﻿F. 
  W. 
  Very 
  — 
  Solar 
  Radiation. 
  

  

  629 
  

  

  The 
  result 
  is 
  still 
  affected 
  by 
  any 
  uncompensated 
  depletions 
  in 
  

   addition 
  to 
  those 
  considered. 
  Thus 
  the 
  lower 
  value 
  of 
  A 
  from 
  

   the 
  sea-level 
  measurement 
  is 
  cause.d 
  by 
  the 
  greater 
  infringe- 
  

   ment 
  of 
  dust 
  in 
  the 
  lower 
  air. 
  

  

  That 
  lower 
  values 
  of 
  solar 
  radiation 
  are 
  obtained 
  at 
  low- 
  

   level 
  stations 
  when 
  compared 
  with 
  mountain 
  observations 
  for 
  

   identical 
  air-masses 
  was 
  recognized 
  by 
  Langley, 
  who 
  found 
  

   when 
  he 
  computed 
  by 
  the 
  inadequate 
  secant 
  formula, 
  from 
  

   valley 
  observations 
  at 
  Lone 
  Pine, 
  California, 
  the 
  radiation 
  

   which 
  might 
  be 
  expected 
  at 
  his 
  " 
  Mountain 
  Camp 
  " 
  on 
  Mt. 
  

   Whitney, 
  and 
  compared 
  this 
  with 
  the 
  observed 
  value, 
  the 
  latter 
  

   exceeded 
  the 
  calculated 
  amount. 
  The 
  reason 
  for 
  this 
  may 
  be 
  

   evident 
  from 
  the 
  following 
  considerations 
  : 
  The 
  exponent 
  of 
  

  

  Fig. 
  3. 
  

  

  Fig. 
  3. 
  a 
  and 
  b 
  — 
  observing 
  stations, 
  c 
  = 
  outer 
  limit 
  of 
  air. 
  d 
  = 
  upper 
  

   limit 
  of 
  dust 
  envelope. 
  

  

  the 
  dust-coefficient 
  does 
  not 
  vary 
  according 
  to 
  the 
  total 
  air 
  

   mass. 
  At 
  a 
  certain 
  altitude, 
  in 
  itself 
  variable, 
  the 
  dust 
  disap- 
  

   pears 
  and 
  the 
  term 
  representing 
  the 
  dust 
  effect 
  must 
  drop 
  out 
  

   from 
  the 
  complete 
  formula. 
  The 
  condition 
  as 
  to 
  dust 
  is 
  shown 
  

   in 
  fig. 
  3, 
  where 
  the 
  more 
  elevated 
  of 
  two 
  stations, 
  a 
  and 
  5, 
  expe- 
  

   riences 
  but 
  a 
  small 
  fraction 
  of 
  the 
  depletion 
  of 
  radiation 
  by 
  

   dust 
  which 
  affects 
  the 
  lower 
  station, 
  although 
  the 
  air 
  masses 
  

   are 
  not 
  very 
  different. 
  

  

  In 
  my 
  paper 
  on 
  " 
  The 
  Solar 
  Constant," 
  * 
  I 
  have 
  treated 
  the 
  

   dust 
  depletion 
  separately 
  and 
  have 
  used 
  a 
  modified 
  air 
  mass 
  (e') 
  

   computed 
  by 
  Lambert's 
  formulaf 
  where 
  it 
  is 
  necessary 
  to 
  evai- 
  

  

  * 
  U. 
  S. 
  Weather 
  Bureau 
  Publication, 
  No. 
  254, 
  1901. 
  

  

  f 
  The 
  word 
  "kilometer" 
  (op. 
  cit., 
  p. 
  14, 
  1. 
  1) 
  should 
  be 
  erased. 
  The 
  five 
  

   is 
  an 
  approximate 
  numerical 
  ratio, 
  and 
  not 
  a 
  distance, 
  as 
  may 
  be 
  seen 
  from 
  

   the 
  derivation 
  of 
  the 
  formula, 
  for 
  which 
  consult 
  Ferrel, 
  " 
  Eecent 
  Advances 
  

   in 
  Meteorology," 
  Appendix 
  71, 
  p. 
  61. 
  Annual 
  Eeport 
  of 
  the 
  Chief 
  Signal 
  

   Officer, 
  1885, 
  War 
  Department, 
  U. 
  S. 
  A. 
  There 
  are 
  two 
  other 
  typographical 
  

   errors 
  in 
  W. 
  B. 
  No. 
  254: 
  The 
  expression 
  forp 
  on 
  p. 
  18 
  should 
  have 
  the 
  expo- 
  

   nent 
  m, 
  and 
  " 
  log" 
  should 
  precede 
  w 
  in 
  equation 
  (a) 
  p. 
  27. 
  In 
  the 
  footnote 
  

   to 
  my 
  " 
  Note 
  on 
  Atmospheric 
  Eadiation," 
  this 
  Journal 
  for 
  April, 
  1913 
  (p. 
  536), 
  

   the 
  exponent 
  of 
  10 
  should 
  be 
  —8, 
  instead 
  of 
  —4, 
  and 
  the 
  black-body 
  radi- 
  

   ations 
  should 
  be 
  371*1 
  and 
  136'3 
  (m. 
  k. 
  s.), 
  the 
  values 
  in 
  small 
  calories 
  re- 
  

   maining 
  unchanged. 
  The 
  same 
  error 
  in 
  the 
  exponent 
  occurs 
  in 
  Bigelow's 
  

   paper 
  in 
  the 
  March 
  number 
  of 
  the 
  Journal, 
  p. 
  258, 
  1. 
  9 
  from 
  bottom. 
  

  

  