CONTENTS. 



CHAPTER XXXII. 



SCIENCE OF THE NINETEENTH CENTURY. 



PAGB 



Difficulties of Contemporary History Discovery of Asteroids and 

 Minor Planets between Mars and Jupiter Dr. Olbers suggests 

 they may be fragments of a larger Planet Encke's Comet, and 

 the correction of the size of Jupiter and Mercury Biela's 

 Comet, noticed in 1826 It divides into two Comets in 1845 

 Irregular movements of Uranus Adams and Leverrier calcu- 

 late the position of an Unknown Planet Neptune found by 

 these calculations in 1846 A Survey of the whole Heavens 

 made by Sir John Herschel His work in Astronomy 

 Comets and Meteor-systems Use of improved Telescopes in 

 discovery Leverrier's analysis of Planetary Orbits . . 297 



CHAPTER XXXIII. 



SCIENCE OF THE NINETEENTH CENTURY (CONTINUED). 



Discoveries concerning Light made in the Nineteenth Century 

 Birth and History of Dr. Young He explains the Interference 

 of Light Cause of Prismatic Colours in a Shadow And in a 

 Soap-bubble Mains discovers the Polarization of Light caused 

 by Reflection Birth and History of Fresnel Polarization of 

 Light explained by Young and Fresnel Complex Vibrations 

 of a Ray of Light How these Waves are reduced to two 

 separate Planes in passing through Iceland -spar Sir David 

 Brewster and M. Biot explain the colours produced by Polar- 

 ization Fizeau and Foucault on Velocity of Light Colour 

 Theory of Young and Helmholtz . . . . . 315 



CHAPTER XXXIV. 



SCIENCE OF THE NINETEENTH CENTURY (CONTINUED). 



History of Spectrum Analysis Discovery of Heat-rays by Sir W. 

 Herschel And of Chemical Rays by Ritter of Jena Photo- 

 graphy first suggested by Davy and Wedgwood Carried out 

 by Daguerre and Talbot Dark Lines in the Spectrum first 



