﻿C. 
  Bar 
  us 
  — 
  Continuity 
  of 
  Solid 
  and 
  Liquid. 
  129 
  

  

  pressure 
  measurement 
  1 
  am 
  now 
  able 
  .to 
  avail 
  myself 
  of 
  

   ) 
  Amagat 
  " 
  manometre 
  a 
  pistons 
  libres," 
  which 
  can 
  be 
  

  

  For_ 
  

  

  superb 
  Amagat 
  ' 
  

  

  attached 
  to 
  my 
  compressor 
  without 
  further 
  mechanism 
  and 
  

   with 
  advantage.* 
  The 
  instrument 
  is 
  adapted 
  to 
  measure 
  

   3000 
  atm. 
  

  

  6. 
  The 
  volume 
  tube. 
  — 
  This 
  is 
  shown 
  in 
  the 
  annexed 
  figure 
  

   (diagram). 
  It 
  consists 
  of 
  an 
  external 
  cylindrical 
  

   envelope 
  AB 
  of 
  glass, 
  closed 
  below, 
  open 
  above, 
  

   about 
  26 
  cra 
  long' 
  and 
  '4 
  cm 
  or 
  -5 
  cm 
  in 
  diameter. 
  

   Throughout 
  the 
  greater 
  part 
  of 
  its 
  length, 
  the 
  

   tube 
  is 
  divided 
  into 
  two 
  coaxial 
  cylindric 
  compart- 
  

   ments, 
  by 
  a 
  central 
  glass 
  partition 
  tube 
  CkC, 
  

   open 
  at 
  both 
  ends, 
  and 
  fused 
  to 
  the 
  tube 
  AB 
  

   along 
  the 
  ring 
  CC, 
  about 
  7 
  cm 
  from 
  the 
  top. 
  CJcC 
  C$ 
  

   is 
  about 
  I7 
  cm 
  long 
  and 
  *13 
  cm 
  in 
  internal 
  diameter, 
  

   drawn 
  as 
  thin-walled 
  and 
  even 
  in 
  calibre 
  as 
  possi- 
  

   ble, 
  so 
  that 
  the 
  greater 
  part 
  of 
  its 
  lower 
  length 
  

   may 
  be 
  available 
  for 
  measurement. 
  

  

  The 
  substance 
  to 
  be 
  examined 
  is 
  introduced 
  into 
  

   the 
  annular 
  space 
  EE, 
  care 
  being 
  taken 
  that 
  when 
  

   fused 
  under 
  the 
  highest 
  temperature 
  and 
  lowest 
  

   pressure 
  to 
  be 
  applied, 
  its 
  lower 
  boundary 
  may 
  be 
  

   4 
  cm 
  or 
  more 
  above 
  the 
  end 
  k. 
  Immediately 
  in 
  

   contact 
  with 
  EE 
  and 
  extending 
  upward 
  into 
  the 
  

   central 
  tube 
  is 
  a 
  plug 
  of 
  mercury 
  EE, 
  with 
  its 
  

   free 
  meniscus 
  at 
  g. 
  When 
  EE 
  is 
  solid, 
  g 
  must 
  be 
  

   (say) 
  2 
  cm 
  above 
  the 
  end 
  k, 
  and 
  when 
  EE 
  is 
  liquid 
  •** 
  

   g 
  must 
  even 
  in 
  the 
  extreme 
  case 
  be 
  at 
  about 
  an 
  

   equal 
  distance 
  below 
  the 
  end 
  CC 
  of 
  the 
  tube 
  CkC. 
  The 
  

   remainder 
  of 
  this 
  tube, 
  above 
  g, 
  is 
  quite 
  tilled 
  with 
  a 
  con- 
  

   centrated 
  solution 
  of 
  zinc 
  sulphates 
  Ghg, 
  into 
  which 
  an 
  amal- 
  

   gamated 
  zinc 
  terminal 
  D, 
  has 
  been 
  submerged 
  and 
  fixed 
  in 
  

   position 
  by 
  the 
  platinum 
  wire 
  a, 
  fused 
  to 
  the 
  sides 
  of 
  the 
  tube 
  

   AB 
  as 
  shown. 
  The 
  other 
  terminal 
  b 
  passing 
  through 
  the 
  

   sealed 
  bottom 
  of 
  AB, 
  is 
  in 
  metallic 
  connection 
  with 
  the 
  mer- 
  

   cury 
  EE 
  therein 
  contained. 
  

  

  The 
  tube 
  thus 
  adjusted 
  is 
  completely 
  submerged 
  in 
  the 
  oil 
  

   within 
  the 
  insulated 
  tubular 
  piezometer, 
  with 
  which 
  the 
  termi- 
  

   nal 
  a 
  connects. 
  The 
  terminal 
  b 
  completely 
  insulated 
  from 
  the 
  

   piezometer 
  by 
  a 
  coating 
  of 
  glass 
  tube, 
  is 
  in 
  metallic 
  connection 
  

   with 
  the 
  barrel. 
  Thus 
  the 
  tube 
  AB 
  is 
  held 
  in 
  position 
  by 
  

   tensely 
  stretching 
  the 
  fixed 
  wires 
  a 
  and 
  b, 
  and 
  so 
  adjusting 
  

   their 
  lengths 
  that 
  the 
  parts 
  EE 
  and 
  hg 
  with 
  reference 
  to 
  which 
  

   the 
  measurements 
  are 
  made, 
  may 
  lie 
  wholly 
  within 
  the 
  vapor 
  

  

  * 
  Results 
  thus 
  obtained 
  in 
  comparing 
  various 
  high 
  pressure 
  gauges 
  and 
  methods 
  

   of 
  manipulation 
  will 
  be 
  given 
  in 
  a 
  current 
  number 
  of 
  the 
  Phil. 
  Mag., 
  xxxi, 
  p. 
  400, 
  

   1891. 
  

  

  