﻿APPENDIX 
  7 
  

   KEPORT 
  ON 
  THE 
  ASTROPHYSICAL 
  OBSERVATORY 
  

  

  Sir 
  : 
  I 
  have 
  the 
  honor 
  to 
  submit 
  the 
  following 
  report 
  on 
  the 
  activi- 
  

   ties 
  of 
  the 
  Astrophj^sical 
  Observatory 
  for 
  the 
  fiscal 
  year 
  ended 
  June 
  

   30, 
  1929 
  : 
  

  

  PLANT 
  AND 
  OBJECTS 
  

  

  This 
  observatory 
  operates 
  regularly 
  the 
  central 
  station 
  at 
  Wash- 
  

   ington 
  and 
  two 
  field 
  stations 
  for 
  observing 
  solar 
  radiation 
  on 
  Table 
  

   Mountain, 
  Calif., 
  and 
  Mount 
  Montezuma, 
  Chile. 
  By 
  arrangement 
  

   with 
  the 
  National 
  Geographic 
  Society, 
  the 
  director 
  of 
  the 
  observatory 
  

   has 
  charge 
  of 
  the 
  cooperating 
  solar 
  radiation 
  station 
  of 
  the 
  society 
  

   on 
  Mount 
  Brukkaros, 
  South 
  West 
  Africa. 
  In 
  addition, 
  the 
  observa- 
  

   tory 
  controls 
  a 
  station 
  on 
  Mount 
  Wilson, 
  Calif., 
  where 
  occasional 
  

   expeditions 
  are 
  sent 
  for 
  special 
  investigations. 
  

  

  The 
  principal 
  aim 
  of 
  the 
  observatory 
  is 
  the 
  exact 
  measurement 
  of 
  

   the 
  intensity 
  of 
  the 
  radiation 
  of 
  the 
  sun 
  as 
  it 
  is 
  at 
  mean 
  solar 
  distance 
  

   outside 
  the 
  earth's 
  atmosphere. 
  This 
  is 
  ordinarily 
  called 
  the 
  solar 
  

   constant 
  of 
  radiation, 
  but 
  the 
  observations 
  of 
  past 
  years 
  by 
  this 
  

   observatory 
  have 
  proved 
  it 
  variable. 
  As 
  all 
  life 
  as 
  well 
  as 
  the 
  weather 
  

   depends 
  on 
  solar 
  radiation, 
  the 
  observatory 
  has 
  undertaken 
  the 
  con- 
  

   tinued 
  measurement 
  of 
  solar 
  variation 
  on 
  all 
  available 
  days. 
  These 
  

   measurements 
  have 
  now 
  continued 
  all 
  the 
  year 
  round 
  for 
  11 
  years, 
  

   but 
  should 
  continue 
  at 
  least 
  11 
  years 
  more 
  to 
  cover 
  the 
  Hale 
  22.6-year 
  

   solar 
  cycle. 
  In 
  addition 
  to 
  this 
  principal 
  object, 
  the 
  observatory 
  

   undertakes 
  spectroscopic 
  researches 
  on 
  radiation 
  and 
  absorption 
  of 
  

   atmospheric 
  constituents, 
  radiation 
  of 
  special 
  substances 
  such 
  as 
  

   water 
  vapor, 
  ozone, 
  carbonic-acid 
  gas, 
  liquid 
  water 
  and 
  others, 
  and 
  

   the 
  radiation 
  of 
  the 
  other 
  stars 
  as 
  well 
  as 
  of 
  the 
  sun. 
  

  

  WORK 
  AT 
  WASHINGTON 
  

  

  Continuous 
  series 
  of 
  solar 
  observations 
  having 
  been 
  made 
  as 
  

   hitherto 
  at 
  several 
  field 
  stations 
  on 
  desert 
  mountains 
  in 
  distant 
  lands, 
  

   these 
  observations 
  have 
  been 
  critically 
  studied 
  and 
  prepared 
  for 
  

   publication 
  at 
  Washington. 
  Several 
  new 
  investigations 
  based 
  on 
  

   these 
  observations 
  have 
  been 
  made 
  and 
  published 
  and 
  we 
  have 
  carried 
  

  

  93 
  

  

  