SOME PHYSICAL PROBLEMS 



ed to prove the actual transformation of one element 

 into another, Professor Ramsay himself was by no 

 means ready to declare the absolute certainty of this. 

 Yet the presumption in favor of this interpretation 

 of the observed phenomena is very strong; and so 

 cautious a reasoner as Professor Rutherford has de- 

 clared recently that "there can be no doubt that 

 helium is derived from the emanations of radium 

 in consequence of changes of some kind occurring 

 init." c 



" In order to explain the presence of helium in radi- 

 um on ordinary chemical lines," says Professor Ruther- 

 ford, "it has been suggested that radium is not a true 

 element, but a molecular compound of helium with 

 some substance known or unknown. The helium 

 compound gradually breaks down, giving rise to the 

 helium observed. It is at once obvious that this postu- 

 lated helium compound is of an entirely different char- 

 acter to any other compound previously observed in 

 chemistry. Weight for weight, it emits during its 

 change an amount of energy at least one million times 

 greater than any molecular compound known. In ad- 

 dition, it must be supposed that the rate of breaking 

 up of the helium compound is independent of great 

 ranges of temperature a result never before observed 

 in any molecular change. The helium compound in 

 its breaking up must give rise to the peculiar radia- 

 tions and also pass through the successive radio-active 

 change observed in radium. . . . On the other hand, 

 radium, as far as it has been examined, has fulfilled 

 every test required of an element. It has a well- 

 marked and characteristic spectrum, and there is no 



105 



