250 



SCIENCE OF COMMON THINGS. 



When are shadows large, and when small ? 



enough from the dark street to enable us to see 

 into ^t. 



1657 Why do we often see the fire reflected in our windows in winter- 

 time f 



Because glass is a good reflector, and the rays of the 

 fire (striking against the window-glass) are reflected 

 back into the room again. 



1058 If the shadow of an object be thrown on a wall, the closer the object 



is held to the candle, the larger 

 ,.---|I will be its shadow : why is thisf 



,,/"'' Because the rays of 



light diverge (from the 

 flame of a candle) in 

 straight lines, like lines 

 drawn from the centre 

 of a circle. 



Here the arrow A, held close 

 to the candle, will cast the 

 shadow B F on a wall ; while 

 ~^\, V the same arrow, held at C, 

 "x would cast only the little sha- 



*.* dowDE - 



1659 How do we judge of the position, distance, and size of an object f 



We judge of the position and distance and size of an 

 object by the relative direction of lines drawn from the 

 object to the eye, and by the angle which the intersec- 

 tion of these lines makes with the eye. This angle is 

 called the angle of vision. 



""" > 



"~ti 



Fig, 50. 



The student will bear in mind that an angle is simply the inclination 

 of two lines without any regard to their length. Thus, in Fig. 59, the 

 inclination of the lines, caused by rays of light proceeding from A and B, 



