﻿Positive 
  Jons 
  emitted 
  from 
  various 
  Hot 
  Bodies. 
  653 
  

  

  place 
  by 
  the 
  stopper 
  at 
  the 
  bottom. 
  The 
  disk 
  c 
  was 
  o£ 
  thm 
  

   copper 
  or 
  platinum. 
  It 
  was 
  adjusted 
  to 
  its 
  place 
  after 
  the 
  

   adjustment 
  of 
  the 
  thermionic 
  radiator 
  H. 
  This 
  radiator 
  in 
  

   the 
  experiments 
  with 
  gold, 
  silver, 
  palladium, 
  aluminium 
  

   phosphate, 
  and 
  iron, 
  was 
  in 
  the 
  form 
  of 
  a 
  disk 
  of 
  approxi- 
  

   mately 
  3 
  mm.^ 
  area. 
  In 
  the 
  other 
  experiments 
  the 
  form 
  was 
  

   a 
  strip 
  or 
  a 
  wire. 
  The 
  radiator 
  was 
  attached 
  directly 
  or 
  

   indirectly 
  to 
  two 
  copper 
  wires 
  shown 
  in 
  the 
  figure. 
  The 
  

   gold 
  disk 
  was 
  welded 
  to 
  the 
  uppermost 
  point 
  of 
  a 
  platinum- 
  

   wire 
  loop, 
  in 
  order 
  that 
  the 
  temperature 
  measurements 
  might 
  

   be 
  checked 
  by 
  the 
  measurement 
  of 
  the 
  resistance 
  of 
  the 
  

   platinum-wire 
  loop. 
  

  

  The 
  apparatus 
  just 
  described, 
  together 
  with 
  the 
  electro- 
  

   meter 
  and 
  its 
  connexions, 
  were 
  placed 
  inside 
  a 
  galvanized 
  

   iron 
  box 
  24x24x18 
  inches, 
  in 
  order 
  to 
  be 
  free 
  from 
  

   moisture 
  eftects 
  which 
  are 
  so 
  aggravating 
  in 
  our 
  climate 
  

   during 
  the 
  summer 
  months. 
  The 
  top 
  of 
  the 
  box 
  was 
  in 
  four 
  

   parts. 
  Each 
  part 
  turned 
  down 
  at 
  the 
  edge 
  into 
  a 
  trough, 
  so 
  

   that 
  when 
  melted 
  paraffin 
  was 
  poured 
  into 
  the 
  trough, 
  the 
  

   top 
  of 
  the 
  box 
  became 
  air-ti^ht. 
  This 
  box 
  arrangement 
  was 
  

   found 
  quite 
  satisfactory. 
  Wires 
  inside 
  such 
  a 
  box 
  do 
  not 
  

   need 
  any 
  additional 
  shielding 
  in 
  order 
  to 
  be 
  free 
  from 
  

   electrical 
  disturbances. 
  

  

  The 
  electrical 
  connexions 
  are 
  shown 
  in 
  fig. 
  2 
  (p. 
  654). 
  The 
  

   surface 
  of 
  the 
  thermionic 
  radiator 
  was 
  placed 
  at 
  H 
  and 
  was 
  

   in 
  the 
  same 
  plane 
  as 
  the 
  surface 
  of 
  the 
  lower 
  disk 
  L 
  and 
  from 
  

   0*5 
  to 
  I'O 
  mm. 
  below 
  the 
  upper 
  disk 
  U. 
  It 
  was 
  attempted 
  to 
  

   have 
  the 
  two 
  disks 
  so 
  near 
  each 
  other 
  that 
  only 
  a 
  com- 
  

   paratively 
  small 
  number 
  of 
  ions 
  would 
  escape 
  to 
  the 
  guard- 
  

   ring 
  G. 
  The 
  upper 
  disk 
  was 
  connected 
  to 
  one 
  pair 
  of 
  

   quadrants 
  of 
  a 
  Dolezalek 
  electrometer 
  and 
  the 
  condenser 
  C 
  

   through 
  the 
  keys 
  k2 
  and 
  Jci, 
  The 
  other 
  pair 
  of 
  quadrants 
  are 
  

   seen 
  to 
  connect 
  electrically 
  to 
  the 
  following 
  : 
  the 
  key 
  ki, 
  the 
  

   guard-ring 
  G, 
  one 
  terminal 
  of 
  the 
  batteries 
  which 
  charged 
  

   the 
  electrometer 
  needle, 
  and 
  to 
  a 
  variable 
  point 
  .v 
  in 
  the 
  

   resistance 
  Hv. 
  The 
  last 
  was 
  a 
  resistance 
  of 
  about 
  90 
  ohms 
  

   across 
  which 
  there 
  was 
  a 
  fall 
  of 
  potential 
  of 
  2 
  volts. 
  It 
  was 
  

   earthed 
  at 
  one 
  end, 
  as 
  shown 
  in 
  the 
  diagram. 
  By 
  adjusting 
  

   the 
  point 
  x 
  various 
  potentials 
  could 
  be 
  applied 
  to 
  the 
  plate 
  U, 
  

   the 
  values 
  of 
  which 
  could 
  be 
  read 
  on 
  a 
  voltmeter 
  placed 
  

   at 
  y. 
  By 
  separating 
  the 
  quadrants 
  by 
  the 
  key 
  k^, 
  the 
  rate 
  of 
  

   charging 
  up 
  of 
  the 
  electrometer 
  indicated 
  the 
  current 
  to 
  the 
  

   upper 
  disk 
  against 
  the 
  given 
  potential. 
  Usually 
  about 
  

   240 
  divisions 
  on 
  the 
  electrometer 
  scale 
  represented 
  one 
  volt. 
  

   However, 
  the 
  method 
  does 
  not 
  require 
  that 
  the 
  sensibility 
  be 
  

   known 
  accurately. 
  The 
  capacity 
  of 
  the 
  electrometer 
  system 
  

  

  