﻿492 
  Transactions. 
  — 
  Chemistry. 
  

  

  highly 
  resinoid 
  substance 
  or 
  a 
  pure 
  resin 
  according 
  to 
  the 
  time 
  

   it 
  has 
  been 
  exposed 
  to 
  the 
  &h\ 
  

   It 
  only 
  remains 
  for 
  us 
  now 
  to 
  discuss 
  the 
  subject 
  of 
  the 
  cause 
  of 
  the 
  

   production 
  of 
  the 
  figures 
  in 
  question, 
  and 
  for 
  tliis 
  1 
  need 
  not 
  do 
  more 
  than 
  

   point 
  out 
  to 
  you, 
  that 
  if 
  the 
  nature 
  of 
  these 
  figures 
  is 
  as 
  I 
  have 
  just 
  

   described, 
  their 
  cause 
  — 
  tliat 
  is 
  of 
  course 
  their 
  more 
  immediate 
  cause 
  — 
  can 
  be 
  

   no 
  other 
  tlian 
  the 
  oxidation 
  of 
  a 
  portion 
  of 
  tlie 
  oil 
  employed 
  to 
  produce 
  

   them, 
  and 
  the 
  aggregation 
  of 
  the 
  remainder 
  into 
  annular 
  patches 
  to 
  form 
  

   the 
  markings 
  which 
  characterize 
  them. 
  

  

  How 
  oil 
  and 
  resinous 
  matters 
  do 
  thus 
  dissociate, 
  is 
  a 
  question 
  which 
  is 
  

   scarcely 
  within 
  the 
  scope 
  of 
  this 
  .paper 
  to 
  discuss. 
  It 
  is, 
  however, 
  one 
  of 
  

   such 
  interest, 
  and 
  is 
  moreover 
  so 
  intimately 
  connected 
  with 
  my 
  subject, 
  that 
  

   I 
  cannot 
  refrain 
  from 
  doing 
  this 
  in 
  a 
  brief 
  manner, 
  although 
  to 
  do 
  so 
  some- 
  

   what 
  trenches 
  upon 
  a 
  subject 
  which 
  I 
  intend 
  soon 
  to 
  treat 
  of 
  in 
  a 
  further 
  

   communication 
  to 
  you. 
  

  

  According 
  to 
  ideas 
  now 
  in 
  vogue, 
  one 
  word 
  would 
  be 
  sufficient 
  to 
  name 
  in 
  

   answer 
  to 
  this 
  question. 
  AVhy 
  do 
  these 
  two 
  substances 
  dissociate 
  ? 
  And 
  

   that 
  word 
  is 
  repulsion. 
  The 
  resinous 
  parts 
  of 
  these 
  figures 
  would 
  be 
  held 
  in 
  

   accordance 
  with 
  these 
  ideas 
  to 
  repel 
  the 
  oily 
  part. 
  

  

  But 
  from 
  several 
  observations 
  I 
  have 
  recently 
  made, 
  I 
  have 
  reason 
  for 
  

   asserting 
  that 
  this 
  appearance 
  of 
  repulsion 
  is 
  at 
  bottom 
  due 
  to 
  the 
  effects 
  

   of 
  cohesion. 
  One 
  of 
  these 
  observations 
  is 
  that 
  greasy 
  matters 
  generally, 
  

   contrary 
  to 
  present 
  scientific 
  and 
  popular 
  opinion, 
  instead 
  of 
  repelling 
  water, 
  

   adhere 
  thereto 
  when 
  placed 
  in 
  juxtaposition 
  with 
  it.* 
  

  

  The 
  phenomenon 
  of 
  dissociation 
  then 
  has, 
  I 
  consider, 
  to 
  be 
  explained 
  by 
  

   a 
  hypothesis 
  in 
  which 
  the 
  property 
  of 
  cohesion 
  only 
  has 
  to 
  be 
  taken 
  into 
  

   account, 
  and 
  I 
  would 
  form 
  it 
  as 
  follows 
  : 
  — 
  Oil 
  has 
  a 
  certain 
  degree 
  of 
  

   cohesion 
  for 
  itself, 
  also 
  for 
  water 
  ; 
  but 
  the 
  products 
  arising 
  from 
  its 
  oxidation 
  

   have 
  a 
  greater 
  cohesion 
  both 
  as 
  among 
  themselves 
  aiud 
  for 
  water, 
  and 
  

   it 
  is 
  in 
  direct 
  proportion 
  to 
  the 
  degree 
  in 
  which 
  they 
  are 
  chemically 
  

   removed 
  from 
  the 
  oil 
  which 
  furnishes 
  them 
  ; 
  until, 
  as 
  the 
  final 
  products 
  of 
  

   this 
  process 
  are 
  reached, 
  a 
  notable 
  affinity 
  for 
  water 
  (that 
  is 
  an 
  intense 
  

   cohesion) 
  developes 
  ; 
  but 
  this 
  great 
  cohesion 
  for 
  water 
  on 
  the 
  part 
  of 
  such 
  

   products 
  is 
  attained 
  only 
  by 
  a 
  corresponding 
  loss 
  of 
  cohesion 
  between 
  them 
  

   and 
  the 
  oil, 
  that 
  is 
  the 
  unaltered 
  or 
  less 
  altered 
  oil. 
  These 
  products 
  

   therefore 
  have 
  a 
  constant 
  tendency 
  to 
  monopolize 
  the 
  surface 
  of 
  the 
  water 
  

   upon 
  which 
  they 
  are 
  formed, 
  and 
  the 
  unaltered 
  or 
  but 
  slightly 
  altered 
  oil, 
  

  

  * 
  If 
  solid 
  grease 
  is 
  placed 
  in 
  contact 
  with 
  water, 
  the 
  water-surface 
  in 
  the 
  immediate 
  

   vicinity 
  of 
  the 
  grease 
  is 
  not 
  depressed 
  below 
  the 
  general 
  surface 
  of 
  the 
  water 
  ; 
  and 
  if 
  the 
  

   grease 
  is 
  lifted 
  just 
  above 
  this 
  surface, 
  the 
  water 
  in 
  its 
  vicinity 
  is 
  also 
  lifted 
  above 
  it, 
  

   showing 
  very 
  clearly 
  that 
  the 
  two 
  substances 
  cohere. 
  

  

  