﻿the 
  Thermoelectromotive 
  Force 
  of 
  Nickel 
  and 
  Iron. 
  185 
  

  

  form 
  more 
  strongly 
  marked 
  on 
  the 
  hot 
  side 
  (the 
  reverse 
  of 
  

   Tait's 
  observation). 
  

  

  The 
  temperature 
  of 
  inversion, 
  cold 
  junction 
  at 
  0°, 
  is 
  found 
  

   to 
  be 
  536° 
  C, 
  and 
  is 
  given 
  by 
  the 
  intercept 
  on 
  the 
  axis 
  of 
  

   temperature, 
  between 
  0° 
  and 
  the 
  point 
  of 
  section 
  by 
  the 
  curve 
  

   of 
  thermoelectric 
  power 
  (fig. 
  6, 
  p. 
  188). 
  

  

  The 
  neutral 
  point 
  is 
  at 
  262° 
  C. 
  

  

  Fio-. 
  5. 
  

  

  800 
  900 
  

  

  Scale 
  of 
  Temperature. 
  

  

  Above 
  700°, 
  Cu-Fe 
  E.M.F. 
  increases 
  almost 
  as 
  a 
  linear 
  

   function 
  of 
  the 
  temperature 
  till 
  900° 
  is 
  reached, 
  when 
  a 
  rapid 
  

   increase 
  in 
  the 
  E.M.F. 
  is 
  noticed, 
  with 
  no 
  indication 
  of 
  a 
  

   second 
  neutral 
  point 
  (fig. 
  5). 
  

  

  In 
  the 
  case 
  of 
  Cu-Ni, 
  maximum 
  variations 
  occur 
  at 
  about 
  

   70° 
  C. 
  and 
  340° 
  C. 
  The 
  divergence 
  at 
  340° 
  is 
  very 
  marked, 
  

   and 
  after 
  500° 
  C. 
  increases 
  rapidly. 
  There 
  appears 
  to 
  be 
  a 
  

   small 
  hysteresis 
  effect 
  at 
  the 
  maximum. 
  The 
  temperature 
  of 
  

   inversion, 
  if 
  there 
  be 
  one, 
  does 
  not 
  occur 
  within 
  the 
  limits 
  of 
  

   the 
  experiment, 
  and 
  there 
  is 
  no 
  neutral 
  point. 
  Above 
  700°,. 
  

   the 
  Cu-M 
  curve 
  (fig. 
  5) 
  remains 
  almost 
  linear 
  up 
  to 
  1050°, 
  

   the 
  limit 
  of 
  the 
  experiments, 
  while 
  the 
  slope 
  of 
  the 
  curve 
  is 
  

   practically 
  unchanged. 
  

  

  The 
  E.M.F. 
  curve 
  for 
  Ni-Fe 
  couple 
  (fig. 
  3) 
  up 
  to 
  700° 
  C. 
  

   was 
  obtained 
  by 
  adding 
  the 
  ordinates 
  of 
  the 
  copper-nickel 
  

  

  