﻿Molecules 
  of 
  the 
  Elements 
  and 
  their 
  Compounds. 
  29 
  

  

  suspended 
  as 
  a 
  pendulum 
  from 
  a 
  common 
  point 
  by 
  long 
  

   conducting 
  fibres 
  or 
  wires. 
  If 
  the 
  deflexion 
  is 
  small 
  com- 
  

   pared 
  with 
  the 
  length 
  o£ 
  the 
  pendulum, 
  so 
  that 
  the 
  value 
  of 
  

   the 
  angle 
  does 
  not 
  differ 
  appreciably 
  from 
  its 
  sine, 
  the 
  force 
  

   of 
  gravity 
  tends 
  to 
  return 
  each 
  sphere 
  to 
  the 
  centre 
  or 
  lowest 
  

   point 
  with 
  a 
  force 
  proportional 
  to 
  the 
  deflexion, 
  and 
  by 
  this 
  

   mean? 
  the 
  positive 
  sphere 
  in 
  the 
  atom 
  is 
  simulated 
  by 
  the 
  

   weight 
  of 
  the 
  spheres. 
  

  

  If 
  the 
  spheres 
  are 
  equally 
  charged 
  with 
  electricity 
  of 
  the 
  

   same 
  kind 
  and 
  the 
  distance 
  between 
  adjacent 
  spheres 
  is 
  

   large 
  compared 
  with 
  their 
  radii, 
  then 
  the 
  force 
  of 
  repulsion 
  

   between 
  any 
  two 
  of 
  them 
  is 
  inversely 
  proportional 
  to 
  the 
  

   square 
  of 
  the 
  distance 
  between 
  them. 
  This 
  meets 
  the 
  second 
  

   required 
  condition, 
  and 
  such 
  an 
  arrangement 
  should 
  give 
  

   the 
  required 
  equilibrium 
  figures. 
  Many 
  practical 
  difficulties 
  

   in 
  securing 
  these 
  conditions 
  are 
  apparent 
  at 
  once. 
  How 
  

   shall 
  each 
  sphere 
  be 
  given 
  an 
  equal 
  charge, 
  and 
  how 
  can 
  the 
  

   disturbing 
  effect 
  of 
  the 
  charge 
  upon 
  the 
  supporting 
  fibre 
  or 
  

   wire 
  be 
  avoided? 
  

  

  The 
  facilities 
  available 
  in 
  making 
  these 
  experiments 
  were 
  

   limited, 
  but 
  having 
  secured 
  the 
  results 
  described 
  below 
  with 
  

   the 
  means 
  at 
  hand, 
  a 
  preliminary 
  account 
  is 
  given 
  partly 
  to 
  

   show 
  that 
  it 
  is 
  very 
  desirable 
  to 
  make 
  an 
  exhaustive 
  study 
  

   of 
  the 
  subject 
  with 
  every 
  means 
  that 
  is 
  known 
  for 
  making 
  

   exact 
  measurement 
  5 
  :. 
  A 
  steady 
  source 
  of 
  direct 
  potential 
  

   such 
  as 
  that 
  from 
  a 
  storage-battery 
  would 
  be 
  an 
  ideal 
  

   electrical 
  supply 
  for 
  this 
  purpose, 
  but 
  since 
  it 
  requires 
  

   between 
  5000 
  and 
  10,000 
  volts 
  electromotive 
  force 
  this 
  was 
  

   not 
  used. 
  The 
  available 
  power-supply 
  was 
  60 
  cycles 
  alter- 
  

   nating 
  current 
  at 
  101 
  or 
  208 
  volts, 
  and 
  this 
  was 
  stepped 
  up 
  

   to 
  several 
  thousand 
  volts 
  alternating 
  potential 
  by 
  transformers 
  

   of 
  the 
  closed 
  circuit 
  type. 
  

  

  For 
  a 
  preliminary 
  trial 
  aluminium 
  spheres 
  0*607 
  cm. 
  

   diameter 
  were 
  turned 
  accurate 
  to 
  about 
  0'0025 
  cm., 
  and 
  a 
  

   small 
  hole 
  drilled 
  through 
  on 
  a 
  diameter 
  to 
  facilitate 
  fastening 
  

   the 
  supporting 
  wire. 
  A 
  coj>per 
  wire 
  0*0038 
  cm. 
  diameter 
  

   was 
  first 
  used. 
  The 
  length 
  of 
  the 
  pendulum 
  was 
  203 
  cm., 
  

   and 
  even 
  with 
  this 
  fine 
  wire 
  the 
  weight 
  of 
  the 
  aluminium 
  

   ball 
  was 
  not 
  sufficient 
  to 
  keep 
  it 
  taut. 
  Two 
  spheres 
  were 
  

   suspended 
  from 
  the 
  same 
  point, 
  being 
  30*5 
  cm. 
  above 
  the 
  

   floor 
  in 
  the 
  open 
  space 
  of 
  the 
  room, 
  the 
  wires 
  being 
  adjusted 
  

   to 
  the 
  same 
  length. 
  One 
  terminal 
  of 
  the 
  power 
  was 
  con- 
  

   nected 
  to 
  the 
  point 
  of 
  support, 
  and 
  the 
  other 
  to 
  a 
  metal 
  plate 
  

   lying 
  upon 
  the 
  floor 
  under 
  the 
  point 
  of 
  suspension. 
  With 
  

   4000 
  volts 
  alternating, 
  the 
  spheres 
  separated 
  several 
  cm., 
  

   and 
  an 
  interesting 
  feature 
  was 
  the 
  fact 
  that 
  the 
  supporting 
  

  

  