﻿Alternating- 
  Current 
  Spark 
  Potentials. 
  707 
  

  

  In 
  the 
  following 
  table 
  is 
  set 
  forth 
  the 
  comparison 
  of 
  onr 
  

   determinations 
  with 
  those 
  o£ 
  other 
  physicists 
  : 
  — 
  

  

  

  Freyberg. 
  

  

  Heydweiller. 
  

  

  Kowalski 
  

  

  & 
  Eappel. 
  

  

  d 
  in 
  cm. 
  

  

  1-0 
  20 
  

  

  1-0 
  2-0 
  

  

  2-0 
  

  

  3-85 
  { 
  

  

  X 
  : 
  d=0-l 
  

  

  0-18 
  0-19 
  

  

  ... 
  0-18 
  

  

  0-18 
  

  

  0-18^ 
  

  

  0-2 
  

  

  0-37 
  D-32 
  

  

  0-32 
  O-c'2 
  

  

  0-32 
  

  

  0-32 
  

  

  0-3 
  

  

  0-45 
  0-44 
  

  

  ... 
  45 
  

  

  0-^4 
  

  

  0-44 
  

  

  0-4 
  

  

  0-54 
  0-55 
  

  

  0-53 
  0-58 
  

  

  0-55 
  

  

  0-53 
  

  

  Oo 
  

  

  0-65 
  0G5 
  

  

  ... 
  0-69 
  

  

  0-66 
  

  

  

  0-6 
  

  

  0-75 
  0-74 
  

  

  0-74 
  0-79 
  

  

  0-75 
  

  

  

  0-7 
  

  

  0-82 
  ... 
  

  

  

  0-83 
  

  

  

  0-8 
  

  

  0-90 
  ... 
  

  

  0-90 
  ... 
  

  

  0-90 
  

  

  

  0-9 
  

  

  0-98 
  ... 
  

  

  

  

  0-96 
  

  

  ! 
  

  

  * 
  0-18 
  was 
  taken 
  as 
  the 
  basis 
  in 
  these 
  calculations. 
  

  

  The 
  table 
  shows 
  that 
  the 
  general 
  results 
  obtained 
  agree 
  

   very 
  well 
  with 
  those 
  found 
  by 
  other 
  physicists. 
  Nevertheless 
  

   the 
  absolute 
  values 
  are 
  from 
  4 
  to 
  6 
  per 
  cent, 
  smaller 
  than 
  

   those 
  which 
  the 
  direct 
  current 
  yields 
  (application 
  of 
  the 
  law 
  

   of 
  Paschen). 
  Whether 
  the 
  cause 
  lies 
  in 
  the 
  elimination 
  of 
  

   dilatation 
  or 
  in 
  the 
  nature 
  of 
  determinations 
  w^ith 
  alternating 
  

   current 
  is 
  difficult 
  to 
  determine. 
  Eesearches 
  in 
  this 
  direction 
  

   are 
  now 
  in 
  progress. 
  

  

  Fart 
  II. 
  

  

  Relation 
  of 
  the 
  Spark 
  Potential 
  to 
  the 
  Radius 
  of 
  Curvature 
  

   of 
  the 
  Electrodes. 
  

  

  Recently 
  A. 
  Russell 
  f 
  has 
  endeavoured 
  to 
  establish 
  a 
  theory 
  

   on 
  the 
  relation 
  of 
  the 
  spark 
  potential 
  to 
  the 
  curvature 
  of 
  the 
  

   electrodes. 
  Previously 
  it 
  was 
  commonly 
  accepted 
  that 
  the 
  

   spark 
  would 
  jump 
  \\\iqi\ 
  the 
  maximum 
  electric 
  intensity 
  

   between 
  the 
  electrodes 
  had 
  passed 
  certain 
  definite 
  limits. 
  

   Since 
  this 
  theory 
  failed 
  to 
  explain 
  all 
  observed 
  facts 
  A. 
  Russell 
  

   has 
  added 
  an 
  hypothesis 
  of 
  his 
  own. 
  He 
  assumes 
  that 
  for 
  

   explosive 
  distances 
  greater 
  than 
  0*1 
  cm. 
  a 
  certain 
  value 
  S 
  

   is 
  to 
  be 
  deducted, 
  in 
  the 
  determination 
  of 
  the 
  maximum 
  

   stress, 
  which 
  he 
  terms 
  lost 
  volts. 
  For 
  air 
  he 
  takes 
  this 
  

   value 
  to 
  be 
  800 
  volts. 
  The 
  following 
  reflexions 
  are 
  to 
  serve 
  

   as 
  a 
  test 
  for 
  the 
  proposed 
  theory 
  of 
  Russell. 
  

  

  t 
  A. 
  Kussell, 
  Phil. 
  Mag. 
  vol 
  xi. 
  [6] 
  p. 
  237 
  (1906). 
  

  

  