xi ACROSS THE BORDER 307 



discovery of so many new radioactive substances that 

 any attempt at christening them seems to have been 

 abandoned, and they are denoted, like policemen, by the 

 letters of the alphabet." 



It is an axiom of scientific theory that you cannot 

 create energy any more than you can add or destroy a 

 single atom of matter in the universe. If light or heat 

 are being given out in any way, energy is being expended 

 to produce it, and the same is true of other effects. 

 Radium, however, is a spontaneous producer of light, 

 heat and electricity ; in other words, it continually 

 produces luminous, thermal and electrical effects with- 

 out using up energy capable of being measured. 

 Unlike ordinary phosphorescent substances, which only 

 shine after exposure to light, radium is luminous over 

 its whole mass, and the luminosity does not diminish at 

 any time. Moreover, radium salts give off heat con- 

 tinuously, without any chemical change such as occurs 

 in ordinary combustion ; and the amount of heat is 

 sufficient to keep the temperature of the radium salts 

 nearly three degrees Fahr. above that of their 

 surroundings. 



It is believed that the rays emitted by a radioactive 

 substance represent the results of the breaking-up of 

 atoms of the substance, and mark, therefore, stages of 

 atomic disruption. Radium, for example, gives off a 

 gas called " radium emanation " by the first observers, 

 Sir Ernest Rutherford and Prof. F. Soddy which repre- 

 sents the product of the disruption of radium atoms. 

 On this view, which is based upon substantial experi- 

 mental investigation, there must be a limit to the life 

 of a radioactive element. In the case of radium, 

 one grain would be reduced to half a grain in -1760 

 years ; but the emanation has a much shorter span 



