26 SODDY, Evolution of Matter by Radio-active Elements, 



production of the helium followed at once from the 

 result of the next experiment. The emanation from 

 the two quantities of the radium solution was allowed to- 

 accumulate until the equilibrium quantity was sufficiently 

 nearly attained, which occurs practically in a period of 

 two or three weeks. This was then pumped off with the ^ 

 hydrogen and oxygen simultaneously produced from the. 

 decomposition of the water, and freed from the latter by 

 condensation with liquid air, and pumping off the volatile 

 gases. As the tube warmed up a momentary glimpse of a , 

 spectrum characterised by bright green lines was always 

 observed. This is probably the spectrum of the emanation, 

 but it is masked immediately afterwards by the volatilisa- 

 tion of the carbon dioxide, which in our early experiments 

 was never completely excluded. In experiments now in 

 progress we have been able to overcome the difficulty, 

 and the spectrum of the emanation is the subject of 

 closer examination. If the spectrum of the sealed tube 

 in which the emanation has been condensed is examined 

 from day to day, the helium spectrum gradually makes- 

 its appearance and grows in brilliancy. The characteristic 

 Dg line appears generally after the third day, and in the 

 end the complete spectrum is observed. This result has 

 now been obtained many times, and proves that helium 

 is formed from the emanation as one of the products of 

 its disintegration. As the emanation changes into helium 

 in the spectrum tube, a fresh crop of emanation is pro- 

 duced from the radium,and the process goes on indefinitely. 

 The radium is being transformed into helium, via the 

 emanation. 



It must be understood that this result was only 

 obtained by the utmost refinement of the experimental 

 methods employed. In the long and arduous researches 

 of Sir William Ramsay, and his colleagues Drs. Collie 



