PART IV. 



NATURAL RADIO-ACTIVITY : A NEW PROPERTY 

 OF MATTER. 



CHAPTER I. 



ANTECEDENT DISCOVERY. 



The theme of this present part of our book is of a new 

 thing done the discovery of a new natural property of 

 matter, and an explanation of this property in terms of 

 what we already know. 



If one questioned the discoverer the beginner of the 

 work about himself, he would probably say that his work, 

 possibly, was something he himself was nothing; and in a 

 measure he is right ; for in a few years he will pass, while his 

 work will endure forever. Still, we wish to know him for 

 his work's sake, and surely it will not be amiss to say some- 

 thing at least about him. 



Henri Becquerel, Membre de Flnstitut, is the discoverer 

 of Becquerel rays, the basis of the phenomena of radio- 

 activity. He comes very honestly by his powers. His 

 grandfather, Antoine Ce*sar (1788-1878), through sixty years 

 of indefatigable labor, contributed more than five hundred 

 memoirs, works of note on mineralogy and electricity. His 

 father, Alexandre Edmond (1820-1891), was the author of so 

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