THE ADVANCE OF SCIENCE 79 



without loss, under any and all conditions pouring forth 

 by virtue of its own intrinsic property powerful rays 

 capable of penetrating opaque bodies and of exciting 

 phosphorescence and acting on photographic plates, can 

 perhaps be realized when we reflect that it is as mar- 

 vellous as though we should dig up a stone which without 

 external influence or change, continually poured forth 

 light or heat, manufacturing both in itself, and not 

 only continuing to do so without appreciable loss or 

 change, but necessarily having always done so for count- 

 less ages whilst sunk beyond the ken of man in the 

 bowels of the earth. 



Wonderful as the story is, so far it is really simple 

 and commonplace compared with what yet remains to 

 be told. I will only barely and abruptly state the fact 

 that radio-activity has been discovered in other elements, 

 some very rare, such as actinium and polonium ; others 

 more abundant and already known, such as thorium and 

 uranium, though their radio-activity was not known until 

 Becquerel's pioneer-discovery. It is a little strange and 

 no doubt significant that, after all, pure uranium is 

 found to have a radio-activity of its own and not to have 

 been altogether usurping the rights of its infinitesimal 

 associate. 



The winders connected with radium really begin 

 when the experimental examination of the properties of 

 a few grains is made. What I am saying here is not 

 a systematic, technical account of radium ; so I shall 

 venture to relate some of the story as it impresses me. 



Leaving aside for a moment what has been done in 

 regard to the more precise examination of the rays 

 emitted by radium, the following astonishing facts have 

 been found out in regard to it : (i) If a glass tube con- 

 taining radium is much handled or kept in the waistcoat 



