﻿^'^bration 
  Curves 
  of 
  Violin 
  G 
  String 
  and 
  Belly. 
  235 
  

  

  is 
  uniform 
  as 
  the 
  plate 
  passes 
  the 
  doortvay 
  and 
  receives 
  the 
  

   light. 
  Quarter-plates 
  were 
  used 
  and 
  generally 
  those 
  called 
  

   " 
  ^'arwick 
  Rainbow 
  Isochromatic 
  Fast, 
  Backed," 
  though 
  

   sometimes 
  " 
  Imperial 
  Process." 
  

  

  Consider 
  now 
  the 
  second 
  portion 
  of 
  the 
  light 
  from 
  the 
  

   lantern. 
  This 
  was 
  deflected 
  by 
  the 
  plane 
  mirrors 
  M^ 
  and 
  

   Mo, 
  and 
  so 
  directed 
  to 
  the 
  small 
  hole 
  H 
  in 
  a 
  copper 
  plate. 
  

   It 
  passed 
  thence 
  to 
  the 
  concave 
  mirror 
  by 
  Hilger, 
  1*2 
  cms. 
  

   in 
  diameter 
  (fixed 
  on 
  a 
  lever), 
  and 
  marked 
  ni 
  in 
  the 
  figure. 
  

   This 
  mirror 
  focussed 
  the 
  real 
  image 
  of 
  the 
  hole 
  on 
  the 
  plate 
  

   just 
  below 
  the 
  image 
  of 
  the 
  slit 
  crossed 
  by 
  the 
  shadow 
  of 
  the 
  

   string. 
  Hence, 
  as 
  the 
  string 
  and 
  belly 
  vibrate, 
  and 
  the 
  

   plate 
  shoots 
  past, 
  we 
  obtain 
  a 
  photographic 
  negative, 
  the 
  

   positive 
  print 
  of 
  which 
  gives 
  the 
  string's 
  vibration 
  in 
  hlach 
  

   upon 
  a 
  white 
  ground 
  in 
  the 
  upper 
  half, 
  and 
  the 
  helly^s 
  

   vibration 
  in 
  icliite 
  on 
  a 
  dark 
  ground 
  on 
  the 
  low^er 
  half. 
  The 
  

   precise 
  arrangement 
  of 
  the 
  concave 
  mirror 
  will 
  be 
  dealt 
  with 
  

   in 
  connexion 
  with 
  fig. 
  4. 
  The 
  distances 
  M 
  to 
  L2 
  and 
  L2 
  

   to 
  P 
  in 
  fig. 
  1 
  were 
  respectively 
  of 
  the 
  order 
  52 
  and 
  132 
  cms. 
  

   Hence, 
  on 
  the 
  negatives, 
  the 
  string''s 
  motion 
  is 
  magnified 
  

   132 
  52 
  = 
  2*54 
  times 
  nearly. 
  

  

  Mounting 
  the 
  Violin. 
  — 
  The 
  method 
  of 
  holding 
  the 
  violin 
  

   for 
  the 
  experiments 
  (and 
  in 
  a 
  way 
  intended 
  to 
  imitate 
  the 
  

   actual 
  grip 
  of 
  a 
  plaver's 
  shoulder, 
  chin, 
  and 
  left 
  hand) 
  is 
  

   shown 
  in 
  fig. 
  2 
  (PI. 
  iV.). 
  

  

  Two 
  blocks 
  screwed 
  on 
  the 
  table 
  supported 
  a 
  stout 
  brass 
  

   rod, 
  carrying 
  a 
  board 
  which 
  was 
  thus 
  capable 
  of 
  turning 
  

   about 
  a 
  horizontal 
  axis. 
  The 
  board 
  was 
  turned 
  to 
  a 
  suitable 
  

   inclination 
  and 
  then 
  clamped 
  in 
  position 
  on 
  a 
  block 
  as 
  

   shown. 
  This 
  board 
  carried 
  two 
  other 
  blocks, 
  that 
  to 
  the 
  

   right 
  having 
  a 
  groove, 
  lined 
  with 
  wash-leather, 
  to 
  admit 
  

   the 
  neck 
  of 
  the 
  violin, 
  which 
  was 
  then 
  held 
  down 
  by 
  the 
  

   indiarubber 
  cord 
  passing 
  over 
  the 
  peg-box, 
  as 
  seen 
  in 
  the 
  

   photograph'. 
  These 
  arrangements 
  imitate 
  the 
  player''s 
  left 
  

   hand. 
  Near 
  the 
  tail-piece 
  of 
  the 
  violin, 
  i. 
  e. 
  at 
  the 
  left 
  end 
  

   of 
  the 
  figure, 
  wash-leather 
  lies 
  under 
  the 
  back 
  of 
  the 
  violin, 
  

   which 
  was 
  held 
  down 
  by 
  a 
  swinging 
  block 
  over 
  w^hich 
  an 
  

   indiarubber 
  cord 
  passed. 
  These 
  pieces 
  imitate 
  the 
  player's 
  

   shoulder 
  and 
  chin 
  ; 
  the 
  ordinary 
  chin-rest 
  w^as 
  left 
  in 
  

   position. 
  In 
  order 
  to 
  be 
  able 
  to 
  photograph 
  the 
  motions 
  of 
  

   the 
  single 
  string, 
  although 
  all 
  four 
  were 
  present, 
  the 
  finger- 
  

   board 
  was 
  removed 
  from 
  the 
  violin, 
  the 
  mirror 
  M 
  (fig. 
  1) 
  

   placed 
  just 
  behind 
  the 
  string 
  under 
  examination, 
  and 
  the 
  

   other 
  strings 
  kept 
  out 
  of 
  the 
  path 
  of 
  the 
  beam. 
  Thus, 
  when 
  

   the 
  g 
  string 
  was 
  being 
  dealt 
  with 
  (which 
  is 
  the 
  one 
  farthest 
  

   removed 
  from 
  the 
  lantern 
  and 
  plate) 
  the 
  dJ 
  and 
  a' 
  strings 
  

  

  