PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 371 



The beginning of the discoveries included under the head of 

 radioactivity dates back to the year 1896 when Henri Becquerel, 

 Professor of Physics in the laboratory of the Museum of Natural 

 History in Paris, discovered that the element uranium is radio- 

 active; that is, it constantly gives off rays which possess some- 

 thing of the general character of the X-rays. These radiations 

 were found to aft'ect a photographic plate in a manner similar 

 to the X-rays and also to act upon the air and other gases render- 

 ing them conductors of electricity as is evidenced by the fact 

 that a charged electroscope is discharged when uranium is 

 brought near it. Later in 1898 Schmidt discovered that thorium, 

 an element resembling uranium in having a high atomic weight, 

 emitted a similar radiation. These discoveries attracted the at- 

 tention of [Monsieur and Madame Curie. The brilliant investi- 

 gations of these two scientists, culminating in the isolation of 

 the new elements, polonium and radium constitute a story well 

 known even to the layman and need no repetition here. The 

 allurement of the field of work thus opened up naturally drew 

 many investigators, both physicists and chemists, and the discov- 

 eries made by these investigators together with the theoretical 

 bearing of these discoveries upon the constitution of matter have 

 held first place in importance in the history of our science during 

 recent years. Naturally there has been much speculation in 

 regard to the discoveries made and many hypotheses have been 

 advanced to account for the phenomena connected with radio- 

 activity. It is recognized, however, that the development in this 

 field is in its infancy and any hypothesis formed at the present 

 time must be a tentative one only and must be advanced with an 

 almost complete assurance that, if not discarded entirely, it will 

 at least have to be modified to meet the conditions that will be 

 imposed upon it by future discoveries. 



I shall attempt in as few words as possible a brief survey 

 of the present status of our knowledge of radioactivity so far 

 as it has a bearing on chemical science. 



Experiments have shown that the elements, uranium and 

 thorium, are spontaneously disintegrating; that this process is 

 accompanied by, or perhaps it would be better to say that it 



