﻿224 
  

  

  Mr. 
  R. 
  Mallet 
  on 
  the 
  alleged 
  Expansion 
  

  

  the 
  sphere 
  which 
  last 
  solidifies. 
  Now 
  the 
  latter 
  is 
  exactly 
  what 
  has 
  hap- 
  

   pened 
  : 
  a 
  portion 
  of 
  the 
  exterior 
  and 
  first 
  solidified 
  crust, 
  reaching 
  about 
  

   an 
  inch 
  and 
  half 
  inwards 
  from 
  the 
  interior 
  of 
  the 
  shell, 
  was 
  found 
  to 
  have 
  

   a 
  specific 
  gravity 
  of 
  7*150 
  at 
  57° 
  Fahr., 
  while 
  a 
  portion 
  taken 
  close 
  to 
  the 
  

   centre 
  of 
  the 
  sphere 
  had 
  a 
  specific 
  gravity 
  of 
  only 
  7*037 
  ; 
  and 
  this 
  specific 
  

   gravity 
  would 
  have 
  been 
  still 
  lower 
  (or, 
  in 
  other 
  words, 
  the 
  central 
  part 
  

   of 
  the 
  sphere 
  would 
  have 
  been 
  still 
  more 
  " 
  spongy") 
  had 
  it 
  not 
  been 
  fed 
  

   by 
  drawing 
  downwards 
  a 
  portion 
  of 
  the 
  liquid 
  iron 
  which 
  partially 
  filled 
  

   the 
  fuse-hole, 
  the 
  portion 
  so 
  drawn 
  down 
  being 
  estimated 
  by 
  the 
  volume 
  

   of 
  the 
  cavities 
  left 
  at 
  0*400 
  of 
  a 
  cubic 
  inch 
  ; 
  so 
  that 
  but 
  for 
  this 
  the 
  

   specific 
  gravity 
  of 
  the 
  central 
  spongy 
  sphere 
  taken 
  at 
  3" 
  diameter 
  would 
  

   have 
  been 
  reduced 
  to 
  6*776. 
  

  

  If 
  we 
  reduce 
  this 
  central 
  spongy 
  mass 
  of 
  3" 
  diameter 
  and 
  of 
  the 
  last- 
  

   mentioned 
  specific 
  gravity 
  to 
  a 
  density 
  as 
  great 
  as 
  that 
  found 
  for 
  the 
  ex- 
  

   terior 
  crust, 
  namely 
  7*150, 
  the 
  sphere 
  of 
  3" 
  diameter 
  would 
  be 
  reduced 
  

   to 
  one 
  of 
  2"-138 
  ; 
  and 
  it 
  is 
  easy 
  to 
  see 
  that 
  in 
  that 
  case 
  the 
  external 
  

   diameter 
  of 
  the 
  whole 
  sphere 
  of 
  metal 
  and 
  of 
  the 
  containing 
  shell 
  would 
  

   have 
  been 
  less 
  in 
  a 
  corresponding 
  proportion, 
  and 
  that 
  thus 
  the 
  final 
  

   dimensions 
  of 
  the 
  shell 
  would 
  have 
  returned 
  to 
  what 
  they 
  were 
  at 
  the 
  

   commencement, 
  less 
  the 
  permanent 
  enlargement, 
  as 
  measured 
  by 
  that 
  of 
  

   the 
  empty 
  shell. 
  If 
  there 
  existed, 
  on 
  the 
  other 
  hand, 
  any 
  sensible 
  ex- 
  

   pansion 
  in 
  volume 
  of 
  the 
  metal 
  in 
  consolidating, 
  not 
  only 
  would 
  a 
  central 
  

   " 
  spongy" 
  portion 
  be 
  impossible 
  and 
  the 
  central 
  be 
  the 
  densest 
  part 
  of 
  

   the 
  whole 
  sphere, 
  but 
  an 
  enlargement 
  of 
  the 
  entire 
  mass 
  and 
  of 
  the 
  

   covering 
  shell 
  stretched 
  by 
  it 
  must 
  have 
  occurred, 
  so 
  large 
  as 
  to 
  be 
  wholly 
  

   unmistakable. 
  

  

  [The 
  importance 
  of 
  the 
  facts 
  elicited 
  from 
  this 
  experiment 
  cannot 
  be 
  

   too 
  forcibly 
  laid 
  before 
  the 
  reader. 
  Had 
  the 
  sphere 
  of 
  molten 
  iron, 
  

   losing 
  heat 
  from 
  its 
  exterior, 
  expanded 
  in 
  volume 
  as 
  couche 
  after 
  couche 
  

   it 
  solidified 
  from 
  the 
  exterior, 
  the 
  solidification 
  constantly 
  advancing 
  in- 
  

   wards, 
  then 
  the 
  central 
  portions 
  of 
  the 
  sphere 
  when 
  ultimately 
  solidified 
  

   must 
  be 
  found 
  to 
  be 
  the 
  densest 
  portions 
  of 
  the 
  whole 
  mass 
  ; 
  the 
  opposite 
  

   of 
  which 
  was 
  found 
  to 
  be 
  the 
  fact, 
  the 
  central 
  portions 
  of 
  the 
  experi- 
  

   mental 
  sphere 
  being, 
  as 
  stated, 
  the 
  least 
  dense 
  portions 
  of 
  the 
  whole 
  mass. 
  

   This 
  alone 
  seems 
  conclusively 
  to 
  negative 
  the 
  supposition 
  of 
  any 
  expan- 
  

   sion 
  in 
  volume 
  in 
  cast 
  iron 
  in 
  consolidating. 
  On 
  examining 
  the 
  curve 
  

   fig. 
  4 
  in 
  connexion 
  with 
  the 
  Table, 
  it 
  will 
  be 
  remarked 
  that 
  between 
  

   the 
  hours 
  1.50 
  and 
  2.45 
  there 
  is 
  an 
  irregularity 
  in 
  the 
  progress 
  of 
  con- 
  

   traction 
  which 
  shows 
  itself 
  by 
  a 
  hump 
  upon 
  the 
  curve 
  which 
  might 
  be 
  

   assumed 
  to 
  indicate 
  a 
  less 
  rate 
  of 
  contraction 
  within 
  this 
  epoch 
  ; 
  and 
  it 
  

   might 
  be 
  further 
  assumed 
  that 
  this 
  apparent 
  reduction 
  arose 
  from 
  the 
  

   conjoint 
  action 
  of 
  general 
  contraction 
  and 
  partial 
  expansion 
  operating 
  

   together 
  within 
  some 
  part 
  of 
  the 
  mass 
  ; 
  but 
  this 
  view, 
  which 
  the 
  writer 
  

   believes 
  would 
  be 
  entirely 
  incorrect, 
  appears 
  sufficiently 
  negatived 
  by 
  the 
  

   following 
  considerations 
  : 
  — 
  

  

  