CHAPTER XIV 



HEAT AND LIGHT AS COMPANIONS 



<JThe night has a thousand eyes, 

 ~ And the day but one^. 

 Yet the light of the bright world dies 

 With the dying sun." 



136. Most bodies which glow and give out light are hot ; the 

 stove which glows with a warm red is hot and fiery ; smolder- 

 ing wood is black and lifeless; glowing coals are far hotter 

 than black ones. The stained-glass window softens and mel- 

 lows the bright light of the sun, but it also shuts out some 

 of the warmth of the sun's rays ; the shady side of the street 

 spares our eyes the intense glare of the sun, but may chill us 

 by the absence of heat. Our illumination, whether it be oil 

 lamp or gas jet or electric light, carries with it heat ; indeed,, 

 so much heat that we refrain from making a light on a warm 

 summer's night because of the heat which it unavoidably fur- 

 nishes. 



137. Red a Warm Color. We have seen that heat and 

 light usually go hand in hand. In summer we lower the 

 shades and close the blinds in order to keep the house cool, 

 because the exclusion of light means the exclusion of some 

 heat ; in winter we open the blinds and raise the shades in 

 order that the sun may stream into the room and flood it with 

 light and warmth. The heat of the sun and the light of the 

 sun seem boon companions. 



We can show that when light passes through a prism and 

 is refracted, forming a spectrum, as in Section 127, it is accom- 



142 



