118 THE SEASON WHY. 



'As in water face answereth to face, so the heart of man to man." 

 PEOVESBS xxvn. 



Because its atoms are so arranged that they .allow the vibrations 

 of light to continue through their substance. 



507. Does glass obstruct the passage of any portion of 

 light / 



Glass reflects (sends back) a very small portion of light. This 

 may be observed by holding a piece of paper, or a hand, a few inches 

 from a window, when a faint reflection of it will be visible. 

 Probably the small amount of light reflected by transparent glass, 

 which gives a passage to the greater part of the rays, may serve 

 to illustrate the small amount of light reflected from black surfaces, 

 which absorbs the greater portion of light. 



Instead of a piece of white paper, hold a piece of black cloth two or three 

 inches from the window-pane, and you will have two reflections so weak that the 

 image of the cloth will be almost lost. The first reflection is that of the very 

 small amount of light from the black surface on to the glass, and the second 

 reflection is that of the inconceivably small amount returned by the glass, and 

 by which the faint image of the black cloth is produced. But put the black 

 cloth outside of the window-pane, and then hold an object before them, 

 and you will find that the two weak reflectors, acting together, produce an 

 improved image, or reflection. 



508. Why, if a book is held between a candle-light and the 

 wall, does a shadow fall upon the wall ? 



Because the rays of light are intercepted by the book. 



509. Why do the rays pass over the edges of the book in 

 a direct line with the flame of the candle? 



Because light always travels in straight lines. 



510. Why is there some amount of light even where 

 shadows fall? 



Because, as all objects reflect light, some of them throw their 

 light into the field of the shadow. 



511. Why are some substances opaque to light ? 



Because the arrangement of their particles will not admit of the 

 vibrations of the luminous ether passing through them. 

 Opaque impervious to rays of light. 



512. Why do we see our faces reflected in mirrors? 



