CHAPTER VII 



LIGHT AND HEAT 



The ancients worshipped the sun as the source and giver 

 of all good things. And so it is, for without its creating 

 and sustaining energy this world would be a dead and 

 tenantless globe, without sunshine and shower or any 

 green and living thiug. The energy of the sun's rays is 

 manifested to us under two forms : 



1. Light. 



2. Heat. 



The sun is always pouring into space streams of energy. 

 These are transmitted as movements or undulations of 

 the ether, a medium which is supposed to fill all space and 

 penetrate all matter. The vibrations or undulations set 

 up by the sun in the ether travel with incredible speed — 

 186,000 miles per second — ^and in less than nine minutes 

 ^traverse the vast distance (over 90,000,000 miles) which 

 separates the sun and the earth. Light itself is invisible ; 

 it is a sensation or form of consciousness produced in the 

 brain by certain rays when they strike upon the sensitive 

 nerves of the eye. Heat, on the other hand, is produced 

 whenever the rays falling upon a material body are 

 absorbed. What is really absorbed in this case is energy, 

 and the rise in temperature is due to the increase of 

 energy thus received. Since light, then, is a mode of 

 consciousness, sunshine is only light to those that 

 see. Plants cannot see. So far as they are concerned, 

 the world is always in darkness, and what, in the day- 

 time, is streaming upon the vegetation is not light, but 

 energy. 



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