﻿220 
  

  

  Mr.* 
  E. 
  Mallet 
  on 
  the 
  alleged 
  Expansion 
  

  

  meters 
  had 
  been 
  carefully 
  taken 
  when 
  at 
  atmospheric 
  temperature 
  

   (about 
  53° 
  Fahr.), 
  were 
  both 
  heated 
  in 
  an 
  oven-furnace. 
  One 
  of 
  these 
  

   having 
  been 
  thus 
  heated, 
  but 
  not 
  to 
  a 
  very 
  bright 
  red, 
  was 
  permitted 
  

   gradually 
  to 
  cool 
  again, 
  and 
  its 
  final 
  dimension 
  when 
  cold 
  noted. 
  The 
  

   other 
  shell 
  was 
  withdrawn 
  from 
  the 
  oven 
  when 
  at 
  a 
  bright 
  red 
  heat, 
  and 
  

   immediately 
  filled 
  to 
  a 
  little 
  above 
  the 
  inner 
  orifice 
  of 
  the 
  fuse-hole 
  

   (viz. 
  to 
  the 
  line 
  a 
  h, 
  fig. 
  3) 
  with 
  molten 
  cast 
  iron, 
  the 
  quality 
  of 
  this 
  

   being 
  the 
  very 
  dense 
  mottled 
  grey 
  iron 
  smelted 
  at 
  Elswick 
  Works 
  from 
  

   the 
  Eiddesdale 
  ores, 
  and 
  used 
  in 
  the 
  arsenal 
  for 
  casting 
  projectiles. 
  The 
  

   fuse-hole 
  was 
  closed 
  by 
  a 
  screw-plug, 
  which, 
  however, 
  did 
  not 
  reach 
  

   within 
  an 
  inch 
  of 
  the 
  surface 
  of 
  the 
  molten 
  metal, 
  and 
  the 
  whole 
  sur- 
  

   rounded 
  by 
  a 
  sheet- 
  iron 
  screen 
  to 
  keep 
  

   off 
  currents 
  of 
  air, 
  was 
  allowed 
  to 
  cool 
  

   gradually, 
  the 
  dimensions 
  being 
  taken 
  

   of 
  the 
  sphere 
  as 
  it 
  cooled 
  and 
  con- 
  

   tracted 
  at 
  intervals 
  of 
  half 
  an 
  hour 
  

   until 
  it 
  had 
  become 
  cold. 
  The 
  enve- 
  

   loping 
  shell 
  was 
  then 
  cut 
  through 
  by 
  

   the 
  lathe 
  in 
  a 
  great 
  circle 
  at 
  right 
  an- 
  

   gles 
  to 
  the 
  axis 
  passing 
  through 
  the 
  

   fuse-hole. 
  One 
  of 
  the 
  halves 
  of 
  the 
  

   shell 
  being 
  detached, 
  the 
  interior 
  sur- 
  

   faces 
  of 
  both 
  hemispheres 
  were 
  found 
  

   in 
  perfect 
  contact 
  with 
  that 
  of 
  the 
  

   ball 
  of 
  iron 
  they 
  had 
  contained, 
  but 
  

   no 
  elastic 
  tension 
  seemed 
  to 
  exist 
  in 
  the 
  shell. 
  The 
  ball 
  of 
  iron 
  

   was 
  drilled 
  into 
  and 
  split 
  by 
  steel 
  taper 
  plugs, 
  and 
  sections 
  of 
  it 
  

   exposed 
  passing 
  through 
  the 
  diameter 
  in 
  a 
  line 
  with 
  the 
  axis 
  of 
  the 
  

   fuse-hole. 
  There 
  was 
  no 
  large 
  cavity 
  or 
  " 
  draw 
  " 
  anywhere 
  in 
  the 
  in- 
  

   terior, 
  but 
  there 
  were 
  two 
  very 
  small 
  irregular 
  cavities 
  very 
  near 
  

   the 
  fuse-hole 
  ; 
  and 
  the 
  central 
  portion 
  of 
  the 
  mass 
  embraced 
  by 
  

   an 
  imaginary 
  sphere 
  of 
  about 
  3" 
  in 
  diameter, 
  as 
  shown 
  in 
  fig. 
  3, 
  

   proved 
  to 
  be 
  " 
  spongy 
  " 
  and 
  granular, 
  as 
  compared 
  with 
  the 
  very 
  

   dense 
  and 
  close-grained 
  iron 
  that 
  constituted 
  the 
  remainder 
  of 
  the 
  

   baU. 
  

  

  The 
  following 
  Table 
  shows 
  the 
  course 
  of 
  contraction 
  in 
  dimensions 
  of 
  

   the 
  filled 
  shell 
  and 
  also 
  of 
  the 
  empty 
  shell 
  in 
  their 
  progress 
  of 
  cooling, 
  

   and 
  the 
  change 
  in 
  dimensions 
  and 
  in 
  volume 
  of 
  the 
  filled 
  shell 
  are 
  

   shown 
  by 
  the 
  curves 
  (figures 
  4, 
  5, 
  6, 
  p. 
  222) 
  : 
  — 
  

  

  rig. 
  3. 
  

  

  