Chap. 3 .] [ 185 ] 



CHAP. HI. 



GENERAL VIEW OF THE PHENOMENA 

 OF REFLEXION. 



Opale Bodies do not reflet! the Whole of the Light that falls on them. 

 Law of Reflexion.; Reflexion from plane Surfaces. Reflexionfrcm 

 convex Surfaces.- From concave Surfaces. Phenomena of Reflexion 

 ' from plane Mirrors explained. r-From convex Mirrors. From con- 

 cave Mirrors. -^-Prominent Image from a concave Mirror .f^-The 

 cylindrical Mirror^ T/ie Rectification of diftorted Figures by this 

 Mirror. The conical Mirror. 



IT has been already intimated that the rays of light, 

 which proceed from any luminous body, move al- 

 ways in ftrait lines, unlefs this direction or motion 

 is changed by certain circumftances, and thefe are re- 

 flection, refraction, and inflexion. Of the firft of thefe 

 it will be proper to treat in this chapter, becaufe by 

 purfujng the fubject in this order, it will I conceive be 

 more eafily comprehended by the unfcientific reader. 



A common paftime of children with a piece of glafs 

 oppofed to the fun, and cafting by means of it a vivid 

 ipot of light in various places at will, proves that the 

 rays of light may be reflected by certain bodies ; and 

 more accurate obfervation will convince us, that every- 

 body that is not luminous in itfelf is made vifible to 

 qur fenfe by reflected light. 



We are not to fuppofe, however, that every opal^e 

 body reflects the whole of the light which falls upon 

 it. On the contrary, it is only a limited portion which 

 is regularly reflected according to the known law of 

 reflexion ; .another portion may be confidered as ab- 

 forbed by the body, or as rendered latent by feme 



caufe. 



