MAKING THE INVISIBLE 

 VISIBLE 



Radium, as explained in 

 the text, emits rays the 

 "Alpha," the "Beta" 

 (electrons), and " Gamma " 

 rays. The above illustra- 

 tion indicates the method 

 by which these it 

 rays are made visible, and 

 enables the nature <>{ the 

 rays to be investigated. 

 To the right of the dia- 

 gram is the instrument 

 used, the Spinthariscope, 

 making the impact of 

 radium rays visible on a 

 screen. 



The radium rays shoot 

 out in all directions; those 

 that fall on the screen 

 make it glow with points 

 of light. These points of 

 light are observed by the 

 magnifying lens. 



A. Magnifying lens. B. 

 A zinc sulphite screen. C. 

 A needle on whose point is 

 placed a speck of radium. 



The lower picture show* 

 the screen and needle 

 magnified. 





