Triboluminescence and Piezoluminescence 385 



Thus the century came to a close ^^ with a large amount of infor- 

 mation on triboluminescence, but no generalization and no theory 

 to account for the heterogeneous collection of facts. It was not even 

 certain Avhat part electrification might play. Indeed, even today the 

 phenomena of triboluminescence cannot be explained by any one 

 theory, since they represent diverse effects gathered together under 

 one name. 



nineteenth-century research 



One of the important and comprehensive studies was made by 

 Dessaignes (1809, 1811, 1812) who endeavored to bring the tribo- 

 luminescences which he observed in line with his theory of a phos- 

 phorescent fluid, which is fundamentally electricity, bound with 

 water. As reported in his first paper (1809), he ground his ma- 

 terials (glass, moonstone and pumice) in a mortar and held that 

 the triboluminescence was brighter in a metal mortar than a porce- 

 lain one and brighter in dry weather than in damp weather. The 

 material previously ground in the metal mortar would not lumi- 

 nesce if strewn on a hot plate because the electric fluid had escaped 

 through the metal, but the same material powdered in a porcelain 

 mortar did luminesce on a hot plate, because some of its phospho- 

 rescent (electric) fluid was retained. It is hard to understand on 

 what change this finding is based. 



In the second paper, Dessaignes (1811), tried other methods of 

 crushing. Many powders hammered on an anvil gave a scintillating 

 light without being appreciably warmed. He found that water will 

 luminesce if compressed and that certain powdered materials when 

 added to water, also lighted on compression. 



Dessaignes' third paper (1812) contained a list of minerals which 

 would luminesce " on collision." The organic materials, sugar and 

 resin, behaved in a similar way. Other minerals, metals, sulphur, 

 and most metal salts were not triboluminescent. He observed that 

 the light arose at particular points where the material was fractured 

 and held that a certain diamond, not previously luminescent after 

 exposure to light, or on rubbing, would show both phosphorescence 

 and triboluminescence after it was struck in such a way that one 

 of its edges was damaged. 



Triboluminescent light is usually of very short duration, but 

 Dessaignes observed that sometimes the light near a fracture would 

 last 4-5 minutes (moonstone) , depending on the material, what 



^^ Other obsei-vers, who contributed no new facts, were Dr. Juch (1799) on sugar, 

 William Hamilton (1800) and L. von Buch (1800) on calcite from Vesuvius. Compte 

 de Bournon (Phil. Traiis. 92: 248, 1802) noticed that the corundum stone would 

 luminesce when struck, if the stone was of a red color. 



