﻿tlie 
  Thermoelectromotive 
  Force 
  of 
  Nickel 
  and 
  Iron, 
  181 
  

  

  glass 
  tubes, 
  which 
  together 
  with 
  a 
  mercury 
  thermometer 
  

   reading 
  to 
  1/10 
  degree 
  0. 
  were 
  placed 
  in 
  a 
  large 
  test-tube 
  full 
  

   of 
  water, 
  the 
  test-tube 
  itself 
  being 
  also 
  immersed 
  in 
  water. 
  

   This 
  arrangement 
  formed 
  the 
  cold 
  junctions, 
  and 
  their 
  

   temperature 
  always 
  varied 
  with 
  the 
  temperature 
  of 
  the 
  room. 
  

   Every 
  observation 
  is 
  reduced 
  to 
  cold 
  junction 
  at 
  0° 
  C. 
  by 
  

   means 
  of 
  a 
  separate 
  series 
  of 
  observations 
  applied 
  graphically. 
  

   Observations 
  at 
  the 
  higher 
  temperatures 
  were 
  taken 
  first 
  in 
  

   each 
  case, 
  so 
  that 
  any 
  change 
  that 
  might 
  be 
  caused 
  by 
  the 
  

   heating 
  would 
  occur 
  at 
  the 
  beginning 
  of 
  the 
  experiments. 
  

   Confirmatory 
  observations 
  were 
  made 
  in 
  steam, 
  aniline 
  

   vapour, 
  and 
  sulphur 
  vapour. 
  In 
  the 
  case 
  of 
  steam 
  an 
  

   ordinary 
  hypsometer 
  was 
  used, 
  the 
  couple-tube 
  and 
  pyrometer 
  

   being 
  placed 
  in 
  it 
  simultaneously, 
  and 
  the 
  temperature 
  of 
  the 
  

   steam 
  calculated 
  as 
  well 
  as 
  observed 
  by 
  the 
  pyrometer. 
  The 
  

   aniline 
  was 
  boiled 
  in 
  a 
  glass 
  beaker 
  about 
  2 
  ft. 
  high, 
  

   provided 
  with 
  " 
  tin 
  " 
  plates 
  at 
  intervals 
  up 
  its 
  length 
  to 
  

   prevent 
  convection-currents. 
  For 
  the 
  sulphur 
  point 
  an 
  

   ordinary 
  sulphur 
  boiling-point 
  apparatus 
  was 
  used. 
  

  

  The 
  effect 
  of 
  heating 
  the 
  junctions 
  in 
  hydrogen 
  and 
  in 
  

   carbon 
  was 
  tried 
  in 
  every 
  case. 
  A 
  large 
  rubber 
  bag 
  was 
  

   filled 
  with 
  96% 
  hydrogen 
  from 
  a 
  cylinder. 
  The 
  bag 
  commu- 
  

   nicated 
  with 
  one 
  arm 
  of 
  a 
  three-way 
  tap, 
  the 
  other 
  two 
  arms 
  

   of 
  which 
  went 
  to 
  the 
  pump 
  and 
  couple-tube 
  respectively. 
  

   The 
  couple-tube 
  was 
  washed 
  out 
  with 
  hydrogen 
  by 
  alternately 
  

   exhausting 
  the 
  apparatus 
  and 
  letting 
  in 
  the 
  gas, 
  and 
  observa- 
  

   tions 
  were 
  taken 
  at 
  pressures 
  slightly 
  in 
  excess 
  of 
  atmospheric 
  

   pressure. 
  The 
  hot 
  junctions 
  when 
  packed 
  in 
  bone-black 
  in 
  

   the 
  porcelain 
  tube 
  gave 
  consistent 
  results 
  up 
  to 
  700°, 
  but 
  

   quite 
  inconsistent 
  results 
  above 
  that 
  temperature. 
  Finally, 
  in 
  

   each 
  case 
  observations 
  were 
  taken 
  in 
  liquid 
  air. 
  The 
  

   junctions 
  were 
  put 
  naked 
  into 
  the 
  liquid 
  with 
  the 
  platinum 
  

   thermometer, 
  also 
  without 
  its 
  tube, 
  beside 
  them. 
  Tempera- 
  

   ture 
  of 
  the 
  air 
  was 
  recorded. 
  

  

  Method 
  of 
  avoiding 
  Oxidation. 
  

  

  For 
  observations 
  above 
  500° 
  it 
  was 
  necessary 
  to 
  protect 
  

   the 
  couples 
  as 
  far 
  as 
  possible 
  from 
  any 
  gases 
  that 
  might 
  

   chemically 
  affect 
  them. 
  Owing 
  to 
  the 
  difficulty 
  of 
  obtaining 
  

   any 
  argon 
  at 
  the 
  time 
  of 
  the 
  experiments, 
  it 
  was 
  finally 
  

   decided 
  to 
  use 
  as 
  good 
  a 
  vacuum 
  as 
  possible. 
  The 
  porcelain 
  

   tube 
  containing 
  the 
  junction 
  was 
  closed 
  with 
  a 
  rubber 
  cork 
  

   through 
  which 
  a 
  glass 
  tube 
  passed. 
  The 
  three 
  wires 
  were 
  

   brought 
  up 
  between 
  the 
  cork 
  and 
  the 
  sides 
  of 
  the 
  tube, 
  and 
  

   were 
  gently 
  burnt 
  into 
  the 
  former. 
  Marine 
  glue 
  was 
  melted 
  

  

  