﻿38 
  Mr. 
  C. 
  F. 
  Brush 
  on 
  the 
  Transmission 
  of 
  

  

  shown 
  in 
  connexion 
  with 
  section 
  C. 
  To 
  avoid 
  confusion 
  of 
  

   lines 
  I 
  have 
  omitted 
  the 
  secondary 
  curves 
  corresponding 
  with 
  

   section 
  B. 
  

  

  PL 
  111. 
  shows 
  the 
  curves 
  for 
  carbon 
  monoxide. 
  This 
  gas 
  

   was 
  chosen 
  for 
  comparison 
  with 
  air, 
  because 
  its 
  absorptive 
  

   power 
  for 
  radiant 
  heat 
  is 
  ninety 
  times 
  greater, 
  while 
  its 
  

   specific 
  heat 
  is 
  almost 
  exactly 
  the 
  same. 
  The 
  principal 
  curve, 
  

   representing 
  the 
  rate 
  of 
  heat 
  transmission 
  from 
  15 
  degrees 
  

   to 
  10 
  degrees, 
  differs 
  very 
  little 
  from 
  that 
  of 
  air. 
  It 
  shows 
  

   a 
  slightly 
  better 
  rate 
  than 
  air 
  at 
  very 
  small 
  pressures 
  ; 
  not 
  

   quite 
  so 
  good 
  a 
  rate 
  as 
  air 
  at 
  intermediate 
  pressures 
  ; 
  and 
  the 
  

   same 
  rate 
  at 
  atmospheric 
  pressure. 
  But 
  the 
  curves 
  a, 
  a 
  a, 
  

   a 
  a 
  a, 
  representing 
  equivalent 
  amounts 
  of 
  cooling 
  at 
  smaller 
  

   temperature 
  differences, 
  are 
  materially 
  unlike 
  those 
  of 
  air. 
  

   At 
  high 
  pressures 
  they 
  have 
  about 
  the 
  same 
  ratio 
  values 
  as 
  

   with 
  air 
  ; 
  but 
  the 
  ratio 
  diminishes 
  much 
  less 
  at 
  intermediate 
  

   and 
  low 
  pressures 
  ; 
  that 
  is 
  to 
  say, 
  the 
  curves 
  remain 
  further 
  

   apart. 
  It 
  is 
  equally 
  noticeable 
  that 
  the 
  curves 
  a 
  a, 
  a 
  a 
  a 
  

   retain 
  their 
  full 
  relative 
  ratio 
  values 
  at 
  low 
  pressures, 
  while 
  

   with 
  air 
  they 
  nearly 
  coalesce. 
  

  

  PL 
  IY. 
  shows 
  the 
  curve 
  for 
  ethylene. 
  It 
  was 
  thought 
  that 
  

   this 
  gas 
  might 
  transmit 
  heat 
  more 
  rapidly 
  than 
  air 
  ; 
  because 
  

   of 
  its 
  much 
  higher 
  specific 
  heat. 
  But 
  it 
  does 
  not 
  do 
  so. 
  

   Its 
  curve 
  has 
  the 
  same 
  form 
  as 
  those 
  of 
  air 
  and 
  carbon 
  

   monoxide. 
  It 
  transmits 
  heat 
  nearly 
  as 
  well 
  as 
  air 
  at 
  atmo- 
  

   spheric 
  pressure, 
  but 
  not 
  nearly 
  so 
  well 
  at 
  intermediate 
  

   pressures. 
  At 
  a 
  very 
  few 
  millionths, 
  however, 
  it 
  conducts 
  a 
  

   trifle 
  better 
  than 
  air. 
  The 
  curves 
  a, 
  a 
  a, 
  and 
  aaa 
  have 
  the 
  

   same 
  characteristics, 
  and 
  about 
  the 
  same 
  ratios, 
  as 
  those 
  of 
  

   carbon 
  monoxide. 
  

  

  Hydrogen 
  was 
  next 
  tried, 
  on 
  account 
  of 
  its 
  very 
  low 
  co- 
  

   efficient 
  of 
  viscosity, 
  as 
  well 
  as 
  its 
  very 
  high 
  specific 
  heat. 
  

   PL 
  V. 
  illustrates 
  the 
  hydrogen 
  curve 
  on 
  the 
  same 
  scale 
  as 
  

   the 
  others. 
  While 
  in 
  general 
  form 
  it 
  resembles 
  the 
  air 
  curve, 
  

   all 
  the 
  ordinates 
  are 
  immensely 
  increased. 
  It 
  is 
  noticeable 
  

   that 
  the 
  intermediate 
  section 
  B 
  of 
  the 
  curve 
  lies 
  much 
  nearer 
  

   A 
  than 
  C, 
  quite 
  different 
  from 
  its 
  relative 
  position 
  in 
  the 
  

   curves 
  of 
  the 
  other 
  gases. 
  This 
  section 
  of 
  the 
  curve 
  shows 
  

   that 
  hydrogen 
  retains 
  about 
  two-thirds 
  of 
  its 
  initial 
  heat- 
  

   transmitting 
  power 
  at 
  a 
  pressure 
  nearly 
  two 
  hundred 
  times 
  

   smaller 
  than 
  does 
  air. 
  . 
  The 
  curves 
  A, 
  a, 
  a 
  a, 
  and 
  a 
  a 
  a 
  have 
  

   something 
  like 
  the 
  same 
  ratios 
  as 
  they 
  have 
  in 
  the 
  cases 
  of 
  

   carbon 
  monoxide 
  and 
  ethylene. 
  In 
  general, 
  it 
  may 
  be 
  said 
  

   of 
  hydrogen 
  in 
  the 
  large 
  radiation 
  bulb 
  ; 
  that 
  it 
  transmits 
  heat 
  

   nearlv 
  four 
  times 
  as 
  fast 
  as 
  air 
  at 
  atmospheric 
  pressure 
  ; 
  more 
  

   than 
  twice 
  as 
  fast 
  at 
  a 
  very 
  few 
  niillionths, 
  and 
  more 
  than 
  

  

  