﻿480 
  Prof. 
  S. 
  R. 
  ( 
  look 
  on 
  

  

  3. 
  Observations 
  with 
  Suspended 
  Spheres, 
  

  

  A 
  small 
  hole 
  was 
  blown 
  at 
  the 
  centre 
  of 
  a 
  ventral 
  segment 
  

   in 
  the 
  Kundt 
  resonance-tube, 
  and 
  a 
  small 
  cork 
  was 
  fitted 
  flush 
  

   with 
  the 
  inner 
  surface 
  o£ 
  the 
  tube. 
  To 
  this 
  cork 
  two 
  spheres 
  

   were 
  suspended 
  on 
  the 
  end 
  of 
  fine 
  spider-threads 
  about 
  two 
  

   centimetres 
  in 
  length, 
  and 
  at 
  any 
  desired 
  distance 
  apart. 
  

  

  Two 
  spheres, 
  whose 
  diameter 
  was 
  about 
  '0*9 
  mm., 
  thus 
  

   suspended, 
  with 
  their 
  line 
  of 
  centres 
  parallel 
  to 
  the 
  stream- 
  

   lines, 
  were 
  repelled, 
  but 
  with 
  their 
  line 
  of 
  centres 
  per- 
  

   pendicular 
  to 
  the 
  stream-lines 
  they 
  were 
  attracted. 
  When 
  the 
  

   line 
  of 
  centres 
  was 
  at 
  an 
  angle 
  of 
  about 
  45°, 
  or 
  less, 
  they 
  

   would 
  rotate 
  their 
  line 
  of 
  centres 
  perpendicular 
  to 
  the 
  stream- 
  

   lines 
  and 
  approach 
  each 
  other. 
  

  

  The 
  sealing-wax 
  spheres 
  were 
  replaced 
  by 
  glass 
  spheres 
  of 
  

   the 
  same 
  size. 
  The 
  results 
  were 
  the 
  same, 
  but 
  not 
  so 
  

   pronounced. 
  

  

  These 
  observations 
  were 
  repeated 
  with 
  other 
  sealing-wax 
  

   spheres, 
  whose 
  diameters 
  were 
  from 
  *5 
  mm. 
  to 
  °7 
  mm,, 
  their 
  

   distance 
  apart 
  being 
  from 
  "1 
  mm. 
  to 
  *8 
  mm. 
  The 
  same 
  

   results 
  were 
  observed. 
  

  

  Spheres 
  of 
  from 
  *2 
  mm. 
  to 
  '3 
  mm. 
  were 
  then 
  suspended 
  in 
  

   like 
  manner 
  with 
  similar 
  results, 
  except 
  that 
  the 
  forces 
  were 
  

   more 
  pronounced. 
  With 
  these 
  small 
  spheres 
  suspended 
  

   within 
  half 
  of 
  their 
  diameter 
  apart, 
  it 
  was 
  observed 
  that 
  the 
  

   suspensions 
  approached 
  each 
  other 
  when 
  the 
  spheres 
  were 
  in 
  

   contact. 
  

  

  In 
  order 
  to 
  eliminate 
  this 
  attraction 
  of 
  the 
  fibres, 
  one 
  of 
  

   the 
  spheres 
  was 
  mounted 
  on 
  the 
  end 
  of 
  a 
  fine 
  glass 
  fibre, 
  

   which 
  was 
  brought 
  in 
  from 
  the 
  side 
  of 
  the 
  Kundt 
  resonance- 
  

   tube, 
  and 
  the 
  other 
  was 
  mounted 
  on 
  a 
  single 
  fibre-suspension 
  

   as 
  before. 
  

  

  When 
  the 
  two 
  spheres 
  were 
  brought 
  within 
  a 
  distance 
  of 
  

   about 
  half 
  their 
  own 
  diameter, 
  with 
  their 
  lines 
  of 
  centres 
  

   perpendicular 
  to 
  the 
  stream-lines, 
  the 
  suspended 
  sphere 
  was 
  

   repelled 
  from 
  the 
  sphere 
  mounted 
  on 
  the 
  glass 
  fibre. 
  When 
  

   their 
  line 
  of 
  centres 
  was 
  parallel 
  to 
  the 
  stream-lines, 
  and 
  

   their 
  distance 
  apart 
  less 
  than 
  half 
  their 
  diameter, 
  the 
  sus- 
  

   pended 
  sphere 
  approached 
  the 
  fixed 
  sphere 
  and 
  moved 
  around 
  

   until 
  their 
  line 
  of 
  centres 
  was 
  perpendicular 
  to 
  the 
  stream- 
  

   lines. 
  

  

  These 
  observations 
  were 
  verified 
  by 
  other 
  sets 
  of 
  spheres 
  

   in 
  other 
  ventral 
  segments. 
  

  

  4. 
  Influence 
  of 
  Surface 
  on 
  the 
  Forces 
  between 
  hvo 
  Spheres. 
  

   In 
  order 
  to 
  determine 
  whether 
  or 
  not 
  a 
  surface 
  would 
  

  

  