﻿230 
  

  

  Mr. 
  R. 
  Mallet 
  on 
  the 
  alleged 
  Expansion 
  

  

  of 
  which 
  was 
  estimated 
  at 
  from 
  750° 
  to 
  880° 
  Fahr., 
  the 
  half 
  of 
  a 
  large 
  

   pig 
  of 
  newly 
  smelted 
  lead, 
  being 
  a 
  semicylindrical 
  bar 
  of 
  about 
  5" 
  x 
  2|" 
  

   and 
  about 
  18" 
  long, 
  was 
  gently 
  laid 
  down 
  horizontally 
  ; 
  it 
  immediately 
  

   sank 
  to 
  the 
  bottom 
  and 
  there 
  remained. 
  When 
  about 
  half 
  its 
  volume 
  

   was 
  melted 
  away, 
  the 
  unfused 
  portion 
  was 
  drawn 
  up 
  to 
  the 
  surface 
  and 
  

   let 
  go, 
  when 
  it 
  at 
  once 
  sunk 
  to 
  the 
  bottom 
  again. 
  

  

  2nd. 
  A 
  ball 
  of 
  such 
  lead 
  was 
  cast, 
  weighing 
  17| 
  lbs., 
  diameter 
  about 
  

   4^-" 
  ; 
  this 
  was 
  put 
  into 
  an 
  empty 
  hand-ladle, 
  which 
  was 
  gently 
  placed 
  upon 
  

   the 
  surface 
  of 
  the 
  pot 
  of 
  melted 
  lead 
  ; 
  the 
  ladle 
  was 
  depressed 
  sufficiently 
  

   to 
  fill 
  with 
  lead, 
  and 
  being 
  left 
  free 
  was 
  carried 
  to 
  the 
  bottom 
  of 
  the 
  pot 
  

   with 
  sufficient 
  impetus 
  to 
  produce 
  a 
  sensible 
  blow 
  of 
  the 
  exterior 
  of 
  the 
  

   ladle 
  upon 
  the 
  bottom 
  of 
  the 
  pot. 
  

  

  3rd. 
  A 
  flat 
  circular 
  disk 
  of 
  about 
  1*25 
  inch 
  in 
  thickness, 
  being 
  laid 
  

   gently 
  upon 
  the 
  surface, 
  after 
  a 
  moment's 
  hesitation 
  slowly 
  went 
  to 
  the 
  

   bottom. 
  Another 
  disk 
  of 
  6" 
  diameter, 
  by 
  rather 
  less 
  than 
  an 
  inch 
  in 
  

   thickness, 
  remained 
  a 
  few 
  seconds 
  longer 
  on 
  the 
  surface 
  and 
  then 
  sunk 
  

   to 
  the 
  bottom 
  ; 
  both 
  disks, 
  while 
  they 
  floated, 
  had 
  their 
  top 
  surfaces 
  but 
  

   very 
  slightly 
  elevated 
  above 
  that 
  of 
  the 
  liquid 
  lead. 
  One 
  of 
  the 
  disks 
  

   being 
  gently 
  lowered 
  into 
  the 
  liquid 
  lead 
  vertically 
  and 
  edgeways, 
  at 
  once 
  

   went 
  to 
  the 
  bottom. 
  

  

  4th. 
  Two 
  disks, 
  each 
  6" 
  diameter, 
  the 
  one 
  0*57 
  inch 
  and 
  the 
  other 
  

   0*4 
  inch 
  in 
  thickness, 
  being 
  gently 
  laid 
  flat 
  upon 
  the 
  surface 
  of 
  the 
  

   molten 
  lead, 
  floated, 
  and 
  with 
  an 
  emergent 
  portion 
  sensibly 
  greater 
  than 
  

   that 
  of 
  the 
  disks 
  in 
  experiments 
  2 
  and 
  3, 
  and 
  remained 
  floating 
  until 
  about 
  

   1-25 
  of 
  the 
  radius 
  had 
  been 
  melted 
  away 
  all 
  round, 
  when 
  they 
  slowly 
  

   sunk 
  in 
  the 
  liquid, 
  as 
  was 
  proved 
  by 
  the 
  slow 
  disappearance 
  of 
  the 
  slender 
  

   iron 
  wire 
  cast 
  into 
  the 
  middle 
  of 
  the 
  disk 
  for 
  the 
  purpose 
  of 
  lowering. 
  

   The 
  thinner 
  of 
  these 
  two 
  disks 
  floated 
  rather 
  longer 
  than 
  the 
  thicker. 
  

  

  5th. 
  A 
  plate 
  of 
  sheet 
  or 
  laminated 
  lead, 
  clean 
  from 
  the 
  rolling-mill, 
  of 
  

   about 
  0"-5 
  in 
  thickness 
  and 
  about 
  10" 
  square, 
  being 
  gently 
  placed 
  flat 
  

   on 
  the 
  surface 
  of 
  the 
  liquid 
  lead, 
  floated, 
  its 
  top 
  surface 
  being 
  nearly 
  

   level 
  with 
  that 
  of 
  the 
  liquid. 
  After 
  about 
  ten 
  seconds 
  a 
  piece 
  was 
  melted 
  

   off 
  from 
  one 
  of 
  the 
  edges, 
  when 
  the 
  plate 
  canted 
  in 
  the 
  opposite 
  direction 
  

   and 
  sunk. 
  

  

  6th. 
  Plates 
  of 
  about 
  0"'18 
  thick 
  floated 
  much 
  in 
  the 
  same 
  manner 
  as 
  

   the 
  preceding. 
  The 
  temperature 
  of 
  the 
  solid 
  lead 
  employed 
  was 
  in 
  all 
  

   cases 
  about 
  70° 
  Fahr. 
  

  

  It 
  follows 
  from 
  these 
  experiments 
  that, 
  as 
  in 
  the 
  case 
  of 
  cast 
  iron, 
  the 
  

   solid 
  does 
  not 
  float 
  upon 
  the 
  liquid 
  lead 
  through 
  buoyancy, 
  that, 
  on 
  the 
  

   contrary, 
  the 
  negative 
  buoyancy 
  is 
  very 
  marked, 
  and 
  that 
  the 
  repellent 
  

   force, 
  whatever 
  be 
  its 
  nature, 
  by 
  which 
  flotation 
  is 
  produced 
  is 
  dependent 
  

   upon 
  the 
  effective 
  surface 
  as 
  compared 
  with 
  the 
  volume 
  of 
  the 
  solid. 
  

  

  They 
  present 
  also 
  a 
  corroboration 
  of 
  the 
  view 
  that 
  the 
  repellent 
  force 
  

   upon 
  the 
  unit 
  of 
  effective 
  surface 
  is 
  greater 
  as 
  the 
  difference 
  of 
  tempera- 
  

   ture 
  between 
  the 
  solid 
  and 
  liquid 
  metal 
  is 
  so. 
  

  

  