46 Mr. John Finnegan on 



skin sores that heal slowly. M. Curie allowed an impure radium 

 salt for ten hours to rest upon his arm ; immediately a red spot 

 appeared, and a sore was produced that required some months to 

 heal, leaving a very marked scar. 



M. and Madame Curie observed that every substance which 

 remains some hours near a radio-active salt becomes itself radio- 

 active, possessing induced radio-activity. Professor Curie found 

 that the zinc, iron, and lead fittings, the air of his laboratory, the 

 clothing of the workers, their very persons, in presence of radium, 

 start into activity, and give out rays capable of affecting a photo- 

 graphic plate and discharging electricity. Sometimes he himself 

 could not enter his laboratory or approach his electrometer for 

 days. It has been found that these substances are continually 

 giving out a kind of gas, and this is called elimination ; the radio- 

 activity is caused by particles from this emanation depositing on 

 the surrounding bodies. We have five disintegration products of 

 radium — (1) a very active substance continually produced called 

 radium X ; (2) the luminous emanations arising from it ; (3) the 

 resulting precipitate of this, also self-luminous ; (4) Cathode rays ; 

 (5) "Alpha" rays, and accompanying these a continuous emission 

 of heat. 



Rutherford explains the phenomenon of radioactivity by the 

 theory that radium atoms are disintegrated, producing others of 

 less intrinsic energy. 



He supposes that a small number of atoms, perhaps one in one 

 hundred thousand millions, becomes unstable every second, and 

 explodes, a part the "Alpha" particle is violently expelled. 



The remainder is the radium exonation. This is also unstable 

 and expels another " Alpha " particle, becoming emanation X, 

 which behaves like a solid. 



This again is unstable, disintegrating with production of "Alpha," 

 " Beta," and " Gamma " rays. All these are lost to the original 

 radium, and the loss is continuous, but so small that we cannot 

 detect it by weighing. Radium, then, cannot survive indefinitely, 

 and the wonder is that it has survived so long. 



