﻿130 
  C. 
  Barus 
  — 
  Continuity 
  of 
  Solid 
  and 
  Liquid. 
  

  

  reservoir 
  of 
  the 
  cylindrical 
  vapor 
  bath 
  surrounding 
  the 
  piezom- 
  

   eter. 
  Many 
  of 
  these 
  operations 
  are 
  delicate, 
  but 
  descriptions 
  

   must 
  be 
  omitted. 
  

  

  An 
  inspection 
  of 
  the 
  figure 
  shows 
  at 
  once 
  that 
  if 
  a 
  current 
  

   enter 
  the 
  outside 
  of 
  the 
  barrel, 
  it 
  will 
  pass 
  through 
  o, 
  k, 
  A, 
  D 
  

   and 
  a, 
  into 
  the 
  outside 
  of 
  the 
  piezometer, 
  and 
  thence 
  back 
  to 
  

   the 
  battery. 
  The 
  only 
  relatively 
  significant 
  resistance 
  en- 
  

   countered 
  in 
  such 
  a 
  course, 
  can 
  be 
  confined 
  to 
  the 
  path 
  between 
  

   g 
  and 
  h, 
  through 
  the 
  thread 
  of 
  the 
  zinc 
  sulphate 
  solution 
  ; 
  but 
  

   this 
  resistance, 
  cset. 
  par., 
  varies 
  directly 
  with 
  the 
  length 
  of 
  gh 
  

   and 
  therefore 
  proportionally 
  to 
  the 
  volume 
  contraction 
  of 
  the 
  

   substance 
  EE. 
  If 
  Kohlrausch's 
  method* 
  of 
  intermittent 
  cur- 
  

   rents, 
  bridge 
  and 
  telephone 
  be 
  used 
  for 
  the 
  resistance 
  measure- 
  

   ment 
  of 
  the 
  electrolyte, 
  solidification 
  or 
  fusion 
  of 
  EE 
  breaks 
  

   upon 
  the 
  ear 
  with 
  a 
  loud 
  roar, 
  whereas 
  the 
  ordinary 
  volume 
  

   changes 
  (solid 
  or 
  liquid) 
  are 
  indicated 
  by 
  intensifications 
  of 
  the 
  

   sound 
  in 
  the 
  telephone, 
  sufficiently 
  pronounced 
  however 
  to 
  

   subserve 
  the 
  purposes 
  of 
  measurement. 
  

  

  It 
  is 
  seen 
  that 
  any 
  breakage 
  of 
  the 
  surface 
  of 
  separation 
  

   between 
  EE 
  and 
  EE 
  is 
  entirely 
  without 
  influence 
  on 
  these 
  

   results, 
  and 
  that 
  even 
  in 
  case 
  of 
  solidification 
  of 
  EE, 
  when 
  the 
  

   mercury 
  is 
  forced 
  into 
  the 
  interstices 
  left 
  after 
  contraction, 
  the 
  

   compressibility 
  of 
  i^will 
  still 
  be 
  measurable. 
  

  

  The 
  charging 
  of 
  the 
  tube 
  free 
  from 
  air, 
  is 
  an 
  operation 
  

   which 
  I 
  have 
  not 
  yet 
  accomplished 
  satisfactorily. 
  If 
  a 
  volatile 
  

   substance 
  like 
  naphthalene 
  be 
  filled 
  into 
  EE 
  and 
  fused 
  in 
  

   vacuo, 
  vapors 
  objectionably 
  condense 
  in 
  the 
  tube 
  hk. 
  If 
  EE 
  

   be 
  not 
  fused, 
  I 
  doubt 
  whether 
  the 
  air 
  can 
  be 
  eliminated 
  in 
  

   vacuo. 
  Hence 
  in 
  the 
  present 
  work, 
  the 
  substance 
  was 
  not 
  air- 
  

   free, 
  a 
  condition 
  to 
  which 
  I 
  gave 
  less 
  attention 
  because 
  I 
  do 
  

   not 
  believe 
  the 
  melting 
  points 
  are 
  appreciably 
  influenced 
  by 
  

   dissolved 
  air, 
  nor 
  that 
  the 
  other 
  measurements 
  made 
  are 
  seri- 
  

   ously 
  distorted 
  by 
  this 
  error. 
  In 
  further 
  measurements, 
  how- 
  

   ever, 
  I 
  will 
  endeavor 
  to 
  meet 
  the 
  difficulty 
  by 
  fusing 
  the 
  end 
  

   A 
  of 
  the 
  inverted 
  tube 
  AB, 
  to 
  the 
  top 
  of 
  a 
  barometer 
  tube, 
  

   provided 
  with 
  a 
  lateral 
  tubulure 
  leading 
  to 
  a 
  Sprengel 
  pump. 
  

   If 
  then, 
  after 
  exhaustion 
  the 
  lower 
  meniscus 
  is 
  adjustible, 
  so 
  

   that 
  the 
  whole 
  barometric 
  column 
  can 
  be 
  raised 
  quite 
  into 
  the 
  

   tube 
  AB 
  or 
  withdrawn 
  from 
  it 
  at 
  pleasure, 
  a 
  thorough 
  vacuum 
  

   filling 
  may 
  be 
  effected. 
  Rubber 
  connections 
  must 
  be 
  scrupu- 
  

   lously 
  avoided. 
  

  

  Method 
  of 
  Measurement. 
  

  

  7. 
  Constants 
  of 
  the 
  tube. 
  — 
  In 
  order 
  that 
  the 
  present 
  meas- 
  

   urements 
  may 
  be 
  carried 
  out 
  absolutely, 
  it 
  is 
  necessary 
  to 
  

  

  * 
  Kohlrausch: 
  Verh. 
  med. 
  phys. 
  Ges. 
  Wurzburg, 
  xv, 
  p. 
  1, 
  1880; 
  Wied. 
  Ann., 
  

   xi, 
  p. 
  653, 
  1880. 
  Long: 
  Wied. 
  Ann 
  , 
  xi, 
  p. 
  37, 
  1880. 
  

  

  