﻿112 
  

  

  Mr. 
  G. 
  F. 
  Rodwell 
  on 
  the 
  

  

  [Dec. 
  10, 
  

  

  Time. 
  

  

  Upper 
  

   thermometer. 
  

  

  Lower 
  

   thermometer. 
  

  

  Differences. 
  

  

  li 
  m 
  

  

  

  

  

  O 
  OO 
  ir.M. 
  

  

  970° 
  TT 
  

  

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  991 
  

  

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  250 
  

  

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  -24 
  

  

  6 
  20 
  

  

  245 
  

  

  221 
  

  

  —24 
  

  

  

  240 
  

  

  217 
  

  

  -23 
  

  

  6 
  30 
  

  

  198 
  

  

  182 
  

  

  -16 
  

  

  7 
  20 
  

  

  144 
  

  

  144 
  

  

  

  

  It 
  will 
  be 
  observed 
  that 
  while 
  observations 
  were 
  made 
  at 
  intervals 
  of 
  

   5 
  minutes 
  (and 
  at 
  first 
  at 
  each 
  of 
  the 
  intervening 
  minutes), 
  the 
  interval 
  

   between 
  the 
  last 
  two 
  is 
  50 
  minutes, 
  and 
  the 
  mass 
  partly 
  solidified 
  had 
  

   fallen 
  to 
  144° 
  F. 
  The 
  greatest 
  difference 
  between 
  the 
  upper 
  and 
  lower 
  

   thermometers 
  during 
  the 
  cooling 
  through 
  a 
  range 
  of 
  200° 
  F. 
  is 
  no 
  less 
  than 
  

   26° 
  F., 
  and 
  only 
  for 
  an 
  instant, 
  at 
  a 
  temperature 
  of 
  about 
  355° 
  F., 
  have 
  

   the 
  two 
  thermometers 
  coincided. 
  

  

  Determination 
  of 
  the 
  coefficient 
  of 
  expansion 
  of 
  solid 
  paraffine 
  betiveen 
  

   32° 
  F. 
  (0° 
  C.) 
  and 
  the 
  fusing-point, 
  142° 
  F. 
  (61-11 
  C). 
  

  

  The 
  above 
  examples 
  show 
  us 
  the 
  extreme 
  difficulty 
  of 
  obtaining 
  uni- 
  

   formity 
  of 
  temperature 
  in 
  either 
  a 
  solid 
  or 
  liquid 
  mass 
  of 
  paraffine, 
  and 
  

   help 
  to 
  explain 
  various 
  incongruities 
  which 
  presented 
  themselves 
  in 
  the 
  

   course 
  of 
  the 
  following 
  determinations. 
  The 
  coefficient 
  of 
  expansion 
  of 
  

   the 
  solid 
  was 
  determined 
  by 
  weighing 
  a 
  piece 
  of 
  compact 
  paraffine 
  in 
  

   water 
  at 
  different 
  temperatures, 
  the 
  expansion 
  of 
  water 
  (as 
  determined 
  

   by 
  M. 
  Despretz 
  to 
  seven 
  places 
  of 
  decimals) 
  being 
  of 
  course 
  well 
  known. 
  

  

  