CONTENTS. 



PAGB 



Irregular movements of Uranus — Adams and Leverrier calculate 

 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 287 



CHAPTER XXXII. 



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 — Malus discovers the Polarisation of Light caused 

 by Reflection — Birth and History of Fresnel — Polarisation 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 Polarisation . . 302 



CHAPTER XXXIII. 



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 ob- 

 served by Wollaston — Mapped by Fraunhofer— Life of Fraun- 

 hofer — He discovers that the Dark Lines are different in Sun- 

 light and Star-light — Experiments on the Spectra of different 

 Flames — Four new Metals discovered by Spectrum Analysis — 

 Artificial Dark Lines produced in the Spectrum by Sir David 

 Brewster — Bunsen and Kirchhoff explain the Dark Lines in the 

 Solar Spectrum — Metals in the Atmosphere of the Sun — Huggins 

 and Miller examine the Stars and Nebulae by Spectrum Analysis . 315 



