SYMPOSIUM OX RADIOACTmTY. 59 



material measure, the progress of atomic disintegration. Xor do 

 any known changes of chemical union or disunion, of concentra- 

 tion or diffusion, or of freedom or confinement seem materially 

 to retard or accelerate the spontaneous dissolution. There is 

 probably no warrant for an unqualified affirmation that neither 

 temperature, pressure, concentration, exposure, nor combination 

 affects the progress of radioactive decomposition, but no specific 

 effects of a critical value have been certainly disclosed by experi- 

 mentation. These conditions that so much qualify most geologic 

 processes must apparently be regarded as negUgible for the present 

 so far as radioactivity in the earth's crust is concerned. It is 

 thought by the leaders in radioactive science permissible to treat 

 radioactive substances as undergoing disintegration persistently 

 and uniformly under all known terrestrial conditions. In the ther- 

 mal problem of the earth radioactive particles may be dealt with 

 tentatively as centers of heat-generation whose efficiency and 

 endurance are conditioned simply by their atomic constitutions 

 and their mass values. In so far as these remarkable deductions 

 from experimentation may be thought to fall short of full warrant 

 weakness in equal degree must of course be held to enter into the 

 geological inferences based on them; and in view of the radical 

 nature of the conclusions to which they lead, we cannot perhaps 

 too constantly bear in mind that the postulate of immunity to con- 

 ditions is the main basis of the geologic contributions credited to 

 radioactivity. But the remarkable verifications of skill and accu- 

 racy that have followed the multiplication of tests furnish an 

 ample warrant for a serious discussion of present deductions. 

 There is strong presumption that future tests will further sub- 

 stantiate present conclusions so far as their main bearings on 

 immediate terrestrial problems are concerned, whatever interro- 

 gations one may be disposed to indulge in regarding ulterior 

 problems. 



The clue to this extraordinary- tenacity of radioactive dissolution 

 in spite of conditions that profoundly influence most terrestrial 

 processes, probably Hes in the fact that the action springs from the 

 internal motions of the atomic constituents and that these are of 

 such an intense nature and are actuated by such prodigious ener- 

 gies that the influences of ordinan.- chemical and physical condi- 

 tions are relatively insignificant. 



At the same time, the radioactive substances show a decided 

 aptitude to enter into chemical combination under common condi- 



