﻿404 
  Dr. 
  J. 
  Ersldne- 
  Murray 
  on 
  

  

  Two 
  hours 
  later 
  the 
  same 
  plate 
  gave 
  

  

  •92 
  volt, 
  

  

  showing 
  that 
  the 
  effect 
  is 
  nearly 
  permanent. 
  By 
  burnishing 
  

   the 
  plate 
  again 
  a 
  finer 
  polish 
  was 
  obtained. 
  With 
  the 
  same 
  

   standard 
  the 
  potential 
  is 
  now 
  

  

  1-00 
  volt, 
  

   still 
  further 
  burnishing 
  giving 
  

  

  1-02 
  volt. 
  

  

  If 
  the 
  zinc 
  be 
  now 
  polished 
  on 
  glass-paper 
  it 
  returns 
  to 
  its 
  

   original 
  potential. 
  Now 
  steel, 
  of 
  which 
  the 
  burnisher 
  was 
  

   made, 
  is 
  negative 
  to 
  zinc 
  ; 
  hence 
  this 
  rise 
  cannot 
  have 
  been 
  

   due 
  to 
  particles 
  of 
  steel 
  on 
  the 
  zinc, 
  but 
  must 
  have 
  been 
  

   caused 
  by 
  some 
  change 
  involved 
  in 
  the 
  smoothing 
  process 
  to 
  

   which 
  the 
  zinc 
  had 
  been 
  subjected, 
  possibly 
  by 
  a 
  hardening 
  

   of 
  the 
  surface 
  layer. 
  

  

  § 
  14. 
  Intermediate 
  states 
  of 
  polish 
  give 
  intermediate 
  values 
  

   of 
  potential. 
  For 
  instance, 
  if 
  a 
  zinc 
  plate 
  be 
  filed 
  it 
  will 
  not 
  

   be 
  so 
  sharply 
  scratched 
  as 
  it 
  would 
  be 
  by 
  glass-paper, 
  and 
  of 
  

   course 
  not 
  so 
  smooth 
  as 
  if 
  burnished. 
  Its 
  potential 
  is 
  also 
  

   found 
  to 
  be 
  between 
  those 
  of 
  scratched 
  and 
  burnished 
  zinc. 
  

   Each 
  polishing, 
  with 
  any 
  given 
  material, 
  was 
  usually 
  suf- 
  

   ficiently 
  thorough 
  to 
  efface 
  the 
  effects 
  of 
  all 
  previous 
  polishings; 
  

   the 
  potential 
  observed 
  thus 
  depended 
  only 
  on 
  the 
  state 
  of 
  

   surface 
  produced 
  by 
  the 
  polisher 
  used 
  just 
  before 
  the 
  ob- 
  

   servation. 
  The 
  results 
  of 
  experiments 
  show 
  that 
  the 
  smoother 
  

   the 
  surface 
  the 
  more 
  positive 
  it 
  becomes. 
  

  

  § 
  1 
  5. 
  The 
  generalization 
  given 
  in 
  § 
  14 
  is 
  supported 
  by 
  the 
  

   results 
  of 
  over 
  one 
  hundred 
  similar 
  experiments 
  with 
  a 
  

   number 
  of 
  metals. 
  The 
  actual 
  results 
  are 
  given 
  in 
  Table 
  I. 
  

   (pp. 
  406, 
  407); 
  it 
  will 
  be 
  well, 
  however, 
  to 
  discuss 
  some 
  of 
  

   these 
  in 
  greater 
  detail 
  than 
  is 
  possible 
  in 
  tabular 
  form. 
  

  

  § 
  16. 
  In 
  order 
  to 
  eliminate 
  the 
  use 
  of 
  different 
  polishing 
  

   agents, 
  1 
  tried 
  the 
  effect 
  of 
  producing 
  different 
  states 
  of 
  

   surface 
  by 
  rubbing 
  the 
  plate 
  against 
  another 
  of 
  the 
  same 
  

   metal. 
  Two 
  copper 
  plates 
  which 
  had 
  been 
  polished 
  on 
  glass- 
  

   paper 
  gave 
  

  

  (a) 
  +-01 
  volt, 
  

  

  {b) 
  +'04 
  volt, 
  

  

  with 
  the 
  standard 
  plate. 
  They 
  were 
  next 
  gently 
  rubbed 
  

   together 
  until 
  parts 
  of 
  each 
  were 
  shiny, 
  and 
  now 
  gave, 
  with 
  

   the 
  same 
  standard, 
  

  

  (a) 
  + 
  -07 
  volt, 
  

  

  (6) 
  +-07 
  volt, 
  

  

  