﻿SOLAR 
  ENERGY 
  SPOEHR. 
  181 
  

  

  POSSIBILITIES 
  OF 
  PHOTOSYNTHESIS. 
  

  

  In 
  considering 
  the 
  sun 
  as 
  a 
  source 
  of 
  energy 
  two 
  possibilities 
  sug- 
  

   gest 
  themselves. 
  The 
  first 
  is 
  a 
  direct 
  utilization 
  of 
  solar 
  energy 
  

   through 
  some 
  device 
  by 
  means 
  of 
  which 
  the 
  energy 
  could 
  be 
  trans- 
  

   formed 
  and 
  stored; 
  the 
  other 
  is 
  by 
  means 
  of 
  the 
  natural 
  process 
  of 
  

   photosynthesis. 
  Disregarding 
  as 
  inadequate 
  those 
  arrangements 
  

   that 
  transform 
  solar 
  energy 
  into 
  heat 
  and 
  attempt 
  to 
  use 
  boilers 
  of 
  

   various 
  kinds, 
  no 
  advance 
  has 
  been 
  made 
  in 
  the 
  direct 
  utilization 
  of 
  

   solar 
  energy. 
  A 
  transformation 
  of 
  the 
  energy 
  based 
  upon 
  chemical 
  

   methods 
  has 
  received 
  little 
  attention. 
  The 
  reason 
  for 
  this 
  is 
  that 
  

   such 
  known 
  photochemical 
  reactions 
  as 
  are 
  endothermal 
  — 
  that 
  is, 
  

   processes 
  in 
  which 
  energy 
  is 
  stored 
  — 
  are 
  not 
  of 
  a 
  nature 
  to 
  encourage 
  

   development. 
  The 
  process 
  of 
  photosynthesis 
  in 
  the 
  green 
  plant 
  is 
  

   such 
  a 
  transformation 
  and 
  storing 
  of 
  energy. 
  Nature 
  has 
  worked 
  

   out 
  this 
  problem 
  and 
  has 
  done 
  it 
  in 
  a 
  most 
  remarkable 
  manner. 
  

  

  We 
  are 
  therefore 
  still 
  centering 
  our 
  speculations 
  on 
  the 
  plant 
  as 
  a 
  

   transformer 
  of 
  energy 
  through 
  the 
  production 
  of 
  carbohydrate 
  mate- 
  

   rial. 
  With 
  complete 
  disregard 
  of 
  biological 
  facts, 
  chemists 
  have 
  

   continued 
  to 
  develop 
  schemes 
  for 
  the 
  employment 
  of 
  the 
  photosyn- 
  

   thetic 
  process 
  and 
  to 
  evolve 
  theories 
  of 
  the 
  chemistry 
  of 
  photosyn- 
  

   thesis. 
  One 
  of 
  the 
  fundamental 
  fallacies 
  in 
  these 
  speculations 
  may 
  

   be 
  indicated 
  by 
  a 
  quotation 
  from 
  a 
  recent 
  technical 
  article 
  : 
  " 
  Photo- 
  

   synthesis 
  is 
  simply 
  a 
  manufacture 
  that 
  provides 
  material 
  used 
  in 
  the 
  

   process 
  of 
  living." 
  It 
  is 
  falsely 
  conceived 
  that 
  this 
  process 
  of 
  manu- 
  

   facture 
  is 
  not 
  a 
  function 
  of 
  the 
  living 
  plant. 
  

  

  There 
  have 
  also 
  been 
  many 
  erroneous 
  and 
  misleading 
  statements 
  

   regarding 
  the 
  amount 
  of 
  energy 
  radiated 
  from 
  the 
  sun 
  which 
  reaches 
  

   the 
  surface 
  of 
  the 
  earth. 
  In 
  nearly 
  all 
  the 
  technical 
  discussions 
  on 
  

   this 
  subject 
  that 
  have 
  appeared 
  recently 
  the 
  calculations 
  are 
  based 
  

   upon 
  the 
  value 
  of 
  3 
  calories 
  per 
  square 
  centimeter 
  per 
  minute. 
  Now, 
  

   this 
  value 
  does 
  not 
  represent 
  the 
  amount 
  of 
  energy 
  which 
  reaches 
  the 
  

   earth. 
  It 
  is 
  the 
  old 
  value 
  of 
  the 
  solar 
  constant 
  ; 
  i. 
  e., 
  the 
  amount 
  of 
  

   solar 
  energy 
  at 
  the 
  outside 
  of 
  the 
  earth's 
  atmosphere. 
  

  

  The 
  true 
  value 
  of 
  this 
  solar 
  constant 
  is 
  still 
  a 
  subject 
  of 
  some 
  

   dispute, 
  and 
  it 
  is 
  in 
  fact 
  of 
  secondary 
  interest 
  to 
  the 
  immediate 
  prob- 
  

   lem 
  of 
  the 
  utilization 
  of 
  solar 
  energy 
  on 
  the 
  earth. 
  A 
  great 
  many 
  

   determinations 
  of 
  the 
  amount 
  of 
  energy 
  received 
  on 
  the 
  earth 
  have 
  

   been 
  made, 
  and 
  it 
  is 
  certain 
  that 
  a 
  very 
  considerable 
  amount 
  of 
  solar 
  

   radiation 
  is 
  absorbed 
  in 
  the 
  atmosphere 
  of 
  the 
  earth. 
  For 
  the 
  present 
  

   purpose 
  the 
  intensity 
  of 
  solar 
  radiation 
  reaching 
  the 
  earth 
  can 
  be 
  

   placed 
  at 
  1.5 
  calories 
  per 
  square 
  centimeter 
  per 
  minute. 
  On 
  this 
  basis 
  

   we 
  would 
  receive 
  5,400 
  large 
  calories 
  per 
  square 
  meter 
  during 
  six 
  

   hours. 
  Now, 
  1 
  kilogram 
  of 
  coal 
  when 
  burned 
  develops 
  about 
  8,000 
  

  

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