298 History of Luminescence 



paper in 1863, Later, between 1878 and 1883 Warren de la Rue 

 (1815-1889) , a wealthy London physicist, published (with H. Mul- 

 ler) some beautiful plates (see fig. 27) of the various effects in 

 rarefied gases excited by his famous silver chloride battery of 25,400 

 cells, while the papers (1879) of Wm. Crookes (1832-1919) on 

 molecular discharge in high vacua contained a colored plate of 

 cathode ray effects. These contributions all appeared in the Phil. 

 Trans, of the Royal Society, together with the paper (1879) of Wil- 

 liam Spottiswood (1825-188Z3) , another wealthy Londoner. The 

 unusual luminescent effects in vacuum tubes seemed to attract men 

 of independent means. 



Other early observers of electroluminescence not primarily in- 

 terested in spectra were E, Reitlinger (1862) and Quet et Sequin 

 (1862) on stratification, J. F. A. Morren (1861-1869) on the after- 

 glow, A. Wiillner (1874) on stratification, E. Goldstein (1874 to 

 1899) on cathode rays, and B. Hasselberg (1879, 1880) on low 

 temperature effects. 



The research on rarified gases required special tubes, many of 

 which were made by Heinrich Geissler,°° a glass blower of Bonn, 

 engaged by Pliicker to make vacuum tubes with sealed-in platinum 

 electrodes. The light, of all colors depending on the gas, could be 

 concentrated in capillary spaces and made to follow the tortuous 

 curves imparted to the glassware. Figure 28 is a plate of the various 

 shapes, taken from the book of O. Lehmann (1898: 485) . By the 

 use of uranium glass in parts of the apparatus, really striking and 

 beautiful effects were obtained. These were the Geissler or Pliicker 

 tubes, which fascinated audiences in the sixties and seventies, and 

 played so important a role in understanding the nature of matter. 



Gassiot's " cascade " (1860) was obtained by means of a large 

 goblet of uranium glass, the inner surface lined with tin foil and 

 the base resting on a metal plate. When covered with a bell jar 

 and evacuated to the proper degree, with the tin foil and plate con- 

 nected to an " influence machine," spectacular electroluminescent 

 effects appeared in the gas which seemed to flow over the edge of 

 the goblet itself, glowing with uranium glass fluorescence of a beauti- 

 ful greenish yellow. 



In the last third of the nineteenth century, noted for the develop- 

 ment of spectroscopy and its application in every branch of science, 

 particularly chemistry and astronomy, the study of electrolumines- 

 cence in vacuum tubes was pursued in minutest detail by a host of 



*" Geissler published a short paper in 1868 on tubes which would luminesce when 

 rubbed. 



