﻿SOLAR 
  ENERGY 
  SPOEHR. 
  177 
  

  

  inadequate 
  and 
  insignificant 
  when 
  compared 
  with 
  the 
  primal 
  source 
  

   of 
  our 
  energy, 
  the 
  sun. 
  The 
  radiations 
  from 
  the 
  sun 
  constitute 
  

   our 
  main 
  source 
  of 
  energy. 
  This 
  is 
  our 
  main 
  and 
  most 
  consequen- 
  

   tial 
  import, 
  the 
  only 
  potent 
  factor 
  which 
  counteracts 
  the 
  tendency 
  

   of 
  complete 
  running 
  down. 
  It 
  is 
  important 
  not 
  only 
  in 
  such 
  reac- 
  

   tions 
  as 
  the 
  smelting 
  of 
  ores, 
  but 
  equally 
  to 
  the 
  life 
  on 
  the 
  planet. 
  

  

  All 
  living 
  things 
  on 
  the 
  earth 
  demand 
  for 
  their 
  maintenance 
  and 
  

   propagation 
  a 
  continuous 
  supply 
  of 
  energy. 
  The 
  immediate 
  source 
  

   of 
  this 
  energy 
  for 
  living 
  things 
  is 
  derived 
  from 
  food. 
  All 
  animals, 
  

   including 
  man, 
  are 
  fundamentally 
  dependent 
  upon 
  plants 
  for 
  their 
  

   food. 
  Just 
  as 
  the 
  herbivorous 
  land 
  animals 
  are 
  the 
  source 
  of 
  food 
  

   of 
  the 
  carnivora, 
  the 
  diatoms 
  are 
  the 
  fundamental 
  source 
  of 
  food 
  

   of 
  the 
  sea. 
  The 
  object 
  of 
  agriculture 
  is 
  essentially 
  to 
  provide 
  man 
  

   with 
  such 
  materials 
  from 
  which 
  he 
  is 
  able 
  to 
  derive 
  the 
  energy 
  nec- 
  

   essary 
  for 
  the 
  maintenance 
  of 
  his 
  bodily 
  activities, 
  his 
  growth 
  and 
  

   propagation. 
  

  

  MEANING 
  OF 
  " 
  PHOTOSYNTHESIS." 
  

  

  So 
  far 
  as 
  the 
  composition 
  of 
  food 
  material 
  is 
  concerned, 
  there 
  

   exists 
  a 
  closed 
  cycle. 
  Man 
  feeds 
  on 
  animals, 
  and 
  animals 
  on 
  plants 
  ; 
  

   the 
  plants 
  feed 
  on 
  the 
  carbon 
  dioxide 
  given 
  to 
  the 
  air 
  by 
  the 
  animals 
  

   as 
  a 
  result 
  of 
  the 
  latter's 
  use 
  of 
  food. 
  Thus 
  the 
  plant 
  reconverts 
  

   the 
  waste 
  products 
  of 
  animal 
  metabolism 
  into 
  food. 
  The 
  latter 
  

   process 
  is 
  called 
  photosynthesis. 
  The 
  plant 
  absorbs 
  through 
  its 
  

   leaves 
  the 
  carbon 
  dioxide 
  which 
  is 
  universally 
  present 
  in 
  the 
  atmos- 
  

   phere, 
  and 
  which 
  is 
  formed 
  by 
  the 
  burning 
  of 
  coal, 
  fuel 
  oil, 
  etc., 
  

   and 
  is 
  also 
  exhaled 
  by 
  animals. 
  By 
  means 
  of 
  the 
  light 
  from 
  the 
  

   sun 
  the 
  carbon 
  dioxide 
  thus 
  absorbed 
  by 
  the 
  leaves 
  is 
  changed 
  into 
  

   material 
  such 
  as 
  sugar 
  or 
  wood, 
  which 
  can 
  again 
  be 
  used 
  as 
  food 
  

   for 
  animals 
  or 
  as 
  fuel. 
  The 
  net 
  result, 
  as 
  far 
  as 
  the 
  changes 
  of 
  mate- 
  

   rials 
  are 
  concerned 
  in 
  this 
  interrelation 
  of 
  plants 
  and 
  animals, 
  is 
  nil. 
  

   Thus, 
  in 
  brief, 
  a 
  plant 
  yields 
  a 
  certain 
  amount 
  of 
  substance 
  which 
  

   can 
  be 
  used 
  as 
  food. 
  The 
  food 
  is 
  consumed 
  by 
  man 
  and 
  thus 
  enables 
  

   him 
  to 
  do 
  some 
  work. 
  Thereby 
  the 
  food 
  material 
  is 
  burned 
  in 
  the 
  

   body 
  and 
  is 
  exhaled 
  as 
  the 
  gas, 
  carbon 
  dioxide. 
  Or 
  the 
  fuel 
  is 
  

   burned 
  and 
  the 
  products 
  of 
  combustion 
  escape 
  into 
  the 
  atmosphere. 
  

  

  The 
  fundamentally 
  important 
  point 
  is 
  in 
  relation 
  to 
  the 
  energy 
  

   changes. 
  The 
  energy 
  expended 
  by 
  the 
  man 
  has 
  been 
  permanently 
  

   lost 
  to 
  a 
  large 
  extent; 
  similarly, 
  that 
  obtained 
  from 
  fuel. 
  The 
  

   reconversion 
  of 
  the 
  carbon 
  dioxide 
  into 
  food 
  or 
  fuel 
  material 
  can 
  

   be 
  accomplished 
  only 
  by 
  the 
  use 
  of 
  a 
  great 
  deal 
  of 
  energy. 
  The 
  

   cycle 
  is 
  made 
  possible 
  only 
  by 
  the 
  introduction 
  of 
  energy 
  from 
  

   without. 
  This 
  energy 
  is 
  derived 
  from 
  the 
  sunlight, 
  which 
  the 
  plant, 
  

   unlike 
  the 
  animal, 
  is 
  able 
  to 
  utilize 
  and 
  convert 
  the 
  waste 
  carbon 
  

   dioxide 
  again 
  into 
  food 
  or 
  fuel 
  material. 
  

  

  