RADIOACTIVITY. 125 



this question. We are satisfied to have established the fact that there 

 are atomic processes, that an atom is not indivisible, and that smaller 

 particles may be isolated from it. 



We Avere attemptino- to find an explanation of the enormous quan- 

 tity of energy given out by radium, but has the knowledge of the 

 composite nature of the atom brought us farther in this direction? 

 Yes, undoubtedly, for there are many reasons to believe that if a 

 body so apparently indivisible as the atom, one which so long resisted 

 all our efforts, may be subdivided, that there nmst be enormous stores 

 of energy which can be set free, differing entirely from those we 

 have had an opportunity to study in the molecular processes and by 

 the ordinary chemical methods. The question then folloAvs: Is there 

 ground for the belief that a similar atomic disintegration may take 

 place in radium? Undoubtedly so, for the ])resent condition favors 

 the belief that radium is constantly sending out cathode rays and 

 generating electrons. We are furthermore able to produce a more 

 direct proof which may be postulated directly from the electron 

 theory, and which admits of demonstration quite independent of 

 that hypothesis. 



When an atom gives off an elemental electron its Aveight must thus 

 be lessened, wdiich is in effect to say that the atom is no longer a 

 component part of the former element but has united with another. 

 We assert, therefore, emphatically that since proof has been given 

 that atomic processes are possible, that atoms separate and can sub- 

 divide themselves, it nuist be possible that one element may convert 

 itself into another, or, for example, that gold may come from lead. 

 Whether we shall ever succeed in couA^erting gold into lead is quite 

 another question, Avhich I Avill not discuss noAV, but tlie iuA^estigation 

 of the electron favors the belief that such a transformation is not 

 impossible. And in radium it has in fact been made possible to 

 observe the process of the change of one element into another. 

 Rutherford foretold it, and Ramsay and Soddy AA-ere the first to bring 

 proof of the transmutation of the radium emanation into helium. 



If a radium preparation is placed in a glass container in a dark- 

 ened room, a Aveird, grayish, but slightly luminous, sort of a mist is 

 seen to arise from it. If the container is closed, it is gradually 

 filled by this mist, or gas, which steadily gains so much in luminosity 

 that in a day or two one can tell the time on a watch by it. If this 

 luminous fog is bloAvn out of the glass, the play begins over again 

 until the container emits light as before. The so-called radium 

 emanation is thus seen to dcA'elop itself continuously. 



What is it? I conduct the luminous air Avhich contains the emana- 

 tion through the strongest gases and lyes and it remains unchanged. 

 I conduct it oA'er incandescent copper or magnesium and it is the 

 same. I have no poAver over it. I transmit it through a tube Avhich 



