﻿706 
  Prof. 
  J. 
  de 
  Kowalski 
  and 
  Dr. 
  U. 
  J. 
  Eappel 
  on 
  

  

  Table 
  VII. 
  

  

  Diameter 
  o£ 
  the 
  spheres 
  30 
  cm. 
  Ratio 
  1*43. 
  Alternating 
  

   current 
  frequency 
  33, 
  Barometric 
  pressure 
  716*9 
  mm. 
  

   'Temperature 
  19° 
  C. 
  

  

  Explosive 
  Distance 
  

  

  Effective 
  

  

  Maximum 
  

  

  j 
  in 
  cm. 
  

  

  Voltage. 
  

  

  Yoltage. 
  

  

  0-1144 
  

  

  3273 
  

  

  4680 
  

  

  0-1493 
  

  

  4029 
  

  

  5761 
  

  

  0-2311 
  

  

  .")758 
  

  

  8233 
  

  

  0-2846 
  

  

  6801 
  

  

  9725 
  

  

  0-3777 
  

  

  8644 
  

  

  12360 
  

  

  0-4()66 
  

  

  10335 
  

  

  14779 
  

  

  0-5380 
  

  

  11700 
  

  

  16731 
  

  

  0-6485 
  

  

  13783 
  

  

  19709 
  

  

  0-8040 
  

  

  16540 
  

  

  23652 
  

  

  1-0360 
  

  

  20618 
  

  

  29483 
  

  

  1-1166 
  

  

  22100 
  

  

  31600 
  

  

  1 
  2470 
  

  

  24324 
  

  

  34783 
  

  

  1-3595 
  

  

  26311 
  

  

  37624 
  

  

  1-4606 
  

  

  28023 
  

  

  40072 
  

  

  A 
  direct 
  comparison 
  of 
  our 
  figures 
  with 
  the 
  measurements 
  

   undertaken 
  by 
  other 
  physicists 
  is 
  hardly 
  possible. 
  Spark 
  

   potentials 
  for 
  alternating 
  current 
  have 
  seldom 
  been 
  deter- 
  

   mined 
  under 
  well-defined 
  conditions. 
  The 
  researches 
  of 
  

   Steinmetz, 
  which 
  up 
  to 
  the 
  present 
  were 
  the 
  most 
  reliable, 
  

   do 
  not 
  make 
  allowance 
  for 
  tardiness 
  or 
  dilatation, 
  which 
  is 
  

   apt 
  to 
  give 
  values 
  that 
  are 
  too 
  high, 
  as 
  has 
  been 
  sufficiently 
  

   proved 
  by 
  Warburg"^ 
  and 
  Starke 
  f. 
  Consequently, 
  our 
  

   figures 
  are 
  smaller 
  than 
  those 
  found 
  by 
  Steinmetz. 
  As 
  

   Steinmetz 
  J, 
  in 
  his 
  series 
  of 
  researches, 
  allows 
  a 
  divergence 
  

   of 
  from 
  4 
  per 
  cent, 
  to 
  6 
  per 
  cent., 
  it 
  seems 
  clear 
  that 
  these 
  

   differences 
  are 
  traceable 
  to 
  this 
  source. 
  We 
  are 
  able, 
  however, 
  

   to 
  make 
  an 
  indirect 
  comparison 
  with 
  the 
  values 
  found 
  by 
  

   other 
  physicists, 
  who 
  employed 
  the 
  direct 
  current. 
  Ac- 
  

   cording 
  to 
  M. 
  Toepler 
  § 
  the 
  following 
  holds 
  true 
  : 
  — 
  Taking 
  

  

  as 
  unity 
  the 
  spark 
  potential 
  corresponding 
  to 
  -, 
  = 
  1, 
  where 
  

  

  ^ 
  = 
  the 
  explosive 
  distance 
  and 
  d 
  the 
  diameter 
  of 
  the 
  spheres, 
  

   the 
  spark 
  potentials 
  corresponding 
  for 
  the 
  same 
  distances 
  are 
  

   independent 
  of 
  the 
  values 
  of 
  d. 
  

  

  * 
  Warburg, 
  Ann. 
  d. 
  Phijs. 
  v. 
  p. 
  811 
  (1901). 
  

   t 
  Starke, 
  Wied. 
  Ann. 
  Ixvi. 
  p. 
  1009 
  (1898). 
  

   I 
  Russell, 
  Phil. 
  Mag. 
  vol. 
  xi. 
  [61 
  p. 
  265 
  (1906). 
  

   § 
  M. 
  Toepler, 
  EleUr. 
  Zeitsch. 
  p."998 
  (1907). 
  

  

  