﻿On 
  the 
  Energy 
  required 
  to 
  Ionize 
  an 
  Atom. 
  18$ 
  

  

  The 
  agreement 
  between 
  the 
  two 
  eyes 
  o£ 
  each 
  observer 
  

   and 
  between 
  the 
  two 
  observers 
  is 
  as 
  close 
  as 
  was 
  to 
  bo 
  

   expected 
  from 
  the 
  method 
  employed. 
  

  

  It 
  should 
  be 
  pointed 
  out 
  that 
  atropine, 
  or 
  its 
  derivative 
  

   homatropine, 
  acts 
  exclusively 
  upon 
  the 
  myoneural 
  junction 
  

   of 
  the 
  nerve 
  fibres 
  which 
  supply 
  the 
  sphincter 
  muscle. 
  The 
  

   dilator 
  muscle 
  fibres, 
  which 
  have 
  a 
  nervous 
  control 
  totally 
  

   different 
  from 
  that 
  of 
  the 
  sphincter 
  muscle 
  fibres, 
  are 
  not 
  

   affected 
  by 
  the 
  atropine. 
  The 
  objection 
  to 
  the 
  experiment 
  

   just 
  described, 
  might 
  be 
  raised 
  that 
  the 
  musculus 
  dilator 
  

   pupilhv 
  might 
  still 
  respond 
  to 
  the 
  light 
  stimulus 
  and 
  so 
  serve 
  

   as 
  the 
  physiological 
  process 
  upon 
  which 
  flicker 
  sensation 
  

   depends. 
  A 
  priori, 
  it 
  is 
  hardly 
  conceivable 
  that 
  the 
  dilator 
  

   fibres 
  could 
  effect 
  any 
  change 
  by 
  themselves 
  alone. 
  Tim 
  

   size 
  of 
  the 
  normal 
  pupil 
  depends 
  at 
  any 
  time 
  upon 
  the 
  

   opposed 
  action 
  of 
  the 
  dilator 
  and 
  sphincter 
  muscle 
  fibres. 
  

   When 
  either 
  muscle 
  of 
  the 
  pair 
  is 
  paralysed, 
  its 
  opponent 
  

   acts 
  exclusively, 
  with 
  the 
  result 
  that 
  a 
  very 
  large 
  or 
  very 
  

   small 
  pupil 
  appears. 
  But 
  once 
  the 
  very 
  large 
  (mydriatic) 
  

   pupil 
  or 
  its 
  opposite 
  condition 
  the 
  very 
  small 
  (myotic) 
  pupil 
  

   is 
  achieved, 
  there 
  can 
  be 
  no 
  change 
  in 
  the 
  size 
  of 
  the 
  pupil 
  

   so 
  long 
  as 
  the 
  paralysis 
  exists. 
  The 
  pupil 
  is 
  inactive 
  in 
  the 
  

   presence 
  of 
  changing 
  light 
  intensities. 
  The 
  objection 
  „ 
  

   therefore, 
  is 
  groundless. 
  

  

  University 
  of 
  "Washington, 
  

   Seattle, 
  Washington. 
  

  

  IX. 
  On 
  the 
  Energy 
  required 
  to 
  Ionize 
  an 
  Atom. 
  By 
  R. 
  T. 
  

   Beatty, 
  M.A., 
  D.Sc, 
  Emmanuel 
  College, 
  Clerk 
  Maxwell 
  

   Student 
  of 
  the 
  University, 
  Cambridge* 
  '. 
  

  

  r 
  |^HE 
  energy 
  required 
  to 
  ionize 
  an 
  atom, 
  that 
  is, 
  to 
  detach 
  

   A 
  an 
  election 
  from 
  an 
  atom, 
  is 
  a 
  quantity 
  of 
  importance 
  

   in 
  checking 
  theories 
  of 
  atomic 
  constitution. 
  Let 
  us 
  suppose 
  

   that 
  we 
  specify 
  the 
  constitution 
  of 
  an 
  atom 
  by 
  assigning 
  to 
  

   it 
  a 
  central 
  positive 
  charge 
  ne, 
  surrounded 
  by 
  n 
  electrons 
  

   distributed 
  in 
  rings 
  of 
  known 
  radii 
  round 
  the 
  central 
  charge. 
  

   Then 
  we 
  can 
  calculate 
  the 
  energy 
  required 
  to 
  remove 
  one 
  of 
  

   the 
  electrons 
  from 
  the 
  system. 
  

  

  It 
  is 
  now 
  widely 
  believed 
  that 
  the 
  atom 
  contains 
  a 
  central 
  

   positive 
  charge 
  surrounded 
  by 
  a 
  number 
  of 
  electrons 
  equal 
  

   to 
  about 
  half 
  the 
  atomic 
  weight. 
  Some 
  of 
  these 
  electrons 
  

   are 
  supposed 
  to 
  be 
  attached 
  tightly 
  to 
  the 
  central 
  charge 
  

   and 
  to 
  possess 
  a 
  vibration 
  frequency 
  much 
  greater 
  than 
  that 
  

   associated 
  with 
  light- 
  waves. 
  A 
  few 
  electrons 
  are 
  supposed 
  

   * 
  Communicated 
  bv 
  the 
  Author. 
  

  

  