l6 PRESIDENTIAL ADDRESS. — SECTION I. 



experienced in separating them — as time goes on the number of 

 elements will probably increase. Undoubtedly the most important 

 of the many discoveries during the past twelve years is the isolation 

 of radium. I do not now, however, propose to discuss the subject 

 save in so far as it bears upon the question of the immutability 

 of the chemical elements, for in radium the impossible has been 

 found possible — that is, one kind of matter has been changed 

 into another kind. It must be considered as being definitely 

 established that radium itself is formed, at least in part, from 

 uranium, not in one stage, but by way of several intermediate 

 products. Now, radium and uranium have several chemical 

 properties in common. Their atomic weights are not far from 

 each other, and we have every reason to believe that they have 

 other properties closely related. Radium, however, is not a per- 

 manent body : it changes — very slowly, it is true — but it does 

 change into helium, and this change is one of a character altogether 

 different from that of the change from uranium to radium. 

 Uranivmi is a metal of high atomic weight, which forms well- 

 derined basic and acidic oxides, and shows marked affinity for 

 other elements. Helium, on the other hand, is a gas of low atomic 

 weight (it is the lightest body next to hydrogen). It seems to 

 be absohitely destitute of chemical affinity, so that it will not 

 combine with any other element. 



Now the change — uranium to radium to helium — is brought 

 about spontaneously ; as far as I know we cannot accelerate or 

 retard the process, but this much is certain, that here we have a 

 case about which, at present, there cannot be any doubt but that 

 one kind of matter has been transformed into another — i.e., the 

 transmutation of elements has been proved. I must not lay 

 myself open to misapprehension — in making this statement it must 

 be clearly understood that this change has not been brought about 

 by human agency : we can observe the change — we cannot initiate 

 it. It has been claimed for radium that it can induce other 

 elements to change. Copper, for instance, has been stated to have 

 been changed under the influence of radium emanation into 

 lithium — water vapour, again, into neon, l^ut these observations 

 lack confirmation. 



The change uranium-radium-hclium is a breaking-down 

 process — perhaps this is the only way in which transmutation 

 may be possible. An element of high atomic weight may change 

 into one of low atomic weight ; but the reverse change may not 

 be possible, so that the alchemists' dream of changing copper into 

 gold may still be as far from realisation as ever. 



Do we know anything at all as to why the elements differ one 

 from another ? The answer is : " Very little." But that little 

 is very interesting, and from it great things may follow. 



What are the views held at present by physicists on the con- 

 stitution of matter ? I say " physicists " because the chemist 

 does not like the idea of his sacred atom being dethroned. The 

 physicist is a believer in the corpuscular theory of matter, as 

 formulated by J. J. Thomson, which is based on the behaviour of 

 the minute electrified j)articles called electrons or corpuscles. Let 



