﻿304 
  

  

  Dr. 
  C. 
  Chree's 
  Notes 
  on 
  Thermometry. 
  

  

  Also 
  for 
  this 
  degree 
  of 
  accuracy 
  it 
  may 
  prove 
  that 
  specifica- 
  

   tion 
  of 
  the 
  standard 
  latitude, 
  45°, 
  alone 
  is 
  not 
  sufficient. 
  It 
  

   is 
  desirable, 
  of 
  course, 
  that 
  the 
  definitions 
  of 
  212° 
  F. 
  and 
  

   100° 
  C. 
  should 
  be 
  absolutely 
  equivalent. 
  

  

  § 
  23. 
  When 
  we 
  leave 
  definitions 
  and 
  come 
  to 
  actual 
  

   determinations 
  of 
  boiling-points, 
  we 
  encounter, 
  as 
  has 
  recently 
  

   been 
  emphasized 
  by 
  Mr. 
  E. 
  H. 
  Griffiths 
  "^ 
  uncertainties 
  in 
  

   barometric 
  determinations. 
  Differences 
  of 
  *002 
  inch, 
  or 
  

   more, 
  in 
  the 
  readings 
  of 
  the 
  same 
  barometer 
  by 
  two 
  skilled 
  

   observers, 
  due 
  mainly 
  to 
  personal 
  equation 
  in 
  setting 
  the 
  

   ivory 
  pointer, 
  are 
  not 
  unusual. 
  Mr. 
  Griffiths 
  does 
  not 
  refer 
  

   to 
  this 
  point, 
  but 
  directs 
  his 
  attention 
  to 
  possible 
  differences 
  

   between 
  barometers 
  themselves. 
  A 
  comparison 
  of 
  a 
  Tonnelot 
  

   barometer 
  examined 
  at 
  the 
  Bureau 
  International 
  and 
  an 
  

   English 
  barometer 
  verified 
  at 
  Kew 
  Observatory 
  leads 
  him 
  

   to 
  the 
  conclusion 
  "f 
  " 
  that 
  a 
  discrepancy 
  of 
  as 
  much 
  as 
  *2 
  mm. 
  

   would 
  appear 
  to 
  exist 
  between 
  the 
  Sevres 
  (Bureau 
  Inter- 
  

   national) 
  and 
  Kew 
  standards." 
  He 
  adds, 
  however, 
  that 
  the 
  

   conditions 
  of 
  the 
  comparison 
  " 
  were 
  not 
  entirely 
  satisfactory." 
  

  

  Several 
  more 
  direct 
  comparisons 
  of 
  the 
  standard 
  barometers 
  

   at 
  the 
  principal 
  European 
  institutions 
  have 
  been 
  made 
  by 
  

   skilled 
  observers, 
  using 
  portable 
  barometers 
  as 
  intermediaries. 
  

   The 
  more 
  important 
  comparisons 
  prior 
  to 
  1 
  890 
  are 
  summarized 
  

   in 
  a 
  table 
  in 
  Waldo's 
  ' 
  Modern 
  Meteorology/ 
  from 
  which 
  I 
  

   have 
  extracted 
  the 
  following 
  results 
  : 
  — 
  

  

  Table 
  IX. 
  

  

  

  

  

  Corrections 
  in 
  mm 
  

  

  . 
  to 
  reduce 
  to 
  normal 
  

  

  

  

  Tvpe 
  of 
  

  

  barometer 
  (Wild's) 
  at 
  St. 
  Petersburg. 
  

  

  

  

  

  

  

  

  

  Barometer. 
  

  

  Chistoni 
  r 
  

  

  Waldo, 
  

  

  Sundell, 
  

  

  Bromaow, 
  

  

  

  

  

  1881. 
  

  

  1883. 
  

  

  1886. 
  

  

  1887. 
  

  

  Paris. 
  

  

  Meteorological 
  

   Bureau. 
  

  

  Eegnault. 
  

  

  -•04 
  

  

  -•05 
  

  

  +•16 
  

  

  +-11 
  

  

  

  Bureau 
  Interna- 
  f 
  

   tional. 
  \ 
  

  

  Wild-Pernet 
  

  

  

  -•24 
  

  

  

  

  

  Marek. 
  

  

  

  -•20 
  

  

  +•21 
  

  

  +-10 
  

  

  Berlin. 
  

  

  Normal 
  Standard 
  

   Commission. 
  

  

  Normal. 
  

  

  

  

  -•25 
  

  

  -•05 
  

  

  

  Vienna. 
  

  

  Central 
  Meteorolo- 
  

   gical 
  Institute 
  ... 
  

  

  Pistor. 
  

  

  -07 
  

  

  -•08 
  

  

  + 
  •13 
  

  

  + 
  11 
  

  

  Hamburg. 
  

  

  Deutsche 
  Seewarte. 
  

  

  Normal. 
  

  

  +'11 
  

  

  -04 
  

  

  +•14 
  

  

  +•07 
  

  

  Kew. 
  

  

  Observatory 
  

  

  Standard. 
  

  

  -•01 
  

  

  -•10 
  

  

  -•05 
  

  

  

  

  If 
  the 
  discrepancies 
  shown 
  by 
  Table 
  IX. 
  actually 
  existed, 
  

  

  * 
  * 
  Oamb. 
  Phil. 
  Sec. 
  Proceedings/ 
  vol. 
  ix. 
  p. 
  224. 
  

   t 
  Loc. 
  tit. 
  p. 
  229. 
  

  

  