﻿Theory 
  and 
  Planetary 
  Temperatures. 
  467 
  

  

  (Table 
  85, 
  p. 
  98, 
  loc. 
  cit.), 
  it 
  may 
  be 
  inferred 
  that 
  the 
  solar 
  

   radiation 
  at 
  the 
  same 
  hour, 
  l 
  h 
  40 
  m 
  p.m., 
  was 
  usually 
  about 
  

   1*84 
  cal./cm. 
  2 
  min. 
  For 
  comparison 
  with 
  my 
  observation, 
  

   I 
  will 
  suppose 
  the 
  shade 
  temperature 
  to 
  have 
  been 
  the 
  same 
  

   as 
  mine, 
  giving 
  a 
  reduced 
  hot-box 
  temperature 
  

  

  whence 
  

  

  = 
  35 
  + 
  98-5 
  + 
  273 
  = 
  406°-5 
  A, 
  

  

  X= 
  {jgj 
  x 
  (406-5)*y 
  = 
  463° 
  A. 
  

  

  These 
  temperatures 
  are 
  also 
  in 
  approximate 
  agreement 
  

   with 
  that 
  which 
  I 
  have 
  found 
  for 
  the 
  moon 
  at 
  midday 
  

   (454° 
  A.)*. 
  The 
  moon, 
  unlike 
  the 
  earth, 
  has 
  a 
  sufficiently 
  

   prolonged 
  insolation 
  to 
  produce 
  a 
  steady 
  state 
  of 
  temperature, 
  

   and 
  it 
  has 
  so 
  little 
  atmosphere 
  that 
  very 
  little 
  heat 
  is 
  conveyed 
  

   to 
  cold 
  parts 
  of 
  the 
  planet 
  through 
  convection 
  currents. 
  

  

  Sun 
  temperatures 
  at 
  planetary 
  surfaces 
  are 
  very 
  greatly 
  

   modified 
  by 
  atmospheric 
  agencies. 
  In 
  nature 
  the 
  effect 
  of 
  

   convection 
  is 
  very 
  marked, 
  for 
  the 
  atmosphere 
  acquires 
  its 
  

   heat 
  mainly 
  by 
  convection 
  of 
  hot 
  air, 
  as 
  well 
  as 
  by 
  evapo- 
  

   ration 
  of 
  moisture 
  from 
  a 
  heated 
  surface, 
  and 
  by 
  the 
  distri- 
  

   bution 
  of 
  these 
  thermal 
  increments 
  by 
  means 
  of 
  atmospheric 
  

   circulation. 
  

  

  Atmospheric 
  heating 
  by 
  the 
  absorption 
  of 
  radiation 
  is 
  

   accomplished 
  with 
  especial 
  efficacy 
  in 
  two 
  layers 
  — 
  one 
  high 
  

   up, 
  the 
  other 
  near 
  the 
  surface. 
  The 
  multiple 
  greenhouse 
  

   has 
  therefore 
  a 
  further 
  analogue 
  ; 
  for 
  the 
  incoming 
  solar 
  rays 
  

   are 
  most 
  efficacious 
  in 
  warming 
  the 
  air 
  in 
  the 
  upper 
  layers 
  of 
  

   the 
  atmosphere 
  where 
  these 
  rays 
  first 
  meet 
  the 
  atmospheric 
  

   moisture. 
  A 
  very 
  considerable 
  fraction 
  of 
  infra-red 
  solar 
  

   radiation 
  is 
  taken 
  out 
  by 
  line 
  and 
  band 
  absorption 
  in 
  the 
  

   upper 
  air. 
  In 
  passing 
  through 
  the 
  first 
  ten 
  kilometres 
  of 
  air 
  

   containing 
  appreciable 
  moisture, 
  or 
  what 
  may 
  be 
  called 
  the 
  

   aqueous 
  atmosphere, 
  certain 
  rays 
  are 
  struck 
  out 
  from 
  the 
  

   spectrum 
  completely. 
  These 
  rays 
  do 
  not 
  enter 
  into 
  our 
  

   formula 
  for 
  atmospheric 
  absorption. 
  They 
  have 
  been 
  lost 
  

   completely 
  and 
  do 
  not 
  reach 
  the 
  earth's 
  surface. 
  Conse- 
  

   quently 
  the 
  readings 
  of 
  actinometers 
  which 
  take 
  no 
  account 
  

   of 
  these 
  lost 
  rays, 
  even 
  after 
  correction 
  for 
  the 
  apparent 
  

   absorption 
  of 
  the 
  atmosphere 
  determined 
  by 
  high 
  and 
  low 
  sun 
  

   comparisons, 
  give 
  only 
  the 
  solar 
  radiation, 
  minus 
  an 
  unknown 
  

   line 
  and 
  band 
  absorption. 
  The 
  solar 
  radiant 
  energy 
  kept 
  back 
  

  

  * 
  F. 
  TV. 
  Very, 
  u 
  The 
  Probable 
  Range 
  of 
  Temperature 
  on 
  the 
  Moon/' 
  

   Astrcphysical 
  Journ. 
  vol. 
  viii. 
  p. 
  284, 
  December 
  1898. 
  

  

  212 
  

  

  