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  XLIII. 
  On 
  Volta 
  Electricity 
  of 
  Metals. 
  By 
  J. 
  Erskink- 
  

   Murray, 
  B.Sc, 
  F.R.S.E., 
  Heriot- 
  Watt 
  College*. 
  

  

  I. 
  Introductory. 
  

   II. 
  Method 
  of 
  Experiment. 
  

  

  II[. 
  Effects 
  of 
  Different 
  Methods 
  of 
  Cleansing 
  ths 
  M3tallic 
  Surfaces 
  

   IV. 
  Thin 
  Solid 
  Films 
  of 
  Oxides, 
  Iodides, 
  &c. 
  

   V. 
  Atmospheric 
  or 
  Time 
  Effects. 
  

   VI. 
  Very 
  Thin 
  Liquid 
  Surface-Films 
  on 
  Metals. 
  

   VII. 
  Thick 
  Liquid-Films 
  on 
  Metals. 
  

   VIII. 
  Films 
  Formed 
  from 
  Gases. 
  

   IX. 
  Temperature 
  Variations. 
  

   X. 
  Elimination 
  of 
  Metal-Air 
  Potentials 
  by 
  Solid 
  Nonconducting 
  

   Films 
  on 
  the 
  Metallic 
  Surfaces. 
  

  

  I. 
  Introductory. 
  

  

  §. 
  1. 
  rilHE 
  experimental 
  investigation 
  described 
  in 
  this 
  

   JL 
  communication 
  had 
  as 
  its 
  primary 
  object 
  the 
  

   elucidation 
  and 
  measurement 
  of 
  the 
  variations 
  of 
  volta 
  contact 
  

   electricity 
  of 
  a 
  pair 
  of 
  conductors, 
  due 
  to 
  changes 
  in 
  the 
  state 
  

   of 
  that 
  portion 
  of 
  the 
  surface 
  of 
  each 
  conductor 
  which 
  was 
  

   separated 
  from 
  the 
  other 
  conductor 
  by 
  an 
  insulating 
  medium. 
  

  

  § 
  2. 
  The 
  discovery 
  of 
  contact 
  electricity 
  of 
  dry 
  metals 
  in 
  

   air 
  by 
  Volta 
  at 
  the 
  beginning 
  of 
  the 
  present 
  century, 
  extended 
  

   a 
  quarter 
  of 
  a 
  century 
  later 
  by 
  Pfaff 
  to 
  dry 
  varnished 
  metals 
  

   in 
  other 
  gases, 
  has 
  been 
  confirmed 
  by 
  many 
  subsequent 
  

   experimenters. 
  The 
  reality 
  of 
  the 
  electrostatic 
  force 
  in 
  air 
  

   near 
  an 
  interface 
  between 
  copper 
  and 
  zinc, 
  inferred 
  as 
  an 
  

   obvious 
  consequence 
  from 
  it 
  by 
  Lord 
  Kelvin, 
  was 
  experi- 
  

   mentally 
  demonstrated 
  by 
  him 
  in 
  186 
  1 
  1- 
  In 
  the 
  next 
  twenty 
  

   years 
  many 
  investigations 
  were 
  made, 
  the 
  more 
  important 
  

   being 
  those 
  of 
  Hankel, 
  Gerland, 
  Clifton, 
  Ayrton 
  and 
  Perry, 
  

   and 
  von 
  Zahn. 
  In 
  1881 
  a 
  paper 
  of 
  great 
  importance 
  was 
  

   published 
  by 
  M. 
  Pellat 
  J, 
  and 
  as 
  the 
  present 
  paper 
  is, 
  in 
  some 
  

   respects, 
  only 
  an 
  amplification 
  and 
  extension 
  of 
  his 
  work, 
  it 
  

   may 
  he 
  of 
  advantage 
  to 
  give 
  a 
  short 
  resume 
  of 
  it 
  before 
  going 
  

   further. 
  

  

  M. 
  Pellat's 
  most 
  important 
  results 
  appear 
  to 
  be 
  (1) 
  his 
  

   demonstration 
  of 
  the 
  influence 
  of 
  the 
  physical 
  condition 
  of 
  

   the 
  metallic 
  surfaces 
  on 
  their 
  volta-potential 
  ; 
  thus 
  he 
  found 
  

   that 
  a 
  sharply 
  scratched 
  plate 
  is 
  positive 
  to 
  a 
  more 
  smoothly 
  

   polished 
  one 
  of 
  the 
  same 
  metal, 
  the 
  metals 
  being 
  washed 
  with 
  

   alcohol 
  after 
  polishing 
  in 
  both 
  cases 
  and 
  allowed 
  to 
  dry 
  before 
  

   the 
  measurement 
  of 
  their 
  potential 
  : 
  (2) 
  his 
  measurements 
  of 
  

  

  * 
  Communicated 
  by 
  Lord 
  Kelvin. 
  

  

  f 
  Electrostatics 
  and 
  Magnetism, 
  § 
  400 
  et 
  seq. 
  

  

  % 
  Ann. 
  de 
  Chimie 
  et 
  de 
  Physique, 
  1881. 
  

  

  