312 THE COMING OF MAN 



As for the light we receive from it, who can ever 

 look at the sun when it is shining brightly in the sky? 

 Have you noticed how feeble and dull even the 

 brightest electric lights look in bright daylight? 



Now the heat and the light that come to us from 

 the sun are the very things upon which the whole 

 life of the world depends; yet what causes this light 

 and heat has been a study to many great men. 

 Wonderful inventions they have made, trying to 

 find out, if possible, what is in the light of the sun, 

 and much has been already learned about the 

 quality of that light, and about the sun from which 

 it comes. 



You know what a rainbow is, for you have been 

 taught at school. It is the beautiful, white light of 

 the sun divided into its seven principal parts by the 

 drops of falling rain. You can divide a sunbeam 

 into its seven rainbow colors yourself with a prism 

 of glass. 



What a simple-looking object a three-sided piece 

 of glass is, yet with that simple device men have 

 discovered a great thing, — that the white light of 

 the sun is made up of the seven brilliant colors that 

 we see in the rainbow. 



Men have discovered also by means of these 

 prisms of what the sun is composed, what makes 

 its heat and its light, and even which side of the 

 sun is turning toward us. They tell us that the sun 

 is an immense ball of burning gases, and what those 

 gases are. For by a combination of prisms they 

 spread out a beam of white light into a band of 

 colored light crossed by dark lines. This they call 



