PHYSICAL PARADOXES. 



in all directions at a speed of less than 20,000 

 miles per second. They are therefore unable 

 to get through the first glass wall. 



Other things which fly out from the dis- 

 integrating atoms of radium are the beta rays, 

 tiny bodies about the two-thousandth size of the 

 alpha rays and ten times as swift, which means 

 that they have a striking energy a hundred 

 times as great in proportion to their weight. 

 These are swift and small enough to pierce 

 their way through the glass walls, and get 

 clear away from the radium chamber. 



The small beta rays have a charge of nega- 

 tive electricity, which they carry away with 

 them. The larger alpha rays have a positive 

 charge, which remains with them, so that there 

 arises an accumulation of positive electricity 

 in the radium chamber, which by induction 

 causes an accumulation of positive electricity 

 in the leaves of the electroscope. 



Both leaves being charged with the same 

 kind of electricity, they begin to repel each 

 other, as similar poles of magnets do. As the 

 charge accumulates, the repulsion increases 

 until the leaves touch the foil placed at the 

 sides of the tube, which, having a metallic con- 

 nection to earth through the glass, discharge 

 the leaves and allow them to fall together again. 



But the radium is constantly at work, a 

 fresh charge of positive electricity is soon, 

 accumulated, and the separation of the leaves 



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