ON OUR KNOWLEDGE OF SPECTRUM ANALYSIS. 



303 



Table sliowing the coincidence of Iron Lines with certain lines in the 

 Solar Spectrum. The wave-lengths were determined by taking 

 photographs with a Nobert's grating ruled on quartz.^ 



§ 4. Absorption- Spectra of the Rats op High Refrangibility, Report by 

 A, K. Huntington, Professor of Metallurgy, King's College, London. 



■ In the year 1852 it was discovered by Prof. Stokes that quai-tz absorbs 

 the ultra-violet rays of the solar spectrum less than glass,^ and in 1853 he 

 ascertained that the length of the spectrum of the electric light obtained 

 by means of lenses and prisms of quartz was greatly in excess of that 

 of the solar spectrum under the same conditions.^ 



These discoveries made it pi-acticable to investigate spectroscojsically 

 the properties of the extreme rays of the ultra-violet spectrum — rays the 

 existence of which had previously been unknown. 



On June 19, 1862, Prof. Stokes and Prof. W. A. Miller communicated 

 to the Royal Society the results of the investigations which they 

 simultaneously but independently had made on the permeability of matter 

 for the rays of high refrangibility, and on the spectra of metals photo- 

 graphed by means of quartz apparatus. The absorbent action of various 

 solids and liquids upon the chemical rays had been described in 1843 by 



' M. Cornu, A>i>>ales dc VEcole Normale, 1880. 



- ' On the Change of Refrangibility of Light,' Phil. Tram. 1852. 



' ' On the Long Spectrum of the Electric Light,' Phil. Trails. 1863. 



