Vlll 



Preface 



six periods and including chapters dealing with (1) Far Eastern 

 and Classical antiquity, (2) the Middle Ages, (3) the scientific 

 renaissance of the fifteenth and sixteenth centuries, (4) the seven- 

 teenth century, (5) the eighteenth century, and (6) the nineteenth 

 century. These first six chapters are concerned with the general 

 development of knowledge concerning various luminescences and 

 the writers who may be said to have had a special interest in lumi- 

 nescence study. 



Parts II and III deal with special types of luminescence associated, 

 respectively, with the non-living and the living world. They con- 

 tain the detailed history of observations and experiments on lumi- 

 nescence, beginning about 1600, the approximate time of the new 

 rational approach to learning, inaugurated by Francis Bacon, and 

 the period when science became divorced from magic. Part II in- 

 cludes chapters on electroluminescence, phosphorescence, thermo- 

 luminescence, triboluminescence, fluorescence, radioluminescence, 

 and chemiluminescence; Part III deals with shining fish, flesh and 

 wood, the phosphorescence of the sea, and animal luminescence. 

 Each chapter of Parts II and III is complete in itself, and may be 

 read without reference to other chapters. Much of the popular and 

 some scientific speculation regarding the aurora borealis has been 

 omitted, and the wealth of folklore and opinion concerning the 

 glowworm and the firefly in both prose and poetry is being prepared 

 for a later volume. 



There is ample justification for including the history of inorganic 

 luminescences and light production by plants and animals in one 

 volume. During the long period of observation on the subject, the 

 origin of many weak lights remained unknown until fairly recent 

 times. For example, the light of wood and flesh was not finally con- 

 nected with fungi and bacteria until 1823 to 1853, and hence was a 

 subject for research by physicist and chemist as well as biologist. 

 Indeed, every textbook of physics or chemistry which discussed the 

 inorganic " Bolognian phosphor " also included the " spontaneous 

 light " which appeared on wood and meat. 



The attempt has been made in the special sections to indicate the 

 first discovery of an important fact or principle, although the author 

 realizes how dangerous such a pronouncement is. Not only is the 

 literature of science so vast that no one person can hope to master it, 

 but frequently a number of men are approaching a discovery simul- 

 taneously. It is often difficult or impossible to decide on the actual 

 discoverer. The qualifying expression " appears to have been dis- 

 covered by so and so " is a more realistic attitude. 



Throughout the book, special attention has been paid to the views 



