﻿EFFECTS 
  OF 
  SOLAR 
  RADIATION 
  — 
  O'BRIEN 
  

  

  119 
  

  

  The 
  antirachitic 
  effect 
  of 
  sunlight 
  for 
  the 
  several 
  conditions 
  of 
  

   ozone 
  and 
  air 
  mass 
  can 
  now 
  be 
  calculated 
  at 
  each 
  wave 
  length 
  by 
  

   multiplying 
  the 
  antirachitic 
  response 
  per 
  unit 
  energy 
  (fig. 
  5) 
  by 
  the 
  

   solar 
  energy 
  at 
  that 
  wave 
  length 
  (figs. 
  7 
  and 
  8). 
  This 
  has 
  been 
  done 
  

   and 
  the 
  product 
  at 
  each 
  wave 
  length 
  plotted 
  to 
  form 
  the 
  family 
  of 
  

   curves 
  in 
  figures 
  9 
  and 
  10. 
  For 
  each 
  condition 
  of 
  ozone 
  and 
  air 
  mass 
  

   the 
  solar 
  antirachitic 
  effect 
  is 
  represented 
  by 
  the 
  integral 
  of 
  the 
  

  

  Figube 
  6. 
  — 
  Distribution 
  of 
  energy 
  at 
  the 
  ultraviolet 
  end 
  of 
  the 
  solar 
  spectrum 
  at 
  

   sea 
  level 
  through 
  zenith 
  atmosphere 
  (air 
  mass=1.0). 
  

  

  relative 
  efficiency 
  as 
  a 
  function 
  of 
  wave 
  length. 
  This 
  is 
  represented 
  

   by 
  the 
  area 
  under 
  the 
  appropriate 
  curve 
  of 
  figure 
  9 
  or 
  figure 
  10. 
  The 
  

   functions 
  are 
  not 
  analytic, 
  so 
  the 
  integration 
  must 
  be 
  carried 
  out 
  by 
  

   graphical 
  or 
  mechanical 
  means, 
  but 
  this 
  is 
  easily 
  done 
  with 
  the 
  aid 
  

   of 
  a 
  planimeter. 
  The 
  results 
  of 
  this 
  integration 
  are 
  plotted 
  in 
  figure 
  

   11 
  in 
  which 
  the 
  antirachitic 
  efficiency 
  of 
  solar 
  radiation 
  is 
  shown 
  as 
  a 
  

   function 
  of 
  air 
  mass 
  for 
  2.0 
  and 
  2.8 
  millimeters 
  of 
  ozone 
  S. 
  T. 
  P. 
  in 
  

   the 
  atmosphere. 
  

  

  