﻿Electrification 
  of 
  the 
  Atmosphere 
  and 
  Surface 
  of 
  the 
  Earth. 
  375 
  

  

  these 
  measurements 
  and 
  diagrams 
  indicate 
  that 
  the 
  effect 
  is 
  

   due 
  to 
  absorption, 
  and 
  is 
  caused 
  primarily 
  by 
  foreign 
  vapours 
  

  

  (a,) 
  

  

  (b) 
  

   (c) 
  

  

  1 
  

  

  i_i_ 
  

  

  u 
  

  

  bright 
  line, 
  or 
  bcmd 
  

  

  dark 
  line. 
  

  

  (a) 
  Janicki 
  effect, 
  brightest 
  central 
  line 
  made 
  to 
  correspond 
  with 
  main 
  

  

  line 
  in 
  normal 
  pattern 
  (b). 
  The 
  5 
  brightest 
  lines 
  in 
  (a) 
  do 
  not 
  

  

  correspond 
  well 
  with 
  those 
  of 
  (b). 
  

   (c) 
  Janicki 
  effect, 
  central 
  dark 
  line 
  made 
  to 
  correspond 
  with 
  main 
  line 
  

  

  of 
  {b). 
  The 
  six 
  best 
  defined 
  dark 
  lines 
  of 
  (c) 
  correspond 
  fairly 
  

  

  well 
  with 
  the 
  six 
  brightest 
  of 
  (6). 
  

  

  in 
  the 
  tube 
  either 
  left 
  behind 
  in 
  exhausting 
  or 
  obtained 
  

   from 
  the 
  aluminium 
  electrodes, 
  or 
  the 
  P 
  2 
  r 
  , 
  tube, 
  tempera- 
  

   ture 
  and 
  discharge 
  being 
  secondary 
  factors. 
  

  

  F. 
  F. 
  S. 
  Bryson. 
  

  

  J. 
  LOGIE. 
  

  

  XXVII. 
  Remarks 
  on 
  the 
  Note 
  of 
  Mr. 
  W. 
  A. 
  Douglas 
  Kudge: 
  

   " 
  On 
  the 
  Electrification 
  of 
  the 
  Atmosphere 
  and 
  Surface 
  of 
  the 
  

   Earths 
  

  

  To 
  the 
  Editors 
  of 
  the 
  Philosophical 
  Magazine. 
  

   Gentlemen, 
  — 
  

  

  MR. 
  W. 
  A. 
  Douglas 
  Rudge, 
  Professor 
  of 
  Physics, 
  Uni- 
  

   versity 
  College, 
  Bloemfontein, 
  publishes 
  in 
  the 
  Philo- 
  

   sophical 
  Magazine 
  (vol. 
  xxiii. 
  p 
  t 
  137, 
  1912) 
  a 
  note 
  which, 
  if 
  

   remaining 
  uncontradicted, 
  might 
  perhaps 
  cause 
  the 
  erroneous 
  

   opinion, 
  that 
  there 
  is 
  any 
  abnormity 
  in 
  South 
  Africa 
  as 
  to 
  the 
  

   electrification 
  of 
  the 
  surface 
  of 
  the 
  Earth. 
  Mr. 
  Pudge 
  affirms 
  

   that, 
  with 
  respect 
  to 
  South 
  Africa, 
  the 
  opinion 
  is 
  false 
  that 
  

   the 
  surface 
  of 
  the 
  earth 
  generally 
  possesses 
  a 
  negative 
  charge. 
  

   He 
  believes 
  to 
  have 
  found 
  an 
  experiment 
  by 
  which 
  he 
  can 
  

   easily 
  prove 
  a 
  positive 
  charge 
  of 
  the 
  surface 
  of 
  the 
  earth. 
  

   The 
  method 
  of 
  proving 
  this 
  is 
  as 
  follows 
  : 
  A 
  long 
  rod 
  of 
  

   wood 
  is 
  balanced 
  upon 
  a 
  pivot. 
  The 
  left 
  shorter 
  arm 
  is 
  

   counterpoised 
  by 
  a 
  weight. 
  The 
  rod 
  is 
  balanced 
  in 
  every 
  

   position. 
  The 
  right 
  arm 
  has 
  a 
  well-isolated 
  aluminium 
  plate 
  

   about 
  -j 
  sq. 
  metre 
  in 
  area. 
  From 
  this 
  plate 
  a 
  wire 
  is 
  taken 
  

   to 
  an 
  electroscope. 
  If 
  the 
  longer 
  end 
  of 
  the 
  rod 
  is 
  raised 
  to 
  

   a 
  height 
  of 
  about 
  4 
  metres 
  above 
  the 
  earth, 
  the 
  leaves 
  of 
  the 
  

  

  