﻿384 
  Mr. 
  H. 
  P. 
  Walmsley 
  on 
  the 
  Distribution 
  of 
  the 
  

  

  concentrated 
  sulphuric 
  acid. 
  The 
  velocity 
  of 
  the 
  air 
  current 
  

   was 
  regulated 
  by 
  the 
  number 
  of: 
  bubbles 
  per 
  second 
  passing 
  

   through 
  the 
  acid. 
  The 
  copper 
  wire 
  DE 
  was 
  marked 
  into 
  

   sections 
  before 
  being 
  placed 
  in 
  the 
  tube, 
  and 
  was 
  adjusted 
  

   with 
  a 
  known 
  mark 
  opposite 
  the 
  opening 
  0. 
  The 
  exposures 
  

   lasted 
  at 
  least 
  two 
  hours, 
  i. 
  e, 
  until 
  the 
  emanation 
  and 
  the 
  

   active 
  deposit 
  were 
  nearly 
  in 
  equilibrium. 
  The 
  wire 
  was 
  

   then 
  cut 
  up 
  into 
  sections 
  and 
  the 
  activity 
  of 
  each 
  measured 
  

   with 
  an 
  a-ray 
  electroscope. 
  To 
  ensure 
  a 
  uniform 
  distribution 
  

   of 
  deposit 
  over 
  the 
  surface 
  of 
  the 
  wire, 
  a 
  light 
  ebonite 
  pulley 
  

   F 
  was 
  attached 
  to 
  it 
  and 
  was 
  slowly 
  rotated 
  by 
  a 
  small 
  motor 
  

   during 
  the 
  exposure. 
  

  

  The 
  active 
  deposit 
  on 
  each 
  section 
  was 
  found 
  to 
  decay 
  with 
  

   the 
  same 
  period, 
  namely, 
  that 
  of 
  the 
  long-period 
  product 
  

   actinium 
  B. 
  To 
  obtain 
  the 
  distribution 
  of 
  activity 
  along 
  the 
  

   wire, 
  measurements 
  were 
  commenced 
  ten 
  minutes 
  after 
  the 
  

   completion 
  of 
  the 
  exposure, 
  and 
  the 
  activities 
  corrected 
  back 
  

   to 
  this 
  time. 
  It 
  was 
  found 
  that 
  rotating 
  the 
  wire 
  did 
  not 
  

   always 
  ensure 
  a 
  uniform 
  distribution 
  of 
  active 
  deposit. 
  

   Hence 
  after 
  each 
  reading 
  the 
  section 
  of 
  wire 
  was 
  rotated 
  

   inside 
  the 
  electroscope, 
  and 
  another 
  observation 
  taken. 
  As 
  a 
  

   rule 
  four 
  measurements 
  were 
  available 
  to 
  obtain 
  a 
  mean 
  value 
  

   for 
  the 
  activity 
  on 
  each 
  section. 
  In 
  the 
  case 
  of 
  sections 
  near 
  

   the 
  centre 
  of 
  the 
  tube 
  still 
  more 
  observations 
  were 
  taken. 
  

  

  Fig. 
  3. 
  

  

  350 
  

  

  300 
  

  

  250 
  

  

  £ 
  150 
  

  

  b 
  100 
  

  

  

  

  

  

  

  

  

  

  

  

  Si 
  

  

  ?TRIBUT)C 
  

  

  HorAa 
  

  

  VITY 
  ALO 
  

  

  NG 
  WIRE 
  

  

  

  

  

  

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  1 
  

  

  2 
  

  

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  4 
  

  

  5 
  

  

  6 
  

  

  7 
  

  

  

  

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  r/fOAf 
  CENTRE 
  O 
  //V 
  MILLIMETRES 
  

  

  The 
  results 
  of 
  a 
  typical 
  experiment 
  are 
  shown 
  in 
  fig. 
  3, 
  which 
  

   represents 
  the 
  distribution 
  of 
  activity 
  on 
  half 
  the 
  wire. 
  

  

  