TKANSMUTATION OF MATTER 



By Lord Rutherford, D. Sc, LI. D., Ph. D., F. R. S. 



Toward the close of the nineteenth century, when it seemed cer- 

 tain that the atoms of the elements were unchangeable by the forces 

 then at our command, a discovery was made which has revolutionized 

 our conception of the nature and relations of the elements. I refer 

 to the discovery in 1896 of the radioactivity of the two heaviest 

 elements, uranium and thorium. It was soon made clear that this 

 radioactivity is a sign that the atoms of these elements are undergoing 

 spontaneous transmutation. At any moment, a small fraction of the 

 atoms concerned become unstable and break up with explosive 

 violence, hurling out either a charged atom of helium, known as an 

 a-particle, or a swift electron of light mass called a /3-particle. As a 

 result of these explosions, a new radioactive element is formed, and 

 the process of transmutation once started continues through a 

 number of stages. Each of the radioactive elements formed in this 

 way breaks up according to a simple universal law but at very differ- 

 ent rates. In a surprisingly short time, these successive transforma- 

 tions were disentangled and more than 30 new types of elements 

 brought to light, while the simple chemical relations between them 

 were soon made clear. 



We had thus been given a vision of a new and startling subatomic 

 world where atoms break up spontaneously with an enormous release 

 of energy quite uninfluenced by the most powerful agencies at our 

 disposal. Apart from uranium and thorium and the elements derived 

 from them, only a few other elements showed even a feeble trace of 

 radioactivity. The great majority of our ordinary elements appeared 

 to be permanently stable under ordinary conditions on our earth. 

 Science was then faced with the problem, whether artificial methods 

 could be found to transmute the atoms of the ordinary elements. 

 Before this problem could be attacked with any hope of success, it 

 was necessary to know more of the actual constitution of atoms. 

 This information was provided by the rise of the nuclear theory of 



1 Shortly before his death on October 19, 1937, Lord Rutherford completed the presidential address which 

 he proposed to deliver at the meeting of the Indian Science Congress Association on January 3-9, 1938. 

 The latter part of the address is here reproduced and represents Lord Rutherford's last pronouncement on 

 a subject with which his name will always be associated. Reprinted by permission from Nature, vol. 141, 

 No. 3558, January 8, 1938. 



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