﻿and 
  other 
  Properties 
  of 
  Thin 
  Oily 
  Films. 
  159 
  

  

  material 
  modification 
  of 
  the 
  effects 
  observed. 
  The 
  moisture 
  

   of 
  tlie 
  breath, 
  or 
  drowning 
  in 
  water 
  whether 
  clean 
  or 
  soapy, 
  

   developed 
  the 
  same 
  stickiness 
  as 
  before. 
  

  

  The 
  next 
  series 
  of 
  experiments 
  was 
  a 
  little 
  more 
  elaborate. 
  

   In 
  order 
  to 
  obtain 
  measures 
  more 
  readily, 
  and 
  to 
  facilitate 
  

   drowning 
  of 
  the 
  contacts, 
  the 
  slab 
  was 
  used 
  in 
  the 
  horizontal 
  

   position 
  and 
  the 
  movable 
  piece 
  was 
  pulled 
  by 
  a 
  thread 
  which 
  

   started 
  horizontally, 
  and 
  passing 
  over 
  a 
  pulley 
  carried 
  a 
  small 
  

   pan 
  into 
  which 
  weights 
  could 
  be 
  placed. 
  The 
  pan 
  itself 
  

   weighed 
  1 
  oz. 
  (28 
  grams). 
  Another 
  change 
  was 
  the 
  substi- 
  

   tution 
  for 
  the 
  bottle 
  of 
  a 
  small 
  carriage 
  standing 
  on 
  glass 
  

   legs 
  terminating 
  in 
  three 
  feet 
  of 
  hemispherical 
  form 
  and 
  

   5 
  mm. 
  in 
  diameter. 
  The 
  whole 
  weight 
  of 
  the 
  carriage, 
  as 
  

   loaded, 
  was 
  7 
  J 
  oz. 
  The 
  object 
  of 
  the 
  substitution 
  was 
  to 
  

   eliminate 
  any 
  effects 
  which 
  might 
  arise 
  from 
  the 
  compara- 
  

   tively 
  large 
  area 
  of 
  approximate 
  contact 
  presented 
  by 
  the 
  

   rim 
  of 
  the 
  bottle, 
  although 
  in 
  that 
  case 
  also 
  the 
  actual 
  con- 
  

   tacts 
  would 
  doubtless 
  be 
  only 
  three 
  in 
  number 
  and 
  of 
  very 
  

   small 
  area. 
  

  

  With 
  -J 
  oz. 
  in 
  pan 
  and 
  surfaces 
  treated 
  with 
  the 
  hand, 
  the 
  

   carriage 
  would 
  move 
  within 
  a 
  second 
  or 
  two 
  after 
  being 
  

   placed 
  in 
  position, 
  but 
  after 
  four 
  or 
  five 
  seconds' 
  contact 
  

   would 
  stick. 
  After 
  a 
  few 
  minutes' 
  contact 
  it 
  may 
  require 
  

   1^ 
  oz. 
  in 
  pan 
  to 
  start 
  it. 
  When 
  the 
  slab 
  is 
  breathed 
  upon 
  it 
  

   requires, 
  even 
  at 
  first, 
  3^ 
  oz. 
  in 
  the 
  pan 
  to 
  start 
  the 
  motion. 
  

   As 
  soon 
  as 
  the 
  breath 
  has 
  evaporated, 
  \ 
  oz. 
  in 
  pan 
  again 
  

   suffices. 
  When 
  the 
  weight 
  of 
  the 
  pan 
  is 
  included, 
  the 
  forces 
  

   are 
  seen 
  to 
  be 
  as 
  1 
  : 
  3. 
  When 
  the 
  feet 
  stand 
  in 
  a 
  pool 
  of 
  

   water 
  the 
  stickiness 
  is 
  nearly 
  the 
  same 
  as 
  with 
  the 
  breath, 
  and 
  

   the 
  substitution 
  of 
  soapy 
  for 
  clean 
  water 
  makes 
  little 
  

   difference. 
  

  

  In 
  another 
  day's 
  experiment 
  paraffin 
  (lamp) 
  oil 
  was 
  used. 
  

   After 
  handling, 
  there 
  was 
  free 
  motion 
  with 
  1 
  oz. 
  in 
  pan. 
  

   When 
  the 
  feet 
  stood 
  in 
  the 
  oil, 
  from 
  2 
  j 
  to 
  3 
  oz. 
  were 
  needed 
  

   in 
  the 
  pan. 
  Most 
  of 
  the 
  oil 
  was 
  next 
  removed 
  by 
  rubbing 
  

   with 
  blotting-paper 
  until 
  the 
  slab 
  looked 
  clean. 
  At 
  this 
  stage 
  

   | 
  oz. 
  in 
  pan 
  sufficed 
  to 
  start 
  the 
  motion. 
  On 
  again 
  wetting 
  

   with 
  oil 
  2 
  oz. 
  sufficed 
  instead 
  of 
  the 
  2| 
  oz. 
  required 
  before. 
  

   After 
  another 
  cleaning 
  with 
  blotting-paper 
  ^ 
  oz. 
  in 
  pan 
  

   sufficed. 
  From 
  these 
  results 
  it 
  appears 
  that 
  the 
  friction 
  is 
  

   greater 
  with 
  a 
  large 
  dose 
  than 
  with 
  a 
  minute 
  quantity 
  of 
  the 
  

   same 
  oil, 
  and 
  this 
  what 
  is 
  hard 
  to 
  explain. 
  When 
  olive 
  oil 
  

   was 
  substituted 
  for 
  the 
  paraffin 
  oil, 
  the 
  results 
  were 
  less 
  

   strongly 
  marked. 
  

  

  Similar 
  experiments 
  with 
  a 
  carriage 
  standing 
  on 
  brass 
  

  

  N2 
  

  

  