﻿Eaergy 
  of 
  the 
  Ions 
  emitted 
  hy 
  Hot 
  Bodies. 
  

  

  683 
  

  

  screwed, 
  at 
  the 
  ends. 
  The 
  platinum 
  strips 
  C 
  (fig. 
  2) 
  were 
  

   cut 
  by 
  means 
  o£ 
  a 
  dividing 
  engine, 
  so 
  that 
  their 
  edges 
  were 
  

   accurately 
  parallel. 
  They 
  were 
  0*02 
  cm. 
  broad 
  in 
  some 
  

   experiments 
  and 
  004 
  cm. 
  in 
  others. 
  In 
  order 
  to 
  cut 
  the 
  

   thiu 
  platinum-foil 
  it 
  was 
  cemented 
  on 
  to 
  plate-glass 
  with 
  

   shellac 
  and 
  afterwards 
  loosened 
  with 
  alcohol. 
  The 
  strips 
  

   were 
  welded 
  to 
  stout 
  platinum 
  plates 
  about 
  2 
  mm. 
  square, 
  

   and 
  subsequently 
  boiled 
  in 
  nitric 
  acid 
  and 
  distilled 
  water. 
  

   The 
  plates 
  were 
  then 
  soldered 
  to 
  the 
  screws 
  D, 
  E. 
  As 
  the 
  

   plates 
  were 
  of 
  substantial 
  thickness 
  compared 
  with 
  that 
  of 
  

   the 
  strip 
  it 
  was 
  believed 
  that 
  this 
  method 
  would 
  prevent 
  the 
  

   solder 
  from 
  diffusing 
  into 
  the 
  hot 
  strip 
  during 
  the 
  experi- 
  

   ments. 
  When 
  thus 
  mounted 
  the 
  strip 
  lay 
  in 
  the 
  front 
  of 
  a 
  

   narrow 
  slit 
  in 
  the 
  plate 
  A 
  of 
  the 
  shape 
  shown 
  by 
  the 
  trans- 
  

   verse 
  section 
  in 
  fig. 
  1. 
  The 
  narrowest 
  part 
  of 
  this 
  slit 
  was 
  

   abour 
  0"0o 
  cm. 
  wide, 
  and 
  was 
  a 
  little 
  behind 
  the 
  plane 
  surface 
  

   (about 
  0*01 
  cm.) 
  as 
  the 
  edges 
  were 
  cut 
  away, 
  so 
  as 
  to 
  give 
  a 
  

  

  Fi^. 
  2. 
  

  

  M 
  

  

  very 
  slight 
  taper 
  for 
  about 
  0*1 
  cm. 
  distance. 
  The 
  strip 
  w^as 
  

   set 
  so 
  as 
  to 
  be 
  exactly 
  parallel 
  to 
  the 
  plane 
  A, 
  but 
  the 
  least 
  

   bit 
  behind 
  it, 
  probably 
  about 
  O'OOo 
  cm. 
  The 
  object 
  of 
  these 
  

   precautions 
  was 
  to 
  prevent 
  the 
  ions 
  emitted 
  by 
  the 
  sides 
  and 
  

   back 
  of 
  the 
  strip 
  from 
  straying 
  into 
  the 
  field 
  between 
  the 
  

   plates 
  A 
  and 
  B. 
  To 
  the 
  same 
  end 
  the 
  slit 
  was 
  backed 
  by 
  an 
  

   insulated 
  plate 
  F, 
  which 
  could 
  be 
  connected 
  by 
  the 
  wire 
  

   shown 
  with 
  the 
  plate 
  B. 
  This 
  ensured 
  that 
  whenever 
  there 
  

   was 
  a 
  field 
  between 
  A 
  and 
  B 
  there 
  was 
  a 
  field 
  of 
  the 
  same 
  

   sign 
  and 
  of 
  somewhat 
  greater 
  magnitude 
  tending 
  to 
  drag 
  

   back 
  the 
  ions 
  from 
  the 
  back 
  of 
  the 
  strip. 
  

  

  Trouble 
  was 
  experienced 
  at 
  first 
  in 
  keeping 
  the 
  strip 
  C 
  in 
  

  

  2Z2 
  

  

  / 
  

  

  