﻿DEC. 
  4, 
  1922 
  proceedings: 
  philosophical 
  society 
  463 
  

  

  By 
  means 
  of 
  these 
  screens, 
  which, 
  either 
  singly 
  or 
  in 
  combination, 
  had 
  a 
  

   uniformly 
  high 
  transmission 
  over 
  a 
  fairly 
  narrow 
  region 
  of 
  the 
  spectrum 
  and 
  

   terminating 
  abruptly 
  to 
  complete 
  opacity 
  in 
  the 
  rest 
  of 
  the 
  spectrum, 
  it 
  was 
  

   possible 
  to 
  obtain 
  for 
  the 
  first 
  time 
  the 
  radiation 
  intensity 
  in 
  the 
  complete 
  

   stellar 
  spectrum 
  as 
  transmitted 
  by 
  our 
  atmosphere. 
  

  

  The 
  recent 
  measurements 
  of 
  the 
  spectrol 
  radiation 
  components, 
  made 
  prin- 
  

   cipally 
  on 
  the 
  sun, 
  the 
  temperature 
  of 
  which 
  was 
  used 
  as 
  a 
  standard 
  of 
  com- 
  

   parison, 
  verify 
  the 
  previous 
  measurements 
  of 
  stellar 
  temperatures, 
  which 
  

   range 
  from 
  3000° 
  K 
  for 
  red, 
  class-M 
  stars, 
  to 
  12000° 
  K 
  for 
  blue, 
  class-B 
  

   stars. 
  

  

  Planetary 
  radiation. 
  — 
  The 
  thermal 
  radiation 
  emitted 
  from 
  a 
  planet 
  as 
  a 
  

   result 
  of 
  warming 
  by 
  exposure 
  to 
  solar 
  radiation, 
  including 
  heat 
  which 
  may 
  

   be 
  radiated 
  by 
  virtue 
  of 
  a 
  possible 
  high 
  internal 
  temperature 
  of 
  the 
  planet 
  

   itself, 
  is 
  essentially 
  of 
  long 
  wave 
  lengths 
  7^i 
  to 
  12/x. 
  Hence, 
  by 
  means 
  of 
  a 
  

   1 
  cm. 
  cell 
  of 
  water, 
  interposed 
  in 
  the 
  path 
  of 
  total 
  radiation 
  emanating 
  from 
  

   the 
  planet, 
  this 
  long 
  wave-length 
  radiation 
  can 
  be 
  separated 
  from 
  the 
  reflected 
  

   solar 
  radiation, 
  and 
  in 
  this 
  manner 
  a 
  measurement 
  obtained 
  of 
  the 
  energy 
  

   reradiated. 
  If 
  there 
  is 
  planetary 
  radiation 
  then 
  the 
  water 
  cell 
  transmission 
  

   will 
  be 
  less 
  than 
  that 
  of 
  direct 
  solar 
  radiation. 
  

  

  It 
  was 
  observed 
  that 
  the 
  water 
  cell 
  transmission 
  of 
  the 
  total 
  radiation 
  

   emanating 
  from 
  Jupiter 
  is 
  practically 
  the 
  same 
  as 
  that 
  of 
  the 
  direct 
  solar 
  radia- 
  

   tion. 
  From 
  this 
  it 
  appears 
  that 
  the 
  outer 
  atmosphere 
  of 
  Jupiter 
  does 
  not 
  

   radiate 
  appreciable 
  long 
  wave 
  length 
  infra-red 
  energy 
  as 
  the 
  result 
  of 
  warming 
  

   by 
  solar 
  rays, 
  and 
  that 
  the 
  atmosphere 
  is 
  sufficiently 
  thick 
  and 
  opaque 
  to 
  

   trap 
  all 
  the 
  energy 
  reradiated 
  as 
  the 
  result 
  of 
  warming 
  of 
  its 
  interior 
  by 
  solar 
  

   radiation, 
  or 
  by 
  internal 
  heating, 
  if 
  the 
  interior 
  of 
  Jupiter 
  is 
  still 
  highly 
  

   heated. 
  

  

  The 
  radiometric 
  measurements 
  of 
  Venus, 
  Jupiter, 
  and 
  Saturn 
  are 
  in 
  good 
  

   agreement 
  with 
  similar 
  measurements 
  made 
  at 
  Mt. 
  Hamilton, 
  Calif., 
  in 
  1914, 
  

   showing 
  a 
  decidedly 
  lower 
  transmission 
  of 
  radiation 
  through 
  the 
  water 
  cell 
  

   in 
  the 
  case 
  of 
  Venus 
  and 
  Saturn. 
  

  

  The 
  intensity 
  of 
  the 
  planetary 
  radiation 
  increases 
  with 
  decrease 
  in 
  the 
  

   density 
  of 
  the 
  surrounding 
  atmosphere 
  and 
  (as 
  interpreted 
  from 
  the 
  water 
  

   cell 
  transmissions) 
  in 
  per 
  cent 
  of 
  the 
  total 
  radiation 
  emitted 
  is 
  as 
  follows: 
  

   Jupiter 
  (0), 
  Venus 
  (5), 
  Saturn 
  (15), 
  Mars 
  (30), 
  and 
  the 
  Moon 
  (80). 
  

  

  The 
  water 
  cell 
  transmission 
  of 
  the 
  radiations 
  from 
  the 
  Southern 
  (50.6%) 
  

   and 
  northern 
  (53.1%) 
  hemispheres 
  of 
  Mars 
  should 
  be 
  and 
  are 
  higher 
  {i.e., 
  

   the 
  planetary 
  radiation 
  is 
  lower) 
  than 
  that 
  of 
  the 
  radiations 
  emanating 
  from 
  

   the 
  equatorial 
  (47.3%) 
  region, 
  owing 
  to 
  the 
  depletion 
  of 
  the 
  reradiated 
  energy 
  

   by 
  the 
  greater 
  air 
  mass. 
  Moreover, 
  the 
  intensity 
  of 
  the 
  planetary 
  radiation 
  

   from 
  the 
  northern 
  hemisphere 
  of 
  Mars 
  was 
  found 
  to 
  be 
  less 
  than 
  from 
  the 
  

   southern 
  hemisphere. 
  This 
  is 
  to 
  be 
  expected 
  in 
  view 
  of 
  the 
  observed 
  cloudi- 
  

   ness 
  over 
  the 
  northern 
  hemisphere 
  which 
  is 
  approaching 
  the 
  winter 
  season 
  and 
  

   hence 
  is 
  at 
  a 
  lower 
  superficial 
  temperature. 
  

  

  The 
  radiometric 
  measurements 
  of 
  Mars 
  are 
  of 
  especial 
  interest 
  in 
  view 
  of 
  

   the 
  question 
  of 
  the 
  temperature 
  of 
  this 
  planet. 
  

  

  The 
  calculations 
  of 
  Lowell, 
  based 
  on 
  the 
  heat 
  retained, 
  give 
  a 
  mean 
  tem- 
  

   perature 
  of 
  9° 
  C. 
  for 
  the 
  surface; 
  while 
  another 
  calculation 
  gives 
  a 
  tempera- 
  

   ture 
  of 
  22° 
  C. 
  He 
  points 
  out 
  that 
  owing 
  to 
  cloudiness, 
  only 
  60 
  per 
  cent 
  of 
  

   the 
  incident 
  solar 
  radiation 
  is 
  effective 
  in 
  warming 
  the 
  earth, 
  while 
  99 
  per 
  

   cent 
  is 
  effective 
  in 
  warming 
  the 
  surface 
  of 
  Mars. 
  

  

  