144 THE NEW KNOWLEDGE. 



x^~^ r ** ' 7 



qualities. Uranium is soluble in excess of ammonium car- 

 bonate while the uranium X is not. In a mixture of ether 

 and water, the uranium dissolves in the ether while the 

 uranium X dissolves in the water. There is no better 

 criterion for a difference in nature than a difference in 

 chemical property. " But how do you know," says he, 

 " that the element uranium has anything to do with the 

 matter? You use the uranium in the form of a compound. 

 It is a property of the compound, not of the element." 

 No, it ' is not. The radio-activity of the compounds of ura- 

 nium, and hence the amount of uranium X formed-, de- 

 pends solely upon the per cent, of uranium which the com- 

 pounds contain; and it is a matter of indifference whether 

 it is in the form of nitrate, oxide or what not. Not only 

 so, but the free element itself is radio-active and on being 

 dissolved will give rise to uranium X. There is no escape 

 from .the fact that the phenomenon is a function of the 

 -element uranium itself. "Well," says the old gentleman, 

 testily, " you say that the uranium X is a transitory ele- 

 ment, (save the mark !), and that it decays. Now, what 

 does it decay into ? What becomes of the dead uranium 

 X?" 



This is an awkward question, so far as uranium is con- 

 cerned. We do not know what becomes of the uranium 

 X for the reason that it decays into a body which does 

 not emit rays, and its radio-activity is the only means 

 by which we can measure it. The amount of uranium X 

 formed is so small that it would take geological epochs 

 of waiting to secure enough to weigh, much less examine 

 chemically. But if we cannot follow the process farther in 

 the case of uranium, we certainly can in that of an anal- 

 ogous radio-active body. For just as uranium gives rise 

 to uranium X, so does the element thorium give rise to 



