LIGHT. 



Structure of the Eye. Manner in which distant Objects become Visible. Corpuscular Theory. 

 Undulatory Theory. Its general Reception. Velocity of Light. Account of its Discovery by 

 Hoemer. Measurement of the Waves of Light by Newton. Color produced by Waves of dif- 

 ferent Magnitudes. Magnitudes of Waves of different Color. Summary View of the Corpus- 

 cular Theory. Summary View of the Undulatory Theory. These Theories compared. Discov- 

 eries of Dr. Young. Discoveries of Mains, Arago, Poisson, Herschel, and Airy. Relations of 

 Light and Heat. 



