﻿the 
  Electrical 
  Resistances 
  of 
  Pure 
  Metals. 
  531 
  

  

  iron, 
  nickel, 
  and 
  cobalt, 
  as 
  regards 
  their 
  temperature- 
  

   coefficients, 
  constitute 
  an 
  exceptional 
  and 
  highly 
  charac- 
  

   teristic 
  group, 
  the 
  discussion 
  of 
  which 
  must 
  be 
  reserved 
  for 
  

   a 
  future 
  occasion. 
  

  

  The 
  results 
  discussed 
  in 
  the 
  paper 
  may 
  be 
  summarized 
  

   thus 
  : 
  — 
  

  

  KmYd 
  

  

  (1) 
  A 
  relation 
  cr 
  = 
  — 
  r 
  ^— 
  which 
  roughly 
  holds 
  for 
  

  

  ex. 
  

  

  Silver, 
  Platinum, 
  

  

  Copper, 
  Palladium, 
  

  

  Magnesium, 
  Thallium, 
  

  

  Sodium, 
  Lead, 
  

  

  Zinc, 
  Mercury, 
  

  

  Cadmium, 
  Arsenic, 
  

  

  Calcium, 
  Antimony, 
  

  

  Potassium, 
  Bismuth 
  ; 
  

  

  but 
  fails 
  for 
  gold, 
  indium, 
  tin, 
  and 
  aluminium. 
  It 
  also 
  If 
  ails, 
  

   as 
  we 
  should 
  expect, 
  for 
  iron, 
  nickel, 
  and 
  cobalt 
  — 
  while 
  in 
  

   the 
  case 
  of 
  the 
  remaining 
  metals 
  data 
  cannot 
  be 
  obtained 
  to- 
  

   test 
  the 
  matter. 
  

  

  (2) 
  A 
  temperature 
  factor 
  

  

  fl 
  = 
  (l 
  +e 
  *)[l 
  + 
  l( 
  |3 
  '-S<) 
  *+,..] 
  

  

  obtained 
  from 
  the 
  relation 
  q 
  cc 
  — 
  , 
  approximately 
  true 
  for 
  

  

  tin, 
  copper, 
  cadmium, 
  lead, 
  zinc, 
  silver, 
  and 
  aluminium, 
  but 
  

   not 
  for 
  platinum 
  and 
  palladium, 
  and 
  of 
  course 
  the 
  metals 
  of 
  

   the 
  Iron 
  group. 
  

  

  2*1/3 
  

  

  (3) 
  A 
  specific 
  heat 
  relation 
  e 
  = 
  — 
  --> 
  approximately 
  true 
  

  

  for 
  

  

  Aluminium, 
  

  

  Copper, 
  

  

  Tin, 
  

  

  Cadmium, 
  

  

  Palladium, 
  

  

  Silver, 
  

  

  Iridium, 
  

  

  Platinum 
  ; 
  

  

  but 
  not, 
  of 
  course, 
  for 
  the 
  metals 
  of 
  the 
  Iron 
  group. 
  The 
  

   results 
  are 
  uncertain 
  in 
  the 
  case 
  of 
  lead, 
  magnesium, 
  and 
  

  

  