﻿by 
  Collision 
  of 
  Positive 
  and 
  Negative 
  Ions 
  in 
  a 
  Gas. 
  287 
  

  

  4. 
  For 
  those 
  cases 
  in 
  the 
  preceding 
  tables 
  in 
  which 
  more 
  

   than 
  three 
  currents 
  were 
  measured 
  the 
  agreement 
  of 
  the 
  n 
  

   and 
  q 
  numbers 
  affords 
  a 
  satisfactory 
  verification 
  of 
  Prof. 
  

   Townsend's 
  theory. 
  Further 
  confirmation 
  is 
  obtained 
  by 
  

   calculation 
  of 
  the 
  sparking 
  potential 
  under 
  the 
  given 
  force 
  

   and 
  its 
  comparison 
  with 
  experiment. 
  In 
  the 
  following 
  tables 
  

   the 
  sparking 
  distance 
  " 
  a 
  " 
  for 
  the 
  given 
  pressure 
  and 
  electric 
  

   force 
  was 
  calculated 
  from 
  the 
  formula 
  a 
  — 
  ySe 
  (a- 
  ^ 
  )a 
  = 
  0. 
  

   The 
  plates 
  were 
  set 
  at 
  the 
  distance 
  a 
  apart 
  and 
  the 
  sparking 
  

   potential 
  V 
  determined 
  at 
  the 
  first 
  appearance 
  of 
  a 
  flash 
  

   in 
  the 
  gas. 
  The 
  increase 
  of 
  Y 
  by 
  a 
  volt 
  or 
  two 
  at 
  most 
  

   was 
  found 
  sufficient 
  to 
  maintain 
  a 
  continuous 
  current. 
  

   The 
  agreement 
  between 
  V 
  as 
  determined 
  experimentally 
  

   and 
  the 
  product 
  a 
  x 
  X 
  may 
  be 
  seen 
  from 
  the 
  following 
  

   tables. 
  

  

  Table 
  XIII. 
  — 
  Argon, 
  Sparking 
  Potentials. 
  

  

  X. 
  

  

  P- 
  

  

  a. 
  

  

  axX. 
  

  

  V. 
  

  

  505 
  

  

  10 
  

  

  1087 
  

  

  549 
  

  

  549 
  

  

  610 
  

  

  4 
  

  

  •471 
  

  

  287 
  

  

  276 
  

  

  410 
  

  

  4 
  

  

  •947 
  

  

  388 
  

  

  380 
  

  

  618 
  

  

  2 
  

  

  •378 
  

  

  234 
  

  

  233 
  

  

  401 
  

  

  2 
  

  

  •618 
  

  

  248 
  

  

  245 
  

  

  615 
  

  

  1 
  

  

  •399 
  

  

  245 
  

  

  248 
  

  

  517 
  

  

  1 
  

  

  •482 
  

  

  249 
  

  

  244 
  

  

  401 
  

  

  1 
  

  

  •580 
  

  

  233 
  

  

  235 
  

  

  309 
  

  

  1 
  

  

  •770 
  

  

  248 
  

  

  237 
  

  

  402 
  

  

  •66 
  

  

  •599 
  

  

  241 
  

  

  248 
  

  

  301 
  

  

  •66 
  

  

  •802 
  

  

  242 
  

  

  238 
  

  

  Table 
  X1Y. 
  — 
  Helium 
  (before 
  purification 
  with 
  liquid 
  air), 
  

   Sparking 
  Potentials. 
  

  

  X. 
  

  

  P- 
  

  

  a. 
  

  

  axX. 
  

  

  V. 
  

  

  404 
  

  

  13 
  

  

  •674 
  

  

  272 
  

  

  

  

  305 
  

  

  8 
  

  

  •845 
  

  

  258 
  

  

  262 
  

  

  385 
  

  

  10 
  

  

  •650 
  

  

  250 
  

  

  252 
  

  

  305 
  

  

  6 
  

  

  •781 
  

  

  238 
  

  

  236 
  

  

  304 
  

  

  4 
  

  

  •760 
  

  

  231 
  

  

  234 
  

  

  506 
  

  

  6 
  

  

  •462 
  

  

  234 
  

  

  232 
  

  

  772 
  

  

  6 
  

  

  •326 
  

  

  254 
  

  

  246 
  

  

  304 
  

  

  2 
  

  

  •863 
  

  

  262 
  

  

  262 
  

  

  402 
  

  

  2 
  

  

  •694 
  

  

  279 
  

  

  274 
  

  

  