VARIOUS IMAGES. 



237 



is of a regular and mathematical form, the precise effect 

 which it will produce upon the rays, and the condition in 

 which they will enter the eye after reflection, can be cal- 

 culated, and the kind of image which will be formed ascer- 

 tained beforehand. Sometimes the image is diminished, 

 sometimes it is magnified ; sometimes it is multiplied, and 

 sometimes it is reversed. The latter takes place when the 

 rays are made to cross each other before they form the 

 image on the retina, as maybe illustrated by the image of a 

 candle formed upon a screen in a dark room, after the rays 

 cross each other in passing through a very small orifice. 



The effects produced by the reflection of light in mirrors 

 of various kinds, in respect to the conformation of the re- 



ENLAEGEMENT IN A CONCAVE MIEEOK. 



