﻿180 
  Mr. 
  E. 
  P. 
  Harrison 
  on 
  the 
  Temperature 
  Variation 
  of 
  

   B. 
  Measurement 
  of 
  Temperature. 
  

  

  In 
  all 
  cases 
  the 
  hot-junction 
  temperatures 
  were 
  measured 
  

   by 
  a 
  platinum 
  thermometer 
  and 
  recorded 
  automatically 
  by 
  

   Callendar's 
  Recorder, 
  the 
  advantage 
  of 
  this 
  method 
  being 
  

   that 
  simultaneous 
  readings 
  of 
  E.M.F. 
  and 
  of 
  temperature 
  are 
  

   obtained 
  without 
  the 
  necessity 
  for 
  two 
  observers. 
  While 
  

   the 
  temperature 
  was 
  changing 
  slowly 
  (say 
  \° 
  per 
  minute) 
  the 
  

   readings 
  at 
  500° 
  were 
  correct 
  to 
  1/10 
  degree. 
  Observations 
  

   were 
  taken 
  in 
  all 
  cases 
  with 
  rising 
  and 
  falling 
  temperatures 
  

   in 
  order 
  to 
  make 
  sure 
  that 
  the 
  u 
  lag 
  " 
  of 
  the 
  thermometer 
  or 
  

   recorder 
  did 
  not 
  introduce 
  appreciable 
  errors. 
  

  

  The 
  heating 
  -apparatus 
  (fig. 
  2) 
  

   consisted 
  of 
  several 
  concentric 
  Fig. 
  2. 
  

  

  iron 
  cylinders 
  closed 
  at 
  one 
  end. 
  

   For 
  temperatures 
  below 
  700° 
  this 
  

   arrangement 
  was 
  placed 
  on 
  a 
  small 
  

   Fletcher 
  burner, 
  and 
  the 
  whole 
  

   surrounded 
  by 
  a 
  cylinder 
  o£ 
  

   polished 
  tin-plate 
  large 
  enough 
  to 
  

   leave 
  an 
  air-space 
  of 
  two 
  or 
  three 
  

   cms. 
  between 
  itself 
  and 
  the 
  iron 
  

   heater. 
  The 
  inner 
  wall 
  of 
  the 
  

   " 
  tin 
  " 
  cylinder 
  was 
  lined 
  with 
  

   J 
  inch 
  asbestos 
  board. 
  

  

  For 
  heating 
  above 
  700° 
  C. 
  a 
  

   Fletcher 
  gas-furnace 
  with 
  an 
  air 
  

   draught 
  was 
  used, 
  two 
  dampers 
  

   being 
  arranged 
  for 
  regulating 
  the 
  

   temperature. 
  

  

  The 
  hot 
  junction 
  formed 
  by 
  

   fusing 
  together 
  in 
  a 
  reducing 
  

   blowpipe-flame 
  the 
  ends 
  of 
  the 
  

   copper, 
  nickel, 
  and 
  iron 
  wires, 
  

   was 
  placed 
  nearly 
  at 
  the 
  bottom 
  

   o£ 
  a 
  12-inch 
  porcelain 
  tube 
  of 
  

  

  9 
  mm. 
  internal 
  diameter. 
  The 
  platinum 
  thermometer-tube 
  

   was 
  then 
  placed 
  by 
  the 
  side 
  of 
  the 
  tube 
  containing 
  the 
  

   couple, 
  and 
  the 
  two 
  were 
  bound 
  together 
  with 
  several 
  layers 
  

   of 
  thick 
  sheet-copper, 
  extending 
  six 
  inches 
  from 
  the 
  bottom 
  

   of 
  the 
  tubes, 
  which 
  were 
  then 
  placed 
  in 
  the 
  heater 
  and 
  packed 
  

   round 
  with 
  asbestos. 
  The 
  top 
  of 
  the 
  heater 
  was 
  covered 
  

   with 
  4 
  or 
  5 
  layers 
  of 
  asbestos-paper 
  separated 
  from 
  one 
  

   another 
  by 
  air-spaces. 
  

  

  The 
  other 
  ends 
  of 
  the 
  nickel 
  and 
  iron 
  wires 
  were 
  soldered 
  

   to 
  copper 
  leads, 
  and 
  the 
  junctions 
  placed 
  in 
  very 
  small 
  

  

  V 
  V 
  

  

  tf£A 
  T£H. 
  

  

  