﻿Chaige 
  of 
  the 
  Jons 
  emitted 
  by 
  Hot 
  Bodies. 
  745 
  

  

  was 
  cut 
  from 
  foil 
  *0024 
  cm. 
  thick, 
  and 
  was 
  usually 
  about 
  

   •03 
  cm. 
  wide, 
  was 
  soldered 
  to 
  the 
  inner 
  side 
  of 
  the 
  plates 
  so 
  

   as 
  to 
  stretch 
  along 
  this 
  rectangular 
  aperture. 
  In 
  order 
  to 
  

   eliminate 
  as 
  far 
  as 
  possible 
  any 
  lack 
  of 
  uniformity 
  in 
  the 
  

   electric 
  field 
  caused 
  by 
  the 
  rectangular 
  aperture, 
  an 
  additional 
  

   plate 
  li 
  was 
  placed 
  behind 
  it 
  and 
  soldered 
  to 
  one 
  of 
  the 
  

   plates 
  /*. 
  A 
  transverse 
  section 
  through 
  the 
  centre 
  of 
  the 
  

   strip 
  is 
  shown 
  below 
  on 
  the 
  right. 
  This 
  shows 
  the 
  plates 
  

   / 
  and 
  h 
  and 
  the 
  ebonite 
  support 
  b. 
  In 
  both 
  this 
  and 
  the 
  

   next 
  figure 
  ebonite 
  parts 
  are 
  indicated 
  throughout 
  by 
  cross 
  

   hatching. 
  It 
  will 
  be 
  observed 
  that 
  the 
  only 
  metallic 
  connexion 
  

   between 
  the 
  plates 
  ff 
  is 
  by 
  means 
  of 
  the 
  metal 
  strip. 
  The 
  

   terminals 
  gg 
  led 
  to 
  mercury 
  cups, 
  by 
  means 
  of 
  which 
  a 
  

   current 
  could 
  be 
  supplied 
  which 
  served 
  to 
  heat 
  the 
  metal 
  

   strip. 
  

  

  The 
  " 
  lower 
  " 
  plane 
  is 
  represented 
  by 
  the 
  plates 
  cc, 
  shown 
  

   in 
  plan 
  on 
  the 
  left 
  above. 
  These 
  were 
  insulated 
  from 
  and 
  

   supported 
  by 
  a 
  brass 
  carriage 
  e, 
  which 
  slid 
  on 
  ways 
  d, 
  cut 
  

   out 
  of 
  a 
  brass 
  plate 
  nn. 
  The 
  edges 
  of 
  the 
  topmost 
  of 
  the 
  

   two 
  plates 
  c, 
  which 
  was 
  fixed 
  relatively 
  to 
  the 
  carriage, 
  were 
  

   bent 
  round 
  and 
  soldered 
  to 
  two 
  stiff 
  straight 
  brass 
  wires. 
  

   The 
  edges 
  of 
  the 
  other 
  plate 
  c 
  were 
  similarly 
  bent 
  round 
  but 
  

   not 
  soldered 
  to 
  the 
  wires, 
  so 
  that 
  this 
  plate 
  could 
  be 
  slid 
  

   along 
  the 
  wires 
  and 
  the 
  width 
  of 
  the 
  slit 
  thus 
  adjusted. 
  The 
  

   top 
  plate, 
  c, 
  had 
  a 
  brass 
  wire, 
  k, 
  soldered 
  to 
  it, 
  on 
  which 
  a 
  

   thread 
  was 
  cut. 
  This 
  passed 
  through 
  to 
  an 
  ebonite 
  button, 
  

   which 
  fitted 
  into 
  a 
  hole 
  in 
  the 
  carriage 
  <?, 
  then 
  through 
  an 
  

   ebonite 
  washer, 
  and 
  was 
  finally 
  screwed 
  tight 
  by 
  means 
  of 
  a 
  

   brass 
  nut. 
  A 
  wire 
  soldered 
  to 
  this 
  nut 
  made 
  connexion 
  with 
  

   the 
  electrometer. 
  It 
  will 
  be 
  observed 
  that 
  in 
  this 
  way 
  the 
  

   plates 
  cc 
  were 
  thoroughly 
  insulated. 
  The 
  catching 
  electrode 
  

   behind 
  the 
  slit 
  is 
  shown 
  at 
  i. 
  This 
  consisted 
  of 
  an 
  outer 
  box 
  

   in 
  metallic 
  connexion 
  with 
  the 
  carriage, 
  enclosing 
  a 
  [_] 
  shaped 
  

   electrode 
  insulated 
  from 
  it. 
  The 
  method 
  of 
  fixing 
  and 
  

   insulating 
  the 
  inner 
  electrode 
  was 
  identical 
  with 
  that 
  for 
  

   the 
  plate 
  c, 
  with 
  the 
  addition 
  that 
  strips 
  of 
  ebonite 
  were 
  

   placed 
  between 
  its 
  ends 
  and 
  the 
  sides 
  of 
  the 
  outer 
  box, 
  to 
  

   prevent 
  it 
  from 
  coming 
  into 
  contact 
  with 
  the 
  latter. 
  A 
  

   metal 
  bracket 
  soldered 
  to 
  the 
  outside 
  of 
  the 
  box 
  enabled 
  it 
  to 
  

   be 
  rigidly 
  screwed 
  into 
  metallic 
  connexion 
  with 
  the 
  carriage 
  

   at 
  m, 
  the 
  sequence 
  of 
  nuts 
  &c. 
  being 
  similar 
  to 
  Jc 
  and 
  /. 
  

   The 
  connexion 
  of 
  I 
  to 
  the 
  electrometer 
  was 
  made 
  by 
  means 
  

   of 
  a 
  wire 
  soldered 
  to 
  its 
  nut. 
  A 
  section 
  near 
  the 
  slit 
  showing 
  

   the 
  manner 
  in 
  which 
  the 
  carriage 
  slid 
  on 
  the 
  ways 
  d 
  is 
  

   shown 
  below 
  on 
  the 
  left. 
  The 
  openings 
  into 
  the 
  box 
  and 
  the 
  

   electrode 
  inside 
  it 
  were 
  made 
  considerably 
  wider 
  than 
  the 
  

  

  