Electroluminescence 299 



workers.®^ Research was of two kinds: (1) on the spectroscopic 

 composition of the light ''' and (2) on the physics of the discharge 

 itself. One of the early workers (1869-1873) on spectroscopy was 

 Paul Emile Lecoq de Boisbaudran (1838-1912) , a private chemist 

 in Cognac and in Paris, who received the Bordin prize in 1872 for 

 his study of spectra. He later became known, together with Wm. 

 Crookes of England, for investigation of the cathodoluminescent 

 spectra of the rare earths, described in Chapter XII. 



At this time spectra were recorded under " normal " conditions, 

 but it was early recognized that changing the pressure, temperature 

 and the electrical conditions of the discharge would greatly change 

 the character of the spectra, leading to intensity differences, to 

 broadening and to actual reversion of lines. A. Schuster (1877) 

 was particularly impressed with the totally different spectral com- 

 position of light from a gas when a Leyden jar was incorporated in 

 the electrical circuit. 



These studies received a great impetus when Gustav Robert 

 Kirchoff (1824-1887) , in 1859 explained the Fraunhofer lines of 

 the sun's spectrum as due to absorption by vapors of metals in the 

 sun's atmosphere. The new science of astrophysics made excellent 

 use of the laboratory finding on gases in vacuum tubes for interpre- 

 tation of the materials and the physical condition in stars, nebulae, 

 comets, and the aurora borealis. As early as 1869, E. Frankland and 

 J. N. Lockyer contributed a paper, " Researches on Gaseous Spectra 

 in Relation to the Physical Constitution of the Sun, Stars and 

 Nebulae," in which they studied the effect of low temperatures 

 and pressure on the hydrogen spectrum. Space will permit an 

 account of only one of the many lines of spectral inquiry. 



"See the account in Vols. I (Chap. 2) and II (Chap. 3, 4, 5 and 6) of Kayser's 

 Handbuch der Spectroscopie (1900 and 1902) . Also J. J. Thomson. Recent researches 

 in electricity and magnetism (Oxford, 1893) and Conduction of electricity through 

 gases (Cambridge, 1903; 2nd ed., 1906; 3rd ed. with G. P. Thomson (2 v.) , 1928 and 

 1933) ; O. Lehmann, Molecular physik, etc. (Halle a S., 1888, 1889) and Die elektrische 

 Lichterscheinungen oder Entladungen, etc. (Halle a S., 1898) and J. Stark, Die Elek- 

 trizitat in Gaseji (Leipzig, 1902) . 



«^ In addition to Pliicker, Pliicker and Hittorf, Van der Willigen, Lecoq de Bois- 

 baudran, and others to be mentioned, the following men have studied the spectral 

 composition of the electroluminescence of gases: J. S. Ames, 1890; A. J. Angstrom, 



1871, 1893; M. Berthelot, 1897; T. W. Best, 1887; J. R. Capron, 1880; J. Chautard. 

 1864; G. Ciamician, 1878; J. N. Collie and W. Ramsay, 1896; A. Cornu, 1886; H. 

 Deslandres, 1888; H. Ebert, 1888; J. M. Eder and E. Valenta, 1896; S. Friedlaner. 

 1896; E. Goldstein, 1874, 1881; B. Hasselberg, 1879-1885; A. Kalahne, 1898; H. Kayser, 

 1896; K. R. Koch, 1889; H. Lagarde, 1885; B. Lengyel, 1878; P. Lewis, 1899; H. F. 

 Newall, 1895; A. Paalzow and H. W. Vogel, 1881; C. Runge and F. Paschen, 1897; G. 

 Salet, 1871-1876; J. Scheiner, 1898; O. Schenk, 1873; A. Schuster, 1877-1884; C. P. Smythe, 

 1882; C. P. Smythe and A. S. Herschel, 1883; D. Van Monckhoven, 1877, 1882; H. W. 

 Vogel, 1879; A. von Waltenhoften, 1865; E. Wiedemann, 1878-1883; G. Wiedemann. 



1872, 1876; A. Wullner, 1869-1889; E. Zollner, 1871. 



