CHAPTER VII. 

 EMANATIONS. 



Having thus analyzed the rays from radium into three 

 different kinds apparently identical with the positive ions, 

 corpuscles and X-rays, it may seem to the reader that we 

 have now explained the whole mystery of radium in terms 

 of what we already know. But this is far from being the 

 case. The mystery of radium is still a mystery as beau- 

 tiful and fascinating as ever. Let us now consider one more 

 remarkable property of radium which opens up a new world 

 of wonders. Professor and Madame Curie have discovered 

 that any substance placed near radium becomes itself a 

 false radium. " We have found," say the Curies, "that any 

 substance placed in the neighbourhood of radium acquires a 

 radio-activity which persists for many hours, and even days, 

 after the removal of the radium. This induced radio-ac- 

 tivity increases with the time during which it is exposed 

 to the action of the radium up to a certain limit. After 

 the radium is removed, it decreases rapidly, and tends to 

 disappear. The kind of substance exposed to the action 

 of the radium is almost a matter of indifference. They all 

 acquire a radio-activity of their own." This fact has been 

 verified over and over again by every experimenter in the 

 field. The zinc, iron and lead fittings, the air of the labo- 

 ratory, the water, the clothing of the workers, their very 

 persons, in the presence of radium, start into activity and 

 give out rays comparable to radium in affecting a photo- 

 graphic plate and discharging electricity. This becomes 

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