﻿REPORT 
  OF 
  THE 
  SECRETARY. 
  105 
  

  

  the 
  director, 
  prepared 
  the 
  sensitive 
  parts 
  of 
  a 
  galvanometer 
  and 
  

   a 
  vacuum 
  bolometer 
  of 
  usual 
  types 
  for 
  solar 
  work, 
  and 
  also 
  of 
  a 
  

   vacuum 
  galvanometer 
  and 
  vacuum 
  bolometer 
  of 
  very 
  unusual 
  design 
  

   suited 
  to 
  observing 
  the 
  energy 
  distribution 
  in 
  the 
  spectra 
  of 
  the 
  

   stars. 
  These 
  extremely 
  delicate 
  and 
  sensitive 
  instruments 
  required 
  

   extraordinary 
  skill 
  and 
  patience 
  for 
  their 
  construction 
  and 
  testing. 
  

   Acknowledgments 
  are 
  due 
  the 
  Director 
  of 
  the 
  Bureau 
  of 
  Standards, 
  

   the 
  Director 
  of 
  the 
  Nela 
  Research 
  Laboratory, 
  and 
  also 
  Dr. 
  Elihu 
  

   Thomson, 
  of 
  Lynn, 
  for 
  aiding 
  these 
  preparations. 
  

  

  The 
  instrument 
  making 
  for 
  these 
  new 
  pieces 
  and 
  others 
  required 
  

   in 
  the 
  expedition 
  to 
  Mount 
  Wilson, 
  including 
  a 
  special 
  spectrometer, 
  

   plate 
  carrier, 
  and 
  other 
  apparatus, 
  was 
  done 
  by 
  the 
  instrument 
  

   maker, 
  Mr. 
  A. 
  Kramer. 
  

  

  A 
  great 
  many 
  of 
  the 
  " 
  solar 
  constant 
  " 
  observations 
  made 
  at 
  Mount 
  

   Harqua 
  Hala, 
  Ariz., 
  were 
  reduced 
  by 
  Mr. 
  Fowle 
  and 
  Mrs. 
  Bond 
  in 
  

   consultation 
  with 
  the 
  director. 
  Despite 
  our 
  long 
  experience 
  in 
  

   solar-radiation 
  work, 
  new 
  problems 
  and 
  difficulties 
  still 
  crop 
  up. 
  

   The 
  publication 
  of 
  the 
  Mount 
  Harqua 
  Hala 
  results 
  has 
  hitherto 
  been 
  

   withheld 
  so 
  that 
  a 
  comprehensive 
  discussion 
  of 
  them 
  might 
  be 
  made 
  

   to 
  reveal 
  and 
  correct 
  any 
  systematic 
  errors. 
  

  

  Expedition 
  to 
  Chile. 
  — 
  It 
  became 
  necessary 
  for 
  the 
  director 
  to 
  un- 
  

   dertake 
  a 
  visit 
  to 
  Chile 
  to 
  inspect 
  the 
  observing 
  station 
  at 
  Monte- 
  

   zuma 
  maintained 
  by 
  the 
  Hodgkins 
  fund 
  for 
  the 
  study 
  of 
  the 
  solar 
  

   variations, 
  in 
  cooperation 
  with 
  the 
  stations 
  in 
  California 
  and 
  Ari- 
  

   zona. 
  Leaving 
  Washington 
  near 
  the 
  end 
  of 
  October, 
  1921, 
  he 
  spent 
  

   the 
  month, 
  November 
  15 
  to 
  December 
  15, 
  at 
  the 
  station 
  and 
  returned 
  

   to 
  Washington 
  early 
  in 
  January, 
  1922. 
  During 
  the 
  month 
  at 
  Mon- 
  

   tezuma 
  he 
  revised 
  all 
  the 
  adjustments 
  of 
  apparatus 
  and 
  some 
  of 
  the 
  

   methods 
  employed 
  there, 
  besides 
  assisting 
  in 
  the 
  daily 
  observations 
  

   and 
  reductions 
  on 
  26 
  daj^s. 
  Silver 
  disk 
  pyrheliometer 
  S. 
  I. 
  No. 
  5, 
  

   loaned 
  by 
  the 
  Department 
  of 
  Agriculture 
  for 
  the 
  purpose, 
  was 
  com- 
  

   pared 
  with 
  instruments 
  at 
  Montezuma, 
  and 
  before 
  and 
  afterwards 
  

   with 
  instruments 
  at 
  Washington. 
  No 
  change 
  in 
  the 
  scale 
  of 
  pyr- 
  

   heliometry 
  was 
  disclosed 
  by 
  these 
  comparisons. 
  

  

  Expedition 
  to 
  Mount 
  Wilson. 
  — 
  In 
  June 
  an 
  expedition, 
  including 
  

   the 
  director 
  and 
  Mr. 
  L. 
  B. 
  Aldrich, 
  went 
  out 
  to 
  Mount 
  Wilson. 
  

   Four 
  objects 
  were 
  in 
  view. 
  First, 
  to 
  inspect 
  the 
  station 
  at 
  Mount 
  

   Harqua 
  Hala 
  and 
  compare 
  pyrheliometers 
  there 
  with 
  silver 
  disk 
  

   pyrheliometer 
  S. 
  I. 
  No. 
  5, 
  above 
  mentioned, 
  so 
  as 
  to 
  connect 
  the 
  

   fundamental 
  scales 
  of 
  pyrheliometry 
  in 
  Arizona 
  and 
  Chile. 
  Second, 
  

   to 
  repeat 
  with 
  all 
  possible 
  precautions 
  and 
  variations 
  of 
  method 
  the 
  

   determination 
  of 
  the 
  form 
  of 
  the 
  solar 
  spectrum 
  energy 
  curve 
  out- 
  

   side 
  the 
  atmosphere*. 
  Third, 
  to 
  undertake 
  preliminary 
  measurements 
  

   of 
  the 
  distribution 
  of 
  energy 
  in 
  the 
  spectra 
  of 
  the 
  brighter 
  stars. 
  

  

  