The Groundwork of the Universe, &c. 57 



perties and to display considerable beta-ray activity. These 

 results are expressed in the following scheme : — 



ORIGINAL " URANIUM." 

 (Gives off ;8-rays) 



I 



I I 



URANIUM- 1 URANTUM-Xi 



(Emits no ^S-rays) (P]mits /i^-rays) 



On 

 standing 



URANIUM-Xi 



(Emits /i^-rays) 



There is nothing abnormal in the separation of " uranium " 

 into two fractions, one of which is radioactive whilst the other 

 is inactive ; for the radioactive material might be there as an 

 impurity in the original mass of uranium." What is extra- 

 ordinary is the fact that after all the radioactive impurity is 

 removed, the remaining inactive material gradually becomes 

 again radioactive. This is practically parallel to the complete 

 removal of silver from a lead-silver alloy and the slow reappear- 

 ance of silver after a time in the carefully purified lead. It can 

 be accounted for only by assuming that the substance uranium-1 

 is breaking up and giving rise to a new element, nranium-Xi, 

 which possesses beta-ray activity. 



The phenomena mentioned in the last lecture in connection 

 with radium throw further light upon the matter. Kadium, it 

 was foiuid, gave off continually a gas, niton, which has radio- 

 active properties different from those of radium itself. Here, 

 obviously, since both radium and niton are known to be ele- 

 mentary forms of mattei-, we have the case of one element giving 

 birth to another ; and the older idea of the permanence of the 

 elements has received a severe shock. 



When the chemical properties of niton were investigated by 

 Sir Ernest Kutherfoid and Mr, Soddy, it was found that they 



