PHYSICS 



two quantities separately. It appears that the 

 experimental data are satisfied about as well by an 

 isotope of hydrogen of charge i and mass 2 as 

 by the helium isotope of charge 2 and mass 3. 

 If the hydrogen isotope is taken as the solution, 

 it is found to have considerably less energy than 

 the ejecting a particle ; so that the proof of the 

 generation of energy falls to the ground. I should 

 like to add that there are qualitative considerations 

 which would take us too long to go into which 

 make the body of mass 3 the more probable 

 alternative. The position may therefore be sum- 

 marised by saying that the experimental results 

 make the controlled generation of energy from 

 the nucleus a probable fact, but they do not 

 establish it with absolute certainty. 



Apart from the question just under discussion, 

 of the magnitude of the energy, it does not seem 

 possible to reconcile all the data which have been 

 obtained without assuming that the fragments are 

 ejected as the result of a secondary nuclear ex- 

 plosion rather than a merely dynamical impact 

 between the nucleus and the a particle. So far 

 the projectiles (a particles) which have been able 

 to cause these explosions possess an enormous 

 concentration of momentum, such as it would 

 be impossible to obtain except from radioactive 

 sources. The application to large-scale phenomena 

 is therefore far from being realised. It may be 



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