50 A. W. Steivart on 



most important branch which will allow them to compete on 

 even terms with graduates from other Universities. It is especially 

 Hppi-oi)riate that the Heron gift should have been devoted to a 

 branch of Chemistry with which the name of Belfast is connected- 

 through the fame of Andrews. 



III.— THE TRANSMUTATION OF THE ELEMENTS 

 AND KINDRED PROBLEMS. 



In the first of this series of lectures, it Avas tacitly assumed 

 that what we call "chemical elements" are forms of matter which 

 exist unchanged through their history and which are not capable 

 of decomposition into simpler materials. With the second lecture 

 in the course, following the historical development of the subject, 

 it was found necessary to modify this view in order to bring it 

 into line with modern work on the radioactive elements : for these 

 forms of matter have been found to disintegrate spontaneously 

 into simpler substances, though the experimental resources at 

 our dis])Osal fail to initiate such decompositions among the non- 

 radioactive elements or even to influence the rate at which 

 the radioactive elements disintegrate. In the present lecture, 

 the subject will be brought up to date and the discoveries of the 

 past year will be described, which show that even this voluntary 

 break-down of certain elements is possible at the present time. 

 But before entering upon this field, it may be well to go back to 

 the beginning of the century, when Sir William Crookes was 

 investigating the radioactive propefties of the element uranium. 



Crookes found that a certain specimen of uranium showed 

 marked radioactive character ; but when he applied the processes 

 of chemical analysis to it, he was able to separate it into two parts. 

 The one ])ortion showed strong beta-ray activity (like the parent 

 specimen) ; but the second portion exhibited no beta-ray activity 

 whatever. After being left aside for some months, however, the 

 non-active specimen was found to have acquired radioactive pro- 



