REFRACTION OF LIGHT. 159 



wards, sideways, anywhere within its sphere of 

 action ; they are all picked up and sent forward. 

 You thus see what a beautiful and important 

 invention is that of the parabolic reflector for 

 throwing forward the rays of light. 



Before I go further into the subject of reflec- 

 tion let me point out a further mode of dealing 

 with the direction of the light. For instance, 

 here is a candle, and I can employ the principle 

 of refraction to bend and direct the rays of 

 light, and if I want to increase the light in any 

 one direction, I must either take a reflector or 

 use the principle of refraction. I will place 

 this lens (fig. 56) in front of the candle and you 



Fig. 56. 



will easily see that by its means I can throw on 

 to that sheet of paper a great light, that is to 

 say, that instead of the light being thrown all 

 about, it is refracted and concentrated on to 

 that paper ; so here I have another means of 

 bending the light and sending it in one direc- 



