﻿Experiments 
  on 
  Columnar 
  Ionization. 
  511 
  

  

  any 
  rate 
  within 
  the 
  range 
  of 
  sizes 
  tested 
  by 
  Carman 
  and 
  

   Stewart, 
  and 
  thus 
  rejects 
  the 
  " 
  crushing 
  formula 
  " 
  of 
  Lame* 
  . 
  

   In 
  my 
  opinion. 
  Lame's 
  theory 
  should 
  be 
  restricted 
  to 
  the 
  

   failure 
  of 
  tubes 
  by 
  internal 
  pressure, 
  and 
  any 
  practical 
  size 
  

   of 
  tube, 
  if 
  subjected 
  to 
  external 
  pressure, 
  will 
  fail 
  by 
  

   instability. 
  The 
  foregoing 
  theory 
  leaves 
  untouched 
  the 
  

   difficult 
  problem 
  of 
  determining 
  the 
  strengthening 
  effects 
  

   of 
  circular 
  ends 
  in 
  cases 
  where 
  elastic 
  breakdown 
  precedes 
  

   collapse 
  ; 
  but 
  this 
  is 
  a 
  question 
  of 
  theoretical 
  rather 
  than 
  

   practical 
  interest, 
  for 
  it 
  would 
  be 
  dangerous 
  in 
  any 
  case 
  to 
  

   allow 
  the 
  material 
  to 
  be 
  stressed 
  up 
  to 
  the 
  yield-point, 
  and 
  

   this 
  restriction 
  limits 
  the 
  permissible 
  pressure, 
  in 
  the 
  case 
  of 
  

   a 
  short 
  tube 
  of 
  ordinary 
  dimensions, 
  to 
  a 
  value 
  for 
  which 
  

   there 
  is 
  no 
  danger 
  of 
  collapse 
  by 
  instability. 
  

  

  I 
  wish 
  to 
  acknowledge 
  my 
  indebtedness 
  to 
  Messrs. 
  H. 
  J. 
  

   Howard 
  and 
  D. 
  P. 
  Scott, 
  for 
  assistance 
  in 
  the 
  prosecution 
  of 
  

   the 
  experiments 
  described 
  above, 
  and 
  to 
  Messrs. 
  Stewart 
  and 
  

   Lloyds, 
  Ltd., 
  of 
  Glasgow, 
  for 
  gifts 
  of 
  steel 
  tubes 
  for 
  test. 
  

   These 
  tubes 
  exceeded 
  all 
  expectations 
  in 
  point 
  of 
  accuracy 
  

   and 
  uniformity 
  of 
  material. 
  

  

  July 
  2nd, 
  1913. 
  

  

  XXXIX. 
  Experiments 
  on 
  Columnar 
  Ionization. 
  By 
  E. 
  M. 
  

   Wellisch, 
  Assistant 
  Professor 
  of 
  Physics, 
  Yale 
  University, 
  

   and 
  J. 
  W. 
  TVoodrow, 
  Ph.D., 
  Yale 
  University 
  t 
  . 
  

  

  Introduction. 
  

  

  1. 
  TN 
  their 
  experiments 
  on 
  the 
  distribution 
  of 
  the 
  active 
  

   A 
  deposit 
  of 
  radium 
  in 
  an 
  electric 
  field, 
  Wellisch 
  and 
  

   Bronson 
  % 
  found 
  that 
  the 
  fraction 
  of 
  the 
  total 
  amount 
  of 
  

   active 
  deposit 
  that 
  settled 
  on 
  the 
  cathode 
  increased 
  with 
  the 
  

   potential- 
  difference 
  in 
  a 
  manner 
  quite 
  similar 
  to 
  the 
  increase 
  

   of 
  the 
  electric 
  current 
  which 
  passed 
  through 
  the 
  gas 
  during 
  

   the 
  process 
  of 
  activation. 
  The 
  curve 
  connecting 
  the 
  cathode 
  

   activity 
  and 
  the 
  potential-difference 
  exhibited 
  the 
  charac- 
  

   teristic 
  " 
  lack 
  of 
  saturation 
  " 
  which 
  had 
  previously 
  been 
  

   investigated 
  by 
  Bragg, 
  Moulin, 
  and 
  others 
  in 
  the 
  case 
  of 
  

   the 
  electric 
  current 
  due 
  to 
  alpha-ray 
  ionization. 
  This 
  ex- 
  

   perimental 
  result 
  suggested 
  the 
  probability 
  that 
  the 
  electric 
  

   current 
  would 
  attain 
  its 
  saturation 
  value 
  only 
  when 
  all 
  the 
  

  

  * 
  S. 
  E. 
  Slocnm, 
  he. 
  tit., 
  equation 
  (2). 
  

   f 
  ComraiiDicated 
  bv 
  the 
  Authors. 
  

  

  t 
  Welliscn 
  & 
  Bronson, 
  Phil. 
  Mag. 
  [6] 
  xxiii. 
  p. 
  714, 
  May 
  1912. 
  

   2 
  M 
  2 
  

  

  