﻿Hypothesis, 
  and 
  the 
  Periodic 
  Law. 
  407 
  

  

  will 
  first 
  become 
  equal 
  to, 
  and 
  then 
  greatly 
  exceed 
  the 
  attrac- 
  

   tive 
  force. 
  Now 
  conceive 
  the 
  atom, 
  as 
  enveloped 
  by 
  an 
  

   imaginary 
  spherical 
  surface 
  or 
  shell, 
  whose 
  radius 
  is 
  the 
  half 
  

   distance 
  at 
  which 
  these 
  forces 
  become 
  equal, 
  two 
  such 
  atoms 
  

   would 
  evidently 
  act 
  upon 
  each 
  other 
  like 
  perfectly 
  elastic 
  spheres 
  

   of 
  that 
  radius 
  ; 
  that 
  is, 
  they 
  would 
  strongly 
  repel 
  each 
  other 
  

   when 
  separated 
  by 
  less 
  than 
  their 
  imaginary 
  diameter, 
  and 
  

   yet 
  the 
  atoms 
  themselves 
  if 
  they 
  have 
  magnitude 
  and 
  are 
  not 
  

   mere 
  Boscovitch 
  points 
  may 
  be 
  small 
  as 
  compared 
  to 
  their 
  

   imaginary 
  diameters, 
  and 
  so 
  the 
  approach 
  of 
  two 
  such 
  atoms 
  

   might 
  be 
  checked 
  and 
  reversed 
  without 
  any 
  actual 
  contact 
  

   between 
  them. 
  

  

  Now 
  the 
  force 
  which 
  binds 
  atom 
  to 
  atom 
  within 
  the 
  mole- 
  

   cule 
  must 
  do 
  so 
  in 
  opposition 
  to 
  this 
  force 
  of 
  repulsion, 
  and 
  if 
  

   resembling 
  (it 
  is 
  probably 
  closely 
  connected 
  with) 
  electrical 
  

   attraction 
  it 
  would 
  vary 
  as 
  the 
  inverse 
  square 
  of 
  distance, 
  and 
  

   two 
  similar 
  atoms 
  drawn 
  together 
  by 
  it 
  to 
  form 
  a 
  molecule 
  

   would 
  approach 
  each 
  other, 
  until 
  this 
  force 
  plus 
  gravitation 
  

   became 
  equal 
  to 
  the 
  force 
  of 
  repulsion. 
  The 
  stronger 
  this 
  

   attractive 
  force 
  the 
  less 
  the 
  distance 
  between 
  the 
  atoms 
  of 
  a 
  

   diatomic 
  molecule 
  compared 
  to 
  the 
  distance 
  nearer 
  than 
  which 
  

   two 
  such 
  molecules 
  could 
  not 
  approach, 
  which 
  latter 
  distance, 
  

   as 
  between 
  two 
  diatomic 
  molecules, 
  will 
  be 
  that 
  at 
  which 
  the 
  

   various 
  attractions 
  and 
  repulsions 
  are 
  equally 
  balanced 
  (disre- 
  

   garding 
  kinetic 
  energy 
  of 
  translation 
  which 
  will 
  tend 
  to 
  reduce 
  

   this 
  distance). 
  Now 
  when 
  the 
  force 
  drawing 
  the 
  atoms 
  

   together 
  is 
  large 
  compared 
  to 
  that 
  of 
  gravity, 
  the 
  distance 
  

   between 
  the 
  atoms 
  within 
  the 
  molecule 
  will 
  be 
  small 
  compared 
  

   with 
  their 
  least 
  distance 
  of 
  approach, 
  and 
  the 
  greater 
  the 
  dif- 
  

   ference 
  between 
  these 
  quantities 
  the 
  less 
  the 
  action 
  of 
  atom 
  

   upon 
  atom, 
  which 
  is 
  the 
  action 
  tending 
  to 
  produce 
  internal 
  

   rotations, 
  and 
  the 
  closer 
  will 
  the 
  action 
  between 
  two 
  molecules 
  

   during 
  an 
  encounter 
  approximate 
  to 
  that 
  of 
  two 
  repulsive 
  

   forces 
  concentrated 
  at 
  their 
  respective 
  centers 
  of 
  gravity. 
  

  

  Here 
  we 
  can 
  apply 
  the 
  principle 
  made 
  use 
  of 
  in 
  astronomy 
  

   to 
  simplify 
  the 
  problem 
  of 
  the 
  three 
  bodies 
  in 
  the 
  case 
  of 
  per- 
  

   turbations, 
  viz 
  : 
  That 
  when 
  the 
  distance 
  between 
  two 
  systems 
  

   of 
  bodies 
  is 
  large 
  compared 
  to 
  the 
  distance 
  between 
  their 
  com- 
  

   ponents, 
  each 
  system 
  practically 
  affects 
  the 
  other 
  as 
  if 
  all 
  its 
  

   matter 
  were 
  concentrated 
  at 
  its 
  own 
  center 
  of 
  gravity. 
  Evi- 
  

   dently 
  the 
  nearer 
  the 
  approach 
  to 
  this 
  condition 
  (i. 
  e. 
  the 
  

   stronger 
  the 
  force 
  which 
  aggregates 
  the 
  atoms 
  within 
  the 
  mole- 
  

   cule 
  against 
  the 
  force 
  of 
  repulsion) 
  the 
  less 
  the 
  tendency 
  to 
  

   produce 
  internal 
  rotation.* 
  

  

  * 
  The 
  assumption 
  here 
  made 
  is 
  that 
  the 
  force 
  of 
  aggregation 
  differs 
  from 
  gravi- 
  

   tation 
  and 
  other 
  forces, 
  in 
  what 
  chemists 
  refer 
  to 
  when 
  they 
  speak 
  of 
  an 
  affinity 
  

   being 
  saturated 
  or 
  satisfied, 
  thereby 
  recalling 
  the 
  mutual 
  saturation 
  of 
  the 
  two 
  

  

  