INTRODUCTION vii 



something shared in common, the selfless search after truth. 

 Short as the Hves are, in each case the essence of the achieve- 

 ment is brought before us in a few words. 



A strong individuaHty Hke that of the writer of this book 

 is bound to show strongly individual judgments, and yet 

 I venture to assert that no one will be found to deny that 

 every name appearing in the book represents a major con- 

 tribution to science and is distinguished by the originality 

 which the author has made the password for entrance. If 

 the character of the writer pervade the book it is rather by 

 the circumstance that his admiration for uprightness of 

 character and devotion to high ideals, his love of scientific 

 truth appear on every page, than by any personal prejudices. 

 I am glad to think that it was in England that Professor 

 Lenard's scientific work was first recognised, perhaps, at its 

 true worth, and I feel sure that all English-speaking men of 

 science will rejoice to greet, in the year of his seventieth 

 birthday, this work of the brilliant pioneer of phosphor- 

 escence, cathode rays and the ionisation potential. 



E. N. DA C. Andrade 



Physics Laboratory 

 University College 



