﻿640 
  Mr. 
  A. 
  E. 
  Tutton 
  on 
  the 
  

  

  Table 
  showing 
  Values 
  of 
  a 
  = 
  a 
  + 
  2bt 
  for 
  various 
  Temperatures. 
  

  

  Temperature. 
  

  

  Tutton. 
  

  

  Chappuis. 
  

  

  6 
  

  

  0-000 
  002 
  522 
  

  

  0000 
  002 
  824 
  

  

  10 
  

  

  2 
  671 
  

  

  2 
  947 
  

  

  20 
  

  

  2819 
  

  

  3 
  071 
  

  

  30 
  

  

  2 
  967 
  

  

  3194 
  

  

  40 
  

  

  3116 
  

  

  3 
  317 
  

  

  50 
  

  

  3 
  265 
  

  

  3 
  441 
  

  

  60 
  

  

  3 
  414 
  

  

  3 
  564 
  

  

  70 
  

  

  3 
  562 
  

  

  3 
  688 
  

  

  80 
  

  

  3711 
  

  

  3 
  811 
  

  

  90 
  

  

  3 
  859 
  

  

  

  100 
  

  

  4 
  008 
  

  

  

  110 
  

  

  4157 
  

  

  

  120 
  

  

  4 
  305 
  

  

  

  The 
  value 
  for 
  120°, 
  calculated 
  from 
  the 
  formula 
  of 
  Chappuis, 
  

   is 
  0*000 
  004 
  305, 
  exactly 
  the 
  same 
  as 
  the 
  author's 
  value. 
  

  

  Chappuis 
  offered, 
  towards 
  an 
  explanation 
  of 
  the 
  difference 
  

   between 
  Bedford's 
  results 
  and 
  his 
  ov\n, 
  the 
  observation 
  that 
  

   some 
  rotation 
  of 
  the 
  fringes 
  occurred, 
  indicating 
  inequality 
  

   of 
  expansion 
  and 
  curving 
  of 
  the 
  tube 
  ; 
  and 
  further, 
  that 
  the 
  

   hole 
  through 
  the 
  tube 
  was 
  considerably 
  eccentric, 
  so 
  that 
  

   opposite 
  parts 
  of 
  the 
  wall 
  presented 
  variations 
  in 
  thickness, 
  

   and 
  the 
  effect 
  of 
  a 
  glaze 
  differing 
  in 
  expansibility 
  from 
  the 
  

   ( 
  ' 
  biscuit 
  " 
  might 
  be 
  to 
  slightly 
  deform 
  the 
  tube 
  on 
  heating. 
  

   In 
  the 
  author's 
  opinion 
  this 
  is 
  not 
  the 
  cause 
  of 
  the 
  discrepancy, 
  

   for 
  in 
  the 
  author's 
  experiments 
  the 
  amount 
  of 
  rotation 
  of 
  the 
  

   interference-bands 
  was 
  negligible, 
  and 
  the 
  hole 
  was 
  central. 
  

   The 
  results 
  now 
  presented 
  indicate 
  rather 
  that 
  the 
  discrepancy 
  

   is 
  due 
  to 
  a 
  fundamental 
  real 
  difference, 
  dependent 
  on 
  the 
  

   interval 
  of 
  temperature 
  for 
  which 
  the 
  determinations 
  were 
  

   made. 
  They 
  indicate 
  clearly, 
  in 
  the 
  author's 
  opinion, 
  that 
  

   the 
  character 
  of 
  the 
  expansion 
  between 
  0° 
  and 
  100° 
  is 
  sub- 
  

   stantially 
  that 
  exhibited 
  by 
  the 
  results 
  of 
  Chappuis 
  for 
  the 
  

   interval 
  of 
  0° 
  to 
  83°, 
  those 
  results, 
  however, 
  not 
  going 
  quite 
  

   far 
  enough 
  in 
  their 
  difference 
  from 
  those 
  of 
  Bedford 
  ; 
  also, 
  

   that 
  the 
  considerable 
  difference 
  from 
  the 
  latter 
  observer's 
  

   values 
  is 
  owing 
  to 
  the 
  large 
  interval 
  included 
  by 
  Bedford's, 
  

   0° 
  to 
  830°. 
  In 
  other 
  words, 
  presuming 
  the 
  accuracy 
  of 
  

   Bedford's 
  results 
  (and 
  there 
  is 
  every 
  reason 
  to 
  do 
  so, 
  as 
  they 
  

   are 
  confirmed 
  by 
  the 
  results 
  of 
  other 
  observers 
  with 
  Berlin 
  

   porcelain), 
  it 
  appears 
  proved 
  that 
  the 
  increment 
  per 
  degree 
  

   (A«/A^ 
  = 
  2&), 
  of 
  the 
  coefficient 
  of 
  expansion, 
  in 
  the 
  case 
  of 
  

   porcelain 
  is 
  not 
  a 
  constant 
  quantity, 
  but 
  one 
  which 
  is 
  much 
  

  

  