CONTENTS. 



PA OB 



8. The idea of the undulatory theory entertained by Descartes, 

 Hooke, and others The honour of having reduced the hypothesis 

 to a definite shape attributable to Huygens Dr. Young's mechani- 

 cal reasoning thereon. 9. Malus discovers the polarization of light 

 by reflection The theory greatly extended by Fresnel, Arago, 

 Poisson, Herschel, and others. 10. Relation of light and heat 

 Herschel's discovery apparently establishing the independence of 

 the heating and illuminating effects of the solar rays Berard's 

 experiments. 11. Bodies luminous and non-luminous. 12. Trans- 

 parency and opacity 193 



