﻿Radium 
  Emanation 
  in 
  the 
  Atmosphere. 
  

  

  589 
  

  

  I 
  could 
  run 
  the 
  water 
  out 
  of 
  the 
  collector 
  down 
  to 
  a 
  certain 
  

   mark, 
  and 
  make 
  sure 
  that 
  when 
  I 
  exhausted 
  the 
  testing 
  vessel 
  

   and 
  connected 
  the 
  vessel 
  with 
  the 
  collector 
  all 
  the 
  gas 
  collected 
  

   would 
  pass 
  into 
  the 
  vessel. 
  Tap-water 
  could 
  not 
  be 
  used 
  in 
  

   the 
  aspirators 
  as 
  Cambridge 
  tap-water 
  gives 
  off 
  quits 
  an 
  

   appreciable 
  quantity 
  of." 
  radium 
  emanation. 
  Distilled 
  water 
  

   was 
  therefore 
  used. 
  The 
  aspirators 
  were 
  denoted 
  by 
  (a) 
  and 
  

   (7>) 
  for 
  purposes 
  of 
  reference. 
  

  

  (4) 
  The 
  Manometers 
  for 
  Measuring 
  the 
  Air-Current. 
  — 
  

   During 
  an 
  experiment 
  it 
  is 
  necessary 
  to 
  draw 
  the 
  air-current 
  

   through 
  the 
  charcoal 
  tubes 
  at 
  a 
  steady 
  rate 
  for 
  some 
  time. 
  

   A 
  convenient 
  form 
  of 
  manometer 
  by 
  which 
  the 
  air-current 
  

   could 
  be 
  fairly 
  accurately 
  measured 
  is 
  shown 
  in 
  fig. 
  1. 
  

  

  Fisr. 
  1. 
  

  

  It 
  consists 
  of 
  a 
  piece, 
  AB, 
  of 
  1 
  mm.-bore 
  brass 
  tubing 
  20 
  cms. 
  

   long 
  soldered 
  into 
  two 
  right-angled 
  pieces 
  of 
  brass 
  tubing 
  of 
  

   much 
  larger 
  bore. 
  The 
  parts 
  of 
  the 
  larger 
  tubing 
  in 
  the 
  

   straight 
  line 
  of 
  AB 
  were 
  used 
  to 
  carry 
  the 
  air-current 
  ; 
  the 
  

   other 
  parts 
  were 
  connected 
  by 
  indiarubber 
  joints 
  to 
  a 
  glass 
  

   U-tube 
  manometer 
  containing 
  water 
  and 
  affixed 
  to 
  a 
  paper 
  

   scale. 
  Calibration 
  of 
  the 
  gauge 
  was 
  effected 
  by 
  connecting- 
  

   it 
  to 
  a 
  large 
  aspirator 
  containing 
  water. 
  This 
  water 
  was 
  run 
  

  

  