238 FORMATION OF IMAGES. 



fleeting surface, are very surprising and very beautiful. 

 They are all, however, the subjects of very exact, though 

 quite intricate mathematical calculations. If the mirror is 

 convex, it gives a diminished image of the object, as you 

 see when looking at your face in the back of the bowl of a 

 bright silver spoon. If concave, an enlarged image when 

 the object is held near, but a diminutive one if held at a 

 greater distance, as may be observed in the inside of the 

 bowl of the spoon. 



If the mirror is cylindrical or conical, the image is very 

 curiously distorted ; but the distortion is all subject to ex- 

 act calculation, which is so certain in its character that the 

 reverse effect can be produced by calculating and drawing 

 a distorted picture such that when reflected it shall conie 

 true. 



Toys are often made on this principle, as shown in the 



