﻿of 
  various 
  Substances 
  on 
  Solidification. 
  

  

  211 
  

  

  accepted 
  and 
  become 
  current 
  from 
  book 
  to 
  book 
  of 
  authors 
  up 
  to 
  the 
  

   present 
  day, 
  as 
  when 
  Dr. 
  T. 
  Thomson 
  (' 
  System 
  of 
  Chemistry,' 
  vol. 
  i. 
  

   p. 
  375, 
  5th 
  edit.) 
  says 
  of 
  cast 
  iron 
  that 
  "it 
  contracts 
  considerably 
  when 
  

   it 
  comes 
  into 
  fusion," 
  or 
  that 
  of 
  Kerl 
  (' 
  Metallurgy 
  of 
  Iron,' 
  Crookes 
  and 
  

   B-dhrig's 
  translation, 
  vol. 
  ii. 
  p. 
  291), 
  that 
  cast 
  " 
  iron 
  occupies 
  a 
  smaller 
  

   space 
  after 
  cooling 
  than 
  when 
  in 
  the 
  liquid 
  state 
  ; 
  it 
  contracts 
  in 
  such 
  a 
  

   manner 
  that, 
  at 
  the 
  commencement 
  of 
  its 
  solidification, 
  it 
  first 
  expands 
  so 
  

   as 
  to 
  be 
  able 
  to 
  fill 
  up 
  the 
  smallest 
  depressions 
  and 
  cavities 
  of 
  a 
  mould, 
  but 
  

   after 
  solidifying 
  it 
  contracts" 
  — 
  a 
  loosely 
  worded 
  statement, 
  which 
  in 
  

   various 
  forms 
  may 
  be 
  found 
  in 
  a 
  great 
  number 
  of 
  authors 
  upon 
  metal- 
  

   lurgy 
  and 
  technology. 
  So 
  likewise 
  the 
  statement 
  often 
  repeated, 
  that 
  

   the 
  value 
  of 
  antimony 
  in 
  type-metal 
  consists 
  in 
  its 
  causing 
  the 
  latter 
  to 
  

   expand 
  upon 
  consolidation 
  and 
  so 
  perfectly 
  fill 
  the 
  matrix, 
  is 
  presented, 
  

   so 
  far 
  as 
  the 
  author's 
  reading 
  goes, 
  without 
  the 
  slightest 
  experimental 
  

   proof 
  of 
  its 
  truth, 
  and 
  appears 
  to 
  rest 
  simply 
  upon 
  -Reaumur's 
  statement 
  

   with 
  respect 
  to 
  antimony 
  itself, 
  which, 
  as 
  already 
  mentioned, 
  has 
  been 
  

   controverted 
  by 
  Marx. 
  This 
  subject, 
  however, 
  has 
  now 
  assumed 
  greater 
  

   importance, 
  since 
  it 
  has 
  recently 
  been 
  made 
  by 
  Messrs. 
  Nasmyth 
  and 
  

   Carpenter 
  the 
  foundation 
  upon 
  which 
  they 
  rest 
  their 
  theory 
  of 
  lunar 
  

   volcanic 
  action, 
  as 
  presented 
  to 
  us 
  by 
  the 
  surface 
  of 
  our 
  satellite 
  ; 
  and 
  the 
  

   object 
  of 
  the 
  present 
  communication 
  is 
  to 
  show 
  that, 
  as 
  regards 
  the 
  two 
  

   most 
  pertinent 
  of 
  the 
  substances 
  adduced 
  by 
  these 
  authors, 
  viz. 
  cast 
  iron 
  

   and 
  iron 
  furnace-slag, 
  the 
  facts 
  entirely 
  fail 
  in 
  support 
  of 
  their 
  theory. 
  

  

  First, 
  then, 
  as 
  to 
  cast 
  iron. 
  It 
  is 
  not 
  a 
  fact 
  that 
  all 
  cast 
  iron 
  in 
  the 
  

   solid 
  state 
  will 
  float 
  upon 
  all 
  cast 
  iron 
  in 
  liquid 
  fusion, 
  though 
  such 
  might 
  

   be 
  inferred 
  from 
  the 
  broad 
  and 
  loose 
  statements, 
  of 
  authors. 
  Even 
  in 
  the 
  

   limited 
  form 
  in 
  which 
  the 
  statement 
  is 
  made 
  by 
  Nasmyth 
  and 
  Carpenter 
  — 
  

   viz. 
  " 
  that 
  when 
  a 
  mass 
  of 
  solid 
  cast 
  iron 
  is 
  dropped 
  into 
  a 
  pot 
  of 
  molten 
  

   iron 
  of 
  identical 
  quality 
  the 
  solid 
  is 
  found 
  to 
  float 
  persistently 
  upon 
  

   the 
  molten 
  metal, 
  so 
  persistently 
  that 
  when 
  it 
  is 
  intentionally 
  thrust 
  to 
  

   the 
  bottom 
  of 
  the 
  pot 
  it 
  rises 
  again 
  the 
  moment 
  the 
  submerging 
  agency 
  

   is 
  withdrawn" 
  (' 
  The 
  Moon,' 
  p. 
  21) 
  — 
  is 
  not 
  quite 
  exact. 
  

  

  It 
  is 
  a 
  fact 
  that 
  certain 
  pieces 
  of 
  cast 
  iron 
  in 
  the 
  solid 
  and 
  cold 
  state 
  

   will 
  float 
  on 
  certain 
  descriptions 
  of 
  cast 
  iron 
  in 
  liquid 
  fusion 
  ; 
  but 
  whether 
  

   the 
  solid 
  pieces 
  shall 
  float 
  or 
  not 
  float 
  in 
  any 
  given 
  case 
  is 
  dependent 
  at 
  

   least 
  upon 
  the 
  following 
  conditions, 
  and 
  probably 
  upon 
  others 
  not 
  yet 
  

   ascertained 
  : 
  — 
  

  

  1st. 
  Upon 
  the 
  relative 
  specific 
  gravities 
  of 
  the 
  solid 
  and 
  of 
  the 
  fused 
  

   cast 
  iron 
  both 
  referred 
  to 
  the 
  temperature 
  of 
  the 
  atmosphere. 
  Under 
  the 
  

   commercial 
  name 
  of 
  cast 
  iron 
  is 
  comprehended 
  a 
  wide 
  range 
  of 
  com- 
  

   pounds 
  of 
  iron 
  with 
  other 
  substances, 
  which 
  compounds 
  differ 
  greatly 
  in 
  

   their 
  physical 
  as 
  well 
  as 
  their 
  chemical 
  qualities, 
  and 
  have 
  a 
  range 
  of 
  

   specific 
  gravity 
  of 
  from 
  nearly 
  7*7700 
  for 
  the 
  whitest, 
  most 
  rigid, 
  and 
  

   dense, 
  down 
  to 
  little 
  more 
  than 
  6-300 
  for 
  those 
  which 
  are 
  darkest, 
  softest, 
  

   and 
  most 
  porous. 
  The 
  total 
  dilatation 
  at 
  the 
  fusing-point 
  of 
  the 
  denser 
  

  

  