1896.] on Electric Shadows and Luminescence. 213 



draw your attention to the accompanying table of the different kinds 

 of luminescence with which the physicist has to deal. 



TABLE II. 



Phenomenon. Substance in which it occurs. 



1. Chemi-laminescence Phosphorus oxidising in moist air; 



decaying wood ; decaying fish ; glow- 

 worm ; fire-fly ; marine organisms, 

 &c. 



2. Photo-luminescence : 



(a) transient = Fluorescence . . Fluor-spar ; uranium-glass ; quinine ; 



scheelite ; platino-cyanides of various 

 bases ; eosin and many coal-tar pro- 

 ducts. 



(6) persistent = Phosphorescence Bologna - stone ; Canton's phosphorus 



and other sulphides of alkaline 

 earths ; some diamonds, &c. 



3. Thermo-luminescence Scheelite ; fluor-spar. 



4. Tribo-luminescence Diamonds ; sugar; uranyl nitrate ; 



pentadacylparatolylketone. 



5. Electro-luminescence : 



(a) Effluvio-lumiuescence .. .. Many rarefied gases; many of the 



fluorescent and phosphorescent 

 bodies. 



(b) Kathodo-luminescence .. .. Rubies, glass, diamonds, many gems 



and minerals. 



6. Crystallo-luminescence Arsenious acid. 



7. Lyo-luminescence Sub-chlorides of alkali-metals. 



8. X-luminescencG Platinocyanides, scheelite, &c. 



You will note the names given to discriminate from one another 

 the various sorts of luminescence. Chemi-luminescence denotes that 

 due to chemical action, as when phosphorus oxidises, or when the 

 glow worm emits its cold light. Then there is the photo-lumi- 

 nescence of the bodies which shine when they are shone upon. There 

 is the thermo-luminescence of the bodies which shine when heated. 

 There is tribo-luminescence caused by certain substances when they 

 are rubbed. There is the kathodo-luminescence of the objects placed 



phosphorescence. It refers to all those cases in which light is produced, whether 

 under the stimulus of electric discharge, of heat, of prior exposure to illumina- 

 tion, or of chemical action, and the like, in which the light is emitted at a lower 

 temperature than that which would bu necessary if it were to be emitted by 

 meaus of incandescence. 



