﻿278 
  A. 
  M. 
  Mayer— 
  On 
  the 
  Flotation 
  of 
  

  

  water, 
  it 
  sinks. 
  If 
  the 
  ring 
  is 
  wiped 
  dry, 
  and 
  then 
  placed 
  on 
  

   the 
  water, 
  it 
  sinks; 
  but 
  if 
  wiped 
  dry 
  and 
  exposed 
  to 
  the 
  air 
  for 
  

   from 
  10 
  to 
  15 
  minutes 
  it 
  will 
  float. 
  Also, 
  a 
  ring 
  of 
  one 
  of 
  

   these 
  metals 
  which 
  has 
  been 
  heated 
  to 
  redness 
  and 
  which 
  has 
  

   not 
  been 
  wetted 
  will 
  float 
  after 
  having 
  been 
  exposed 
  to 
  the 
  air 
  

   for 
  about 
  a 
  half 
  hour. 
  

  

  Wires 
  of 
  platinum, 
  gold, 
  and 
  of 
  silver 
  of 
  I 
  ^- 
  mm 
  in 
  diameter, 
  

   and 
  wires 
  of 
  aluminum, 
  copper, 
  brass 
  and 
  german 
  silver 
  of 
  l 
  mm 
  

   in 
  diameter 
  floated 
  when 
  gently 
  placed 
  on 
  the 
  surface 
  of 
  water 
  

   by 
  means 
  of 
  a 
  fork 
  made 
  of 
  fine 
  wire. 
  These 
  wires 
  were 
  5 
  

   cms. 
  long. 
  All 
  of 
  these 
  wires 
  sank 
  after 
  having 
  been 
  passed 
  

   slowly 
  to 
  and 
  fro 
  six 
  times 
  in 
  the 
  lower 
  part 
  of 
  a 
  spirit 
  flame, 
  and 
  

   recovered 
  their 
  property 
  of 
  flotation 
  after 
  they 
  had 
  remained 
  

   from 
  two 
  to 
  five 
  minutes 
  in 
  the 
  air. 
  

  

  Glass 
  rods 
  of 
  J 
  mm 
  in 
  diameter 
  and 
  5 
  cm 
  long 
  behaved 
  in 
  

   similar 
  manner 
  to 
  the 
  wires. 
  If 
  a 
  rod 
  of 
  glass 
  recently 
  drawn 
  

   out 
  in 
  a 
  spirit 
  flame 
  and 
  just 
  cold 
  is 
  placed 
  on 
  water 
  it 
  sinks. 
  

   After 
  a 
  freshly 
  made 
  glass 
  rod 
  has 
  remained 
  exposed 
  to 
  the 
  air 
  

   for 
  about 
  15 
  minutes 
  it 
  will 
  float. 
  If 
  a 
  recently 
  made 
  glass 
  rod 
  

   which 
  has 
  just 
  sunk 
  in 
  water 
  be 
  withdrawn, 
  wiped 
  dry, 
  and 
  

   exposed 
  to 
  the 
  air 
  for 
  from 
  10 
  to 
  15 
  minutes, 
  it 
  will 
  float. 
  

   These 
  floating 
  glass 
  rods, 
  however, 
  do 
  not, 
  as 
  in 
  the 
  case 
  of 
  the 
  

   wires, 
  give 
  straight 
  lines 
  of 
  demarkation, 
  between 
  the 
  surfaces 
  

   of 
  the 
  glass 
  and 
  the 
  water. 
  At 
  some 
  places 
  the 
  water 
  wets 
  and 
  

   covers 
  the 
  glass, 
  at 
  others 
  it 
  does 
  not 
  wet 
  the 
  glass, 
  and 
  the 
  

   lines 
  of 
  demarkation 
  of 
  the 
  glass 
  and 
  water 
  are 
  jagged. 
  This 
  

   rod, 
  placed 
  vertically 
  in 
  the 
  water, 
  shows 
  an 
  ascending 
  meniscus 
  

   at 
  the 
  parts 
  where 
  it 
  was 
  wetted 
  when 
  floating 
  and 
  a 
  depressed 
  

   meniscus 
  at 
  the 
  parts 
  where 
  it 
  repelled 
  the 
  water. 
  If 
  a 
  glass 
  

   rod 
  is 
  sunk 
  and 
  then 
  brought 
  to 
  the 
  surface 
  of 
  the 
  water 
  and 
  

   floated 
  and 
  this 
  operation 
  repeated 
  several 
  times, 
  the 
  rod 
  

   becomes 
  more 
  and 
  more 
  repellent 
  of 
  water, 
  and 
  when 
  depressed 
  

   in 
  the 
  water-surface 
  by 
  a 
  fine 
  wire 
  the 
  lines 
  of 
  separation 
  of 
  the 
  

   glass 
  and 
  water 
  becomes 
  almost 
  straight 
  and 
  the 
  rod 
  acts 
  like 
  

   one 
  of 
  clean 
  metal. 
  The 
  rod 
  can 
  now 
  be 
  depressed, 
  by 
  a 
  fork 
  

   of 
  fine 
  wire, 
  to 
  nearly 
  3 
  mm 
  below 
  the 
  general 
  level 
  of 
  the 
  

   water. 
  These 
  experiments 
  show 
  how 
  soon 
  the 
  surface 
  of 
  glass 
  

   is 
  contaminated 
  by 
  exposure 
  to 
  water 
  and 
  air, 
  this 
  contamination 
  

   reversing 
  indeed 
  the 
  attractive 
  property 
  of 
  clean 
  glass 
  for 
  water. 
  

  

  The 
  experiments 
  on 
  the 
  metals 
  show 
  that 
  when 
  their 
  sur- 
  

   faces 
  are 
  freed 
  of 
  air 
  they 
  sink, 
  and 
  that 
  after 
  the 
  film 
  of 
  air 
  

   has 
  recondensed 
  on 
  their 
  surfaces 
  they 
  float. 
  In 
  other 
  words, 
  

   in 
  the 
  first 
  case 
  the 
  metals 
  are 
  wetted 
  and 
  in 
  the 
  second 
  they 
  

   are 
  not. 
  Considering 
  fig. 
  5, 
  it 
  is 
  evident 
  that 
  the 
  dry 
  surface 
  

   of 
  the 
  wire 
  between 
  the 
  two 
  opposite 
  depressed 
  surfaces 
  of 
  

   water 
  could 
  not 
  exist 
  if 
  the 
  water 
  wetted 
  the 
  wire 
  as 
  it 
  would 
  

   wet 
  a 
  ring 
  made 
  of 
  clean 
  glass. 
  At 
  the 
  same 
  time, 
  though 
  the 
  

   water 
  does 
  not 
  wet 
  the 
  wire 
  as 
  water 
  wets 
  glass, 
  yet 
  the 
  water 
  

  

  

  