﻿236 
  Prof. 
  E. 
  H. 
  Barton 
  and 
  Mr. 
  T. 
  J. 
  Richmond 
  on 
  

  

  (occupying 
  the 
  middle 
  positions) 
  were 
  raised 
  on 
  a 
  specially 
  

   prominent 
  part 
  of 
  the 
  bridge, 
  and 
  the 
  e" 
  string 
  (nearest 
  to 
  

   the 
  lantern 
  and 
  plate) 
  was 
  held 
  down 
  by 
  a 
  cord 
  passing- 
  

   round 
  the 
  neck 
  of 
  the 
  violin. 
  Thus, 
  although 
  three 
  of 
  the 
  

   strings 
  were 
  kept 
  out 
  of 
  the 
  way 
  the 
  conditions 
  were 
  but 
  

   slightly 
  altered 
  from 
  those 
  of 
  actually 
  playing 
  the 
  violin. 
  

   All 
  the 
  strings 
  were 
  there 
  and 
  in 
  tune, 
  two 
  were 
  on 
  a 
  rather 
  

   higher 
  part 
  of 
  the 
  bridge, 
  which 
  would 
  slightly 
  increase 
  the 
  

   pressure 
  on 
  the 
  belly, 
  and 
  one 
  was 
  tied 
  down, 
  which 
  is 
  only 
  

   the 
  same 
  as 
  its 
  being 
  pressed 
  down 
  by 
  the 
  performer's 
  finger 
  

   when 
  " 
  stopping'^ 
  it 
  for 
  a 
  particular 
  note. 
  

  

  Optical 
  Lever 
  for 
  Belly 
  Vibrations. 
  — 
  The 
  violin 
  used 
  was 
  

   an 
  old 
  English 
  instrument 
  without 
  any 
  name 
  or 
  date, 
  but 
  

   full 
  size 
  and 
  of 
  ordinary 
  model, 
  as 
  seen 
  by 
  fig.3 
  (PI. 
  IV.) 
  . 
  

  

  It 
  is 
  easily 
  found 
  by 
  scattering 
  sand 
  or 
  only 
  touching 
  

   lightly 
  with 
  the 
  finger-tips, 
  that 
  the 
  belly 
  of 
  the 
  violin 
  is 
  

   very 
  dead 
  near 
  the 
  edges 
  where 
  supported 
  by 
  the 
  ribs 
  which 
  

   attach 
  it 
  to 
  the 
  back. 
  But 
  spots 
  just 
  inside 
  the 
  /holes 
  are 
  

   specially 
  lively 
  and 
  were 
  accordingly 
  thought 
  preferable 
  aS' 
  

   places 
  whose 
  motion 
  should 
  be 
  recorded. 
  A 
  spot 
  on 
  the 
  

   right 
  hand 
  of 
  the 
  belly 
  was 
  chosen 
  and 
  a 
  little 
  wedge 
  of 
  soft 
  

   wood 
  fastened 
  upon 
  it, 
  so 
  that 
  the 
  upper 
  surface 
  of 
  this 
  

   wedge 
  was 
  kvel 
  when 
  the 
  violin 
  was 
  mounted. 
  On 
  this 
  

   upper 
  surface 
  a 
  piece 
  of 
  microscope 
  cover-glass 
  was 
  then 
  

   fastened 
  by 
  shellac 
  so 
  as 
  to 
  form 
  a 
  support 
  for 
  one 
  leg 
  of 
  

   the 
  three-legged 
  optical 
  lever 
  used 
  to 
  record 
  the 
  vibrations. 
  

   The 
  other 
  two 
  legs 
  rested 
  upon 
  a 
  conical 
  hole 
  and 
  V-groove 
  

   on 
  a 
  small 
  table 
  or 
  disk 
  of 
  brass 
  carried 
  by 
  an 
  adjustable 
  

   bracket. 
  Thus 
  the 
  optical 
  lever 
  was 
  carried 
  on 
  the 
  geo- 
  

   metrical 
  arrangement 
  of 
  the 
  "hole, 
  slot, 
  and 
  plane," 
  and 
  

   turned 
  about 
  the 
  hinge 
  formed 
  by 
  the 
  hole 
  and 
  slot 
  as 
  the 
  

   plane 
  rose 
  and 
  fell. 
  The 
  lever 
  was 
  of 
  aluminium 
  provided 
  

   with 
  steel 
  legs 
  and 
  with 
  the 
  mirror 
  had 
  amass 
  of 
  1*124 
  gram. 
  

   It 
  was 
  held 
  firmly 
  down 
  by 
  an 
  indiarubber 
  ring 
  obtained 
  by 
  

   cutting 
  a 
  slice 
  off 
  a 
  tube. 
  The 
  lever, 
  mirror, 
  and 
  rubber 
  

   ring 
  complete 
  weighed 
  1*254 
  gram. 
  The 
  adjustable 
  bracket 
  

   which 
  carried 
  the 
  optical 
  lever 
  can 
  be 
  seen 
  better 
  in 
  the 
  

   detached 
  view 
  of 
  fig. 
  4. 
  

  

  In 
  both 
  views 
  the 
  hole 
  and 
  slot 
  are 
  shown 
  in 
  white. 
  

  

  Mac/vJ/ication 
  of 
  the 
  Belh/s 
  Motion. 
  — 
  The 
  distance 
  of 
  the 
  

   moving 
  foot 
  of 
  the 
  optical 
  lever 
  from 
  the 
  axis 
  through 
  the 
  

   hole 
  and 
  slot 
  was 
  6 
  mm., 
  and 
  that 
  from 
  the 
  mirror 
  to 
  the 
  

   photographic 
  plate 
  was 
  176 
  cms. 
  (see 
  m. 
  P 
  in 
  fig. 
  1). 
  Hence 
  

   the 
  magnification 
  of 
  the 
  belly's 
  motion 
  on 
  the 
  original 
  

   negatives 
  was 
  2 
  x 
  176 
  -r 
  0*6 
  = 
  587 
  nearly. 
  Thus, 
  on 
  the 
  

   original 
  plates, 
  or 
  any 
  prints 
  reduced 
  from 
  them, 
  the 
  

  

  