THE SCIENCE OF OPTICS. 239 



engraving, where the drawing on the card below, which 

 would seem to be a wholly unmeaning scrawl, is brought, 

 by reflection in a cylindrical mirror, into a very significant 

 image. 



The study of the effects produced by the reflection of 

 light from the various geometrical surfaces forms a branch 

 of mathematical science of a very difficult and complicated 

 character. 



