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  THE 
  

  

  AMERICAN 
  JOURNAL 
  OF 
  SCIENCE 
  

  

  [FOURTH 
  SERIES. 
  ] 
  

  

  Art. 
  XXIY. 
  — 
  An 
  experimental 
  investigation 
  of 
  the 
  equi- 
  

   librium 
  of 
  the 
  forces 
  acting 
  in 
  the 
  flotation 
  of 
  disks 
  and 
  

   rings 
  of 
  metal 
  : 
  leading 
  to 
  measures 
  of 
  surface 
  tension 
  ; 
  

   by 
  Alfred 
  M. 
  Mayer. 
  

  

  It 
  occurred 
  to 
  me 
  that 
  if 
  a 
  ring 
  of 
  metal 
  with 
  a 
  chemically 
  

   clean 
  surface 
  could 
  be 
  floated, 
  and 
  then 
  gradually 
  weighted 
  till 
  

   it 
  broke 
  through 
  the 
  surface 
  of 
  the 
  liquid, 
  one 
  might 
  thus 
  

   directly 
  measure 
  surface 
  tension. 
  At 
  the 
  time 
  I 
  saw 
  little 
  

   prospect 
  of 
  succeeding 
  in 
  floating 
  a 
  ring 
  with 
  a 
  clean 
  surface, 
  

   for 
  all 
  the 
  treatises 
  on 
  physics 
  I 
  had 
  read 
  state 
  that 
  to 
  float 
  a 
  

   metal 
  on 
  water 
  its 
  surface 
  must 
  be 
  coated 
  with 
  a 
  film 
  of 
  grease. 
  

   A 
  ring 
  of 
  aluminum 
  seemed 
  the 
  more 
  likely 
  to 
  float 
  because 
  

   this 
  metal 
  has 
  a 
  peculiar 
  repellent 
  action 
  on 
  melted 
  alloys, 
  like 
  

   ordinary 
  solders. 
  I 
  made 
  a 
  ring 
  of 
  aluminum 
  50 
  mm 
  in 
  diam- 
  

   eter 
  out 
  of 
  wire 
  l 
  mm 
  thick. 
  It 
  floated 
  on 
  water. 
  As 
  I 
  

   gradually 
  added 
  weight 
  to 
  the 
  ring 
  (see 
  iig. 
  4) 
  it 
  sank 
  deeper 
  

   and 
  deeper 
  in 
  a 
  depression 
  in 
  the 
  water, 
  till 
  having 
  reached 
  a 
  

   depth 
  of 
  5 
  mm 
  , 
  it 
  broke 
  through 
  the 
  water-surface. 
  The 
  total 
  

   weight 
  required 
  to 
  make 
  the 
  ring 
  break 
  through 
  the 
  surface 
  

   was 
  2*6 
  grams. 
  

  

  In 
  subsequent 
  experiments 
  I 
  floated 
  a 
  ring 
  of 
  61*8 
  mm 
  in 
  

   diameter 
  made 
  of 
  aluminum 
  rod 
  3'7 
  mm 
  (g- 
  1 
  ^- 
  in.) 
  in 
  diameter. 
  

   This 
  ring 
  weighed 
  5*8 
  grams. 
  To 
  float 
  this 
  ring 
  requires 
  a 
  

   steady 
  hand 
  and 
  patience 
  ; 
  but 
  a 
  ring 
  made 
  of 
  aluminum 
  rod 
  

   3*15 
  mm 
  (-§• 
  in.) 
  in 
  diameter 
  is 
  easily 
  floated. 
  With 
  this 
  ring 
  

   may 
  be 
  made 
  an 
  interesting 
  experiment. 
  The 
  ring 
  with 
  fine 
  

   wire 
  yoke 
  and 
  cup 
  (see 
  fig. 
  4), 
  weighs 
  4*435 
  grains. 
  One 
  gram 
  

   added 
  to 
  the 
  ring 
  causes 
  it 
  to 
  sink, 
  giving 
  5 
  '435 
  as 
  the 
  break- 
  

   ing 
  weight. 
  The 
  unloaded 
  ring 
  therefore 
  weighs 
  19 
  per 
  cent 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  Ill, 
  No. 
  16.— 
  April, 
  1897. 
  

   18 
  

  

  