206 History of Luminescence 



led him to the view that wood and fish luminescence is an oxidation 

 resulting in the formation of water and CO2 (see Chapter XIV) . 



Although the light of luminous animals was specifically excluded 

 from the prize essay, Dessaignes did discuss light of the sea, and 

 spoke of two kinds, " discrete et continue," the first from small 

 living animals (molluscs or fishes) which secrete a luminous slime, 

 the second resulting from such disintegrated slime in the water. 

 Living luminous forms were thought to contain a sap (sue albu- 

 mino-muqueux) in transparent receptacles. The sap absorbed 

 oxygen in bound but not combined form and the resulting oxidation 

 produced the light, dependent on the movement and will of the 

 animals. In all cases of " spontaneous phosphorescence " the prin- 

 ciple of light production was the same, whether in dead or in living 

 creatures. 



Dessaignes' greatest contributions had to do with inorganic phos- 

 phorescence excited by insolation, warming, compression, and col- 

 lision. He occupied a place in France comparable to that of Hein- 

 rich in Germany, but was more active and a better experimenter. 

 As the prize announcement required, Dessaignes did his best to 

 establish the relations between the different types of luminescence 

 and to explain them by a common cause. As Heinrich's principle 

 was acid, Dessaignes' was water. He believed the light substance 

 adhered strongly to water and that all substances containing bound 

 water would luminesce. Dessaignes' greatest difficulty lay in explain- 

 ing the ability to luminesce of substances which apparently con- 

 tained no water. How he endeavored to apply the water principle 

 to his various observations on inorganic phosphors will be described 

 in Chapter VIII on Phosphorescence. 



Inorganic Luminescences 



INTRODUCTION 



After the last installment of Heinrich's book appeared in 1820, 

 no outstanding contributions ® were made to knowledge of non- 

 living luminescences until the work of David Brewster and the 

 Becquerel family in the eighteen-thirties and forties. Brewster's 

 early research (1819-1823) had to do with thermoluminescence of 

 minerals and his later studies (1833-1838) with what came to be 

 known as fluorescences. His twenty-page article, " Phosphorescence," 

 in the Edinburgh Encyclopedia (1832) is particularly compre- 

 hensive. 



The middle of the century will always be noted for the brilliant 



® A general paper on all kinds of luminescence was published by J. J. Virey in 1819. 



