three 
  readings 
  obtained 
  after 
  testing 
  

   the 
  emanation 
  expelled 
  by 
  heat 
  from 
  the 
  charcoal 
  in 
  each 
  of 
  

   the 
  three 
  glass 
  tubes. 
  The 
  figures 
  in 
  the 
  third 
  column 
  are 
  

   obtained 
  by 
  subtracting 
  from 
  those 
  in 
  the 
  second 
  column 
  

   the 
  average 
  electroscope 
  reading 
  deduced 
  from 
  a 
  number 
  of 
  

   " 
  rest 
  " 
  experiments. 
  A 
  " 
  rest 
  " 
  experiment 
  consisted 
  of 
  

   testing 
  the 
  gases 
  from 
  the 
  three 
  tubes 
  after 
  2*7 
  days' 
  rest, 
  

   during 
  which 
  no 
  air 
  was 
  drawn 
  through 
  the 
  contained 
  char- 
  

   coal. 
  Before 
  November 
  12th 
  the 
  " 
  rest 
  " 
  experiments 
  gave, 
  

   in 
  divisions 
  a 
  minute, 
  -251, 
  '221, 
  -243, 
  '233, 
  '276, 
  '243, 
  -277, 
  

   with 
  a 
  mean 
  value 
  *250. 
  This 
  is 
  larger 
  than 
  three 
  times 
  the 
  

   natural 
  leak 
  of 
  the 
  electroscope, 
  which 
  was 
  3 
  x 
  *065, 
  or 
  *19o. 
  

   I 
  have 
  never 
  found 
  the 
  glass 
  tubes, 
  containing 
  the 
  charcoal, 
  

   entirely 
  free 
  from 
  emanation, 
  some 
  of 
  which 
  probably 
  entered 
  

   the 
  tubes 
  during 
  cooling 
  from 
  the 
  previous 
  heating, 
  and 
  some 
  

   was 
  perhaps 
  due 
  to 
  minute 
  traces 
  of 
  radium 
  in 
  the 
  glass 
  or 
  

   the 
  charcoal. 
  The 
  amount 
  was 
  fairly 
  constant, 
  and 
  too 
  small 
  

   to 
  interfere 
  with 
  the 
  main 
  issue 
  under 
  investigation. 
  A 
  very 
  

   slow 
  current 
  of 
  air 
  through 
  the 
  tubes 
  gave 
  rise 
  to 
  about 
  the 
  

   same 
  electroscope 
  readings 
  as 
  a 
  " 
  rest 
  " 
  experiment. 
  

  

  After 
  November 
  12th 
  the 
  " 
  rest 
  " 
  experiments 
  gave 
  '435, 
  

   •456, 
  "432, 
  -449, 
  with 
  a 
  mean 
  of 
  -450 
  divisions 
  a 
  minute, 
  

   whilst 
  three 
  times 
  the 
  natural 
  leak 
  was 
  3 
  x 
  *123 
  divisions 
  a 
  

   minute. 
  

  

  