264 Luminosity and Radio- Activity. [June 11, 



Radio- A ctimty. 



Pursuing the argument a stage further, it appears to us justifiable to 

 regard tne activity of radium tentatively as but an exaggerated form of 

 fluorescence in which radiations unnoticed by substances generally- 

 capable of penetrating substances generally become absorbed and 

 rendered obvious. Such an explanation, from the chemist's point of 

 view, is at least as rational as one which assumes that nature has 

 endowed radium alone of all the elements with incurable suicidal 

 monomania, especially as exothermic changes, when once started, have 

 a tendency to occur rapidly, if not explosively. 



There seems to be no good reason for assuming that in fluorescent 

 and other ordinary substances we possess screens capable of arresting 

 rays of every conceivable kind ; it may well be that our knowledge of 

 solar radiations is not yet complete ; that radium should be more 

 powerful than other substances is not surprising seeing that of all 

 the elements known to us, it perhaps has the highest atomic weight. 

 It is also worth noting that radium stands in close relation to the 

 elements which afford luminous sulphides. 



With regard to " Thorium and Thorium X," the facts, as stated by 

 Rutherford and Soddy, do not seem to be incompatible with the view 

 that these are but isodynamic forms of thorium or their equivalent, 

 their behaviour being very similar to that of the isodynamic 

 forms of nitrocamphor, the rate of decay and recovery of activity 

 proceeding according to a simple logarithmic law just as does the 

 conversion of one form into the other in the case of nitrocamphor. 

 In any case, it appears desirable to approach the problem from this 

 point of view and to investigate the phenomena far more thoroughly 

 on the chemical side. 



Finally, it may be pointed out that the properties discussed in this 

 note are common to not a few substances. Uranium nitrate is not 

 only radio-active but triboluminescent, fluorescent and phosphorescent 

 at low temperatures ; and as Dewar as shown in a recent Royal 

 Institution lecture, it becomes highly electrified when cooled. 

 Platinocyanides also are triboluminescent, fluorescent and phosphor- 

 escent at low temperatures. That the several manifestations all have 

 their origin in the formation and decay of isodynamic or equivalent 

 systems is therefore by no means improbable. 



Whatever the ultimate value of the considerations advanced in 

 this note, they at least serve to show that much may be learnt by 

 further study of the extent to which luminous phenomena generally 

 are to be correlated with structure and structural changes. 



