﻿166 
  Prof. 
  W. 
  A. 
  Douglas 
  Eudge 
  on 
  

  

  that 
  the 
  fall 
  was 
  uniform 
  so 
  that 
  the 
  average 
  pressure 
  Ava* 
  

  

  492 
  + 
  1 
  o,.- 
  , 
  . 
  

  

  ' 
  — 
  ^ 
  — 
  = 
  246*0 
  atmospheres, 
  

  

  hence 
  the 
  cooling 
  effect 
  per 
  atmosphere 
  was 
  

   215 
  

  

  4-56 
  X 
  -21 
  X 
  246-5 
  

  

  = 
  0°-911 
  C. 
  

  

  Other 
  experiments 
  gave 
  similar 
  results, 
  six 
  typical 
  ones- 
  

   being 
  tabulated 
  below. 
  

  

  Weight 
  

   of 
  gas. 
  

  

  Fall 
  in 
  

   Temp. 
  

  

  Heat 
  

   absorbed. 
  

  

  Calculated 
  

   fall 
  * 
  

  

  Pressure 
  

   of 
  gns. 
  

  

  Cooling 
  per 
  

   atmosphere. 
  

  

  4-56 
  

  

  •962 
  

  

  224 
  

  

  223 
  

  

  492 
  

  

  0-911 
  C. 
  

  

  4-14 
  

  

  •926 
  

  

  215 
  

  

  247 
  

  

  445 
  

  

  1-15 
  

  

  4-13 
  

  

  •910 
  

  

  212 
  

  

  244 
  

  

  444 
  

  

  1-09 
  

  

  4-57 
  

  

  1-04 
  

  

  242 
  

  

  252 
  

  

  492 
  

  

  1025 
  

  

  4-68 
  

  

  1-03 
  

  

  240 
  

  

  245 
  

  

  504 
  

  

  •967 
  

  

  4-59 
  

  

  1-04 
  

  

  242 
  

  

  251 
  

  

  494 
  

  

  1-015 
  

  

  * 
  Calculated 
  as 
  on 
  page 
  162. 
  

  

  These 
  results 
  are 
  fairly 
  consistent, 
  and 
  do 
  not 
  differ 
  very 
  

   much 
  from 
  the 
  value 
  originally 
  sjiven 
  by 
  Joule 
  and 
  Thomson. 
  

   The 
  temperature, 
  however, 
  did 
  not 
  remain 
  constant 
  during 
  

   the 
  experiment. 
  

  

  As 
  there 
  was 
  some 
  uncertainty 
  as 
  to 
  the 
  exact 
  value 
  to 
  be 
  

   taken 
  for 
  the 
  fall 
  in 
  temperature, 
  an 
  attempt 
  was 
  made 
  to 
  

   conduct 
  the 
  experiment 
  under 
  such 
  conditions 
  that 
  the 
  tem- 
  

   perature 
  remained 
  constant 
  during 
  the 
  escape 
  of 
  the 
  gas. 
  This 
  

   was 
  done 
  by 
  so 
  regulating 
  the 
  flow 
  of 
  the 
  gas 
  that 
  the 
  

   temperature 
  remained 
  constantly 
  at 
  34° 
  C. 
  After 
  many 
  

   trials 
  the 
  best 
  rate 
  for 
  the 
  gas 
  to 
  escape 
  and 
  also 
  the 
  most 
  

   suitable 
  current 
  to 
  heat 
  the 
  calorimeter 
  were 
  determined,, 
  

   and 
  it 
  was 
  found 
  possible 
  to 
  keep 
  the 
  temperature 
  constant 
  

   within 
  about 
  -^" 
  C. 
  

  

  The 
  amount 
  of 
  heat 
  absorbed 
  was 
  found 
  from 
  the 
  rate 
  of 
  

   rise 
  of 
  temperature 
  just 
  before 
  and 
  after 
  the 
  evolution 
  of 
  the 
  

   gas. 
  The 
  results 
  were 
  not 
  very 
  different 
  from 
  those 
  obtained 
  

   in 
  the 
  previous 
  experiments, 
  but 
  as 
  the 
  flow 
  of 
  gas 
  was 
  not 
  

   free 
  the 
  variations 
  in 
  pressure 
  were 
  probably 
  very 
  con- 
  

   siderable, 
  and 
  this 
  may 
  account 
  for 
  the 
  variations 
  in 
  the 
  

   value, 
  and 
  also 
  for 
  the 
  higher 
  numerical 
  result. 
  

  

  