CH. xxxiii. SPECTRUM ANALYSIS. 315 



CHAPTER XXXIIL 



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 — Photography 

 first suggested by Davy and Wedgwood — Carried out by Daguerrc 

 and Talbot — Dark Lines in the Spectrum first observed by Wollaston 

 — Mapped by Fraunhofer — Life of Fraunhofer — He discovers that 

 the Dark Lines are different in Sun-light and Star-light — Experi- 

 ments on the Spectrum of different Flames — Four new Metals dis- 

 covered by Spectrum Analysis — 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 Nebulse by 

 Spectrum Analysis, 



History of Spectrum Analysis, 1800-1861. — We now 



come to the history of Spectrum analysis^ or the study of 

 the various coloured bands produced by different kinds of 

 light when seen through a prism. This is certainly one of 

 the most wonderful discoveries of our century, and though 

 its history is difficult, partly because it belongs to our own 

 time and is going on even now, yet we may learn something 

 about it. The first step was made, as you will remember, 

 when Newton discovered that white light is composed of 

 different coloured rays, but even he little suspected what 

 histories those rays could be made to telL 



Discovery of Heat-rays by Sir William Herschel, 1800. 

 — One of the first facts which was learnt in this century about 

 the spectrum was, that the coloured band which is seen 

 when a ray of white light is passed through a prism does not 



