Simplified Method of Tracing Rays

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Our purpose is not to treat the whole subject of geometrical Optics, but exclusively, or almost so, that part of it which is called by the short name of ray tracing. This is notoriously the most laborious part of the computer's patient work, and becomes, without question, a formidable task when he has to deal with skew rays and non-centred systems. The problem thus limited can be put shortly - Given the ray incident upon any system of lenses, mirrors, and prisms, find the emergent ray.