SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. /05 



estly sought by the physicists of the best equipped laboratories of 

 Europe. 



Wliilst these investigations were going on Henri Becquerel, noticed 

 that certain crystalline compounds, notably the salts of uranium and 

 several other substances found in pitchblende, not only possess the 

 X-ray power, but under certain conditions emit light without sensible 

 heat, and these were called Becquerel rays in honor of their discoverer. 



But the close of the nineteenth century was signalized by the dis- 

 covery of a new and wonderful element which became an epoch-making 

 event in hastening the transition of theories respecting the nature and 

 ultimate forms of matter, from the old to the new views. Two French 

 chemists, Pierre Curie, in co-operation with his Polish wife, obtained 

 from pitchblende a most remarkable element which was not only daz- 

 zingly self-luminous, but emitted an X-ray more powerful than those 

 proceeding from a Crooke's tube. 



It was appropriately named radium by its discoverers, and is the 

 most striking example of terrestrial radiant energy known. Nearly all the 

 specimens of this substance thus far produced are chlorides or bro- 

 mides of radium, it being very difficult to obtain the element in its pure 

 metallic state. The substance with which chemists experiment is one of 

 its salts — the chloride of radium. It is a white crystalline powder which 

 glows like melted steel when heated to its highest pitch. 



The atomic weight of radium is 22.5, hydrogen being 1, oxygen 16, 

 iron 56, and mercury 200. Only two known elements have a higher 

 atomic weight than radium — thorium 233, and uranium, 240 — both 

 radio-active, and both obtained from pitchblende. 



Pitchblende is a remarkable mineral which, though rare, has long 

 been known. It is found principally in Bohemia, and occurs in pitchy 

 black, or very dark, masses. Its principal constituent is the oxid of 

 uranium. The metal uranium was discovered by Klaproth in 1789, but 

 only in recent years was it found to be radio-active. It was then learned 

 that thorium, discovered by Berzelius in 1828, is also radio-active. It 

 was while investigating this property of uranium and thorium that polo- 

 nium, radium and actinium, were discovered. 



One of the most astounding mysteries connected with these radium 

 emanations is their complexity. This element shines by its own light, 

 apparently without any exciting cause; it sends forth a stream of tha,t 

 recently discovered substance, helium, detected by the spectroscope in 

 the sun's corona; and it emits three different kinds of rays, namely: 



Alpha rays, easily absorbed by solids, and carrying a positive 

 electric charge ; 



Beta rays, more penetrating than Alpha rays, and negatively 

 charged ; and 



Gamma rays, intensely penetrating, and not carrying an electric 

 charge at all. 



At the same time, b_y some wonderful and inexplicable inherent 

 energy, this versatile element maintains a temperature 2.7 degrees F. 

 above that of surrounding objects, or, rather, it imparts that higher 

 temperature to adjacent objects. 



To summarize, radium shines with perpetual light, is an inex- 

 haustible fountain of helium gas, emits positive electrical, negative 

 electrical, and non-electrical rays of enormous penetrative power, and 

 is self -heating, whether at ordinary temperatures, or plunged in a bath 

 of liquid air. Truly, the more this element is studied the more mar- 

 velous and inscrutable seem its powers. 



One of the surprising facts brought out in connection with radio- 



