118 THE NEW KNOWLEDGE. 





in the hands of science- revealed the existence of several ele- 

 ments occurring in quantities too small to be detected by 

 any other means. In a similar way additional elements 

 have now been detected and isolated by this more powerful 

 instrument, the electroscope, which for years has been the 

 toy of every high school laboratory. There is every proba- 

 bility that when greater quantities of radium are at the dis- 

 posal of the investigator the radium emanation will be 

 collected in quantity sufficient to demonstrate clearly its 

 spectrum as an element and its vapour pressure as a gas. 

 The amount of energy radiated by the emanation is almost 

 incredibly large compared with the small amount of matter 

 involved. We have said that the emanation from a grain 

 or two of radium chloride when liberated by solution is ca- 

 pable of illuminating brightly a screen of phosphorescent 

 zinc sulphide for days at a time, and yet this rapid emission 

 of energy arises from a quantity of gaseous matter hundreds 

 of thousands of times beyond the power of the most delicate 

 balance to detect. Professor Rutherford has calculated that 

 if a thimbleful of this active gas could be collected the 

 bombardment of its powerful rays would heat to a red heat, 

 if it would not melt down, the walls of the glass tube con- 

 taining it ! This remarkable fact leads naturally to two 

 very important questions: 



(1) What is the nature of the rays emitted by the emana- 

 tion? Are they alpha-, beta- or gamma-rays; or, to use the 

 terminology of Part III, are they positive ions as big as 

 atoms, corpuscles a thousand times smaller than atoms, or 

 X-rays? 



(2) What becomes of the radium from which the emana- 

 tion has been removed, the de-emanated radium? Has it 

 lost any of its radio-activity, what kind of rays does it still 

 emit? 



