Radioluminescence 411 



anode and remarked that the green light from the glass was similar 

 to that which he had observed in his phosphoroscope when glass was 

 illuminated by sunlight. Pliicker referred to " the beautiful green 

 light whose appearance is so enigmatical." He thought at first that 

 the color was subjective but later realized it was a fluorescence of 

 the glass, and stated that lead glass would fluoresce blue. Pliicker 

 used the expression " magnetic light " for the light which spreads 

 in all directions from the negative pole and can be moved by a 

 magnet. 



Fluorescence of the glass near the cathode led Gassiot (1859: 141) 

 to use the expression " a distinct phenomenon, having the appear- 

 ance of a force or action emanating from the negative terminal." 

 J. W. Hittorf (1824-1914) found in 1869 that a solid body in the 

 path of the action would cast a shadow. This was confirmed and 

 the name " cathode rays " (Kathodenstrahlen) ^ was coined in 1876 

 by E. Goldstein^ (1859-1930), when he found the rays to be de- 

 flected in an electric field. These cathode rays were spoken of as 

 " attenuated particles of matter " and a " molecular torrent " by 

 C. F. Varley * in 1871 and as the " ultragaseous state of matter " by 

 William Crookes (1832-1919) in 1879. Later they were called 

 " radiant matter," and many of their effects were studied extensively 

 by Crookes, who emphasized the " green fluorescent light of mole- 

 cular impact." 



Henrich Hertz (1857-1894) in 1892 showed that they passed 

 through gold and aluminum foil inside the vacuum tube, and in 

 1893 Philip Lenard (1862-1947) had a thin aluminum window built 

 into the walls of the tube, allowing the rays to pass into the air 

 outside, where they were called Lenard rays. The controversy be- 

 tween English and German workers over their nature, whether 

 particles or waves, lasted until 1897 when J. J. Thomson (1856- 

 1940), by measuring the deflection^ in an electric field, accurately 

 measured their mass and established without a doubt their material 

 nature. He used the word " corpuscles " to designate them, and 



^ The "discoverer" of cathode rays has given rise to much controversy. J. J. Thom- 

 son (Conduction of electricity through gases, 1903) named Pliicker (Ann. der Physik 

 107: 77-113, 1859), while W. Ramsay in Elements and electrons (1912) and P. Lenard 

 in Great men of science (translated from the German by H. S. Hatfield, 1935) referred 

 to Hittorff (Ann. der Physik 136: 1-30, 1869) as discoverer. E. Becquerel (1881) 

 claimed observing their effects in 1858 (see Ann. de Chim. et Phys. (3), 55:92-97, 

 1859) , but he did not recognize cathode rays as distinct exciting agents. Crookes 

 (1879) first referred to them as fast moving particles. 



^E. Goldstein, Monatsber. d. Berlin Akad., 284, 1876. See also his book (1880). 



* C. F. Varley, Proc. Roy. Soc. 19: 238, 1871. 



^Jean Perrin (Cotn. Rend. Acad. Sci. 121:1130-1136, 1895) showed that cathode 

 rays carried negative charges. 



