128 THE NEW KNOWLEDGE. 



facture of thorium X, and (2) the decay of the activity 

 of the thorium X, so produced. Here again is- a transmuta- 

 tion of matter! We are not however at the end of this 

 process of change, for it turns out that this thorium X in 

 decaying, decays into an emanation similar in character to 

 the emanation from radium but not identical with it. Both 

 the radium and thorium emanation give rise to alpha-rays 

 only, but while the radium emanation condenses on the 

 walls of the glass vessel at 150 degrees below zero Centi- 

 grade, the thorium emanation condenses at 120 degrees 

 below; furthermore the activity of the radium emanation 

 decays to half value in 3.7 days, while the thorium emana- 

 nation from thorium X decays to half value in one min- 

 ute. The two emanations are therefore not identical, 

 though they are both unaffected by the most drastic 

 methods of chemistry and seem to belong to the same 

 chemical family. The thorium emanation gives rise to an 

 emanation X just as in the case of radium. This emana- 

 tion settles on the walls of the containing vessel apparently 

 with the form of a solid and emits all three radiations, 

 alpha-, beta- and gamma-rays. As with radium emanation, 

 it is soluble in some acids and not in others, but it is no 

 more identical with radium emanation X than thorium is 

 identical with radium just as with the two emanations the 

 time rates of decay of activity in the two emanations X 

 are different. 



Finally, as with radium, the thorium emanation X decays 

 into some end product which does not possess ray-emitting 

 powers and which the instruments of to-day are unable to 

 determine. The main difference between the radio-activity 

 of radium and thorium seems to lie chiefly in a difference in 

 intensity and in the fact that thorium breaks down into a 

 radio-active solid intermediate between the thorium and the 



