﻿606 
  Mr. 
  J. 
  Satterly 
  on 
  the 
  Amount 
  of 
  

  

  lowered 
  into 
  it. 
  When 
  lowered 
  into 
  position, 
  which 
  was 
  as 
  

   near 
  the 
  bottom 
  of 
  the 
  tnbe 
  as 
  possible, 
  more 
  liquid 
  air 
  was 
  

   poured 
  in 
  until 
  the 
  condenser 
  was 
  quite 
  cold 
  and 
  the 
  liquid 
  

   air 
  came 
  to 
  within 
  1 
  cm. 
  of 
  the 
  top 
  of 
  the 
  tube. 
  The 
  inlet 
  

   tube, 
  AB 
  fig. 
  5, 
  was 
  then 
  connected 
  by 
  a 
  length 
  of 
  india- 
  

   rubber 
  tubing 
  to 
  the 
  drying-tube 
  (either 
  a 
  calcium 
  chloride 
  

   tube 
  or 
  a 
  sulphuric 
  acid 
  bottle 
  or 
  a 
  cold 
  spiral 
  (see 
  below) 
  

   which 
  was 
  connected 
  to 
  the 
  dust 
  tube 
  and 
  the 
  open 
  air. 
  

   Since 
  the 
  gauges 
  were 
  calibrated 
  with 
  air 
  at 
  ordinary 
  tem- 
  

   peratures 
  and 
  the 
  air 
  leaving 
  the 
  condenser 
  would 
  be 
  very 
  

   cold 
  and 
  therefore 
  less 
  viscous, 
  it 
  was 
  deemed 
  necessary 
  to 
  

   pass 
  this 
  air 
  through 
  a 
  long 
  copper 
  spiral 
  so 
  that 
  it 
  might 
  

   attain 
  a 
  normal 
  temperature 
  before 
  reaching 
  the 
  gauge. 
  The 
  

   outlet 
  tube 
  CD 
  was 
  therefore 
  connected 
  by 
  a 
  length 
  of 
  india- 
  

   rubber 
  tubing 
  to 
  such 
  a 
  spiral 
  containing 
  230 
  cms. 
  of 
  tubing 
  

   of 
  one 
  centimetre 
  bore, 
  the 
  other 
  end 
  of 
  the 
  spiral 
  being 
  

   connected 
  to 
  one 
  of 
  the 
  gauges. 
  

  

  The 
  connexions 
  being 
  made, 
  air 
  was 
  sucked 
  through 
  the 
  

   condenser 
  by 
  the 
  pump 
  at 
  the 
  steady 
  rate 
  of 
  half 
  a 
  litre 
  per 
  

   minute 
  for 
  a 
  period 
  usually 
  of 
  from 
  2 
  hours 
  to 
  4 
  hours. 
  In 
  

   about 
  40-60 
  minutes 
  the 
  liquid 
  air 
  in 
  the 
  Dewar 
  tube 
  sank 
  to 
  

   just 
  above 
  the 
  top 
  of 
  the 
  condenser 
  and 
  required 
  replenish- 
  

   ment. 
  Meanwhile 
  the 
  air 
  in 
  the 
  testing-vessel 
  was 
  repeatedly 
  

   exhausted 
  and 
  renewed 
  and 
  the 
  steady 
  value 
  of 
  the 
  air 
  leak 
  

   determined. 
  When 
  the 
  time 
  of 
  running 
  the 
  air-current 
  was 
  

   nearly 
  up, 
  the 
  testing-vessel 
  was 
  exhausted 
  and 
  also 
  its 
  

   attached 
  drying-tube. 
  Clips 
  on 
  the 
  tubes 
  connecting 
  to 
  the 
  

   condenser 
  were 
  then 
  closed 
  and 
  the 
  air-current 
  stopped. 
  The 
  

   clip 
  on 
  the 
  inlet 
  tube 
  AB 
  still 
  being 
  closed, 
  the 
  outlet 
  tube 
  

   CD 
  was 
  put 
  in 
  open 
  connexion 
  with 
  the 
  drying-tube 
  and 
  the 
  

   testing-vessel. 
  The 
  liquid 
  air 
  was 
  now 
  removed 
  from 
  the 
  

   condenser 
  and 
  the 
  condenser 
  warmed 
  by 
  a 
  Bunsen 
  burner 
  

   until 
  its 
  temperature 
  rose 
  above 
  0° 
  C. 
  The 
  clip 
  on 
  AB 
  w 
  T 
  as 
  

   now 
  opened 
  and 
  the 
  air 
  admitted 
  slowly. 
  It 
  swept 
  through 
  

   the 
  condenser 
  and 
  carried 
  all 
  the 
  emanation 
  therein 
  to 
  the 
  

   testing-vessel. 
  The 
  leak 
  in 
  the 
  vessel 
  was 
  now 
  taken. 
  

   Usually 
  the 
  vessel 
  and 
  its 
  contents 
  were 
  left 
  to 
  stand 
  for 
  

   three 
  hours 
  in 
  order 
  to 
  see 
  how 
  the 
  leak 
  varied 
  with 
  time. 
  

   When 
  this 
  last 
  leak 
  was 
  taken 
  the 
  vessel 
  was 
  twice 
  ex- 
  

   hausted 
  and 
  refilled 
  and 
  then 
  allowed 
  to 
  stand 
  till 
  the 
  next 
  

   experiment. 
  

  

  Blank 
  experiments 
  were 
  made 
  to 
  see 
  whether 
  warming 
  

   the 
  condenser 
  or 
  rushing 
  the 
  air 
  through 
  it 
  gave 
  any 
  

   increased 
  conductivity 
  to 
  the 
  air, 
  but 
  the 
  results 
  were 
  

   negative. 
  

  

  