336 COLORIFICAT10N IN GENERAL, 



from a luminous body. 3. A body which is* 

 transparent, or affords a passage for the rays of 

 light, is called a medium. 4. Rays of color, 

 which coming from a point, continually sepa- 

 rate as they proceed, are called diverging rays. 

 5. Rays which tend to a common point, are" 

 called converging rays. The divergency or 

 couvergency of rays, is measured by the angle 

 contained between the lines, which the rays 

 describe. 6. Rays are parallel, when the lines 

 which they describe, are parallel. 7. A beam 

 of color, is a body of parallel rays : a pencil of 

 rays, is a body of diverging or converging rays. 

 8, The point from which diverging rays pro-* 

 ceed, is called the radiant point ; that to which 

 converging rays are directed, is called the focus. 

 9. A ray bent from a straight course in the 

 same medium, is said to be inflected. 



Laws of refraction, or the rules which diffe- 

 rent rays of color obey, when they pass through 

 different media. 



1. A ray of light, bent from a straight course, 

 by passing out of one medium into another, is 

 said to be refracted. 



2. The angle of incidence, is that which is 

 contained between the lines described by the 

 incident ray, and a line perpendicular to the 

 surface on which the ray strikes, raised from 

 the point of incidence. 



3. The angle of refraction, is that which is 



