﻿Skey. 
  — 
  On 
  the 
  Movements 
  of 
  CampJwr 
  on 
  Water. 
  479 
  

  

  First 
  tlien 
  in 
  regaxd 
  to 
  the 
  nature 
  of 
  this 
  modification. 
  Camphor, 
  I 
  

   should 
  remind 
  you, 
  has 
  properties 
  affecting 
  this 
  question 
  as 
  follows 
  : 
  — 
  It 
  is 
  

   soluble 
  in 
  water, 
  and 
  so 
  without 
  doubt 
  combines 
  with 
  it 
  ; 
  it 
  is 
  not 
  decom- 
  

   posed 
  by 
  water, 
  even 
  in 
  conjunction 
  with 
  an 
  that 
  is 
  at 
  common 
  temperatm-es, 
  

   and 
  it 
  is 
  a 
  resin 
  slowly 
  volatile 
  at 
  such 
  temperatures. 
  

  

  Now 
  camphor, 
  as 
  we 
  have 
  seen, 
  modifies 
  a 
  very 
  much 
  larger 
  extent 
  of 
  

   surface 
  when 
  placed 
  in 
  contact 
  with 
  water 
  than 
  when 
  suspended 
  over 
  it. 
  

   "We 
  may, 
  therefore, 
  be 
  certain 
  that 
  the 
  modification 
  in 
  question 
  is 
  not 
  

   occasioned 
  simply 
  by 
  a 
  deposit 
  of 
  condensed 
  camphor 
  vapour 
  upon 
  the 
  

   water 
  surface, 
  but 
  rather 
  by 
  some 
  combination 
  of 
  it 
  with 
  water. 
  This 
  

   combination, 
  however, 
  is 
  not 
  that 
  which 
  is 
  obtained 
  by 
  saturating 
  water 
  

   with 
  camphor 
  in 
  the 
  ordinary 
  way 
  (a 
  compound 
  containing 
  one 
  part 
  of 
  

   camphor 
  to 
  one 
  thousand 
  parts 
  of 
  water), 
  as 
  is 
  shown 
  by 
  the 
  fact 
  I 
  have 
  

   already 
  stated 
  to 
  you, 
  that 
  a 
  saturated 
  solution 
  of 
  camphor 
  in 
  water 
  allows 
  

   camphor 
  to 
  describe 
  movements 
  upon 
  its 
  surface 
  ; 
  this 
  compound, 
  therefore, 
  

   is 
  one 
  new 
  to 
  us, 
  it 
  can 
  only 
  exist 
  as 
  a 
  thin 
  surface 
  film, 
  and 
  is 
  therefore 
  

   doubtless 
  one 
  far 
  richer 
  in 
  camphor 
  than 
  that 
  which 
  we 
  already 
  know 
  of, 
  

   a 
  compound 
  indeed 
  so 
  highly 
  camphoretted 
  that 
  it, 
  in 
  all 
  probability, 
  

   partakes 
  in 
  an 
  eminent 
  degree 
  of 
  the 
  characters 
  of 
  an 
  oil.''' 
  However, 
  it 
  is 
  

   impossible 
  for 
  me 
  as 
  yet 
  to 
  obtain 
  dnect 
  evidence 
  as 
  to 
  the 
  nature 
  of 
  a 
  film 
  

   so 
  exceedingly 
  thin 
  as 
  this. 
  We 
  must 
  therefore 
  for 
  the 
  present 
  rest 
  content 
  

   with 
  the 
  indirect 
  evidence 
  which 
  we 
  now 
  have. 
  

  

  Granted, 
  then, 
  that 
  the 
  modification 
  effected 
  upon 
  a 
  surface 
  of 
  water 
  by 
  

   camphor 
  is 
  owing 
  to 
  a 
  combination 
  of 
  the 
  two 
  for 
  the 
  production 
  of 
  a 
  highly 
  

   camphoretted 
  oil, 
  I 
  have 
  only 
  now 
  to 
  show 
  the 
  precise 
  manner 
  in 
  which 
  

   this 
  compound 
  induces 
  camphor 
  to 
  move. 
  

  

  For 
  this 
  purpose 
  I 
  will 
  refer 
  you 
  to 
  the 
  effect 
  which 
  a 
  drop 
  of 
  oil 
  has 
  

   when 
  placed 
  upon 
  water 
  laden 
  with 
  an 
  indicatory 
  substance, 
  such 
  as 
  clay 
  

   in 
  fine 
  particles 
  ; 
  the 
  oil 
  spreads 
  quickly 
  and 
  regularly 
  around, 
  and 
  in 
  the 
  

   act 
  urges 
  the 
  clay 
  to 
  the 
  side 
  of 
  the 
  containing 
  vessel, 
  where 
  it 
  becomes 
  

   stationary. 
  Now 
  the 
  clay 
  and 
  the 
  oil 
  here 
  are, 
  I 
  hold, 
  fairly 
  representative 
  

   of 
  the 
  camphor 
  and 
  its 
  oily 
  compound 
  ; 
  there 
  is 
  this 
  difference, 
  however, 
  in 
  

   the 
  movement 
  of 
  the 
  oils, 
  and 
  it 
  is 
  an 
  important 
  one, 
  it 
  is 
  a 
  difference 
  upon 
  

   which 
  all 
  camphor 
  movement 
  depends, 
  — 
  the 
  spread 
  of 
  oil 
  in 
  the 
  case 
  of 
  

   camphor 
  is 
  not 
  even 
  around 
  it, 
  as 
  is 
  that 
  of 
  the 
  other 
  oil 
  ; 
  were 
  it 
  so 
  there 
  

   would 
  be 
  no 
  such 
  phenomenon 
  as 
  that 
  we 
  are 
  investigating. 
  Eegularity 
  of 
  

   spread 
  is 
  in 
  this 
  case 
  impossible, 
  because 
  the 
  production 
  is 
  kregular, 
  owing 
  

   to 
  the 
  highly 
  crystalhne 
  nature 
  of 
  camphor, 
  and 
  its 
  great 
  fragihty, 
  whereby 
  

  

  * 
  I 
  have 
  lately 
  observed 
  that 
  water 
  thus 
  modified, 
  when 
  compared 
  side 
  by 
  side 
  

   with 
  pure 
  water, 
  exhibits 
  a 
  higher 
  lustre 
  than 
  the 
  pure 
  water 
  does, 
  a 
  fact 
  greatly 
  in 
  

   favour 
  of 
  tliis 
  view. 
  

  

  