﻿184 
  Mr. 
  E. 
  P. 
  Harrison 
  on 
  the 
  Temperature 
  Variation 
  of 
  

  

  Values 
  of 
  D 
  (difference) 
  thus 
  obtained 
  were 
  plotted 
  against 
  

   temperature 
  (Carve 
  D 
  (Ni), 
  fig. 
  4). 
  In 
  a 
  similar 
  way 
  for 
  

   the 
  iron- 
  copper 
  couple 
  a 
  parabola 
  

  

  Et= 
  11*228 
  * 
  --0819241*, 
  

   passing 
  through 
  the 
  ice, 
  aniline, 
  and 
  sulphur 
  points, 
  was 
  

   calculated, 
  and 
  differences 
  from 
  this 
  parabola 
  were 
  plotted. 
  

  

  Fig. 
  4. 
  — 
  Difference 
  Curves. 
  

   OfA/O 
  D(fe) 
  

  

  4-00 
  

  

  600 
  

  

  Scale 
  of 
  Temperature. 
  

   This 
  gives 
  Curve 
  D 
  (Fe), 
  fig. 
  4. 
  In 
  this 
  case 
  differences 
  are 
  

   much 
  smaller 
  than 
  in 
  the 
  case 
  of 
  the 
  nickel. 
  The 
  parabola 
  

   itself 
  is 
  shown 
  in 
  fig. 
  3. 
  

  

  From 
  these 
  differences 
  it 
  is 
  seen 
  that 
  maximum 
  variations 
  

   occur 
  in 
  the 
  case 
  of 
  Cu-Fe, 
  (a) 
  at 
  70°, 
  when 
  the 
  thermo- 
  

   electric 
  E.M.F. 
  is 
  less 
  than 
  the 
  corresponding 
  parabolic 
  

   ordinate 
  by 
  45 
  microvolts; 
  {b) 
  at 
  230°, 
  when 
  the 
  thermo- 
  

   electric 
  E.M.F. 
  is 
  greater 
  than 
  the 
  corresponding 
  parabolic 
  

   ordinate 
  by 
  20 
  microvolts; 
  (c) 
  at 
  370°, 
  when 
  the 
  thermo- 
  

   electric 
  E.M.F. 
  is 
  again 
  less 
  than 
  the 
  corresponding 
  parabolic 
  

   ordinate 
  by 
  5 
  microvolts. 
  Between 
  0° 
  and 
  200°, 
  and 
  between 
  

   400° 
  and 
  750° 
  there 
  is 
  a 
  gradual 
  divergence 
  from 
  parabolic 
  

  

  