﻿30 
  Dr. 
  A. 
  C. 
  Crehore 
  on 
  the 
  Formation 
  of 
  the 
  

  

  wires 
  did 
  not 
  remain 
  straight 
  lines 
  from 
  the 
  point 
  of 
  support 
  

   to 
  the 
  spheres, 
  but 
  each 
  wire 
  curved 
  away 
  from 
  the 
  orher. 
  

   A 
  light 
  weight 
  aluminium 
  ball 
  was 
  first 
  employed 
  in 
  order 
  

   to 
  work 
  with 
  smaller 
  voltages 
  than 
  would 
  be 
  necessary 
  with 
  

   a 
  heavier 
  one. 
  However, 
  as 
  they 
  were 
  not 
  heavy 
  enough 
  to 
  

   keep 
  the 
  wire 
  taut, 
  a 
  larger 
  ball 
  was 
  tried 
  also 
  of 
  aluminium 
  

   having 
  a 
  diameter 
  of 
  "9 
  cm. 
  A 
  photograph 
  of 
  these 
  two 
  

   suspended 
  spheres 
  showing 
  the 
  full 
  length 
  of 
  the 
  wires 
  was 
  

   taken 
  for 
  the 
  purpose 
  of 
  measuring 
  their 
  curvature 
  after 
  

   they 
  had 
  come 
  to 
  rest 
  in 
  their 
  position 
  of 
  equilibrium. 
  To 
  

   keep 
  them 
  from 
  revolving 
  and 
  to 
  maintain 
  their 
  plane 
  at 
  

   right 
  angles 
  to 
  the 
  line 
  of 
  the 
  camera 
  they 
  were 
  suspended 
  

   from 
  separate 
  points 
  near 
  together. 
  By 
  measurements 
  on 
  

   this 
  photograph 
  the 
  curves 
  assumed 
  by 
  the 
  wires 
  were 
  

   obtained, 
  shown 
  in 
  fig. 
  2 
  (PI. 
  I.). 
  

  

  By 
  means 
  of 
  this 
  curve 
  much 
  information 
  may 
  be 
  obtained 
  

   concerning 
  the 
  distribution 
  of 
  charge 
  upon 
  the 
  conductors. 
  

   The 
  problem 
  is 
  the 
  inverse 
  of 
  that 
  of 
  the 
  suspension 
  bridge, 
  

   in 
  which 
  it 
  is 
  usual 
  to 
  assume 
  a 
  uniformly 
  distributed 
  dead 
  

   load 
  and 
  calculate 
  the 
  curve 
  that 
  the 
  cable 
  will 
  assume. 
  

   Here 
  the 
  load 
  is 
  replaced 
  by 
  the 
  distributed 
  chnrge 
  upon 
  

   the 
  wire 
  repelled 
  by 
  the 
  charge 
  upon 
  the 
  other 
  wire. 
  The 
  

   load 
  or 
  charge 
  is 
  the 
  unknown 
  factor, 
  and 
  the 
  resulting 
  

   curvature 
  of 
  the 
  suspension 
  cable 
  is 
  known 
  by 
  measurement. 
  

   In 
  this 
  way 
  differences 
  between 
  the 
  distributions 
  of 
  the 
  

   charges 
  and 
  currents 
  for 
  different 
  kinds 
  of 
  applied 
  voltages 
  

   might 
  be 
  studied. 
  A 
  steady 
  potential 
  is 
  likely 
  to 
  differ 
  

   from 
  an 
  alternating 
  one 
  at 
  different 
  frequencies. 
  There 
  are 
  

   comparatively 
  few 
  cases 
  where 
  the 
  distribution 
  of 
  charge 
  

   upon 
  conductors 
  can 
  be 
  calculated, 
  and 
  a 
  determination 
  of 
  

   the 
  distribution 
  experimentally 
  is 
  likely 
  to 
  add 
  something 
  to 
  

   our 
  knowledge 
  upon 
  this 
  subject. 
  

  

  Even 
  with 
  these 
  heavier 
  spheres 
  it 
  was 
  found 
  that 
  there 
  

   was 
  not 
  enough 
  weight 
  to 
  keep 
  this 
  fine 
  wire 
  sufficiently 
  

   taut 
  to 
  proceed 
  to 
  increase 
  the 
  number 
  of 
  spheres. 
  Another 
  

   kind 
  of 
  suspension 
  was 
  therefore 
  sought. 
  Finally 
  a 
  silk- 
  

   fibre 
  suspension 
  was 
  employed, 
  but 
  as 
  this 
  is 
  a 
  good 
  insulator 
  

   it 
  was 
  necessary 
  to 
  find 
  some 
  means 
  of 
  making 
  it 
  conducting. 
  

   The 
  most 
  practical 
  way 
  was 
  to 
  moisten 
  each 
  fibre 
  with 
  

   glycerine 
  by 
  wetting 
  the 
  thumb 
  and 
  finger 
  after 
  the 
  spheres 
  

   were 
  suspended 
  and 
  rubbing 
  the 
  whole 
  length 
  of 
  the 
  fibre. 
  

   "When 
  the 
  same 
  alternating 
  potential 
  as 
  before 
  was 
  applied 
  

   in 
  the 
  same 
  manner 
  as 
  with 
  the 
  wire 
  suspension, 
  the 
  spheres 
  

   would 
  not 
  separate 
  at 
  all. 
  

  

  It 
  was 
  surmised 
  that 
  the 
  resistance 
  of 
  the 
  fibres 
  was 
  so 
  

   great 
  that 
  the 
  spheres 
  could 
  not 
  receive 
  a 
  sufficient 
  alternating 
  

  

  