278 THE POPULAR SCIENCE MONTHLY 



escapes. High temperature or a powerful electrical field may produce 

 the same effect. 



If our atom belongs to the group of radioactive elements such as 

 radium, thorium, etc., we shall see from time to time, if we watch 

 attentively, a kind of explosion. Perhaps an electron will be hurled 

 forth with enormous velocity, perhaps one of the sub-atoms, sometimes 

 both. The positively charged sub-atom, after it has given up most 

 of its energy by collisions, will attract to itself a pair of neutralizing 

 electrons and settle down, a staid helium atom. The remainder of the 

 original atom rearranges itself into a new condition of more or less 

 stability, and we have a new atom. It is no longer an atom of radium, 

 for instance, but an atom of something else; another element with an 

 atomic mass some four units less, and differing from radium as gold 

 does from mercury. Its spectrum will be different; its properties will 

 be different. It may perhaps be a gaseous atom instead of an atom 

 of a solid. And we shall see this process continuing at irregular 

 intervals, the atom gradually becoming smaller until a state is reached 

 which is so stable as to seem permanent. — And all these processes are 

 taking place within the bounds of our diminutive tennis ball. 



Here we have the transmutation of the elements of which the 

 alchemists dreamed. It is true that these changes now seem to go on 

 £t like the stars without haste without rest " uncontrollable by human 

 agencies, but one would be rash to predict the impossibility of such 

 control. 



I have pictured a radioactive atom. But need we make that 

 limitation? The intervals at which these transformations occur vary 

 greatly. Thus we are told that the average life of a radium atom is 

 about 2,000 years, that of its first product but four days, and a 

 similar product of another element, actinium, lasts but a few seconds. 

 It is estimated that an atom of uranium or thorium lasts some thou- 

 sand million years, but still eventually changes into another form. 

 In our imaginary picture we need set no limits to our measurement 

 of time. The 200,000,000 years that we are told the earth has endured 

 may be but a mere incident in the life of an atom; and an element 

 surpassing uranium as much as that does some of the more rapidly 

 disintegrating substances would appear permanent by all known tests. 



The atoms would thus appear to be crumbling, perishing — indeed 

 their death-knell has already been sounded. I find it in a recent 

 number of a scientific journal. 6 I do not know the author, but the 

 initials appended to it — W. E. — are those of the foremost chemist of 



England. 



Old Time is a'flying; the atoms are dying; 

 Come, list to their parting oration: 

 " We'll soon disappear to a heavenly sphere 

 On account of our disintegration. 



6 Nature, 73, 132. 



