﻿258 
  Lord 
  Kelvin 
  : 
  

  

  by 
  them. 
  As 
  in 
  Aepinus' 
  theory 
  we 
  must 
  have 
  repulsions 
  

   between 
  the 
  electrions; 
  and 
  repulsions 
  between 
  the 
  atoms 
  

   independently 
  of 
  the 
  electrions 
  : 
  and 
  attractions 
  between 
  

   electrions 
  and 
  atoms 
  without 
  electrions. 
  For 
  brevity, 
  in 
  

   future 
  by 
  atom 
  I 
  shall 
  mean 
  an 
  atom 
  of 
  ponderable 
  matter, 
  

   whether 
  it 
  has 
  any 
  electrions 
  within 
  it 
  or 
  not. 
  

  

  § 
  3. 
  In 
  virtue 
  of 
  the 
  discovery 
  and 
  experimental 
  proof 
  by 
  

   Cavendish 
  and 
  Coulomb 
  of 
  the 
  law 
  of 
  inverse 
  square 
  of 
  dis- 
  

   tance 
  forboth 
  electric 
  attractions 
  and 
  repulsions, 
  we 
  may 
  now 
  

   suppose 
  that 
  the 
  atoms, 
  which 
  I 
  assume 
  to 
  be 
  all 
  of 
  them 
  

   spherical, 
  repel 
  other 
  atoms 
  outside 
  them 
  with 
  forces 
  inversely 
  

   as 
  the 
  squares 
  of 
  distances 
  between 
  centres 
  ; 
  and 
  that 
  tlie 
  

   same 
  is 
  true 
  of 
  electrions, 
  which 
  no 
  doubt 
  occupy 
  finite 
  spaces,, 
  

   although 
  at 
  present 
  we 
  are 
  dealing 
  with 
  them 
  as 
  if 
  they 
  were 
  

   mere 
  mathematical 
  points, 
  endowed 
  with 
  the 
  property 
  of 
  

   electric 
  attraction 
  and 
  repulsion. 
  We 
  must 
  now 
  also 
  assume 
  

   that 
  every 
  atom 
  attracts 
  every 
  electrion 
  outside 
  it 
  with 
  a 
  force 
  

   inversely 
  as 
  the 
  square 
  of 
  the 
  distance 
  between 
  centres. 
  

  

  § 
  4. 
  My 
  assumption 
  that 
  the 
  electrions 
  freely 
  permeate 
  the 
  

   space 
  occupied 
  by 
  the 
  atoms 
  requires 
  a 
  knowledge 
  of 
  the 
  law 
  

   of 
  the 
  force 
  experienced 
  by 
  an 
  electrion 
  within 
  an 
  atom. 
  As 
  

   a 
  tentative 
  hypothesis, 
  1 
  assume 
  for 
  simplicity 
  that 
  the 
  

   attraction 
  experienced 
  by 
  an 
  electrion 
  approaching 
  an 
  atom 
  

   varies 
  exactly 
  according 
  to 
  the 
  inverse 
  square 
  of 
  the 
  distance 
  

   from 
  the 
  centre, 
  as 
  long 
  as 
  the 
  electrion 
  is 
  outside 
  ; 
  has 
  no 
  

   abrupt 
  change 
  when 
  the 
  electrion 
  enters 
  the 
  atom 
  ; 
  and 
  

   decreases 
  to 
  zero 
  simply 
  as 
  the 
  distance 
  from 
  the 
  centre 
  when 
  

   the 
  electrion, 
  approaching 
  the 
  centre, 
  is 
  within 
  the 
  spherical 
  

   boundary 
  of 
  the 
  atom. 
  This 
  is 
  just 
  as 
  it 
  would 
  be 
  if 
  the 
  

   electric 
  virtue 
  of 
  the 
  atom 
  were 
  due 
  to 
  uniform 
  distribution 
  

   through 
  the 
  atom 
  of 
  an 
  ideal 
  electric 
  substance 
  of 
  which 
  

   each 
  infinitely 
  small 
  part 
  repels 
  infinitely 
  small 
  portions 
  of 
  

  

  " 
  essentials 
  of 
  Aepinus' 
  theory, 
  and 
  dealing 
  with 
  it 
  according 
  to 
  the 
  

   " 
  doctrine 
  of 
  Father 
  Boscovich, 
  each 
  atom 
  of 
  ponderable 
  matter 
  is 
  an 
  

   u 
  electron 
  of 
  vitreous 
  electricity 
  ; 
  which, 
  with 
  a 
  neutralizing 
  electrion 
  of 
  

   " 
  resinous 
  electricity 
  close 
  to 
  it, 
  produces 
  a 
  resulting 
  force 
  on 
  every 
  

   " 
  distant 
  electron 
  and 
  electrion 
  which 
  varies 
  inversely 
  as 
  the 
  cube 
  of 
  the 
  

   " 
  distance, 
  and 
  is 
  in 
  the 
  direction 
  determined 
  according 
  to 
  the 
  well-known 
  

   " 
  requisite 
  application 
  of 
  the 
  parallelogram 
  of 
  forces." 
  It 
  will 
  be 
  seen 
  

   that 
  I 
  had 
  not 
  then 
  thought 
  of 
  the 
  hypothesis 
  suggested 
  in 
  the 
  present 
  

   communication, 
  that 
  while 
  electrions 
  permeate 
  freely 
  through 
  all 
  space, 
  

   whether 
  occupied 
  only 
  by 
  ether 
  or 
  occupied 
  also 
  by 
  the 
  volumes 
  of 
  finite 
  

   spheres 
  constituting 
  the 
  atoms 
  of 
  ponderable 
  matter, 
  each 
  electrion 
  

   in 
  the 
  interior 
  of 
  an 
  atom 
  of 
  ponderable 
  matter 
  experiences 
  electric 
  

   force 
  towards 
  the 
  centre 
  of 
  the 
  atom, 
  just 
  as 
  if 
  the 
  atom 
  contained 
  

   within 
  it, 
  fixed 
  relatively 
  to 
  itself, 
  a 
  uniform 
  distribution 
  of 
  ideal 
  

   electric 
  matter. 
  

  

  