﻿258 
  

  

  A. 
  M. 
  Mayer 
  — 
  On 
  the 
  Flotation 
  of 
  

  

  being 
  the 
  capillary 
  constant, 
  or 
  surface-tension 
  in 
  grams 
  per 
  

   centimeter. 
  

  

  W 
  is 
  taken 
  as 
  the 
  weight 
  of 
  the 
  disk 
  and 
  superadded 
  weight 
  

   required 
  to 
  make 
  the 
  disk 
  break 
  through 
  the 
  water-surface. 
  

   P—a 
  h 
  d, 
  where 
  a 
  is 
  the 
  area 
  of 
  disk; 
  A, 
  the 
  depth 
  to 
  which 
  

   the 
  bottom 
  of 
  the 
  disk 
  has 
  sunk 
  below 
  the 
  general 
  level 
  of 
  the 
  

   water 
  at 
  the 
  moment 
  it 
  breaks 
  through 
  the 
  water-suface, 
  and 
  d 
  y 
  

   the 
  density 
  of 
  the 
  water. 
  

  

  Fig. 
  i. 
  

  

  The 
  manner 
  of 
  measuring 
  W 
  is 
  as 
  follows 
  : 
  A 
  disk, 
  fig. 
  l 
  r 
  

   has 
  a 
  hollow 
  cylinder 
  soldered 
  or 
  cemented 
  to 
  it. 
  This 
  cylin- 
  

   der 
  is 
  concentric 
  with 
  the 
  circumference 
  of 
  the 
  disk. 
  The 
  disk 
  

   is 
  floated 
  on 
  freshly 
  distilled, 
  clean 
  water 
  contained 
  in 
  a 
  glass 
  

   vessel, 
  and 
  the 
  under 
  surface 
  of 
  the 
  disk 
  is 
  examined 
  to 
  be 
  sure 
  

   that 
  no 
  bubbles 
  of 
  air 
  are 
  adhering 
  to 
  it. 
  Fine 
  wind-blown 
  

   sand, 
  contained 
  in 
  a 
  bottle 
  provided 
  with 
  a 
  bent 
  tube 
  of 
  glass 
  

   having 
  a 
  small 
  aperture, 
  is 
  poured 
  into 
  the 
  cylinder 
  till 
  the 
  

   weight 
  causes 
  the 
  disk 
  to 
  sink. 
  The 
  water 
  has 
  such 
  a 
  depth 
  

   that 
  when 
  the 
  disk 
  has 
  sunk 
  the 
  surface 
  of 
  the 
  water 
  is 
  several 
  

   millimeters 
  below 
  the 
  top 
  of 
  the 
  cylinder. 
  The 
  disk 
  is 
  now 
  

   wiped 
  dry 
  and 
  weighed. 
  The 
  water 
  just 
  used 
  is 
  rejected, 
  

   replaced 
  by 
  clean 
  water 
  and 
  the 
  experiment 
  repeated. 
  The 
  

   water 
  is 
  contained 
  in 
  a 
  shallow 
  cylindrical 
  glass 
  vessel, 
  16*5 
  CU1 
  

   in 
  diameter. 
  The 
  edge 
  of 
  this 
  has 
  been 
  ground 
  flat 
  so 
  that 
  the 
  

   vessel 
  may 
  be 
  closed 
  by 
  a 
  glass 
  plate 
  and 
  the 
  water 
  protected 
  

   from 
  dust 
  till 
  the 
  moment 
  when 
  the 
  disk 
  is 
  floated 
  on 
  it. 
  The 
  

   time 
  which 
  elapses 
  from 
  the 
  moment 
  the 
  disk 
  is 
  floated 
  till 
  the 
  

   load 
  of 
  sand 
  causes 
  it 
  to 
  sink 
  averages 
  25 
  seconds. 
  

  

  The 
  disks 
  experimented 
  on 
  were 
  made 
  of 
  aluminum. 
  They 
  

   were 
  l 
  mm 
  thick 
  and 
  of 
  various 
  diameters. 
  They 
  were 
  flat, 
  and 
  

   the 
  cylindrical 
  surface 
  of 
  the 
  disk 
  was 
  quite 
  smooth 
  and 
  pol- 
  

   ished. 
  To 
  accomplish 
  this 
  one 
  must 
  have 
  a 
  keen 
  turning 
  tool, 
  

   and 
  in 
  turning 
  the 
  aluminum, 
  it 
  and 
  the 
  tool 
  must 
  be 
  constantly 
  

   supplied 
  with 
  petroleum. 
  When 
  finished 
  the 
  disks 
  were 
  cleaned 
  

  

  