﻿REPORT 
  OF 
  THE 
  SECRETARY 
  99 
  

  

  elude 
  a 
  number 
  of 
  silver-disk 
  pyrheliometers, 
  prepared 
  at 
  the 
  expense 
  

   of 
  the 
  private 
  funds 
  of 
  the 
  Institution, 
  but 
  standardized 
  against 
  the 
  

   standard 
  instruments 
  of 
  the 
  Astrophysical 
  Observatory, 
  and 
  sold 
  at 
  

   cost 
  to 
  research 
  institutions 
  of 
  various 
  lands. 
  

  

  Mr. 
  Aldrich 
  has 
  assumed 
  charge 
  of 
  the 
  instrument 
  making 
  and 
  

   standardizing. 
  He 
  has 
  also 
  continued 
  work 
  on 
  the 
  fruitful 
  investi- 
  

   gation 
  of 
  the 
  radiation 
  and 
  cooling 
  of 
  the 
  human 
  body, 
  referred 
  to 
  

   last 
  year. 
  In 
  addition 
  he 
  has 
  assisted 
  in 
  reducing 
  solar-constant 
  ob- 
  

   servations, 
  and 
  has 
  attended 
  to 
  the 
  considerable 
  correspondence 
  on 
  

   physical 
  and 
  astronomical 
  matters. 
  

  

  FIELD 
  WORK 
  

  

  {a) 
  At 
  Mount 
  Wilson, 
  Calif. 
  — 
  Doctor 
  Abbot 
  spent 
  the 
  months 
  of 
  

   July, 
  August, 
  and 
  part 
  of 
  September, 
  1928, 
  at 
  Mount 
  Wilson, 
  Calif., 
  

   where 
  he 
  was 
  assisted 
  by 
  Mr. 
  Freeman. 
  Besides 
  improving 
  the 
  solar 
  

   cooker 
  to 
  greatly 
  increased 
  efficiency, 
  two 
  considerable 
  researches 
  

   were 
  carried 
  through. 
  The 
  first 
  of 
  these 
  is 
  the 
  repetition 
  of 
  the 
  

   bolometric 
  determination 
  of 
  positions 
  of 
  solar 
  and 
  terrestrial 
  absorp- 
  

   tion 
  lines 
  and 
  bands 
  in 
  the 
  infra-red 
  solar 
  spectrum. 
  This 
  had 
  

   formed 
  the 
  main 
  subject 
  of 
  Volume 
  I 
  of 
  the 
  Annals 
  of 
  the 
  Astro- 
  

   physical 
  Observatory. 
  As 
  photography 
  has 
  not 
  as 
  yet 
  reached 
  far 
  

   beyond 
  the 
  extreme 
  red 
  of 
  the 
  spectrum, 
  the 
  best 
  means 
  of 
  observing 
  

   these 
  interesting 
  lines 
  and 
  bands 
  of 
  the 
  infra-red 
  lies 
  in 
  measuring 
  

   the 
  cooling 
  which 
  attends 
  them. 
  For 
  this 
  purpose 
  a 
  well-dispersed 
  

   spectrum 
  is 
  caused 
  to 
  march 
  slowly 
  over 
  a 
  sensitive 
  linear 
  bolometer 
  

   strip, 
  and 
  a 
  continuous 
  curve 
  indicating 
  its 
  temperature 
  is 
  auto- 
  

   matically 
  recorded. 
  As 
  the 
  bolometer 
  strip 
  falls 
  into 
  each 
  successive 
  

   one 
  of 
  the 
  lines 
  of 
  the 
  spectrum, 
  a 
  nick 
  comes 
  in 
  the 
  curve. 
  

  

  Three 
  approximately 
  60° 
  flint-glass 
  prisms 
  in 
  tandem 
  were 
  used 
  to 
  

   disperse 
  the 
  solar 
  rays, 
  and 
  long-focus 
  mirrors 
  to 
  colli 
  mate 
  and 
  focus 
  

   the 
  spectrum. 
  Five 
  photographic 
  plates, 
  each 
  60 
  centimeters 
  long, 
  

   were 
  required 
  to 
  cover 
  the 
  spectrum 
  from 
  "A" 
  in 
  the 
  red 
  to 
  " 
  Q, 
  " 
  

   in 
  the 
  infra-red. 
  Mr. 
  Freeman 
  did 
  most 
  of 
  the 
  final 
  observing, 
  and 
  

   also 
  measured 
  the 
  plates. 
  Over 
  1,200 
  lines 
  and 
  bands 
  of 
  absorption 
  

   were 
  discovered, 
  where 
  only 
  about 
  550 
  had 
  been 
  found 
  in 
  the 
  earlier 
  

   investigation 
  published 
  in 
  1900. 
  A 
  paper 
  on 
  this 
  new 
  work 
  has 
  been 
  

   published 
  as 
  volume 
  82, 
  No. 
  1, 
  of 
  the 
  Smithsonian 
  Miscellaneous 
  

   Collections. 
  

  

  The 
  other 
  research 
  carried 
  through 
  was 
  the 
  observation 
  of 
  the 
  

   distribution 
  of 
  energy 
  in 
  the 
  spectra 
  of 
  18 
  stars 
  and 
  of 
  the 
  planets 
  

   Mars 
  and 
  Jupiter. 
  This 
  was 
  accomplished 
  by 
  Doctor 
  Abbot 
  with 
  

   the 
  aid 
  of 
  Doctor 
  Adams, 
  of 
  Mount 
  Wilson 
  Observatory, 
  employing 
  

   the 
  100-inch 
  telescope 
  and 
  a 
  sensitive 
  radiometer. 
  

  

  Greatly 
  increased 
  sensitiveness 
  had 
  been 
  hoped 
  for 
  by 
  substituting 
  

   hydrogen 
  for 
  air, 
  and 
  an 
  excessively 
  light 
  and 
  small 
  radiometer 
  

   82322—30 
  8 
  

  

  