﻿Dr. 
  C. 
  Chree's 
  Notes 
  on 
  Thermometry. 
  

  

  215 
  

  

  or 
  the 
  fixed 
  and 
  movable 
  zero 
  methods 
  supply 
  the 
  same 
  

   scale. 
  This 
  is 
  pointed 
  out 
  in 
  Guillaume's 
  ' 
  Thermometrie 
  ' 
  *, 
  

   and 
  has 
  also 
  been 
  remarked 
  on 
  recently 
  by 
  Schuster 
  and 
  

   Gannon 
  f. 
  

  

  § 
  9. 
  As 
  examples 
  of 
  the 
  size 
  of 
  d 
  x 
  and 
  d 
  2 
  in 
  different 
  glasses 
  

   are 
  of 
  interest, 
  I 
  have 
  collected 
  the 
  following 
  data 
  from 
  

   Guillaume's 
  ' 
  Thermometrie'' 
  J, 
  adding 
  the 
  corresponding 
  

   calculated 
  values 
  of 
  the 
  zero 
  depressions 
  answering 
  to 
  tem- 
  

   peratures 
  of 
  50° 
  C. 
  and 
  100° 
  C. 
  The 
  results 
  for 
  the 
  French 
  

   glasses 
  appear 
  to 
  be 
  due 
  to 
  Guillaume 
  himself, 
  those 
  for 
  the 
  

   Jena 
  glass 
  to 
  Bottcher 
  §. 
  

  

  Table 
  I. 
  

  

  Glass. 
  

  

  Verredur 
  (experiments 
  — 
  10° 
  to 
  100° 
  O.) 
  

   ( 
  „ 
  -10° 
  to 
  190° 
  C.) 
  

  

  French 
  crystal, 
  hard.. 
  

  

  Jena 
  glass 
  IGh 
  1 
  

  

  ^XlO 
  7 
  . 
  

  

  +8886 
  

   +8557 
  

   +7972 
  

   +7100 
  

  

  cf 
  2 
  xl0 
  7 
  . 
  

  

  +11 
  

  

  +12 
  

  

  +329 
  

  

  Depression 
  Depression 
  

   after 
  after 
  

  

  50 
  u 
  C. 
  100° 
  C. 
  

  

  046 
  C. 
  

  

  •122 
  

   •034 
  

  

  0-099 
  C. 
  

  

  •098 
  

   •409 
  

   •063 
  

  

  The 
  observed 
  depressions 
  in 
  verre 
  dur 
  are 
  *047 
  after 
  50° 
  C-. 
  

   and 
  -100 
  C. 
  after 
  100° 
  C. 
  

  

  I 
  have 
  seen 
  no 
  actual 
  figures 
  for 
  Jena 
  glass 
  59 
  m 
  , 
  but 
  it 
  is 
  

   stated 
  || 
  that 
  the 
  depression 
  after 
  100° 
  C. 
  does 
  not 
  exceed 
  

   0°-02 
  C. 
  

  

  The 
  depression 
  in 
  the 
  French 
  crystal 
  is 
  only 
  slightly 
  larger 
  

   than 
  in 
  the 
  other 
  kinds 
  of 
  glass 
  at 
  atmospheric 
  temperatures, 
  

   but 
  it 
  increases 
  much 
  more 
  rapidly 
  at 
  high 
  temperatures, 
  a 
  

   defect 
  necessarily 
  shared 
  by 
  all 
  glasses 
  in 
  which 
  d 
  2 
  has 
  a 
  large 
  

   positive 
  value. 
  

  

  § 
  10. 
  In 
  the 
  following 
  Table 
  II. 
  I 
  have 
  calculated 
  from 
  

   (25) 
  the 
  algebraical 
  excess 
  of 
  the 
  reading 
  on 
  the 
  fixed 
  zero 
  

   over 
  that 
  on 
  the 
  movable 
  zero 
  scale 
  at 
  certain 
  points, 
  for 
  the 
  

   kinds 
  of 
  glass 
  given 
  in 
  Table 
  I. 
  For 
  verre 
  dur 
  1 
  have 
  taken 
  

   d 
  2 
  = 
  115 
  x 
  10 
  -8 
  throughout 
  the 
  whole 
  range. 
  The 
  application 
  

  

  * 
  P 
  198 
  

  

  t 
  Phil. 
  Trans. 
  A, 
  for 
  1895, 
  p. 
  428. 
  

  

  X 
  Pp. 
  149 
  and 
  318. 
  

  

  § 
  Zeitschrift 
  fur 
  Instrurnentenkunde, 
  vol. 
  viii. 
  p. 
  409 
  (1888). 
  

  

  II 
  Wiss. 
  Abhandl. 
  der 
  Phys. 
  tech. 
  Meichsanstalt, 
  vol. 
  i. 
  1894, 
  p. 
  10. 
  

  

  