﻿of 
  various 
  Substances 
  on 
  Solidification. 
  

  

  231 
  

  

  I 
  proceed 
  to 
  some 
  remarks 
  upon 
  the 
  experiments 
  referred 
  to 
  at 
  the 
  

   commencement 
  of 
  this 
  paper, 
  and 
  quoted 
  by 
  Messrs. 
  Nasmyth 
  and 
  Car- 
  

   penter, 
  as 
  to 
  the 
  floating 
  of 
  pieces 
  of 
  solidified 
  iron 
  furnace-slag 
  upon 
  the 
  

   same 
  slag 
  when 
  in 
  the 
  liquid 
  state. 
  It 
  is 
  a 
  fact 
  that 
  blast-furnace 
  slags 
  

   cooled 
  below 
  the 
  point 
  at 
  which 
  they 
  become 
  rigid 
  do 
  very 
  generally 
  

   float 
  upon 
  the 
  same 
  slag 
  in 
  its 
  molten 
  state. 
  It 
  is 
  equally 
  true 
  that 
  the 
  

   basic 
  silicates 
  which 
  constitute 
  the 
  chief 
  part 
  of 
  terrestrial 
  volcanic 
  lavas 
  

   float 
  upon 
  the 
  surface 
  of 
  these 
  when 
  molten. 
  But 
  these 
  admissions 
  do 
  

   not 
  suffice 
  in 
  any 
  degree 
  to 
  support 
  the 
  conclusion 
  deduced 
  by 
  Messrs. 
  

   Nasmyth 
  and 
  Carpenter, 
  that 
  basic 
  silicates, 
  whether 
  as 
  furnace-slags 
  or 
  

   lavas, 
  are 
  denser 
  in 
  the 
  molten 
  than 
  in 
  the 
  solidified 
  state, 
  nor 
  that 
  these 
  

   bodies 
  in 
  the 
  act 
  of 
  solidification 
  expand 
  in 
  volume 
  or 
  decrease 
  in 
  density 
  

   in 
  any 
  manner, 
  irrespective 
  of 
  the 
  formation 
  or 
  enlargement 
  of 
  cavities 
  

   or 
  gas-bubbles 
  within 
  them. 
  The 
  experiments 
  of 
  the 
  author 
  upon 
  the 
  

   total 
  contraction 
  of 
  iron 
  furnace-slags 
  for 
  the 
  entire 
  range 
  of 
  tempera- 
  

   ture 
  between 
  that 
  of 
  the 
  blast-furnace 
  and 
  the 
  atmosphere, 
  made 
  at 
  the 
  

   Barrow 
  Iron-AYorks, 
  and 
  fully 
  described 
  in 
  the 
  author's 
  paper 
  on 
  " 
  The 
  

   Nature 
  and 
  Origin 
  of 
  Volcanic 
  Heat 
  and 
  Energy," 
  printed 
  in 
  Phil. 
  

   Trans, 
  for 
  1873, 
  leave 
  no 
  doubt 
  as 
  to 
  the 
  following 
  facts 
  : 
  — 
  

  

  1st. 
  That 
  the 
  density 
  of 
  such 
  slags 
  at 
  53° 
  Fahr. 
  is 
  to 
  their 
  density 
  

   when 
  molten 
  and 
  at 
  the 
  temperature 
  of 
  the 
  blast-furnace 
  as 
  1000 
  : 
  933, 
  

   or, 
  taken 
  at 
  the 
  melting-point 
  of 
  slag, 
  as 
  1000 
  to 
  983 
  — 
  molten 
  slag 
  being 
  

   thus 
  very 
  much 
  less 
  dense 
  than 
  the 
  same 
  when 
  solidified. 
  

  

  2ndly. 
  That 
  no 
  expansion 
  in 
  volume 
  whatever 
  occurs 
  in 
  such 
  slags 
  at 
  

   or 
  near 
  the 
  instant 
  of 
  solidification. 
  

  

  The 
  experiments 
  of 
  the 
  author 
  above 
  referred 
  to 
  were 
  made 
  by 
  filling 
  

   cast-iron 
  slightly 
  conical 
  moulds 
  with 
  the 
  slag 
  run 
  direct 
  from 
  the 
  blast- 
  

   furnace, 
  and 
  permitted 
  to 
  consolidate 
  and 
  cool 
  therein, 
  by 
  which 
  per- 
  

   fectly 
  solid 
  slightly 
  conical 
  blocks 
  were 
  obtained. 
  Erom 
  the 
  method 
  em- 
  

   ployed, 
  and 
  the 
  very 
  large 
  scale 
  upon 
  which 
  these 
  experiments 
  were 
  con- 
  

   ducted, 
  it 
  is 
  impossible 
  that 
  any 
  expansion 
  in 
  volume 
  at 
  or 
  near 
  the 
  point 
  

   of 
  consolidation, 
  if 
  even 
  of 
  a 
  very 
  minute 
  amount, 
  could 
  have 
  occurred 
  and 
  

   yet 
  have 
  escaped 
  notice*. 
  It 
  is 
  only 
  necessary 
  for 
  the 
  author 
  here 
  to 
  

   point 
  out 
  that 
  the 
  floating 
  of 
  crusts 
  of 
  slag 
  or 
  lava 
  is 
  not 
  due 
  to 
  the 
  cause 
  

   assigned 
  by 
  Messrs. 
  Nasmyth 
  and 
  Carpenter; 
  nor 
  is 
  it 
  his 
  intention 
  to 
  

   enter 
  at 
  any 
  length 
  into 
  what 
  are 
  the 
  causes 
  of 
  such 
  floating 
  when 
  it 
  

   occurs. 
  

  

  The 
  following 
  remarks, 
  however, 
  may 
  be 
  made 
  : 
  — 
  It 
  is 
  impossible 
  to 
  

   obtain 
  a 
  moderate-sized 
  fragment 
  of 
  solidified 
  slag 
  or 
  lava 
  free 
  from 
  air- 
  

   bubbles, 
  and 
  from 
  involved 
  or 
  superficial 
  cavities, 
  which 
  tend 
  to 
  float 
  the 
  

   mass 
  when 
  thrown 
  upon 
  its 
  own 
  material 
  in 
  the 
  melted 
  state. 
  Those 
  

   who 
  have 
  attentively 
  watched 
  large 
  volumes 
  of 
  slag 
  issuing 
  from 
  the 
  

   blast-furnace 
  are 
  aware 
  that 
  it 
  comes 
  forth 
  carrying 
  with 
  it 
  a 
  large 
  

  

  * 
  [For 
  the 
  proofs 
  of 
  which 
  in 
  detail 
  the 
  author 
  begs 
  to 
  refer 
  to 
  his 
  paper 
  at 
  length, 
  

   Phil. 
  Trans. 
  1873.] 
  

  

  A 
  OL. 
  XXIII. 
  T 
  

  

  