192 History of Luminescence 



And tip with silver all her saffron flowers; 



Warm on her mossy couch the radiant Worm, 



Guard from cold dews her love-illumin'd form, 



From leaf to leaf conduct the virgin light, 



Star of the earth, and diamond of the night. 



Yoii bid in air the tropic Beetle burn, 



And fill with golden flame his winged urn: 



Or gild the surge with insect-sparks, that swarm 



Round the bright oar, the kindling prow alarm; 



Or arm in waves, electric in his ire. 



The dread Gymnotus *^ with ethereal fire. . . . 



Summary 



The eighteenth century may be characterized by the acquisition 

 of a vast collection of tacts regarding luminescences of all kinds, as 

 befits an " Age of Enlightenment." The greatest attention was paid 

 to inorganic phosphors, particularly to the preparation of new light- 

 emitting materials. Although the light might last but a short time, 

 the conclusion was reached that nearly everything, inorganic and 

 organic, was a potential phosphor. If the material did not respond 

 to illumination, slight heating, or friction, or attrition was effective 

 in exciting the luminescence. Particular attention was paid to the 

 interrelation between phosphorescence, thermoluminescence, and 

 triboluminescence. 



During a century concerned with the phenomena of electricity, 

 many investigators turned their attention to the " electric light," 

 little realizing how important electroluminescences were to become 

 in practical illumination. The phosphorescence of the sea was re- 

 garded more and more as due to the light of living organisms, but 

 convincing proof that all sea light could be ascribed to animaculae 

 was still lacking. The light of dead flesh and rotten wood was still a 

 problem for the physicist and chemist, with incorrect ideas of the 

 cause. Bioluminescences were neglected as a group, compared with 

 the very great interest in the inorganic field, and compared with the 

 great revival of interest in luminous animals and plants charac- 

 teristic of the nineteenth century. 



A start was made to discover important details concerning the 

 light emitted, such as its spectrum, or by what new methods a lumi- 

 nescence might be excited, for example, the action of the electric 

 spark. The chemical composition of various luminescent materials 

 was studied, as well as the effect of the newly isolated gases, both 

 on living luminous organisms and on inorganic luminous material. 



*^ Gymnotus, an electric fish, is not luminous. 



