﻿Theory 
  and 
  Planetary 
  Temperatures. 
  165 
  

  

  If 
  we 
  look 
  a 
  little 
  further 
  into 
  the 
  matter, 
  perhaps 
  we 
  shall 
  

   find 
  that 
  my 
  greenhouse 
  raised 
  to 
  the 
  thousandth 
  power 
  is 
  

   not 
  so 
  much 
  of 
  a 
  reductio 
  ad 
  absurdum 
  as 
  one 
  might 
  suppose 
  ; 
  

   for 
  have 
  we 
  not 
  increasing 
  evidence 
  that 
  matter 
  is 
  really 
  dis- 
  

   continuous, 
  or 
  that 
  it 
  is 
  a 
  form 
  consisting 
  of 
  innumerable 
  

   chambers 
  ? 
  Thermal 
  energy 
  is 
  transferred 
  from 
  molecule 
  to 
  

   molecule 
  in 
  the 
  interior 
  of 
  a 
  body 
  by 
  a 
  process 
  which 
  involves 
  

   a 
  time-factor 
  and 
  a 
  discontinuous 
  mechanism. 
  Restore 
  these 
  

   by 
  giving 
  our 
  background 
  conductivity, 
  and 
  we 
  have 
  again 
  

   the 
  analogue 
  of 
  the 
  thousand-story 
  greenhouse 
  in 
  the 
  capacity 
  

   of 
  matter 
  for 
  storing 
  up 
  heat, 
  quite 
  apart 
  from 
  the 
  atmospheric 
  

   effect. 
  

  

  Short 
  of 
  a 
  duplicate 
  thermal 
  effect, 
  there 
  is 
  no 
  reason 
  why 
  

   various 
  mechanisms 
  of 
  this 
  sort 
  may 
  not 
  go 
  on 
  increasing 
  in 
  

   temperature 
  until 
  the 
  emission 
  of 
  short-waved 
  sether 
  vibrations 
  

   which 
  will 
  penetrate 
  the 
  outermost 
  layers 
  of 
  the 
  protecting 
  

   roof 
  limits 
  the 
  further 
  acquisition 
  of 
  stored-up 
  energy 
  — 
  that 
  

   is, 
  there 
  would 
  be 
  none 
  so 
  long 
  as 
  we 
  retain 
  the 
  further 
  

   property 
  which 
  Professor 
  Poynting 
  assumes, 
  that 
  the 
  atmo- 
  

   sphere 
  has 
  no 
  convection. 
  This, 
  however, 
  is 
  too 
  wide 
  a 
  

   departure 
  from 
  actuality 
  to 
  be 
  permissible 
  in 
  considerations 
  

   which 
  are 
  to 
  have 
  any 
  bearing 
  on 
  natural 
  phenomena 
  on 
  this 
  

   earth. 
  Experiment 
  has 
  given 
  the 
  following 
  relative 
  losses 
  of 
  

   temperature 
  by 
  radiation 
  and 
  by 
  convection 
  : 
  For 
  a 
  small 
  

   thermometer, 
  heated 
  to 
  15° 
  C. 
  in 
  sunshine, 
  about 
  three-tenths 
  

   of 
  the 
  heat 
  is 
  lost 
  by 
  convection 
  ; 
  but 
  in 
  a 
  thin 
  strip 
  of 
  

   blackened 
  platinum 
  similarly 
  heated, 
  the 
  loss 
  by 
  convection 
  

   is 
  twice 
  as 
  great 
  as 
  that 
  by 
  radiation. 
  Up 
  to 
  a 
  temperature- 
  

   excess 
  of 
  about 
  15° 
  C, 
  convective 
  emission 
  from 
  a 
  body 
  of 
  

   the 
  size 
  of 
  a 
  thermometer-bulb 
  increases 
  rapidly. 
  After 
  this, 
  

   convection 
  is 
  more 
  nearly 
  a 
  constant 
  proportion 
  of 
  the 
  total 
  

   loss 
  of 
  heat. 
  At 
  high 
  temperatures, 
  radiation, 
  which 
  varies 
  

   nearly 
  according 
  to 
  the 
  fourth 
  power 
  of 
  the 
  absolute 
  tempe- 
  

   rature 
  in 
  solids, 
  is 
  increasingly 
  potent 
  to 
  diminish 
  heat, 
  while 
  

   the 
  air 
  becomes 
  viscous, 
  and 
  convection 
  is 
  impeded 
  ; 
  but 
  for 
  

   small 
  differences 
  of 
  temperature 
  at 
  moderate 
  temperatures, 
  

   such 
  as 
  would 
  exist 
  in 
  successive 
  chambers 
  of 
  the 
  multiple 
  

   greenhouse, 
  convection 
  is 
  of 
  importance 
  in 
  assisting 
  to 
  limit 
  

   the 
  possible 
  accumulation 
  of 
  heat. 
  

  

  I 
  have 
  tried 
  the 
  effect 
  of 
  successive 
  enclosures 
  of 
  ordinary 
  

   glass 
  around 
  a 
  sun-thermometer, 
  and 
  find 
  that 
  there 
  is 
  very 
  

   little 
  heat 
  gained 
  after 
  two 
  or 
  three 
  layers 
  have 
  been 
  added. 
  

   But 
  probably 
  the 
  progression 
  would 
  be 
  more 
  noticeable 
  if 
  

   glass 
  of 
  a 
  very 
  thin 
  lamination 
  could 
  be 
  procured. 
  I 
  have 
  

   indeed 
  used 
  mica 
  with 
  some 
  success. 
  

  

  In 
  an 
  experiment 
  where 
  a 
  black-bulb 
  thermometer 
  in 
  air 
  

   Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  16. 
  jSo. 
  93. 
  Sept. 
  1908. 
  2 
  I 
  

  

  