﻿214 
  

  

  Mr. 
  R. 
  Mallet 
  on 
  the 
  alleged 
  Expansion 
  

  

  wrought 
  iron 
  presents 
  to 
  the 
  eye 
  a 
  clear 
  yellow 
  visible 
  in 
  daylight 
  may, 
  

   in 
  accordance 
  with 
  the 
  views 
  of 
  most 
  physicists, 
  be 
  taken 
  as 
  between 
  the 
  

   fusing-points 
  of 
  silver 
  and 
  of 
  gold, 
  or 
  at 
  2000° 
  Fahr. 
  The 
  mean 
  coeffi- 
  

   cient 
  of 
  linear 
  dilatation 
  for 
  1° 
  Fahr. 
  of 
  wrought 
  iron 
  has 
  been 
  determined 
  

   between 
  the 
  limits 
  of 
  zero 
  and 
  212° 
  by 
  Laplace, 
  Smeaton, 
  Troughton, 
  and 
  

   Dulong, 
  the 
  average 
  of 
  the 
  four 
  being 
  0*00000699 
  for 
  1° 
  Fahr. 
  ; 
  and 
  

   this 
  is 
  certainly 
  below 
  the 
  truth 
  for 
  the 
  whole 
  range 
  of 
  temperature 
  up 
  

   to 
  fusion, 
  as 
  the 
  rate 
  of 
  expansion 
  of 
  all 
  fusible 
  bodies 
  appears 
  to 
  increase 
  

   with 
  the 
  temperature. 
  Binmann 
  has 
  determined 
  the 
  linear 
  dilatation 
  of 
  a 
  

   bar 
  of 
  wrought 
  iron, 
  when 
  raised 
  from 
  60° 
  Fahr. 
  to 
  a 
  white 
  or 
  welding 
  

   heat, 
  to 
  be 
  -g-J^- 
  of 
  its 
  length, 
  or 
  -0125 
  ; 
  and 
  taking 
  the 
  total 
  range 
  of 
  tem- 
  

   perature 
  here 
  at 
  2400°, 
  we 
  have 
  a 
  mean 
  coefficient 
  of 
  linear 
  dilatation 
  

   = 
  0-0000052 
  for 
  1° 
  Fahr. 
  This 
  is 
  a 
  still 
  smaller 
  coefficient 
  than 
  the 
  pre- 
  

   ceding 
  ; 
  the 
  author 
  has, 
  however, 
  preferred 
  to 
  adopt 
  it 
  in 
  order 
  to 
  avoid 
  

   any 
  pretence 
  to 
  exaggerate 
  in 
  his 
  own 
  favour 
  the 
  results 
  arrived 
  at. 
  Ap- 
  

   plying, 
  then, 
  Hinmann's 
  coefficient 
  to 
  the 
  dimensions 
  of 
  the 
  cone 
  at 
  60° 
  

   Fahr., 
  and 
  to 
  its 
  temperature 
  (2000° 
  Fahr.) 
  when 
  at 
  the 
  maximum, 
  we 
  

   are 
  enabled 
  to 
  deduce 
  the 
  true 
  capacity 
  of 
  the 
  cone 
  when 
  expanded 
  to 
  the 
  

   utmost 
  and 
  filled 
  with 
  molten 
  iron, 
  viz. 
  =2691*77 
  cubic 
  inches. 
  The 
  

   iron 
  conical 
  vessel 
  was 
  now 
  cut 
  off 
  by 
  a 
  circular 
  cut 
  at 
  the 
  base 
  and 
  

   another 
  up 
  and 
  down 
  the 
  side 
  of 
  the 
  cone, 
  and 
  separated 
  from 
  the 
  conical 
  

   mass 
  of 
  iron 
  that 
  had 
  filled 
  it 
  ; 
  the 
  interior 
  surface 
  of 
  the 
  iron 
  vessel 
  was 
  

   found 
  in 
  several 
  places 
  about 
  the 
  lower 
  part 
  of 
  the 
  cone 
  in 
  perfect 
  contact 
  

   with 
  that 
  of 
  the 
  cast 
  iron 
  which 
  had 
  filled 
  it 
  ; 
  but 
  in 
  other 
  portions 
  very 
  

   slightly 
  distant 
  from 
  it, 
  as 
  judged 
  by 
  the 
  sound 
  of 
  a 
  hammer 
  upon 
  the 
  

   sides 
  of 
  the 
  vessel 
  before 
  it 
  was 
  cut 
  off. 
  The 
  cast 
  iron 
  was 
  not 
  adherent 
  

   to 
  the 
  vessel 
  anywhere. 
  The 
  cast-iron 
  cone 
  being 
  thus 
  laid 
  bare, 
  had 
  a 
  

   Y-shaped 
  piece 
  cut 
  out 
  of 
  it 
  (in 
  the 
  " 
  slotting 
  "-machine), 
  as 
  shown 
  in 
  fig. 
  2, 
  

   by 
  two 
  planes, 
  each 
  passing 
  through 
  the 
  

   axis 
  and 
  meeting 
  at 
  an 
  angle 
  of 
  about 
  

   60°. 
  The 
  conical 
  mass 
  proved 
  per- 
  

   fectly 
  sound 
  and 
  free 
  from 
  cavities 
  

   or 
  blow-holes 
  anywhere, 
  except 
  very 
  

   near 
  the 
  summit 
  or 
  neck, 
  where 
  there 
  

   was 
  found 
  to 
  be 
  a 
  hollow 
  or 
  cavity 
  

   accidentally 
  left 
  during 
  the 
  feeding 
  (as 
  

   above 
  described). 
  By 
  measurement 
  the 
  

   volume 
  of 
  this 
  cavity 
  was 
  found 
  to 
  be 
  == 
  

   5*5 
  cubic 
  inches 
  ; 
  assuming 
  this 
  cavity 
  

   filled 
  with 
  iron 
  of 
  the 
  same 
  quality 
  as 
  the 
  

   cone, 
  the 
  weight 
  of 
  the 
  latter 
  would 
  be 
  in- 
  

   creased 
  by 
  1-43 
  lb., 
  making 
  thus 
  the 
  corrected 
  total 
  weight 
  of 
  the 
  solid 
  cone 
  

   of 
  cast 
  iron 
  = 
  647*18 
  lbs. 
  From 
  the 
  wedge-shaped 
  piece 
  cut 
  out 
  from 
  

   the 
  cone 
  at 
  half 
  its 
  altitude, 
  and 
  about 
  halfway 
  between 
  the 
  axis 
  and 
  cir- 
  

   cumference 
  of 
  the 
  sector, 
  a 
  piece 
  was 
  cut 
  out, 
  the 
  specific 
  gravity 
  of 
  which, 
  

  

  Fig. 
  2. 
  

  

  