on Radioactive Change. 587 



Thus in the following table the metabolons at present known 

 to result from the disintegration of the three radio-elements 

 have been arranged in order. 



Uranium. Thorium. Radium. 



Uranium X. Thorium X. Radium Emanation. 



I I 1 



? Thorium Emanation. Radium-Excited Activity I. 



* \ 



Thorium-Excited Activity I. ditto II. 



\ I 



ditto II. ditto III. 



p P 



The three queries represent the three unknown ultimate products. 

 The atoms of the radio-elements themselves form, so to speak, 

 the common ground between metabolons and atoms, possessing 

 the properties of both. Thus, although they are disintegrat- 

 ing, the rate is so slow that sufficient quantity can be 

 accumulated to be investigated chemically. Since the rate 

 of disintegration is probably a million times faster for radium 

 than it is for thorium or uranium, we have an explanation of 

 the excessively minute proportion of radium in the natural 

 minerals. Indeed, every consideration points to the con- 

 clusion that the radium atom is also a metabolon in the full 

 sense of having been formed by disintegration of one of the 

 other elements present in the mineral. For example, an 

 estimation of its " life/' goes to show that the latter can 

 hardly be more than a few thousand years (see § 7) . The 

 point is under experimental investigation by one of us, and a 

 fuller discussion is reserved until later. 



There is at present no evidence that a single atom or meta- 

 bolon ever produces more than one new kind of metabolon 

 at each change, and there are no means at present of finding, 

 for example, either how many metabolons of thorium X, or 

 how many projected particles, or "rays," are produced from 

 each atom of thorium. The simplest plan therefore, since it 

 involves no possibility of serious error if the nature of the 

 convention is understood, is to assume that each atom or 

 metabolon produces one new metabolon or atom and one 

 " ray." 



§ 7. The Energy of Radioactive Change, and the Internal 

 Energy of the Chemical Atom. 



The position of the chemical atom as a very definite stage 

 in the complexity of matter, although not the lowest of 

 which it is now possible to obtain experimental knowledge, 



