﻿586 
  |Mr. 
  J. 
  Satterly 
  on 
  the 
  Amount 
  of 
  

  

  the 
  emanation 
  was 
  almost 
  completely 
  abstracted 
  from 
  the 
  air, 
  

   being 
  absorbed 
  in 
  some 
  way 
  or 
  other 
  by 
  the 
  charcoal 
  *. 
  He 
  

   also 
  discovered 
  that 
  the 
  emanation 
  while 
  absorbed 
  by 
  the 
  

   charcoal 
  decayed 
  at 
  the 
  usual 
  rate 
  (half 
  value 
  in 
  3*71 
  days), 
  

   and 
  also 
  that 
  when 
  the 
  charcoal 
  was 
  heated 
  to 
  just 
  below 
  a 
  red 
  

   heat 
  the 
  emanation 
  was 
  released, 
  and 
  could 
  be 
  swept 
  out 
  by 
  

   a 
  current 
  of 
  air. 
  

  

  In 
  the 
  summer 
  of 
  1907 
  I 
  started 
  to 
  adapt 
  this 
  method 
  to 
  

   the 
  measurement 
  of 
  the 
  emanation 
  in 
  the 
  atmosphere; 
  but 
  

   except 
  for 
  getting 
  the 
  apparatus 
  together 
  and 
  obtaining 
  

   practice 
  in 
  the 
  method 
  of 
  work, 
  little 
  progress 
  in 
  actually 
  

   measuring 
  the 
  amount 
  was 
  made 
  till 
  the 
  beginning 
  of 
  this 
  

   year 
  when 
  I 
  obtained 
  the 
  radium 
  solution. 
  

  

  Meanwhile 
  a 
  paper 
  had 
  appeared 
  in 
  the 
  Philosophical 
  

   Magazine 
  of 
  Dec. 
  1907 
  by 
  Mr.*A. 
  S. 
  Eve, 
  of 
  Montreal, 
  who 
  

   had 
  measured 
  the 
  amount 
  of 
  emanation 
  in 
  the 
  air 
  at 
  Montreal 
  

   by 
  the 
  charcoal 
  method. 
  As, 
  however, 
  each 
  one 
  of 
  his 
  expe- 
  

   riments 
  lasted 
  between 
  two 
  and 
  three 
  days, 
  whereas 
  I 
  found 
  

   that 
  I 
  could 
  get 
  a 
  measurable 
  amount 
  in 
  two 
  or 
  three 
  hours, 
  

   I 
  decided 
  to 
  continue 
  my 
  experiments. 
  

  

  J 
  details 
  of 
  the 
  Apparatus. 
  

  

  (1) 
  The 
  Testing 
  Vessel 
  and 
  Electrometer. 
  — 
  The 
  testing 
  

   vessel 
  was 
  a 
  brass 
  cylinder 
  40 
  cms. 
  high 
  and 
  10 
  cms. 
  

   diameter. 
  It 
  was 
  fitted 
  with 
  two 
  side 
  tubes, 
  one 
  of 
  which 
  

   communicated 
  with 
  a 
  U-tube 
  mercury 
  manometer, 
  the 
  other 
  

   served 
  as 
  an 
  inlet 
  and 
  outlet 
  tube, 
  aud 
  communicated 
  with 
  a 
  

   calcium 
  chloride 
  drying-tube. 
  The 
  neck 
  of 
  the 
  can 
  was 
  closed 
  

   by 
  an 
  indiarubber 
  stopper 
  which 
  supported 
  the 
  insulated 
  

   wire 
  electrode. 
  As 
  it 
  was 
  necessary 
  to 
  exhaust 
  the 
  vessel, 
  

   sulphur 
  could 
  not 
  be 
  used 
  as 
  an 
  insulating 
  agent. 
  Amber 
  

   was 
  used 
  instead, 
  a 
  straight 
  amber 
  mouthpiece 
  of 
  a 
  tobacco- 
  

   pipe 
  proving 
  very 
  convenient 
  for 
  the 
  purpose. 
  The 
  wire 
  elec- 
  

   trode 
  was 
  threaded 
  through 
  the 
  amber 
  and 
  fixed 
  in 
  position 
  

   with 
  sealing-wax 
  ; 
  the 
  amber 
  was 
  similarly 
  fixed 
  in 
  a 
  guard- 
  

   tube, 
  which 
  was 
  afterwards 
  earthed, 
  and 
  the 
  guard-tube 
  fitted 
  

   tightly 
  into 
  the 
  indiarubber 
  stopper. 
  Within 
  the 
  vessel 
  the 
  

   wire 
  reached 
  nearly 
  to 
  the 
  bottom; 
  outside 
  the 
  vessel 
  it 
  

   was 
  bent 
  round 
  and 
  passing 
  through 
  an 
  earthed 
  shield-tube 
  

   dipped 
  into 
  a 
  calcium 
  chloride 
  cup 
  supported 
  by 
  one 
  of 
  

   the 
  terminals 
  of 
  a 
  quadrant 
  electrometer. 
  Communication 
  

  

  * 
  See 
  also 
  a 
  paper 
  by 
  E. 
  Henriot, 
  " 
  Sur 
  la 
  Condensation 
  des 
  emanations 
  

   radioactives," 
  in 
  Le 
  Radium, 
  Feb. 
  1908. 
  Using 
  a 
  statical 
  method, 
  he 
  

   found 
  that 
  the 
  emanation 
  is 
  completely 
  absorbed 
  by 
  coconut 
  charcoal 
  at 
  

   ordinary 
  temperatures 
  (18° 
  C), 
  and 
  is 
  completely 
  got 
  rid 
  of 
  by 
  heating 
  

   the 
  charcoal 
  to 
  dull 
  redness. 
  

  

  