﻿Self-Recording 
  Electrometer. 
  207 
  

  

  These 
  results 
  are 
  plotted 
  in 
  fig. 
  3. 
  In 
  fig. 
  -A 
  the 
  mean 
  

   deflexions 
  per 
  mm. 
  for 
  the 
  different 
  potentials 
  across 
  the 
  

   quadrants 
  are 
  plotted. 
  

  

  Fiff. 
  4. 
  

  

  

  1 
  ! 
  

  

  40 
  

  

  3 
  ! 
  

  

  S 
  ! 
  

  

  

  || 
  

  

  

  ■ 
  

  

  

  v 
  4 
  - 
  ! 
  

   1 
  ' 
  

  

  \ 
  

  

  

  1 
  j 
  

  

  i 
  1 
  

  

  

  1 
  ! 
  

  

  

  3 
  

  

  

  

  \ 
  

  

  

  

  

  

  

  

  

  \ 
  

  

  ! 
  | 
  

  

  ! 
  1 
  

  

  

  2*0 
  

  

  3 
  

  

  

  

  K 
  

  

  ! 
  

  

  

  

  

  

  ft 
  

  

  XL 
  

  

  

  

  i 
  

  

  | 
  ! 
  

  

  

  

  i 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  

  1 
  

   1 
  

  

  1 
  

  

  1 
  

  

  

  1 
  

  

  I 
  

  

  £ 
  i 
  a 
  

  

  plaits 
  per 
  mm. 
  defk 
  

  

  The 
  results 
  show 
  that 
  the 
  instrument 
  has 
  a 
  high 
  decree 
  of 
  

  

  •• 
  11** 
  • 
  l 
  « 
  © 
  ^ 
  

  

  sensitiveness, 
  and 
  that 
  it 
  is 
  constant 
  within 
  5 
  per 
  cent, 
  over 
  

   the 
  range 
  of 
  the 
  scale. 
  The 
  error 
  in 
  taking 
  the 
  tangent 
  

   instead 
  of 
  the 
  arc 
  is 
  only 
  2 
  per 
  cent., 
  but 
  it 
  is 
  necessary, 
  of 
  

   course, 
  to 
  calibrate 
  the 
  instrument 
  for 
  the 
  particular 
  potentials 
  

   that 
  are 
  used. 
  

  

  The 
  probable 
  error 
  in 
  the 
  readings 
  of 
  the 
  instrument 
  will 
  

   depend 
  chiefly 
  on 
  the 
  accuracy 
  with 
  which 
  the 
  dots 
  on 
  the 
  

   charts 
  can 
  be 
  read. 
  This 
  error 
  would 
  not 
  be 
  more 
  than 
  *5 
  mm. 
  

   at 
  the 
  most, 
  and 
  would 
  generally 
  be 
  less. 
  

  

  The 
  capacity 
  of 
  the 
  needle 
  and 
  of 
  either 
  pair 
  of 
  quadrants 
  

   is 
  about 
  100 
  cm. 
  

  

  In 
  measuring 
  the 
  potential 
  of 
  the 
  air 
  a 
  polonium 
  collector 
  

   was 
  used. 
  The 
  collector 
  was 
  8 
  ft. 
  6 
  in. 
  above 
  the 
  ground 
  and 
  

   9 
  ft. 
  from 
  the 
  building, 
  which 
  was 
  10 
  ft. 
  high 
  to 
  the 
  eaves 
  : 
  

   one 
  pair 
  of 
  quadrants 
  was 
  attached 
  to 
  the 
  positive 
  terminal 
  of 
  

   a 
  battery 
  of 
  12 
  volts 
  and 
  the 
  other 
  pair 
  to 
  the 
  negative, 
  the 
  

   centre 
  being 
  earthed. 
  A 
  copy 
  of 
  a 
  record 
  of 
  the 
  potential 
  

   Is 
  given 
  in 
  tig. 
  5 
  (p. 
  208). 
  The 
  record 
  was 
  obtained 
  when 
  

  

  