Preface ix 



on luminescence of the famous men in science, but less well-known 

 authors have not been neglected, as they frequently reflect the 

 thought of their day in clear and unmistakable terms. The writ- 

 ings of Kenelm Digby and William Simpson have a definite interest 

 for the historian, although they may not carry the weight of a 

 Galileo, a Newton, a Franklin, or a Davy, all of whom expressed 

 opinions on luminescence which have been recorded in the text. 



It is indeed surprising how frequently luminescences have aroused 

 interest in every branch of science and among the learned (espe- 

 cially the astronomers) of every nation. The history of luminescence 

 is a guide to the history of science in general. Members of the 

 American Philosophical Society have not neglected this important 

 subject. While most of the American advance in knowledge has 

 been connected with the twentieth century, and outside the scope 

 of this history, many of the nineteenth-century pioneers in Europe 

 have been foreign members of the society. In addition to Franklin, 

 the American members, John William Draper and Joseph Henry, 

 took a special interest in luminescence. 



The importance of luminescence at the present time stems from 

 the fact that it is fast becoming the universal method of commercial 

 illumination, and also of communication, through the television 

 screen. Moreover, it has played an all important part in the dis- 

 covery of electrons. X-rays, and radioactivity. What better justifica- 

 tion than this for the history of a subject which is destined to play 

 a still greater role in everyday life as we progress further and further 

 into the atomic age. 



Part of the expenses of acquisition and translation of microfilm 

 and photostat have been defrayed by a grant from the Penrose Fund 

 of the American Philosophical Society and the University Research 

 Fund of Princeton University. The author is particularly grateful 

 for this support. 



Much of the Latin translation has been done by Mrs. Annemarie 

 Holborn of Hamden, Conn., in a most satisfactory manner. It is a 

 pleasure to acknowledge the help and advice given me by colleagues 

 and friends in connection with sources of information, for refer- 

 ences and for interpretation of obscure pages in foreign languages- 

 Professors Gilbert Chinard, P. K. Hitti, and the late Alan C. John- 

 son of Princeton University, Professor W. Norman Brown of the 

 University of Pennsylvania, Professor John F. Fulton of Yale Uni- 

 versity, the late Dr. E. W. Gudger of the American Museum of 

 Natural History, and many others mentioned in the text. Sincere 

 thanks are also expressed to Mrs. Gertrude Hess, Assistant Librarian 

 of the American Philosophical Society, to Mrs. V. T. Phillips of the 



