﻿218 
  

  

  Mr. 
  R. 
  Mallet 
  on 
  the 
  alleged 
  Expansion 
  

  

  Experiment 
  3. 
  Two 
  cylindric 
  pieces 
  of 
  the 
  same 
  grey 
  cast 
  iron 
  and 
  of 
  

   the 
  same 
  diameter 
  (=2-375") 
  were 
  gently 
  placed 
  with 
  their 
  axes 
  hori- 
  

   zontal 
  upon 
  the 
  surface 
  of 
  the 
  molten 
  iron, 
  the 
  one 
  being 
  at 
  60° 
  Fahr., 
  

   the 
  other 
  at 
  about 
  300° 
  Fahr. 
  ; 
  they 
  both 
  floated 
  with 
  a 
  segment 
  of 
  the 
  

   cylinder 
  whose 
  versed 
  sine 
  was 
  0*31 
  in. 
  emergent. 
  The 
  volume 
  of 
  either 
  

   cylinder 
  was 
  22*15 
  cubic 
  inches, 
  and 
  the 
  emergent 
  was 
  to 
  the 
  immersed 
  

   volume 
  as 
  1 
  : 
  8-4. 
  The 
  effective 
  repellent 
  surface 
  in 
  each 
  case 
  (or 
  cylin- 
  

   dric 
  surface 
  below 
  the 
  horizontal 
  diameter) 
  was 
  18*65 
  sq. 
  in. 
  ; 
  but 
  if 
  we 
  

   suppose, 
  as 
  in 
  fact 
  we 
  have 
  done, 
  that 
  the 
  repellent 
  force, 
  whatever 
  be 
  its 
  

   nature, 
  acts 
  everywhere 
  perpendicularly 
  to 
  surfaces 
  of 
  contact 
  of 
  the 
  

   solid 
  and 
  liquid, 
  then 
  the 
  effective 
  repellent 
  surface 
  here 
  is 
  only 
  the 
  differ- 
  

   ence 
  between 
  the 
  immersed 
  surfaces 
  of 
  the 
  cylinder 
  below 
  and 
  above 
  the 
  

   horizontal 
  diameter, 
  or 
  9*3 
  sq. 
  in. 
  From 
  this 
  we 
  may 
  perhaps 
  conclude 
  

   that 
  the 
  repellent 
  force 
  is 
  mainly 
  dependent 
  upon 
  the 
  extreme 
  upper 
  parts 
  

   of 
  the 
  range 
  of 
  temperature 
  between 
  the 
  liquid 
  and 
  the 
  cold 
  body, 
  inas- 
  

   much 
  as 
  an 
  augmentation 
  in 
  temperature 
  of 
  the 
  latter 
  of 
  300°, 
  or 
  about 
  

   \ 
  of 
  the 
  entire 
  range 
  between 
  solidity 
  and 
  fusion 
  of 
  the 
  cast 
  iron, 
  pro- 
  

   duces 
  no 
  very 
  sensible 
  alteration 
  in 
  the 
  tendency 
  to 
  float 
  of 
  the 
  pieces. 
  

  

  Experiment 
  4. 
  Three 
  circular 
  disks 
  of 
  the 
  same 
  grey 
  cast 
  iron, 
  each 
  of 
  

   6" 
  diam. 
  by 
  0-375" 
  in 
  thickness, 
  were 
  provided 
  each 
  with 
  a 
  slender 
  iron 
  

   wire 
  eye, 
  cast 
  into 
  the 
  centre 
  of 
  one 
  surface, 
  so 
  that 
  by 
  a 
  hooked 
  wire 
  

   they 
  could 
  be 
  gently 
  laid 
  upon 
  the 
  surface 
  of 
  the 
  liquid 
  iron 
  of 
  their 
  own 
  

   quality. 
  The 
  lower 
  surface 
  and 
  edge 
  of 
  one 
  disk 
  were 
  left 
  as 
  it 
  came 
  clean 
  

   from 
  the 
  sand, 
  those 
  of 
  another 
  were 
  rusted 
  by 
  wetting 
  with 
  solution 
  of 
  

   sal-ammoniac, 
  and 
  those 
  of 
  the 
  third 
  were 
  ground 
  smooth 
  and 
  polished 
  by 
  

   the 
  grindstone. 
  When 
  the 
  three 
  disks 
  were 
  in 
  succession 
  laid 
  upon 
  the 
  

   surface 
  of 
  the 
  molten 
  iron, 
  they 
  all 
  floated 
  alike 
  as 
  nearly 
  as 
  could 
  be 
  

   judged, 
  each 
  sinking 
  to 
  one 
  half 
  the 
  thickness 
  of 
  the 
  disk, 
  so 
  that 
  the 
  

   immersed 
  was 
  to 
  the 
  emergent 
  volume 
  in 
  the 
  ratio 
  of 
  equality. 
  We 
  

   may 
  conclude 
  from 
  this 
  that 
  the 
  condition 
  of 
  the 
  metallic 
  surface 
  of 
  the 
  

   solid 
  cast 
  iron 
  has 
  no 
  material 
  influence 
  upon 
  its 
  flotation. 
  

  

  Experiment 
  5. 
  Two 
  circular 
  disks, 
  provided 
  with 
  eyes 
  as 
  in 
  experiment 
  4, 
  

   were 
  prepared, 
  the 
  one 
  being 
  6 
  in. 
  in 
  diam. 
  by 
  0*375 
  in 
  thickness, 
  and 
  the 
  

   other 
  3 
  in. 
  in 
  diam. 
  by 
  1*5 
  in. 
  in 
  thickness. 
  The 
  respective 
  volumes 
  of 
  

   these 
  two 
  disks 
  are 
  the 
  same, 
  but 
  the 
  circular 
  flat 
  surfaces 
  respectively 
  

   are 
  as 
  4 
  to 
  1. 
  The 
  surfaces 
  of 
  the 
  two 
  disks 
  being 
  as 
  they 
  came 
  from 
  the 
  

   sand-mould, 
  they 
  were 
  placed 
  gently 
  upon 
  the 
  surface 
  of 
  the 
  molten 
  iron 
  : 
  

   both 
  floated 
  with 
  the 
  same 
  portion 
  in 
  altitude 
  emergent. 
  The 
  larger 
  

   and 
  thin 
  disk 
  had, 
  as 
  stated 
  in 
  experiment 
  4, 
  its 
  emergent 
  and 
  immersed 
  

   volumes 
  in 
  the 
  ratio 
  of 
  equality 
  [or 
  the 
  emergent 
  was 
  to 
  the 
  whole 
  volume 
  

   as 
  1 
  : 
  2]. 
  In 
  the 
  smaller 
  and 
  thicker 
  disk, 
  the 
  emergent 
  volume 
  was 
  to 
  

   the 
  immersed 
  volume 
  as 
  1 
  to 
  7. 
  [Or 
  the 
  emergent 
  volume 
  was 
  to 
  total 
  

   volume 
  as 
  to 
  1 
  : 
  8 
  ; 
  but 
  2 
  : 
  8 
  : 
  : 
  1 
  : 
  4, 
  or 
  the 
  emergent 
  volumes 
  are 
  to 
  the 
  

   total 
  volumes 
  in 
  each 
  case 
  respectively 
  proportionate 
  to 
  the 
  lower 
  or 
  re- 
  

   pellent 
  surfaces 
  of 
  the 
  disk.] 
  

  

  