EVOLUTION THE MASTER-KEY 



the atoms are the unalterable foundation-stones of 

 the universe. They cannot be changed one into 

 another, and so you cannot change lead into gold. 

 Your philosopher's stone is a myth." But this 

 supposed impossible thing is precisely what is 

 happening in the spinthariscope. Let us consider 

 the facts. 



Radium is certainly an "element" as much so 

 as is gold or lead or any other. Now the atoms 

 of an element have a characteristic weight of their 

 own. If we represent the weight of a hydrogen 

 atom the lightest of all by the figure i, then the 

 radium atom, according to Madame Curie, is 225. 

 It is very heavy indeed. Only two heavier sub- 

 stances are known, thorium (232) and uranium 

 (240) ; and these two share the remarkable proper- 

 ties of radium. Now if you confine some of this 

 " element " in a glass tube, there will appear therein, 

 after a short time, a minute quantity of a gas which 

 was not there before. It is not gaseous radium, 

 for when it is examined with the spectroscope it 

 shows a spectrum other than that of radium ; in 

 fact, its spectrum is quite different from that of 

 any other substance. But it was discovered by 

 Sir William Ramsay that if the spectrum of this 

 mysterious gas often known as the radium 

 "emanation" be examined again after an inter- 

 val of about four weeks, it has changed into a 

 familiar spectrum easily recognizable as that of 

 the gaseous "element" known as helium. So here 

 is the astonishing fact: that the "element" radium 

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