﻿256 
  A. 
  M. 
  Mayer— 
  On 
  the 
  Flotation 
  of 
  

  

  But 
  his 
  definition 
  is 
  faulty. 
  It 
  is 
  simply 
  that 
  a 
  molecule 
  of 
  

   water 
  at 
  the 
  lowest 
  part 
  of 
  the 
  floating 
  body 
  draws 
  the 
  neigh- 
  

   boring 
  molecule 
  with 
  it, 
  this 
  a 
  third 
  and 
  so 
  on. 
  " 
  The 
  cohesion 
  

   which 
  unites 
  all 
  the 
  molecules 
  of 
  the 
  surface 
  of 
  the 
  water 
  

   forms 
  a 
  kind 
  of 
  pellicle, 
  and 
  there 
  results 
  a 
  sac 
  at 
  the 
  bottom 
  

   of 
  which 
  the 
  heavy 
  solid 
  rests." 
  

  

  In 
  a 
  second 
  paper 
  Gaillieron* 
  gives 
  an 
  account 
  of 
  further 
  

   experiments. 
  He 
  places 
  a 
  layer 
  of 
  oil 
  upon 
  the 
  water, 
  and 
  

   drops 
  the 
  needle 
  gently 
  into 
  it. 
  It 
  descends 
  to 
  the 
  surface 
  of 
  

   the 
  water. 
  On 
  looking 
  upward 
  at 
  it 
  through 
  the 
  glass, 
  one 
  

   sees, 
  not 
  the 
  surface 
  of 
  the 
  needle, 
  but 
  only 
  the 
  surface 
  of 
  the 
  

   oil 
  depressed 
  by 
  it. 
  He 
  explains 
  these 
  experiments 
  by 
  means 
  

   of 
  the 
  existence 
  of 
  a 
  pellicle. 
  

  

  De 
  Maistref 
  (1841), 
  after 
  describing 
  the 
  floating 
  of 
  metals 
  on 
  

   the 
  surface 
  of 
  water, 
  says: 
  This 
  remarkable 
  phenomenon 
  is 
  

   due 
  to 
  the 
  fact 
  that 
  the 
  molecules 
  which 
  form 
  the 
  surface 
  of 
  

   water 
  have 
  a 
  force 
  of 
  mutual 
  attraction 
  greater 
  than 
  in 
  the 
  

   interior 
  of 
  the 
  liquid. 
  He 
  then 
  goes 
  on 
  to 
  deduce 
  the 
  radius 
  

   of 
  activity 
  of 
  the 
  molecular 
  forces 
  by 
  studying 
  the 
  case 
  of 
  a 
  

   drop 
  of 
  water 
  formed 
  at 
  the 
  end 
  of 
  a 
  glass 
  rod. 
  The 
  largest 
  

   drop 
  he 
  could 
  obtain 
  had 
  a 
  radius 
  of 
  1J 
  line, 
  and 
  he 
  supposes 
  

   the 
  size 
  of 
  the 
  drop 
  to 
  be 
  determined 
  by 
  the 
  molecular 
  attrac- 
  

   tion, 
  which 
  he 
  therefore 
  regards 
  as 
  acting 
  effectively 
  up 
  to 
  a 
  dis- 
  

   tance 
  of 
  1£ 
  line. 
  At 
  the 
  close 
  of 
  his 
  paper 
  he 
  quotes 
  Rumford 
  

   as 
  having 
  occupied 
  himself 
  with 
  the 
  peculiar 
  properties 
  of 
  the 
  

   surface 
  of 
  a 
  liquid, 
  and 
  as 
  having 
  explained 
  them 
  by 
  the 
  sup- 
  

   position 
  of 
  a 
  pellicle, 
  the 
  existence 
  of 
  which 
  he 
  considers 
  to 
  be 
  

   proved 
  4 
  

  

  " 
  M. 
  Artur, 
  in 
  his 
  Theorie 
  elementaire 
  de 
  la 
  Capillarite> 
  

   Paris, 
  1842, 
  is 
  led 
  from 
  theoretic 
  considerations 
  to 
  regard 
  the 
  

   superficial 
  layer 
  of 
  all 
  liquids 
  as 
  having 
  a 
  greater 
  density 
  and 
  

   greater 
  cohesion 
  than 
  exist 
  in 
  the 
  interior, 
  and 
  therefore 
  as 
  

   having 
  a 
  certain 
  resistance. 
  Considering 
  only 
  the 
  laws 
  of 
  

   hydrostatics, 
  the 
  volume 
  of 
  the 
  depression 
  formed 
  in 
  the 
  sur- 
  

   face 
  of 
  water 
  by 
  a 
  floating 
  needle 
  should 
  exceed 
  by 
  six 
  times 
  

   the 
  volume 
  of 
  the 
  needle, 
  the 
  density 
  of 
  steel 
  being 
  7*8; 
  

   but 
  M. 
  Artur 
  and 
  others 
  have 
  estimated 
  the 
  volume 
  of 
  this 
  

   depression, 
  and 
  the 
  highest 
  valuation 
  of 
  it 
  gives 
  only 
  three 
  

   times 
  the 
  volume 
  of 
  the 
  needle." 
  § 
  

  

  In. 
  1 
  869 
  M. 
  Leboucher|| 
  appears 
  as 
  the 
  first 
  physicist 
  to 
  study 
  

  

  *Bibl 
  Univ., 
  vol. 
  xxvii, 
  p. 
  207, 
  1824. 
  

  

  f 
  Notice 
  sur 
  la 
  cause 
  qui 
  fait 
  surnager 
  une 
  aiguille 
  d'acier 
  sur 
  la 
  surface 
  de 
  

   l'eau. 
  Bibl. 
  Univ., 
  vol. 
  xxxv. 
  p 
  192, 
  1841. 
  

  

  \ 
  The 
  foregoing 
  extracts 
  from 
  the 
  Bibl. 
  Univ. 
  were 
  given 
  me 
  by 
  Prof. 
  Arthur 
  

   W. 
  Wright. 
  

  

  § 
  Taken 
  from 
  Plateau's 
  "Statique 
  experimental 
  et 
  theorique 
  des 
  liquides." 
  

   1873, 
  vol. 
  2, 
  p. 
  79. 
  

  

  I 
  " 
  Recherches 
  experimentales 
  et 
  theoriques 
  sur 
  un 
  cas 
  particulier 
  de 
  la 
  theorie 
  

   des 
  corps 
  flottants." 
  Caen, 
  Mem. 
  Soc. 
  Linn, 
  de 
  Normandie, 
  XV, 
  1869, 
  No. 
  2. 
  

  

  